Friday 29 September

"Friday 29 September"

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08:30 - 10:00


Moderators: Jocelyne BLOCH (Médecin Cadre) (Lausanne, Switzerland), Stephan CHABARDÈS (head of the department) (GRENOBLE, France)
08:30 - 08:50 Infrared stimulation : preclinical & clinical preliminary experience. Stephan CHABARDÈS (head of the department) (GRENOBLE, France)
08:50 - 09:10 Pain Surgery. Konstantin V. SLAVIN (professor) (Chicago, USA)
09:10 - 09:25 Evaluating functional connectivity differences between DBS on/off states in essential tremor. Albert FENOY (neurosurgery) (Great Neck, USA)
09:25 - 09:40 #34068 - PL02 Gamma knife central latheral thalamotomy for neuropathic pain: a single-center retrospective study.
PL02 Gamma knife central latheral thalamotomy for neuropathic pain: a single-center retrospective study.

Background: Chronic neuropathic pain can be severely disabling and is difficult to treat. The medial thalamus is thought to be involved in the processing of the affective-motivational dimension of pain and lesioning of the medial thalamus has been used as a potential treatment for neuropathic pain. Within the medial thalamus, the central lateral nucleus has been considered as a target for stereotactic lesioning.


Objective: To study the safety and efficacy of central lateral thalamotomy using Gamma Knife radiosurgery (GKRS) for the treatment of neuropathic pain.


Methods: We retrospectively reviewed all patients with neuropathic pain who underwent central lateral thalamotomy using GKRS. We report on patient outcomes, including changes in pain scores using the Numeric Pain Rating Scale and Barrow Neurological Institute pain intensity score, and adverse events.


Results: Twenty-one patients underwent central lateral thalamotomy using GKRS between 2014 and 2021. Meaningful pain reduction occurred in 12 patients (57%) after a median period of 3 months  and persisted in seven patients (33%) at last follow-up (median follow-up was 28 months). Rates of pain reduction at 1, 2, 3, and 5 years were 48%, 48%, 19%, and 19%, respectively. Meaningful pain reduction occurred more frequently in patients with trigeminal deafferentation pain compared to all other patients (P = .009). No patient had treatment-related adverse events.


Conclusions: Central lateral thalamotomy using GKRS is remarkably safe. Pain reduction following this procedure occurs in a subset of patients and is more frequent in those with trigeminal deafferentation pain; however, pain recurs frequently over time.

Piero PICOZZI, Andrea FRANZINI (Milano, Italy)
09:40 - 10:00 High-dimensional neuroprosthetic control using a generative model of hand biomechanics. Conor KEOGH (Clinical Research Fellow) (Oxford, United Kingdom)

"Friday 29 September"

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10:00 - 10:30

Flash Poster Session 3 - Screen 1

Moderator: Oystein TVEITEN (Neurosurgeon) (Bergen, Norway)
10:10 - 10:15 #34657 - PF21 Gamma knife radiosurgery targeting the trigeminal nerve for tumor-related trigeminal neuralgia: a case series.
PF21 Gamma knife radiosurgery targeting the trigeminal nerve for tumor-related trigeminal neuralgia: a case series.

Purpose: Tumor-related trigeminal neuralgia (TN) is a challenging condition to manage that is commonly treated by surgical resection of the tumor. Stereotactic radiosurgery (SRS) targeting the tumor is used to control pain and tumor growth in patients unsuitable for surgery. SRS targeting the trigeminal nerve has been explored as a viable treatment for patients with tumor-related TN who are unsuitable for surgical removal of the tumor or whose pain is refractory to radiation therapies targeting the tumor. Information regarding the efficacy of this procedure is limited to only a few studies. We report the outcomes of Gamma Knife radiosurgery (GKRS) targeting the trigeminal nerve for tumor-related TN from a case series.


Methods: Retrospective review of our GKRS database identified 6 patients with unilateral tumor-related TN treated with GKRS targeting the trigeminal nerve between 2014 and 2022. Five patients had undergone previous radiation therapies targeting the tumor. Facial pain and sensory function were evaluated with the Barrow Neurological Institute (BNI) scores.


Results: Three patients achieved BNI IIIb or better pain reduction after a mean period of 4.3 months from GKRS. Maximum dose for GKRS ranged from 80 to 88 Gy. Pain recurred in 1 patient at 64 months after GKRS. No patient developed permanent facial sensory disturbances. No adverse event was recorded.


Conclusions: GKRS targeting the trigeminal nerve may be a safe and effective treatment for a subset of patients with tumor-related TN who are unsuitable for surgical removal of the tumor or are refractory to radiation therapies targeting the tumor.

10:15 - 10:20 #34698 - PF22 Is Spinal Cord Stimulation Still Effective After One or More Surgical Revisions?
PF22 Is Spinal Cord Stimulation Still Effective After One or More Surgical Revisions?

Objectives: Spinal cord stimulation (SCS) is burdened with surgical complications that may require one or several surgical

revision(s), challenging its risk/benefit ratio and cost-effectiveness. Our objective was to evaluate its outcome and efficacy after

one or more SCS surgical revisions.

Materials and Methods: We identified and retrospectively analyzed 116 patients treated by tonic paresthesia-based SCS who

experienced one or more complication(s) requiring at least one surgical revision. Data collected included initial indication,

revision indication, number of revisions, and lead design (paddle or percutaneous). Outcome after SCS revision was evaluated by

pain intensity decrease (comparing baseline and postrevision Numerical Rating Scale [NRS] scores) and percentage of patients

reporting pain relief ≥50%. Outcome was analyzed according to the number of surgical revisions and the revision indications.

Results: Most of the patients (61%) underwent only one revision (mean delay after implantation 44 months). The most frequent

causes of revisions were hardware dysfunction (32%), lead migration (23%), and infection (18%). Revision(s) repaired the SCS

issue in 87% of the cases. One year after the first revision, 82% of the patients reported pain relief ≥50%, and the mean NRS

decrease was 4.0 compared with baseline (p < 0.001). Benefit of SCS revision tended to decrease with the number of revisions but

did not differ across revision indications. No serious surgical complications related to the revision occurred, except for three

hematomas occurring after repeated revisions.

Conclusions: Our data suggest that surgical revision of SCS system is safe and led to significant pain relief in most of the cases,

provided that the initial indication was good and that the previous stimulation was effective. However, success of SCS revision

decreases with the number of revisions

Aurélie LEPLUS (NICE), Denys FONTAINE, Jimmy VOIRIN, Philippe RIGOARD, Emmanuel CUNY, Maxime BILLOT, Marie ONNO
10:20 - 10:25 #35668 - PF23 Trigeminal Neuralgia associated with pontine lesions in patients without multiple sclerosis: retrospective study of a new entity.
PF23 Trigeminal Neuralgia associated with pontine lesions in patients without multiple sclerosis: retrospective study of a new entity.

Trigeminal neuralgia (TN) is a debilitating condition characterized by severe facial pain. While TN treatments are generally effective, a minority of patients remains refractory to all interventions. In this population, unexplained pontine lesions in the vicinity of trigeminal system components can sometimes be observed. 



Our main objectives are to ; i) describe the demographics, risk factors and pain characteristics of patients with TN associated with pontine lesion, ii) localize those lesions in relation to the trigeminal system and iii) evaluate clinical outcomes of these patients following radiosurgery. 



We conducted a retrospective study of 1100 patients who underwent radiosurgery at our center as primary TN treatment between 2004 and 2022. Patients without multiple sclerosis (MS) who exhibited pontine lesions were matched 1:1:1 for sex, age and MRI quality with cases of classical or MS-TN. 

Baseline data was collected, including demographics, pain characteristics, MS status, risk factors, and MRI features. Treatment data, pain response and complications were reviewed. Lesion location was determined by nonlinearily coregistering the T1 MRI sequences of each patient in MNI space and computing the intersection of pontine lesions with trigeminal system components, as defined using a tractographic atlas of trigeminal structures. 



Preliminary results suggest that 9% of refered TN cases had a pontine lesion not attributable to MS.  Most lesions associated with TN were located along the brainstem trigeminal tract or dorsal trigemino-thalamic tract. Patients with brainstem lesions (with or without MS) had an inferior response to radiosurgery than classical TN patients. The complete analysis will be presented at the meeting. 



Pontine lesions along trigeminal structures, with or without MS, represent a risk factor for failure after radiosurgery. These lesions should specifically be sought when conseling patients with TN.

Sarra BLAGUI, Maud LABELLE, Raphaëlle FERREIRA, Kevin WHITTINGSTALL, Christian IORIO-MORIN (Sherbrooke, Canada, Canada)

"Friday 29 September"

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10:00 - 10:30

Flash Poster Session 3 - Screen 2

Moderator: Giorgio SPATOLA (Neurosurgeon) (Brescia, Italy)
10:10 - 10:15 #35828 - PF24 Trigeminal nerve length as vulnerability factor for the neurovascular conflict in trigeminal neuralgia.
PF24 Trigeminal nerve length as vulnerability factor for the neurovascular conflict in trigeminal neuralgia.

Objective: The main cause of trigeminal neuralgia is not fully understood, especially how a neurovascular conflict or distortion of the trigeminal nerve can lead to pain. Our aim was to determine whether the anatomical configuration of the trigeminal nerve and its adjacent structures can be a predisposing factor for the occurrence of clinically significant neurovascular conflict in trigeminal neuralgia.

Methods: We analyzed retrospectively 80 patients with idiopathic trigeminal neuralgia and 73 healthy participants with Constructive Interference in Steady State magnetic resonance imaging. The length of both trigeminal nerves from the nerve root entry zone until the entrance into the Meckel’s cave was measured, as well as the intertrigeminal distance and the prepontine distance. The length of the nerve in the painful side was correlated with the nonpainful side. Additionally, side of pain, distribution of pain, and intraoperative findings were recorded, including arterial compression, venous compression and arachnoid membranes distorting the nerve.

Results: Mean age at surgery was 56,9 years (20 to 84 years). The most common intraoperative finding was arterial compression (88,8%), followed by arachnoid adhesions distorting the nerve (73,8%), followed by a venous compression (50%). Most patients had two of these findings (60%), followed by three (26,3%) and then one single finding (13,8%). There was a statistically significant difference between the mean length of the trigeminal nerve on the pain side compared to the non-pain side (10,46 vs. 10,51). When comparing to the control group, the patients with trigeminal neuralgia had shorter trigeminal nerves (10,48 vs 11,11 mm), but no statistically significant difference when comparing the prepontine distance between two groups. Additionally, a shorter trigeminal nerve was correlated with a higher number of intraoperative findings, and especially venous compression and arachnoid adhesions.

Conclusions: Our data supports the hypothesis that a shorter trigeminal nerve is more susceptible for a clinically significant neurovascular conflict.

Filipe WOLFF FERNANDES (Hannover, Germany), Joachim Kurt KRAUSS
10:15 - 10:20 #35889 - PF25 Deep brain stimulation in the treatment of obsessive compulsive disorder: state of the art in the literature and in our center.
PF25 Deep brain stimulation in the treatment of obsessive compulsive disorder: state of the art in the literature and in our center.


Obsessive compulsive disorder (OCD) affects 2-3% of the population and is characterized by the presence of intrusive thoughts (obsessions) that lead to repetitive attitudes (compulsions) to alleviate the anxiety they produce. The main pathophysiological theory is the dysfunction of the cortico-striatal-pallidal-thalamo-cortical circuit. Between 10-25% of patients remain symptomatic despite pharmacological treatment and psychotherapy. Deep brain stimulation (DBS) has been described as an effective treatment, with different targets applied as the  anterior arm of the internal capsule, ventral striatum, nucleus accumbens, and subthalamic nucleus.



To review and understand the publications avaliable for DBS and OCD. To analyze our database of OCD patients implanted with deep brain stimulation system.


Material and methods

We reviewed the scientific literature available in PubMed and presented a series of patients with refractory OCD implanted in our center.



Deep brain stimulation was performed in 13 patients between the years 2006 and 2017. Most suffered from highly disabling obsessions and compulsions of cleaning, checking and repetition. Electrodes were placed through the anterior limb of the internal capsule to nucleus accumbens bilaterally. In 5 cases intraoperative neurophysiological recording was performed. We performed postoperative Mri in all the patients. There were no clinically significant complications, although one patient required repositioning of an electrode. Although the follow-up recorded was irregular, scales such as YBOCS, BDI and STAI were used for evaluation. Nine patients presented significant clinical improvement and are satisfied. We observed no correlation between the clinical pattern and the response to DBS.



Most patients obtained beneficial effect in terms of relief of their symptomatology, being the rate of complications low. Our results are comparable to the published literature. We believe that DBS is a safe treatment option for refractory OCD and should be considered as an option in selected patients.

Marta DEL ÁLAMO DE PEDRO (Madrid, Spain), Pérez MARÍA, García De La Cruz FCO JAVIER, Ibañez ANGELA, Saiz JERÓNIMO, Ignacio REGIDOR
10:20 - 10:25 #35989 - PF26 ERNA recordings in MSA patient suggests ERNA to be location specific, not disease specific.
PF26 ERNA recordings in MSA patient suggests ERNA to be location specific, not disease specific.

Evoked resonant neural activity (ERNA) in subthalamic deep brain stimulation (DBS) for Parkinson’s Disease (PD) is emerging as a promising biomarker for lead placement and postoperative programming. The signal can be described as a high frequency, large amplitude, underdamped oscillation. Studies show stimulating from contacts with larger ERNA amplitudes results in greater clinical effects. However, the ERNA’s origin and its specificity as a PD biomarker are currently still under investigation. We had the unique opportunity to stimulate and record in the STN of a multiple system atrophy (MSA) patient. MSA is a neurodegenerative disease, which can strongly resemble PD in the early stages. Therefore, MSA is regularly misdiagnosed as PD in early stages of the disease. However, as opposed to PD, MSA does not respond well to dopaminergic medications and DBS is considered ineffective. In this analysis, we want to better understand the ERNA’s origin by comparing local evoked potentials from patients implanted in different locations, suffering from different diseases that respond differently to DBS.

We recorded DBS-evoked potentials in three different patients: in the STN in a PD and a MSA patient and in the ventral intermediate nucleus of the thalamus (VIM) of an essential tremor (ET) patient. At time of implantation, the MSA patient was diagnosed with PD. In all patients, stimulation frequency was 10Hz, and the stimulation amplitude corresponded with the side effect threshold at 130Hz (PD: 2.4mA, MSA: 4.2mA, ET: 2.4mA). A differential recording was made from the levels surrounding the stimulating level.

The characteristic oscillating response was observed when stimulating in the STN, both in the PD and MSA patient. For the contact generating the largest response, peak-to-trough amplitudes were 205.2 µV and 62.0 µV and frequency was 309.7 Hz and 303.8Hz respectively. No such response was found in the VIM of the ET patient. This suggests ERNA is not a biomarker for PD in itself, but rather for the STN network. Furthermore, the presence of ERNA in MSA, a disorder not responding well to DBS, indicates that ERNA in itself does not cause the clinical effect.

Tine VAN BOGAERT (Leuven, Belgium), Jana PEETERS, Alexandra BOOGERS, Philippe DE VLOO, Bart NUTTIN, Myles MC LAUGHLIN

"Friday 29 September"

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10:00 - 10:30

Flash Poster Session 3 - Screen 3

Moderator: Kuan Hua KHO (Neurosurgeon) (Enschede, The Netherlands)
10:10 - 10:15 #34063 - PF27 Magnetic Resonance guided Focused Ultrasound (MRgFUS) thalamotomy in treatment of Essential Tremor.
PF27 Magnetic Resonance guided Focused Ultrasound (MRgFUS) thalamotomy in treatment of Essential Tremor.

Background:  Surgical stereotactic lesioning of thalamus and basal ganglia has been used for the treatment of different neurological disorders. In the last years Magnetic Resonance–guided Focused Ultrasound surgery (MRgFUS) has emerged as a noninvasive thermal ablation method, which uses high-intensity focused ultrasound (HI-FU) energy and MRI for anatomical imaging and real-time thermal mapping. It is possible to obtain a rigorous focal point within the planned target and across the intact skull for the treatment of movement disorders.

We carried out a study on use of thalamotomy with MRgFUS in the treatment of tremor. The study was done in collaboration between Unit of Functional Neurosurgery of the University of Catanzaro and IRCCS - Centro Studio Neurolesi '' Bonino Pulejo '' of Messina.

The purpose was to demonstrate efficacy of MRgFUS method in treatment of tremor and verify improvement in quality of life of treated patients.

Methods:  Study population includes 42 patients with unilateral Essential Tremor (TE) refractory to drug therapy, chosen on the basis of inclusion and exclusion criteria and undergoing MRgFUS VIM thalamotomy from March 2019 to December 2022.

Technology used involved InSightec MRgFUS ExAblate Neurosystem with simultaneous use of a 3-Tesla MRI. Outcome assessments were carried out 1 month, 3 months, 6 months, 12 months and 24 months after treatment and t-test was used for statistical analysis. Study included T1, T2, FLAIR, DWI, and T1-weighted MR images after mdc for verification of the lesion. Clinical assessments were performed with Tremor Research Group Essential Tremor Rating Assessment Scale (TETRAS) for assessing tremor and with ADL subsection of TETRAS scale for assessing daily-life disability.

Results:  Mean score on TETRAS scale went from 24.86± 5.27 preoperatively to 5.6 ± 3.2 postoperatively with reduction in tremor of 69.78% and this result remained almost the same in follow-up. TETRAS ADL score went from 32.33 ± 7.08 to 7.93 ± 3.60 postoperatively, with reduction of 75.46%. No adverse events were reported, both in short and medium term, except for mild transient ataxia which regressed completely within six hours of treatment.

Conclusion:  MRgFUS-thalamotomy for treatment of unilateral TE has been shown to be extremely effective, reliable and free of significant adverse events. It is a method with great development potential, but thorough evaluation of its long-term effects is necessary.



Angelo LAVANO (Catanzaro, Italy), Domenico LA TORRE, Giusy GUZZI, Attilio DELLA TORRE

Introduction:Parkinson’s disease (PD) remains a major cause of neurological disability affecting millions of patients around the world. While pharmacotherapy remains the primary treatment of PD symptoms, surgical therapies have showed a resurgence of successful treatment of patients with advanced PD and complications of drug therapy. With appropriate selection of patients, deep brain stimulation (DBS) is now considered one of the most important advances in PD therapy.

Material and methods: 

Since July 2004 to December 2023 eighty three cases (83) patients suffering from PD were operated in our department. . This study included 43 men and 40 women ranging between 44  complete form, 21trembling and18 rigid form; the age range from 37 to 70 years (mean age: 56 years and mean age onset: 40 years (lesionotomy of the GPi in 2 cases, of the VIM in 17cases, 2 cases of unilateral lesionotomy with DBS) and bilateral deep brain stimulation (DBS) in 63 patients. The coordinates X Y Z OF STN and GPI are calculated on work station after realizing a fusion between a stereotactic CT Scan and an MRI. Usually the  Stimulation of the GPI ,the STN and thalamotomy  were performed without anesthesia

Electrophysiological micro recordings and clinical per operative assessment were realized for the accuracy of the location of the electrode in the STN


satisfactory to excellent results were more precocious in surgery of PD than

In DS  where they were tardier .in PD the comparative study of pre and post-operative scores including the UPDRS III (motor score) has noted a significant reduction of 65% in the UPDRS OFF  and  63% in the UPDRS .Thermolesion of the VIM has demonstrated efficacy on tremor in 70% the major post operative complication observed was the stimulator infection in two cases .We deplored no mortality or morbidity.


 Parkinson disease surgery using both ablative and deep brain stimulation seems to be a reasonable option for medically intractable patients. The appropriate selection of patients provide a good outcome.


Lakhdar GUENANE (Algeria, Algeria), Miloud DJAAFER, Said KHIDER, Chemaissa SADEDINE
10:20 - 10:25 #35826 - PF29 Success of stereotactic ablative surgery for involuntary movements after treatment of germinoma in the pineal area.
PF29 Success of stereotactic ablative surgery for involuntary movements after treatment of germinoma in the pineal area.

We experienced two cases of involuntary movements associated with germinoma located pineal area. First case was of a 14-year-old male with shaking of the left hand since the age of 13 who was diagnosed with pineal tumor through comprehensive examination. Combined chemotherapy and radiation therapy were administered. As a result, the patient's course was good, except for gradual worsening of his left-hand tremors. Deep brain stimulation was ruled out from the treatment plan due to the need for regular MRI follow-up, and he was referred to our department for stereotactic thalamotomy. Right Vim thalamotomy was performed, which effectively improved the symptom without any complications. The second case was of a 29-year-old male diagnosed with pineal tumor at the age of 13 after reporting impairment of vision. Tumor removal via craniotomy was performed 1 year later; based on the diagnosis of germinoma through histopathology of the mass, adjuvant radiation therapy was administered. The patient was referred to our department after experiencing involuntary movements mainly in the neck, trunk, and both arms since the age of 23. Stereotactic ablation was performed in two stages in the following order: left pallidotomy followed by right pallidothalamic tractotomy; as a result, his involuntary movements were cured without any obvious complications. In all cases, tumor location at the region of the pineal gland complicated the target plan, especially that of the Vim nucleus, due to deficits or significant deformations at the posterior commissure. Patients with involuntary movement disorders exhibit a wide range of motor symptoms, and need to undergo frequent MRI scans for their primary disease. In such patients, stereotactic ablative surgery showed potential as a useful treatment approach for involuntary motor symptoms due to its capability to simultaneously target multiple loci in the brain.

Kilsoo KIM (NA, Japan), Shiro HORISAWA, Takakazu KAWAMATA, Takaomi TAIRA
10:25 - 10:30 #35952 - PF30 Management of severe habituation to PSA DBS in patient with essential tremor.
PF30 Management of severe habituation to PSA DBS in patient with essential tremor.

Background. According to the consensus statement of International Parkinson and Movement Disorder Society, essential tremor was defined as isolated bilateral upper limb action tremor with or without tremor in another body parts lasting at least 3 years and in the absence of other neurological signs. Deep brain stimulation (DBS) of ventrointermediate nucleus (VIM) has been approved for treatment of patients with refractory essential tremor since 1997. Despite the high efficacy of VIM stimulation, some papers indicate a loss of tremor control years or sometimes even months after programming. J. Peters and S. Tisch defined this so-called habituation phenomenon in their 2021 review paper as “a loss of benefit from electrode reprogramming over time in the setting of optimal electrode placement and programming not explained by disease progression of the tremor syndrome”. The management of this condition is still challenging, as reprogramming improvement is limited and temporary.

Posterior subthalamic area (PSA) is considered an alternative stimulation target for severe essential tremor. M. Barbe and coauthors (2018) demonstrated in randomized double-blind crossover trial that PSA DBS is no less efficient than VIM DBS for essential tremor. To date, the information regarding habituation after PSA DBS is scarce, so the goal of this demonstration is to present the patient with severe habituation after PSA stimulation and approaches to manage this condition.

Methods. Seven bilateral PSA DBS were performed in Meshalkin National Medical Research Centre since 2018. The tremor severity was assessed using Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (FTM) part A. Variables are presented as mean (±SD).

Results. The group mean preoperative FTM part A score was 14.5 (±2.7). Postoperative mean FTM part A score was 5.7 (±5.1) with 60.6% reduction in tremor severity after 19±13.7 months of follow-up. The sixty years old patient with disabling kinetic tremor was treated with PSA DBS. After MRI confirmation of proper lead location, the stimulation was programmed on the 7th postoperative day with evident tremor reduction. Despite the initial efficacy, tremor returned in 3 days, so several reprogramming options were attempted (amplitude and frequency increase, bipolar, interleaved and “on-demand” stimulation) with only temporary and partial tremor improvement. Importantly, severe “ricochet” phenomenon occurred after switching the stimulation off. The patient underwent a left-sided radiofrequency thalamotomy with persistent tremor control and significant functional improvement during one-year follow-up.

Conclusion.  Severe habituation phenomenon may occur after PSA DBS and could be effectively treated with radiofrequency thalamotomy if DBS reprogramming failed.

Roman KISELEV, Martin KILCHUKOV, Vladimir MURTAZIN (Novosibirsk, Russia), Evgeny LEVIN

"Friday 29 September"

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10:30 - 12:00


Moderators: Alexandre CAMPOS (Doctor) (São Paulo, Brazil), Patrick CHAUVEL (Professor of Neurology) (Pittsburgh, USA), Kai LEHTIMÄKI (Associate Professor in Neurosurgery) (Tampere, Finland)
10:30 - 10:50 #33989 - PL03 Statistical Anatomical mapping of DBS of the anterior Nucleus of the Thalamus for intractable epilepsies.
PL03 Statistical Anatomical mapping of DBS of the anterior Nucleus of the Thalamus for intractable epilepsies.

Background : The prospective trial SANTE have demonstrated the benefit of the stimulation of the anterior nucleus of the thalamus (ANT) in intractable epilepsies not remediable by resective surgery. The precise topography of the best target offering the optimum safety efficacy ratio is still a matter of debate.


Material and method : In 46 patients operated in the frame of the prospective multicentric trial « France » and followed at least 2 years with all the anatomical and clinical pre and postoperative data available. The topography of the stimulating contact, the volume of tissue activated (VTA), the recruited fiber tracts were cross matched with seizure reduction and side effects.

Results : Comparison between pre and postoperative seizure frequency is demonstrating at two years a mean seizure reduction rate of 35% with  17, 21 & 8 patients respectively responders, improved and not improved. The analyses of the position of the stimulating contact is showing that in the best responders its location is more posterior and inferior. The study of the VTA is demonstrating that the probability to be improved is correlating on the left with a larger coverage of MD (MedioDorsal nucleus) and on the right side with a larger coverage of AV (Ventral part of the ANT) and MD plus a lower coverage of IL (Internal medullary lamina).  The dynamic of the response in time depends on the category of response to the stimulation. The site for the best response and the probability of best response seems to be depending on the location of the epileptogenic zone.


Conclusion : The white fibers postero-inferior at the AV and specially the mammilo-thalamic tract is turning out to be the main optimum target of DBS for intractable epilepsies. The ANT per se may not be the main target.

Jean REGIS (MARSEILLE), Hamdi HUSSEIN, Milan MAJTANIK, Jurgen MAY, Claire HAEGELEN, Fabrice BARTOLOMEI, Sylvain RHEIMS, Emmanuel CUNY, Sophie COLNAT, Louis MAILLARD, Philippe KAHANE, Stéphane CLEMENCEAU, Romain CARRON, Bertrand DEVAUX, Marc GUENOT, Guillaume PENCHET, Denis FONTAINE, Nica ANCA, Lorella MINOTTI, Sandra DAVID-TCHOUDA
10:50 - 11:10 #33939 - PL04 Patterns of pulvinar-cortical coupling in posterior quadrant epilepsies evaluated by SEEG methodology.
PL04 Patterns of pulvinar-cortical coupling in posterior quadrant epilepsies evaluated by SEEG methodology.

By considering the role of the subcortical regions in the organization of the epileptiform activity, such as the thalamus, clinical outcomes can be improved through more accurate diagnosis and focused therapeutic intervention that aims to modulate the abnormal epileptic network. In the present study, we investigated stereoelectroencephalographic (SEEG) recordings in drug-resistant epilepsy patients to qualitatively and quantitatively analyze the ictal pulvinar activity as well as its synchronization with the different cortical areas, with special attention to the posterior quadrant cortical areas. 

Between March 2020 to March 2022, 18 patients with medically refractory partial epilepsy (MRE), who underwent SEEG exploration at the University of Pittsburgh, were prospectively selected for the study, among a series of 62 SEEG patients operated during the same period. The study has been approved by the University of Pittsburgh Institutional Review Board (protocol #20070113). During ictal recordings, Phase-locking value (PLV) was applied to quantify synchronization of oscillatory activity between the EZ and the Pulvinar nucleus of the thalamus (Lachaux 1999). To calculate the phase locking value, time series from the pulvinar and cortical regions were first spectrally decomposed to obtain an instantaneous phase estimate at each time point. 

In total, 40 ictal and peri-ictal events were analyzed. 22 ictal and peri-ictal events were localized in the occipital lobe, 8 events were localized in the parietal lobe, and 10 events were localized in the mesial temporal lobe. Simultaneously to the neocortical activity, the pulvinar contacts demonstrated baseline changes, with the appearance of infra-slow oscillation that progress to low amplitude and high frequency pattern. The ictal pulvinar activity progress towards lower frequencies and higher amplitude, until its abrupt cessation. Phase-locking value (PLV) calculated between the posterior pulvinar, and neocortical electrodes demonstrated high-frequency synchronization beginning on or before seizure termination.

Posterior quadrant epileptogenic zones showed strong ictal synchronization with the pulvinar nucleus. Further work on thalamocortical network function during focal seizures may lead to improvements in diagnosis as well as treatment of focal epilepsy.

11:10 - 11:30 #36204 - PL05 Machine learning analysis to predict outcome in temporal lobe epilepsy surgery.
PL05 Machine learning analysis to predict outcome in temporal lobe epilepsy surgery.

Temporal lobe epilepsy (TLE) is one of the most frequent epileptic syndromes, often leading to an anterior and mesial temporal lobe surgery to cure the patients. The percentage of patients outgoing Engel 1A/ ILAE 1 outcome after a TLE surgery vary in the literature from 56% to 71% according to the existence of a lesion or not, the histology, the length of postoperative outcome, etc (1,3).

The aim of our study was to identify predictive factors of good postoperative outcome by means of the analyze of the outcome of 73 patients undergoing TLE surgery in Lyon between January 2015 and December 2021, with machine learning (ML) and using 15 clinical, demographic and imaging features. Among the 73 patients, all had preoperative clinical, imaging, video-EEG assessments and 39 had stereo-electroencephalography to delineate the seizure onset zone. Long-term clinical and seizure outcome after at least 12 months were registered with the ILAE outcome scale. The median of the last follow-up was 36 (±16.9) months with an ILAE 1 outcome for 55 patients.

ML was performed on 15 input features using a Random Forest model and 10 fold cross-validation. Best model performances were obtained with a subset of 6 features for the prediction of a good postoperative outcome with an accuracy of 79,2% and a ROC of 0.72. The 6 features were: SEEG or not, resection of dominant or non-dominant hemisphere, side of the resection, number of preoperative anticonvulsive treatments, existence of febrile seizure in the childhood, and age at the epilepsy onset. Univariate analysis showed a significant relation between the preoperative average number of seizures per month (p=0.102, Wilcoxon’s test) and the preoperative number of anti-epileptic treatments (p=0.001, Fisher’s test) with the prediction of an ILAE 1 outcome. Multivariate analysis revealed that only preoperative number of anti-epileptic treatments was deemed as significant with an odd ratio of 0.33 (p=0.003).

When reviewing the recent literature, we observed an increase in the use of multimodal datasets and machine learning analysis for epilepsy surgery outcome (2). Eriksonn et al. (2) did not find necessary to assembly thousands of patients to obtain a better model of postoperative outcome prediction. In our study, we obtained 6 clinical features that helped the model to predict a good postoperative outcome. ML provides us a new interpretation of our data rather than true explicit instructions, but a better understanding of the proper features selection is needed. Our model also needs to be used in new patients to test its robustness.


  1. Barba C, et al. Temporal plus epilepsy is a major determinant of temporal lobe surgery failures. Brain 2016;139(Pt 2):444-51. doi: 10.1093/brain/awv372.

2. Eriksson MH, et al. Predicting seizure outcome after epilepsy surgery: do we need more complex models, large samples, or better data? Epilepsia 2023, doi.10.1111/epi.17637

3. Guo J, et al. Seizure outcome after surgery for refractory epilepsy diagnosed by 18F-fluorordeoxyglucose positron emission tomography (18F-FDG PET/MRI): a systematic review and meta-analysis. World Neurosurg 2023;173:34-43. doi: 10.1016/j.wneu.2023.01.114

Claire HAEGELEN (Lyon), Pauline MOUCHES, Noemie TIMESTIT, Maxime BONJOUR, Julien JUNG, Helène CATENOIX, Alexandra MONTAVONT, Sebastien BOULOGNE, Jean ISNARD, Sylvain RHEIMS, Marc GUENOT
11:30 - 12:00 The network of emotions investigated by SEEG. Patrick CHAUVEL (Professor of Neurology) (Pittsburgh, USA)

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12:30 - 13:30

Sustainably driving DBS innovation

Moderators: Carine KARACHI (MEDECIN) (PARIS, France), Rick SCHUURMAN (neurosurgeon) (Amsterdam, The Netherlands)
12:30 - 13:30 Future landscapes of DBS. Nick MALING
12:30 - 13:30 Integrating Clinical and Research systems. Stephan CHABARDÈS (head of the department) (GRENOBLE, France)
12:30 - 13:30 Optimising high volume surgery. Ludvic ZRINZO (Professor of Neurosurgery) (London, UK, United Kingdom)

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Transforming DBS Therapy in the OR & beyond

Moderator: Alfonso FASANO (Toronto, Canada)
12:30 - 13:30 Optimising DBS Implant Procedure. Rebecca CONDE FASANO (Spain)
12:30 - 13:30 Personalising DBS with BrainSense tm Technology. Alexandre EUSEBIO (Professor) (Marseille, France)

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13:30 - 15:30

Movement Disorder 4

Moderators: Anders FYTAGORIDIS ( (Stockholm, Sweden), Nagako MURASE (Vice President) (Nara City, Japan, Japan), Atilla YILMAZ (Nerosurgeon) (Istanbul, Turkey)
13:30 - 13:35 #36026 - OP091 Better clinical effects of adaptive DBS with the low beta or below the beta range of frequency of interest for Parkinson’s disease.
OP091 Better clinical effects of adaptive DBS with the low beta or below the beta range of frequency of interest for Parkinson’s disease.


To compare the clinical effects of adaptive DBS (aDBS) between the different beta subband of the frequency of interest (FOI).



aDBS is the closed loop system where the stimulation amplitude goes up and down according to the power of local filed potentials (LFPs) obtained from the DBS leads. LFPs are transformed with FFT analysis to the frequency bin in every ten minutes and the power is calculated based on the preset frequency of interest (FOI) with approximately 5 Hz wide. Because the beta power is generally accepted to correlate with rigidity and bradykinesia, it is used as a biomarker in the concept of aDBS. The more correlation was seen in the subband of the low beta range (13-20 Hz) (Neumann WJ et al., Mov Disord 2016). Therefore it is important to evaluate the clinical effect of aDBS with the lower subband of FOI.



Six DBS naïve female patients (mean age 69.2 ± 8.2 (SD) years old, disease duration 12.3 ± 4.9 years) were enrolled at least one month after aDBS (PerceptTM PC Neurostimulator with BrainSenseTM Technology, Medtronic) started. The FOI was usually set to the peak frequency of LFPs during stimulation off (BrainSenseTM Survey). We observed for 31.5 (7-69) days with this condition, where the mean FOI was 19 (15-25) Hz in ten leads. Then we decreased the FOI according to the BrainSenseTM Events analysis which shows the LFP peak frequency while the patients feel troublesome symptoms like tremor or falling, The mean FOI was 12 (8-17) Hz in twelve leads and the observation duration was 26.8 (10-49) days. Clinical effect was assessed using MDS-UPDRS.



By setting the FOI from the higher band (mean 19Hz) to the lower band (mean 12 Hz), MDS-UPDRS scores changed from 6.3 (4.2) to 4.5 (2.2) in Part 1, 8.8 (4.2) to 5.8 (3.8) in Part 2, 20.8 (15.3) to 15.8 (13.9) in Part3, and 5.8 (2.8) to 1.3 (1.5) in Part 4. Only the change was significant in Part 4 (Wilcoxon rank-sum test p=0.03).



Motor fluctuation has significantly decreased by changing the FOI to the lower band around 12 Hz. The peak frequency changes depending on movement, antiparkinsonisan drugs and DBS stimulation (Thenaisie Y, et al. J Neural Eng. 2021) and these factors may relate with our results.



Around 12 (8-17) Hz of FOI in aDBS was more effective to improve the motor fluctuations in PD.

Nagako MURASE (Nara City, Japan, Japan), Ryuji YAMAKAWA, Takaki HIROSE, Hisashi SAKITA, Tatsuo SHIMOKAWARA, Kiyoshi NAGATA, Hidehiro HIRABAYASHI
13:35 - 13:40 #36096 - OP092 Increased subthalamic nucleus delta oscillations during freezing in patients with Parkinson’s disease.
OP092 Increased subthalamic nucleus delta oscillations during freezing in patients with Parkinson’s disease.

Freezing of gait, also known as "freezing," is characterized by a sudden and temporary inability to initiate or continue walking. It is a common symptom experienced by individuals with Parkinson's disease (PD), particularly during the later stages of the condition. Freezing episodes typically involve a temporary sensation of being "stuck" to the ground or an inability to move certain body parts, such as the feet or legs. The exact mechanisms underlying the freezing of gait in PD are not fully understood and it is believed to involve complex interactions between abnormal brain activity, disrupted communication within motor circuits, and impaired dopamine regulation.

Here we report an increase in delta oscillations during freeze in patient with PD that underwent deep brain stimulation implantation. The patient is a 68-year-old male who has been receiving treatment for PD since 2010. Over the past two years, there has been a worsening of the disease characterized by frequent freezing of gait episodes accompanied by sudden general slowness and stiffness. In mid-February 2023, he underwent bilateral deep brain stimulation (DBS) surgery targeting the subthalamic nucleus (STN) with stimulation protocol 1.4 mA, 60 µs, 130 Hz. One and a half months after the operation, bilateral measurement of power spectral density (PSD) of local field potentials (LFP) through the implanted electrode was initiated. In a single day, the patient experienced three episodes of freezing, which showed a statistically significant increase in delta oscillation PSD in both hemispheres compared to phases when he reported being symptom-free.

These results highlight the potential involvement of abnormal brain activity and disrupted communication within motor circuits. This suggests that delta oscillations may play a role in the pathophysiology of freezing of gait. Further research is needed to better understand the underlying mechanisms and to explore the potential of delta oscillations as a biomarker or therapeutic target for freezing of gait in PD.

Fadi ALMAHARIQ (Zagreb, Croatia), Andrea BLAZEVIC, Nikola HABEK
13:45 - 13:50 #35641 - OP094 Decreased hemispheric volume may be associated with occurrence of peri-lead edema in Parkinson disease patients with Deep Brain Stimulation.
OP094 Decreased hemispheric volume may be associated with occurrence of peri-lead edema in Parkinson disease patients with Deep Brain Stimulation.

Background: Postoperative peri-lead edema (PLE) is a poorly understood complication of deep brain stimulation (DBS), which has been described sporadically in patients presenting with profound and often delayed symptoms. The aim of the study was to investigate whether decreased brain hemispheric volume is associated with occurrence of PLE in Parkinson Disease (PD) patients after DBS implantation in subthalamic nuclei (STN).

Methods: This retrospective study included 130 PD patients underwent STN DBS at the Department of Neurosurgery, Dubrava University Hospital in period 2008-2023 year. Magnetic resonance imaging (MRI) sequences were used, preoperative high resolution T1 MPRAGE for volumetric analysis using Freesurfer software, and postoperative T2 images to determine occurrence of PLE, inspected independently by two researchers.

Results: PLE was detected either unilaterally or bilaterally. Mild to moderate association was established between decreased volume of brain hemisphere and occurrence of PLE. In addition, tissue/cerebrospinal fluid ratio presented mild association with occurrence of PLE. Interestingly, in these patients cardiovascular comorbidities were reported previously.

Conclusion: Peri-electrode edema is a common, transient reaction to DBS lead placement, and patients can present with severe symptoms or can be asymptomatic and go undiagnosed. Since no clear risk factors have been identified, further studies are needed.

Marina RAGUŽ (Zagreb, Croatia), Petar MARCINKOVIC, Marin LAKIC, Hana CHUDY, Darko ORESKOVIC, Andelo KASTELANCIC, Vladimira VULETIC, Darko CHUDY
13:50 - 14:00 #35661 - OP095 High burden of perivascular spaces as a potential risk marker for intracerebral hemorrhage in DBS surgery – a retrospective investigation.
OP095 High burden of perivascular spaces as a potential risk marker for intracerebral hemorrhage in DBS surgery – a retrospective investigation.

Objective: Cerebral intraparenchymal hemorrhage due to electrode implantation (CIPHEI) has been associated with higher age, use of microelectrode recording and directional DBS electrodes (Sajonz et al. In preparation). Perivascular spaces (PVS) have been associated with spontaneous intracerebral hemorrhage (Duperron et al. 2019) and vascular events (Gutierrez et al. 2017) and may signal a general vascular vulnerability. We thus investigated the role of PVS as a risk indicator for CIPHEI.

Methods: Retrospective analyses of suitable (3 Tesla, no artifacts) MRI prior to DBS implantation (01/2013-12/2021) comprised PVS burden quantification by the commonly used Frangi-filter for tubular structures (smin=0.4mm, smax=2.0mm, scale ratio=2, α=0.1, β=1, c=0.01) on the normalized T2w isotropic data (Frangi et al. 1998) (Fig. 1). A PVS index was computed by a simple summation of all non-negative filter responses within supratentorial white matter separately for both hemispheres. Postoperative CT scans were assessed for hemorrhages. Data analysis was based on the generalized linear model for binomial responses (BR-GLM) using the bias reduction approach developed by Firth (1993) to account for sparse sampling of CIPHEI. Adjustments of PVS for non-linear effects of age and other potential confounds were performed using a generalized additive model.

Results: 305 suitable cases were included with 17 CIPHEIs observed in 13 procedures (Fig. 2). The corresponding odds ratio for CIPHEI is 2.89 [95% confidence interval 1.09-9.66, p = .041] for adjusted PVS above average. The odds ratio for adjusted PVS below average as baseline reference is 0.02 [0.01-0.04, p < .001]. Extending the BR-GLM model of above-average PVS by the multiplicative term of above-mentioned risk factors the odds ratio is 23.59 [8.69-81.59, p < .001].

Discussion: Our findings indicate that high burden of PVS may represent a further risk factor for CIPHEI. The risk factor combination, namely higher age, use of microelectrode recording and directional DBS electrodes, with a high burden of PVS should be carefully evaluated considering the risk for CIPHEI.

Timo Sebastian BRUGGER, Christoph KALLER, Marco REISERT, Alexander RAU, Nils SCHRÖTER, Karl EGGER, Horst URBACH, Volker Arnd COENEN, Bastian Elmar Alexander SAJONZ (Freiburg, Germany)
14:00 - 14:10 #35771 - OP096 A two-hit model to explain new-onset dystonia after deep brain stimulation in Parkinson’s disease.
OP096 A two-hit model to explain new-onset dystonia after deep brain stimulation in Parkinson’s disease.

Introduction: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an established treatment for advanced Parkinson’s disease (PD). However, the stimulation may induce motor side effects in both acute and chronic settings. Out of 60 PD patients who underwent STN-DBS at our institution, we observed 16 patients displaying de-novo dystonic symptoms after the implantation and 11 patients with pre-existing dystonia who did not obtain significant benefit from stimulation. We hypothesized that a common neural pathway may be responsible for both de novo dystonic symptoms appearance and unresponsiveness of pre-existing dystonic symptoms to stimulation.

Objective: This study aims to investigate the possible clinical and connectivity substrates underlying the emergence of dystonia after STN-DBS. 

Methods: We divided our PD patients’ cohort into four groups: 16 patients who developed dystonic symptoms after STN-DBS, 11 patients with previously known dystonia who did not improve after surgery, 14 patients whose dystonic symptoms were relieved by the stimulation and 19 control who never experienced dystonia. Patient’s clinical data were collected from the database of our institution and the distance of the active contact center from the STN border was calculated with Lead-DBS software. These variables were compared among the four groups with MANOVA.  Finally, we reconstructed the heat maps of the stimulation focusing on the “sour” spot for dystonic symptoms as well as their associated structural and functional connectivity using a Parkinsonian normative connectome.

Results: Compared to controls and patients with improved dystonia, both patients with novel onset dystonia and those without dystonia improvement had a statistically significant longer duration of Parkinson’s disease before surgery (p=0.001) and a greater active contact-STN distance (p<0.001). Moreover, the heat maps were similar in neo-dystonic and non-improved dystonic patients and extended laterally towards striato-pallido-fugal fibers and cranially towards the fasciculus lenticularis in Forel’s H field. Structural and functional connectivity profiles were associated with subcortical structures correlated with dystonia pathophysiology (cerebellum and midbrain) and cortical areas which are known to show altered synaptic plasticity in dystonic patients (parietal, inferior frontal and temporal cortices). 

Conclusion: Based on our results, we formulated a two-hit model for dystonia onset after STN-DBS: a clinical feature of Parkinsonian patients, particularly longstanding Parkinson’s disease, causes predisposing altered plasticity, which contributes to dystonic symptoms development when coupled with the stimulation of dystonia-related subcortical and cortical structures.

Luigi Gianmaria REMORE (Milan, Italy), Delia GAGLIARDI, Valeria LO FASO, Linda BORELLINI, Filippo COGIAMANIAN, Gloria VALCAMONICA, Elena PIROLA, Luigi SCHISANO, Antonella AMPOLLINI, Giulio BERTANI, Antonio D’AMMANDO, Giorgio FIORE, Leonardo TARICIOTTI, Marco LOCATELLI
14:10 - 14:15 #36195 - OP097 Intra-operative Motor Testing during Asleep DBS Correlates With Postoperative Motor Side Effect Thresholds.
OP097 Intra-operative Motor Testing during Asleep DBS Correlates With Postoperative Motor Side Effect Thresholds.


Asleep DBS is a viable alternative to traditional Awake DBS for the treatment of movement disorders. Proposed benefits of Asleep DBS have been cited as increased patient comfort and possible reduced risk of hemorrhage and infection. However, one of the criticisms of this technique is the inability to test intraoperative motor side effect thresholds, theoretically leading to a higher rate of suboptimal lead placement as compared to traditional intraoperative awake MER recording.



The purpose of this study is to evaluate the concordance of Asleep intraoperative motor side effect threshold testing with postoperative awake motor threshold testing.  



 28 patients underwent bilateral Asleep DBS targeting either the STN or the GPi. Intraoperative anesthetics used included ½ MAC of sevoflurane and a remifentanil infusion without paralytics. Stimulation was increased sequentially in each ring contact on the DBS lead, while observation for motor side effects was completed by the attending and fellow neurosurgeon. Each patient was tested using a pulse width of either 120μs, 90μs, or 60μs. Testing was repeated with the patient awake and recovered from anesthesia. Side effects were grouped according to relevant white matter tracts (CST/CBT, CN3). The stimulation at which each side effect occurred at each time was compared using univariate linear regression models and paired sample t-tests. Bulbar side effects of the mouth and tongue were grouped and compared to postoperative dysarthria. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the presence and absence of each side effect group intraoperatively and postoperatively.



The mean age was 64.2 years, with 18(67%) males and 9(33%) females. The STN was targeted in 17(63%) and GPi in 10(37%) patients. Motor side effects in STN patients at 60μs were significantly lower intraoperatively compared to postoperatively(Δ = -0.59, p = 0.4). The linear regression of intraoperative bulbar side effects on postoperative dysarthria in GPi patients at 60μs was statistically significant (β=1.3, R2=.89, F(1,2)=25, p=0.04).



Our results imply that intraoperative motor threshold testing may be a reliable and simple method for prediction of postoperative motor thresholds, specifically regarding the presence of postoperative dysarthria and thus may be a useful tool to reduce rate of revision in Asleep DBS surgery.

John PEARCE (Chicago, USA), Patrick KING, Sepehr SANI
14:15 - 14:20 #36107 - OP098 The use of directional Leads for Deep Brain Stimulation: benefits, technical notes, and our experience.
OP098 The use of directional Leads for Deep Brain Stimulation: benefits, technical notes, and our experience.

Deep brain stimulation (DBS) has become the treatment of choice for advanced stages of Parkinson's disease, medically intractable essential tremor, and complicated segmental and generalized dystonia.

In addition to accurate electrode placement in the target area, effective programming of DBS devices is considered the most important factor for the individual outcome after DBS. Programming of the implanted pulse generator (IPG) is the only modifiable factor once DBS leads have been implanted and it becomes even more relevant in cases in which the electrodes are located at the border of the intended target structure and when side effects become challenging.

We analyzed 10 patients who underwent a DBS procedure with directional leads and an implantable pulse generator (IPG) capable of multiple independent current control and 10 patients who received non-directional leads with a similar IPG. While trajectory planning and most steps of the surgical procedure were identical to conventional DBS lead implantation, differences in indication, electrode handling, lead control, parameters of the stimulation, and complications were documented and analyzed in comparison to a control group with ring electrodes.

We concluded that the use of directional leads decreased the side effects of the stimulation, decreased the need for repositioning of the electrode, and increased the effectiveness of the stimulation.

Fadi ALMAHARIQ (Zagreb, Croatia), Andrea BLAZEVIC, Marina RAGUZ, Domagoj DLAKA, Darko CHUDY
14:20 - 14:25 #35858 - OP099 Thalamic deep brain stimulation in patients with dystonic head tremor: an observational study.
OP099 Thalamic deep brain stimulation in patients with dystonic head tremor: an observational study.

Objective: Dystonic head tremor (DHT) is a particular manifestation of cervical dystonia which poses several challenges for treatment. Deep brain stimulation (DBS) has evolved as a well established therapy for cervical dystonia for patients, who do not respond sufficiently to pharmacotherapy or botulinum toxin injections. However, for treatment of the tremor component in dystonic head tremor pallidal DBS has shown moderate results. In patients with other forms of tremor, like essential tremor and tremor in Parkinson’s Disease stimulaton of the thalamic ventral intermediate nucleus (Vim) has been applied very successfully. Therefore Vim-DBS was also tried in DHT treatment, but only limited to very few cases. We here report a larger case series with long-term follow-up of chronic bilateral Vim DBS in patients with DHT.

Methods: Data of a consecutive series of 21 patients with DHT, who underwent stereotactic CT-guided bilateral implantation of DBS electrodes into the Vim was analyzed retrospectively. Pre- and postoperative dystonia was assessed using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and head tremor with the modified Fahn-Tolosa-Marin Tremor Rating Scale (mFTMTRS), which included tremor amplitude and duration of the head tremor.

Results: Patients significantly benefitted from Vim DBS, which is reflected in the pre- vs. postoperative BFMDRS motor score, which decreased from 16.72 to 9.82 points (p > 0.05) as well as the BFMDRS disability score, which decreased from 4.6 preoperatively to 3.2 points (p > 0.05) after implant of DBS. Tremor improved as well in all patients, with a mean mFTMTRS of 7.95 preoperatively and 2.35 points (p > 0.05) postoperatively. Improvement was sustained after 24 months of chronic DBS.

Conclusion: Vim DBS shows a significant decrease in tremor as well as dystonic symptoms. Long-term follow-up confirms that it is an efficient treatment for DHT. Our results indicate that Vim DBS in DHT might be superior to GPi DBS.

Johanna NAGEL (Hannover, Germany), Assel SARYYEVA, Christian BLAHAK, Marc E. WOLF, Joachim RUNGE, Christoph SCHRADER, Joachim K. KRAUSS
14:25 - 14:30 #35636 - OP100 Microstructural integrity and improvement after subthalamic nucleus deep brain stimulation in patients with Parkinson’s disease.
OP100 Microstructural integrity and improvement after subthalamic nucleus deep brain stimulation in patients with Parkinson’s disease.

Objective. To investigate the effect of substantia nigra (SN) and subthalamic nucleus (STN) microstructural integrity on response to deep brain stimulation (DBS) of the STN using diffusion microstructure imaging (DMI). We hypothesized that an increase in free interstitial fluid  (V-CSF) resulting from the loss of cell bodies and axons in SN and STN is associated with poorer motor response to DBS.

Methods. Patients with Parkinson’s disease who received STN DBS and preoperative 3T MRI were enrolled from our DBS registry. Motor impairment and DBS-associated motor improvement was assessed by MDS-UPDRS III a) preoperative in Med OFF and b) 12 month postoperative in Med OFF Stim ON. DBS-response was calculated as improvement in MDS-UPDRS III-score in percent.

The microstructural free fluid compartment (V-CSF) values from the SN and STN contralateral to the clinically more affected side were analyzed in a ROI-based approach. Partial correlation analyses were used to investigate the association between individual V-CSF-values and and DBS-response, controlling for age and sex.

Results. Inclusion criteria were met by 24 patients (6 females) aged 62 ± 7 years (mean ± SD). We found significant associations between poorer DBS-response and increased free fluid (i.e. decreased structural integrity) in the SN (r = -0.435, p = 0.043) as well as STN (r = -0.425, p = 0.048) (Figure 1&2). 

Conclusion. V-CSF values as a surrogate for structural integrity of the SN and STN correlate with treatment response to STN-DBS and might therefore serve as a biomarker for motor staging and indication of DBS-surgery. Further examination of this finding in a bigger sample is needed to assess the differential contribution of STN and SN structural integrity, respectively.

Marco HERMANN (Freiburg, Germany), Nils SCHRÖTER, Alexander RAU, Marco REISERT, Michel RIJNTJES, Wolfgang H. JOST, Horst URBACH, Cornelius WEILLER, Volker A. COENEN, Bastian E. A. SAJONZ
14:30 - 14:40 #36006 - OP101 Microstructural correlates of subthalamic nucleus deep brain stimulation response.
OP101 Microstructural correlates of subthalamic nucleus deep brain stimulation response.

Objectives: Clinical outcomes of subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) can vary between patients due to multiple factors. Quantitative MRI (qMRI) and probabilistic tractography were used to investigate whether outcome variability is related to targeting methods, changes in brain microstructure within the stimulated region, changes in STN-associated white matter pathways causing altered connectivity, or global brain changes reflecting different disease phenotypes.

Method: Nineteen patients selected for STN-DBS underwent multimodal MRI pre-operatively. Percentage improvement in the Unified Parkinsons Disease Rating Score part III (UPDRS III) and lateralised scores for bradykinesia, rigidity and tremor were the outcome measures. Voxel-wise probabilistic tractography was performed from the sum of all volume tissue activated regions (VTAs) for each patient. Individual VTAs associated with optimal stimulation parametes were used to define optimal tracts for each patient. Group-average optimal tracts for left and right side were generated and compared against voxel-wise tracts from the summed VTA regions of interest (ROIs) to generate heatmaps. The distance between the centre of the heatmap and individual VTAs was calculated, correlation with the top 10% heatmap voxels was obtained, along with the degree of overlap between each VTA and peak voxels. Quantitative MRI (qMRI) was used in voxel-based quantification and morphometry (VBQ/VBM) multiple regression, correlating microstructural changes to STN-DBS outcomes.

Results: Average improvement in UPDRS-III was 46% (± 17.4%). Magnetization transfer (MT) and R1 maps multivariate mixture of Gaussians VBQ demonstrated changes in grey and white matter density in the visual area that correlate with STN-DBS response, in that the lower tissue density was inversely proportional to the degree of improvement in UPDRS-III. Left and right heatmap value mean, maximum and centroid Euclidean distance from individual VTA did not correlate with total or lateralized UPDRS-III improvement. 95% of individual-level VTAs overlapped with peak heatmap voxels, indicating good coverage of the optimal sweet spot.

Conclusion: The factors underpinning variability following STN-DBS are complex and may relate to disease phenotype. There may be sub-types of PD benefiting from earlier surgical intervention. The lack of effect at the local level may relate to the fact that almost all the VTAs overlapped with the calculated sweet spot. This approach could be applied to the use of directional leads, with the heatmaps generated providing an approach that could be used to help inform more complex DBS programming.

Francisca FERREIRA (London, United Kingdom), Harith AKRAM, John ASHBURNER, Hui ZHANG, Christian LAMBERT
14:40 - 14:50 #36216 - OP102 DBS for tremor in multiple sclerosis, patient selection and clinical outcomes.
OP102 DBS for tremor in multiple sclerosis, patient selection and clinical outcomes.

Multiple sclerosis (MS) is the commonest demyelinating disease in the United Kingdom, affecting 130,000 people. Tremor is typically a late symptom of MS, affecting 25-58% of patients with moderate and severe MS, with medical management having limited benefit in published trials. Deep brain stimulation was first used in 1980 to treat MS tremor, however studies investigating the efficacy have small patient numbers. We present our experience with both patient selection and outcomes following DBS in the largest patient series published to date.

All patients with functionally disabling MS tremor who were considered for DBS at our institution were analysed. A total of 45 patients were assessed, with 26 undergoing DBS. Reasons for non-surgical management included patient choice, MS plaque affecting surgical planning, significant brain atrophy reducing accuracy of DBS implantation and the patient’s anaesthetic risk. All surgical patients had a pre-operative Fahn‐Tolosa‐Marin Clinical Rating Scale for tremor (CRS) completed, which was repeated at 6 months and 1 year post operatively. Any early or late complications associated with surgery were collected. DBS was performed asleep with robotic assistance to the zona incerta. 

The total mean improvement in CRS was 40% which was maintained at 1 year. All patients implanted had at least a 20% improvement in their total mean CRS, with the highest being 65%. There was 1 surgical complication requiring removal of the DBS system due to infection. 5 patients had stimulation related side effects, which resolved with reprogramming. 

DBS for MS tremor is an effective and safe treatment. However, the nature of the patient population requires careful selection of those who are suitable and will benefit most from DBS. 

Owain DAVIES (Bristol, United Kingdom), Ana PARDILHO, Konrad SZEWCZYK-KROLIKOWSK, Ali BIENEMAN, Mihaela BOCA, Reiko ASHIDA, Alan WHONE, Steven GILL
14:50 - 14:55 #36049 - OP103 Subthalamic mapping through volume of tissue activated for identifying optimal area of activation in deep brain stimulation for Parkinson’s disease.
OP103 Subthalamic mapping through volume of tissue activated for identifying optimal area of activation in deep brain stimulation for Parkinson’s disease.

Background Deep brain stimulation (DBS) is an effective treatment for Parkinson’s disease (PD). However, individual improvement after deep brain stimulation remains variable. Through analyzing variations in subthalamic anatomy, electrode contact location and stimulation settings; (sub)optimal areas of stimulation can be identified. By subsequently using volume of tissue activated (VTA), the subthalamic nucleus (STN) can be mapped; identifying an optimal patient specific activation site.

Materials and methods 300 patients, representing 600 STNs, were categorized based on percentual hemi-body improvement on the MDS-UPDRS motor examination: (1) non-responding (<30% improvement), (2) responding (30 – 70% improvement) and (3) optimally responding (>70% improvement). STNs were segmented and corticospinal tracts depicted using Brainlab software. The individual VTA’s were visualized using GuideXT and imported in the clinical cloud-based network Quentry for enabling group level analyses in normalized space. For each of the groups of responders, the VTA’s were superimposed into a subthalamic heatmap, showing the area of activation per group. Outcome scores were readily available from our advanced electronic DBS database.

Results The optimal responders group showed the smallest heatmap, with the smallest cubic volume (1,20 cm3). The two other groups showed more heterogeneous heatmaps with larger cubic volumes, 1,66 cm3 for the responders and 2,61 cm3 for the non-responders group, respectively. The heatmap of the optimal responders fell within the volume of the other two groups (Figure 1). Subthalamic mapping analyses are currently being extended.

Conclusion Optimal DBS responders show a smaller area of activation compared to responders and non-responders. Subthalamic mapping through visualization of patient-specific subthalamic anatomy and volume of tissue activated  is a promising technique to improve DBS outcome and optimize DBS programming strategies, and holds promise to reduce the occurrence of DBS-related side-effects.

Yarit WIGGERTS (Amsterdam, The Netherlands), Maarten BOT, Pepijn VAN DEN MUNCKHOF, Rob DE BIE, Rick SCHUURMAN, Martijn BEUDEL
14:55 - 15:00 #35627 - OP104 Choice of implantable pulse generators for deep brain stimulation – results from a global survey.
OP104 Choice of implantable pulse generators for deep brain stimulation – results from a global survey.


The success of deep brain stimulation (DBS) treatment depends on several factors, including proper patient selection, accurate electrode placement, and adequate stimulation settings. Another factor that may impact long-term satisfaction and therapy outcomes is the type of implantable pulse generator (IPG) used:  rechargeable or non-rechargeable. However, there are currently no guidelines on the choice of IPG type. The present study investigates the current practices, opinions, and factors DBS clinicians consider when choosing an IPG for their patients.



Between December 2021 and June 2022, we sent a structured questionnaire with 42 questions to DBS experts of two international, functional neurosurgery societies. The questionnaire included a rating scale where participants could rate the factors influencing their choice of IPG type and their satisfaction with certain IPG aspects. Additionally, we presented four clinical case scenarios and asked participants if they would recommend a rechargeable IPG in each case.



Eighty-seven participants from 30 different countries completed the questionnaire. The three most relevant factors for IPG choice were “existing social support”, “cognitive status”, and “patient age”. Most participants believed that patients valued avoiding repetitive replacement surgeries more than the burden of regularly recharging the IPG. Participants reported that they implanted the same amount of rechargeable as non-rechargeable IPGs, and 20% converted non-rechargeable to rechargeable IPGs. Half the participants estimated that rechargeable is the most cost-effective option.



This present study shows that the decision-making of the choice of IPG is very individualized. We identified the key factors influencing the physician's choice of IPG. Compared to patient-centric studies, clinicians may value different aspects. Therefore, clinicians should rely not only on their opinion but also counsel patients on different types of IPGs and consider the patient's preferences. Uniform global guidelines on IPG choice may not represent regional or national differences in the healthcare systems.

Yara WILLEMS, Niels VAN DER GAAG, Kuan KHO, Østein TVEITEN, Marie KRÜGER, Martin JAKOBS (Heidelberg, Germany)
15:00 - 15:05 #35739 - OP105 Intermittent ultralow-frequency low-amplitude deep cerebellar stimulation for movement disorders.
OP105 Intermittent ultralow-frequency low-amplitude deep cerebellar stimulation for movement disorders.

Recent research has indicated the cerebellum as a new therapeutic target for deep brain stimulation (DBS) in movement disorders. However, the optimal stimulation settings have not been established. In this study, two patients experienced significant improvements of tremor and dystonia by low-amplitude (0.2-1.5mA) deep cerebellar stimulation at 2 Hz, which significantly differs from conventional DBS settings. Furthermore, when administered in a cycle mode (3 min On and 3 min Off), it resulted in sustained effects. Thus, intermittent low-frequency and low-amplitude stimulation may be effective as a stimulation setting in the cerebellum.

Shiro HORISAWA (Shinjyuku, Japan), Takaomi TAIRA
15:05 - 15:10 #35808 - OP106 Comparing gait cycle impairments in patients with Parkinson’s disease and normal pressure hydrocephalus by wearable sensors and machine learning.
OP106 Comparing gait cycle impairments in patients with Parkinson’s disease and normal pressure hydrocephalus by wearable sensors and machine learning.

Gait impairments in patients with Parkinson’s disease (PD) and normal pressure hydrocephalus (NPH) are visually assessed by experts for diagnoses and to decide on pharmaceutical and surgical interventions. Despite standardized tests and clinicians’ expertise, such approaches are subjective. Wearable sensors and machine learning (ML) offer complementary approaches providing more objective, quantitative assessments of gait impairments. We focus on distinguishing PD from NPH and on assessing gait impairment before and after surgical intervention. A cohort of 12 PD and 12 NPH patients was assembled and patients performed standardized walking tests. Measurements were performed employing wearable sensors comprising a three-axes gyroscope, a three-axes accelerometer and eight pressure sensors embedded in each patient’s shoe. Sensors were produced by IEE company, which co-funds this research together with the primary funder, the Luxembourg National Research Fund. Gait cycle parameters such as swing and stance phases were computed from the generated data, by implementing and adapting existing algorithms. Gait cycle parameters within and between PD and NPH patients were compared, assessing significant differences. A subgroup of patients was selected for comparison of gait cycle impairments in untreated patients. ML algorithms, in particular linear Support Vector Machines, where employed to identify major changes in gait cycle parameters between the two groups. To obtain robust results with a limited number of patients, nested cross-validation was employed, with a leave-pair-out scheme in the outer loop, and a leave-one-out scheme in the inner loop. The performance of the approach to distinguish walks from PD patients from walks from NPH patients resulted in a final classification accuracy of 0.86 +- 0.25 and final area under the ROC curve of 0.94 +- 0.22. Mean values are high, indicating good capability to distinguish PD from NPH walks, while the large standard deviations indicate high dependency of these results on which patients are used for training of the algorithms, due to the limited size of the cohort employed. For individual patients, comparisons of gait cycle parameters of patients were made between before and after surgical interventions, such as Deep Brain Stimulation (DBS) implantation in PD and Shunt implantation in NPH, assessing the effect of the intervention. In conclusion, wearable sensors measuring pressure, combined with gait cycle parameters extraction and machine learning algorithms, showed great potential for objective evaluation of gait impairment. In particular, they allowed to characterize what differentiate such impairments between PD and NPH patients.

Stefano MAGNI (Luxembourg, Luxembourg), René Peter BREMM, Sylvie LECOSSOIS, Konstantinos VERROS, Xin HE, Beatriz GARCÍA SANTA CRUZ, Laurent MOMBAERTS, Andreas HUSCH, Jorge GONCALVES, Frank HERTEL
15:10 - 15:15 #35950 - OP107 Accuracy and safety profile of intraoperative 3D fluoroscopy for predicting final electrode position in deep brain stimulation surgery.
OP107 Accuracy and safety profile of intraoperative 3D fluoroscopy for predicting final electrode position in deep brain stimulation surgery.

Background: The effectiveness of deep brain stimulation (DBS) surgery critically depends on accurate electrode position. An anatomical post-implantation confirmation of the electrode position is required to exclude unwanted shifts. This project aims to validate the intraoperative 3D fluoroscopy (3DF) as a tool to determine the final electrode position. Since it is a faster, cheaper, low-radiation method, that is readily available in the OR, it may replace the standard post-operative CT, if similar imaging acuity is verified. 

Methods: This is a retrospective study that includes 64 patients (124 electrodes) who underwent DBS surgery, from May 2019 to January 2022, at our institution. All patients underwent intraoperative 3DF after implantation of the definitive electrodes and a CT scan within 48 hours after surgery. In order to compare the accuracy of both methods, the images were fused in a stereotactic planning station and the electrode tip position was determined, as well as its distance to the midcommissural point in both imaging modalities. Intracranial air (pneumocephalus) volume was also quantified and its potential impact in determining the electrode position analysed. Finally, radiation exposure from 3DF and CT were assessed and compared.

Results: The difference between the electrode position estimated by 3DF and CT was 0,85 mm (± SEM 0,03), which is inferior to the CT resolution (1mm). The distance to the midcommissural point measured in both methodologies was not significantly different (13,00 ± 0,16 mm in 3DF and 13,06 ± 0,16 in CT; p = 0,11), but was, instead, highly correlated (correlation coefficient = 0,91; p < 0,0001). Despite the fact that pneumocephalus was larger in the 3DF images (6,89 ± 1,76 vs 5,18 ± 1,37 mm3 in the CT group; p < 0,001), it was not correlated with the difference in electrode position measured by both techniques (correlation coefficient = 0,17; p = 0,06). Radiation exposure from 3DF was significantly lower than that from CT (0,36 ± 0,03 vs 2,08 ± 0,05; p < 0,05).

Conclusions: 3DF accurately predicts final lead position in DBS surgery. Being a method with fewer radiation, less expensive, faster, and that doesn’t require the patient to be transported outside the OR, it could replace CT as a tool to determine final electrode position.

Manuel J FERREIRA-PINTO (Porto, Portugal), Patrícia NETO-FERNANDES, Carolina SILVA, Rui VAZ, Manuel RITO, Clara CHAMADOIRA
15:15 - 15:20 #36068 - OP108 Comparative Analysis of Suboptimal Lead Placement in Deep Brain Stimulation: Clinical Outcomes and Surgical Considerations.
OP108 Comparative Analysis of Suboptimal Lead Placement in Deep Brain Stimulation: Clinical Outcomes and Surgical Considerations.

Imaging in DBS surgery has become an invaluable tool to warranty the best clinical effect. This study aimed to determine if the location of the lead partially but not totally within the motor part of the STN redeemed a good clinical result.

Consecutive DBS-operated Parkinson's Disease patients were analysed between 2016-2021. Electrode reconstruction was retrospectively made with Lead-DBS software. The location of the lead was categorised into two groups, appropriately located (electrode totally within the motor part of the STN) and suboptimally located (electrode partially in contact with the STN but not entirely within). The clinical change was recorded UPDRS-III rating scale on and off-state before and one year after surgery.

We reconstructed leads for 70 patients, of which 47 had both electrodes appropriately positioned. Nineteen patients had one suboptimally located lead - 7 on the right side (4 medial and three lateral) and 12 on the left (4 lateral and eight medial). Patients with properly positioned leads showed an improvement of 37.36% in the UPDRS III rating scale in the off-state and 63.85% in the on-state compared to preoperative measures. Among patients with suboptimal right electrodes, those with medial placement reported an improvement of 29.66% in the off-state and 51.35% in the on-state, while those with lateral placement showed an improvement of 33.78% in the off-state and 64.28% in the on-state. For patients with suboptimal left electrodes placed medially, an improvement of 22.91% was observed in the off-state and 63.62% in the on-state, whereas for those with lateral placement, an improvement of 42.48% was observed in the off-state and 65.16% in the on state. No patient, although available, was using directional stimulation. The normality of the variables was assessed using the Shapiro-Wilk test. Since they did not follow a normal distribution, the median and interquartile range were presented, and the differences were analysed using the Mann-Whitney U test. Although a slightly less favourable outcome was observed in patients with medial electrodes, no statistically significant differences were found in any of the groups compared to the original group.

In conclusion, 3D reconstructions provide a valuable tool for the neurosurgeon in assessing the accurate placement of the leads. Deviations from the intended target necessitate a second surgery to achieve optimal clinical outcomes. This cohort study presents patients with suboptimally placed leads, partially in touch but not within the STN. It demonstrates that they achieve comparable clinical outcomes to those with electrodes entirely placed within the nucleus. This finding suggests that, from a surgical perspective, partial lead placement may be an acceptable surgical outcome, eliminating the need for additional surgeries while maintaining favourable clinical results.

Edurne RUIZ DE GOPEGUI (Bilbao, Spain), Gaizka BILBAO, Beatriz TIJERO, Marta RUIZ, Tamara FERNANDEZ, Silvia PÉREZ, Ainara DOLADO, Juan Carlos GOMEZ ESTEBAN, Iñigo POMPOSO
15:20 - 15:25 #36091 - OP109 The emperor's new clones: ipscs for the treatment of parkinson's disease.
OP109 The emperor's new clones: ipscs for the treatment of parkinson's disease.

It is 36 years since Medrazo and colleagues published their landmark paper describing the first two humans to undergo intracerebral adrenal medullary cellular grafting as a treatment for Parkinson’s disease (PD). Since then, attempts to restore dopaminergic neurotransmission in the Parkinsonian brain have undergone several iterations, primarily focused on the source of the cells to be grafted. In each case, impressive early successes were followed by dismal failures in pivotal sham-surgery controlled trials. The pooled data from these studies suggest that while placebo is certainly a concern, a more significant problem is observer bias in the initial trials, which results in overly optimistic and misleading results (Alterman et al, Annals of Neurology, 2011).


Undaunted, a new generation of researchers are about to conduct another round of cellular transplantation studies, this time employing induced pluripotent stem cells (iPSCs) as the donor source. Proponents argue correctly that compared to fetal tissue, iPSCs are a superior source of dopaminergic neurons; scientifically because they can be derived directly from the patient, minimizing the risk of rejection, and ethically because the cells can be harvested without the performance of abortions.


However, there are two fatal flaws in the conceptualization of these studies, which I contend will result in another cycle of early success followed by pivotal trial failure. First, while the cellular source may be more palatable than fetal tissue, the concept behind these studies is outdated and ignores virtually all that has been learned about Parkinson’s disease in the last 30 years, particularly that alpha-synuclein-mediated neuronal degeneration is not confined to the nigro-striatal pathway in PD and that the ‘non-motor’ features of PD, which derive from this more widespread degeneration, are as devastating as the motor symptoms, minimizing the potential impact of a cellular replacement therapy targeted just to the Putamen. Second, we know that the PD brain is hostile to dopaminergic neurons, so that the neurons that do survive the grafting process will also degenerate over time as was observed in long-term survivors following fetal cell transplantation. There are other flaws as well.


Most importantly, these researchers ignore the impact that deep brain stimulation (DBS) has had on the management of PD-related motor symptoms during the same 36-year period. The phenomenal success of DBS cannot be challenged and this success raises the bar as to what are acceptable goals and risks for a new and untried invasive therapy that targets the same symptoms yet may not be clinically effective for 1 or more years after surgery. Consequently, the wisdom of subjecting dozens or perhaps hundreds of patients to these new trials requires serious deliberation. This paper seeks to delineate these arguments in an historically and scientifically accurate context.

Ron ALTERMAN (Boston, USA)
15:25 - 15:30 #36128 - OP110 Tractography identifies individuals vulnerable to stimulation-induced side effects during treatment with thalamic DBS for tremor.
OP110 Tractography identifies individuals vulnerable to stimulation-induced side effects during treatment with thalamic DBS for tremor.


Thalamic deep brain stimulation for tremor remains one of the most robust and effective treatments in functional neurosurgery. Nevertheless, in select individuals side effects can limit overall benefit, reduce battery life, and necessitate more intensive programming. We hypothesised that a vulnerability to stimulation induced side effects was present in a subgroup of people with tremor and that diffusion tractography could inform on the underlying mechanisms. 



A prospective series of patients undergoing thalamic DBS for either essential or Parkinson’s tremor was enrolled between 2020 and 2021. Surgery was performed awake with macrostimulation guidance. At initial monopolar review patients were binarized into those that had beneficial stimulation with monopolar stimulation and without side effects, and those that had side effects that were either wholly or partially ameliorated by more advanced programming strategies. Electrode locations were analysed with the Lead-DBS toolbox to identify sweet and sour spots of stimulation. Group-based neuroimaging analyses were performed with 3 Tesla MRI data and 32 direction 2mm isotropic diffusion imaging. Probabilistic tractography was performed to identify tracts hypothesised to be related to side effects and to subdivide the thalamus into its functional components. 



A total of 30 patients were identified (12 essential tremor, 16 Parkinson’s disease, 2 mixed) with 8 having unilateral surgery (52 electrodes). All patients had an objective tremor improvement at initial programming however approximately half required more advanced programming strategies to account for stimulation induced side effects, almost all of which were sensory in nature. Group-based analyses did not identify specific areas vulnerable for side effects. However, individual tractography based segmentation of the thalamus was able to identify variability in thalamic sensory divisions that predisposed to side effects. 



Thalamic DBS for tremor is a remarkably effective therapy yet a significant proportion of individuals are predisposed to stimulation induced side effects albeit not those that preclude at least initial benefit. Follow-up work should use directional stimulation to verify that tractography-based thalamic segmentations are physiologically principled. Potentially patients could be screened pre-operatively to determine their risk of side effects and determine if a specific strategy such as directional stimulation or tractography-based stimulation would be of merit, ideally as part of a randomised trial. Finally, our approach justifies replication in longer-term follow-up studies as side effects are likely to evolve over time and ultimately become more common. 

Michael HART (London, United Kingdom), Chris HONEY

"Friday 29 September"

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13:30 - 15:30


Moderators: Anne BALOSSIER (Dr) (Marseille, France), Felix BREHAR (Ass. Prof.) (Bucharest, Romania), Ido STRAUSS (Neurosurgeon) (Tel Aviv, Israel)
13:30 - 13:35 #34087 - OP111 Bilateral T12 Dorsal Root Ganglion Stimulation for the treatment of low back pain with 20Hz and 4 Hz stimulation.
OP111 Bilateral T12 Dorsal Root Ganglion Stimulation for the treatment of low back pain with 20Hz and 4 Hz stimulation.


Chronic Lumbar back pain (CLBP) is one of the most common chronic pain conditions resulting in both individual suffering and a burden to societies. For these patients there are several interventional treatment options such as surgery, blocks, radiofrequency, and spinal cord stimulation. Lately, also Dorsal Root Ganglion Stimulation (DRG-S) has been mentioned as an option, by targeting bilateral T12 dorsal ganglia. In this study we will present the outcome of 11 patients with CLBP treated with bilateral T12 DRG-S.



13 patients with CLBP with and without leg pain were treated with bilateral T12 DRG-S. Three of the patients also received a third lumbar lead due to leg pain. 11 of the patients had a more than 50% pain relief during the per- or/and postoperative testing and received a fully implantable neurostimulator. Pain intensity, general health status, quality of life, pain catastrophizing, mental status, sleeping disorder, physical activity and patient satisfaction were followed using numeric rating scale (NRS), patient-reported outcomes measurement information system 29, ver. 2.1 (PROMIS-29), pain catastrophizing score (PCS), generalized anxiety disorder 7-item scale (GAD-7), patient health questionnaire depression module (PHQ-9), insomnia severity index (ISI) and patient satisfaction questionnaire at baseline before implantation, 3 months and 6 months. The results were analyzed based on 6 domains: pain relief, sleeping disorder, social ability, mental status, physical activity, and satisfaction. To be identified as a responder the patients should show a significant improvement in the pain relief domain together with at least two other domains. All responders were given the opportunity to test 4 HZ DRG-S and compare it with traditional 20 Hz stimulation.



All 11 patients were identified as responders at six months. 5 of the patients had a more than 80% pain relief with an average NRS score reduction of 71 % for the whole group. Significant improvement could be observed in 3 domains for one patient, 4 domains for three patients, 5 domains for six patients and 6 domains for one patient. Seven patients chose to try 4 Hz stimulation. All seven identified 4 Hz stimulation at least as good or better than 20 Hz stimulation and chose to continue with 4 Hz stimulation.



Bilateral T12 DRG-S seems to be an effective treatment for chronic low back pain with significant beneficial effect not only on pain but also on quality of life, pain catastrophizing, mental status, sleeping disorder and physical activity. 4 Hz DRG-S gave comparable or better result than 20 Hz stimulation.

Pedram TABATABAEI (Umeå, Sweden), Josef SALOMONSSON, Pavlina KAKAS
13:35 - 13:45 #34385 - OP112 Strategy and neurosurgical ablatives procedures in the treatment of spastic foot. (About a series of 243patients).
OP112 Strategy and neurosurgical ablatives procedures in the treatment of spastic foot. (About a series of 243patients).


Spastic desorders are sometimes disabling and their treatment can be very challenging. The basic phenomenon underlying spasticity is hyperexcitability of the stretch reflex Excess spasticity in limb may make residual motor functions makes passive movement difficult and generates pain. When the spasticity is refractory to optimal oral medication, refractory to physical therapy, the neurosurgical procedures aims to reestablish the tonic balance between agonist and antagonist muscles by reducing the excess of spasticity.


Materials and methods :

The aim of our study was to objectify the functional effects of the tibial neurotomy in the spasticfoot .Our material included 243 patients who underwent  369 partials and selectives neurotomies of the tibial nerve (126 patients were operated bilaterally) . The age of our patients varied between 04 and 56 years. Causes of  spasticity were dominated by the cerebral palsy in 138 patients (56,79%), followed by head trauma in 76cases (31,27%). Other etiologies are found in the remaining cases.

All patients were selected by a multidisciplinary team according to a clinical evaluation and analytical assessment after a physical rehabilitation protocol well conducted.The preoperative anesthetic block tests were mandatory to select patients for surgery.


Results :

After a mean of 21 years, our results were rated "good to excellent»: 65% of cases walk and run with correct plantigrade support   .

We observed a clear improvement in confort in 25% of our patients.



Neurotomy of the tibial nerve was followed by orthopedic correction in 34 patients during the same surgical procedure.

All patients benefited from institutional care program in various rehabilitation centers throughout the country.



When pharmacological and physical therapies are not effective in treating spastic components focalized to lower limb, selective tibial neurotomy leade to long- term satisfactory improvement in function and /or comfort with a low morbidity rate in appropriately  selected patients  suffering from severe harmful spasticity localized to the  lower limb.This procedure take place before the onset of irreversible articular disturbances and musculo tendinousre tractions which requiere  complementery orthopedic corrections .

Lila MAHFOUF (Algeria, Algeria), Brahim MERROUCHE
13:45 - 13:50 #35300 - OP113 Clinical outcome after stereotactic radiosurgery of trigeminal schwannomas.
OP113 Clinical outcome after stereotactic radiosurgery of trigeminal schwannomas.


Trigeminal schwannomas (TS) represent less than 10% of intracranial schwannomas. Complete resection can be curative, but, due to intimate relation to critical neurovascular structures, it is associated with high risk of morbidity and mortality. Stereotactic radiosurgery (SRS) is considered a valuable safe and minimally invasive therapeutic alternative for treating benign intracranial tumors, such as nonvestibular schwannomas. This single-centre study aimed to evaluate the clinical outcome of patients with TS who undervent SRS treatment using Leksell gamma knife (LGK).



From 1994 to 2014 we enrolled 31 patients (15F), mean age 49.8 years with the diagnosis of TS. Initial symptoms were headache (19%), face pain (32%), face numbness (55%) and double vision (32%). All patients underwent radiosurgical treatment on LGK (model B, C, 4C and Perfexion). The prescription dose was 12-14Gy on 50% isodose line. We evaluated changes in clinical signs (improvement or impairment) and tumor volume on regular follow up. The mean follow up was 93.7 months (range 12-241 months).



Permanent clinical sign improvement after SRS treatment was achieved in 13 (42%) patients. The mean time to improvement was 25months (2-60months). The symptoms which improved were face pain, diplopia and face numbness. Posttreatment symptomatic brain edema was in 2 (6%) patients with successful conservative treatment. In 3 (9,5%) patients we observed permanent clinical impairment. Overall tumor control rate was 90,3% and tumor decrease rate was 68,3%. The clinical improvement was associated with tumor volume regression in 10 (77%) patients.



Our results confirm that the LGK is an effective treatment modality for TS with low risk of clinical impairment and high rate of tumor control.



Jaromir MAY (Prague, Czech Republic), Roman LISCAK
13:50 - 13:55 #35694 - OP114 Treatment of neuropathic trigeminal neuralgia using sphenopalatine ganglion and supraorbital nerve stimulation. Case report.
OP114 Treatment of neuropathic trigeminal neuralgia using sphenopalatine ganglion and supraorbital nerve stimulation. Case report.

Case Presentation:

We present a case of a 34-year-old Polish female who was  hospitalized at the Neurosurgery Clinic of University Hospital No. 2 in Bydgoszcz due to left hemifacial pain with neuropathic features, mainly in the area of the trigeminal nerve branches V1 and V2. In 2020, the patient underwent two laryngological surgeries due to chronic sinusitis. 

Since then, the patient has reported severe facial pain-8 VAS scale.Between 2021 and 2022, the patient underwent 9 times radiofrequency rhizotomy procedures of the Gasserian ganglion and 5 blockades of the maxillary and mandibular nerve branches, with a slight short-term improvement.

The patient does not have any other chronic illnesses and the head MRI showed no intracranial pathologies. Laboratory tests were within normal range. Neurological examination at admission to the hospital revealed hypoesthesia in the area of V1 and V2 branches on the left side, with no other deviations noted.

Under general anesthesia, the electrode was percutaneously implanted into the left SPG. The electrode was connected to an external battery and tonic stimulation was initiated.

The patient was discharged home for a period of 2 weeks. After the trial stimulation period, the patient reported a resolution of pain in the V2 branch (VAS 2), but pain in the V1 branch on the forehead still persisted at a VAS score of 8.

The patient was then qualified for the implantation of a supraorbital nerve electrode. Under general anesthesia, the lead was introduced and connected to an external battery, and the parameters for tonic stimulation were established as.........

After 5 days of observation, the facial pain in the V1 and V2 branches decreased to a VAS score of 1.

A non-rechargeable battery was implanted in the left subclavicular region of the patient.

Conclusion: In the treatment of neuropathic trigeminal neuralgia, the implantation of more than one electrode may increase the analgesic effect. Such an approach should be considered in every patient with unsatisfactory pain relief with the use of a single lead. Sphenopaltine ganglion stimulation covers pain area of V2 branch mainly.

Sara KIEROŃSKA (Bydgoszcz, Poland)
13:55 - 14:05 #35718 - OP115 Exploring the State of Neurosurgery for Pain in European Centres: A Survey of Expertise and Fellowship Offerings Among Neurosurgical Centres.
OP115 Exploring the State of Neurosurgery for Pain in European Centres: A Survey of Expertise and Fellowship Offerings Among Neurosurgical Centres.

Introduction: With the goal of identifying and fostering opportunities for early-career neurosurgeons, we conducted a survey among members and centres of the European Association of Neurosurgical Societies (EANS) to gather information about their scope of practice in pain surgery, as well as pain-related fellowships and training opportunities across neurosurgery centres across Europe.

 Methods: An online questionnaire with 26 questions was distributed to all EANS individual members and centres listed on the online EANS map of European neurosurgical departments. Responses were tabulated and analysed using descriptive statistics.

 Results: A total of 27 centres fully completed the questionnaire ascertaining details about their pain fellowship offering and expertise. Among the responding centres, 28% offer a single neurosurgical pain fellowship a year, 42% offer two fellowships a year, 14% offer four fellowships a year, and 14% offer five or more such fellowships per year. The majority of centres offer fellowships to applicants from outside the country but only 40% of responding centres offer paid fellowships. 50% of centres offer participation in research projects. A majority of responding centres (70%) were open to receiving visiting surgeons for short-term visits or observerships for educational and research purposes. Microvascular decompression (MVD) was the most common pain surgery procedure performed (62%), followed by spinal cord stimulation (SCS) (53.8%), deep brain stimulation for pain (DBS) (50%), implantation of intrathecal drug delivery pumps (50%), and balloon compression for trigeminal neuralgia (38%). The least common procedures were cordotomy (6%), mesencephalotomy (6%), cryoablation (7.7%), sphenopalatine ganglion stimulation (7.7%), and methylene blue neurolysis (0%). 

 Conclusion: Our study highlights the need for more education and training opportunities in pain-related neurosurgery. The fact that only a small number of European centres offer fellowship programmes has serious implications for the next generation of neurosurgeons, who will be responsible for treating patients with pain-related conditions. Without access to specialized training programmes at their home institutions, these young neurosurgeons may lack the knowledge and skills required to perform specific neurosurgical interventions for pain. This could have a significant impact on patient outcomes, as well as the continued advancement of the field of pain-related neurosurgery. It is therefore essential that more centres offer fellowships and training opportunities in this area, to ensure that this knowledge and these skills are kept alive and passed on to future generations of neurosurgeons.

Jakob NEMIR (Zagreb, Croatia), Aaron LAWSON MCLEAN, Jean RÉGIS
14:05 - 14:10 #35767 - OP116 Hyperactive dysfunction syndrome of the cranial nerves – The relevance of micro-inspection endoscope assisted microvascular decompression.
OP116 Hyperactive dysfunction syndrome of the cranial nerves – The relevance of micro-inspection endoscope assisted microvascular decompression.


Hyperactive dysfunction syndrome of the cranial nerves is defined as a functional disturbance of cranial nerves caused by neurovascular compression in the posterior fossa. The pathogeny involves a direct contact with mechanical irritation of cranial nerves at the root entry zone by a blood vessel. Detailed anatomic visualization of the root entry zone is essential for the success of the surgical intervention. This study aims at evaluating the efficacy and safety of micro-inspection endoscope assisted microvascular decompression to achieve the best neurological outcome. 

Material and Methods

This is a retrospective pilot study of a series of 8 patients diagnosed with neurovascular compression syndrome (six cases with trigeminal neuralgia and two cases with hemifacial spasm) who underwent surgical treatment in our department, over the course of ten months (May 2022 to February 2023). We used high-resolution MRI with dedicated sequences like 3D-FIESTA-C (CISS) to reveal the neurovascular conflict. All patients had a history of complementary pain/spasm-relief therapies, with unsatisfying results. For all patients we used the endoscopic micro-inspection tool (Qevo®, Kinevo 900, Zeiss) to assist the microvascular decompression procedure.


The study included 8 patients, of which 5 (62.5%) were females. The mean (±SD)  age at diagnosis was 57.3 (± 9.8)  years. 6 patients (75%) underwent microvascular decompression for trigeminal neuralgia and 2 patients (25%) for hemifacial spasm. In our study, arterial involvement was noted in 7 cases (87.5%). For one case of trigeminal neuralgia, the MRI examination did not highlight any neurovascular conflict. Intraoperatively, no arterial conflict was detected; a venous neurovascular conflict was objectified, this finding being also confirmed by micro-inspection tool. In all cases, adequate microvascular decompression was achieved, assisted by the endoscopic micro-inspection tool. This tool allowed the surgeon to meticulously visualise the root entry zone of the cranial nerves, the blood vessels, or the placement of Teflon pads, aiding the surgeon to find hidden anatomical details during microsurgical intervention.  Complete remission of symptoms was registered in all cases. Postoperative neurological morbidity rate was 0%. 


Surgical microvascular decompression remains the treatment of choice for neurovascular compression syndromes. The endoscopic micro-inspection tool enhances the 360-degree visualization of the root entry zone of the nerve and helps to identify the neurovascular conflict when it is not readily apparent in the microscopic field. 

Felix Mircea BREHAR (Bucharest, Romania), Alexandra Mihaela PATRASCANU, Andrei POPESCU, Nicoleta Eugenia DIACONU
14:10 - 14:15 #35784 - OP117 Impact of brainstem lesion location on symptoms and treatment response in patients with multiple sclerosis-associated trigeminal neuralgia.
OP117 Impact of brainstem lesion location on symptoms and treatment response in patients with multiple sclerosis-associated trigeminal neuralgia.

Background:  Trigeminal neuralgia (TN) has a higher incidence in patients with multiple sclerosis (MS) than in the general population. It is thought that, in MS, demyelination in the trigeminal system might generate the symptoms of TN. While multiple series have shown that brainstem lesions were present in patients with MS-TN, the impact of their precise location has never been studied. 

Objective: The goal of this study is to assess the impact of brainstem MS plaque location relative to the trigeminal tracts on TN symptoms and response to treatment.   

Methods: We conducted a retrospective, case-control study of MS patients with or without TN. Patients were matched 1:1 (based on gender and age) and brain MRI were analyzed. Brainstem plaques were segmented and coregistered in MNI (Montreal neurological Institute) space. Lesion locations were compared between the MS and MS-TN groups. To estimate the location of the trigeminal tracts, a tractographic atlas of the trigeminal system was created using 30 patients with high resolution diffusion imaging from the human connectome project. The involvement of the trigeminal system was assessed by computing the intersection of the lesions with the atlas trigeminal tracts. Pain intensity and treatment outcome were then correlated to the percentage of tract involvement using a linear regression. 

Results: Final results will be presented at the meeting. Preliminary analysis identified 77 MS-TN patients treated between 2004 and 2018. 83% of MS-TN patients had a brainstem lesion with 97% intersecting the trigeminal tract. Lesion volume did not correlate with treatment response. The MS group without TN is currently being analyzed. 

Conclusion: Brainstem plaques in MS-TN patients intersect with the trigeminal tract defined using a tractography approach. In some patients, no plaque could be identified. The impact of lesion location on treatment response will be reported once the final analysis is complete. 

Raphaëlle FERREIRA, William LEDUC, Samir AKEB, David MATHIEU, Maxime DESCOTEAUX, Pascal TÉTREAULT, Christian IORIO-MORIN (Sherbrooke, Canada, Canada)
14:15 - 14:20 #35827 - OP118 Recurrence of trigeminal neuralgia after microvascular decompression: the histology of Teflon granuloma.
OP118 Recurrence of trigeminal neuralgia after microvascular decompression: the histology of Teflon granuloma.

Objective: Teflon granuloma is a possible cause of recurrence in patients with trigeminal neuralgia who underwent successful microvascular decompression. Its incidence is variable and the pathophysiology and mechanisms for recurrence are not well defined. In this study, we aim to characterize the histological features of Teflon granulomas and to correlate its occurrence with clinical and intraoperative findings.

Methods: Clinical and histological data of patients with recurrent trigeminal neuralgia who underwent posterior fossa re-exploration over a 15-year period was collected and analyzed.

Results: Histopathological specimens were available in a total of 13/41 cases who underwent surgery for recurrent trigeminal neuralgia. In 6 cases the distribution of pain had progressed to an adjacent area, mostly from V2 to V2 and V3. The mean time for recurrence was 30,65 months after the first microvascular decompression. Intraoperatively a “piston-effect” was noted and calcification of the Teflon occurred in 7/13 cases. All samples showed scar tissue and within this scar birefringent Teflon filaments were observed, which were embedded between enlarged and collagenous fibers. The full configuration of foreign body granulomas with Teflon-adherent giant cells and discrete lymphocytic infiltrates was evident in 10/13 cases. Siderophages were found in 4/13 cases. Microcalcifications occurred in 5/13 cases. The presence of siderophages (mean of 3,50 years), macrophages (mean of 3,50 years) and microcalcifications (mean of 6,60 years) was associated with a latter period compared to the presence of macrophages (mean of 2,33 years) and lymphocytes (mean of 3,40 years).

Conclusions: The majority of Teflon granulomas manifested as foreign body granulomas, corresponding to a scar reaction embedding the Teflon material and an immunological component in the form of giant cells. Clinically, expansion of the distribution of pain during recurrence after a prior successful microvascular decompression can be observed. Our data indicates that Teflon is not an inert material when used for microvascular decompression and that alternative materials or techniques might be considered for microvascular decompression.

Filipe WOLFF FERNANDES (Hannover, Germany), Christine Dorothee SCHMEITZ, Christian HARTMANN, Joachim Kurt KRAUSS
14:20 - 14:25 #36025 - OP119 Frequency Effects of Dorsal Root Ganglion Stimulation on Haemodynamics.
OP119 Frequency Effects of Dorsal Root Ganglion Stimulation on Haemodynamics.


Hypertension is the second largest risk factor for disease worldwide.1 Up to 10% of cases are drug-refractory:2 these are typified by increased sympathetic outflow.3 This has led to the investigation of sympatholytic neuromodulatory therapies. One potential approach is stimulation of the dorsal root ganglion (DRGS), an established target for chronic pain. The DRG is known to be a source of inter-ganglionic collaterals between the autonomic and somatic nervous systems, raising the possibility of autonomic neuromodulation at this site. We have previously shown that DRGS with standard analgesic frequencies (20Hz) reduces sympathetic outflow and leads to long-term reductions in blood pressure (BP).4 However, the optimal stimulation parameters for haemodynamic effects have not been established. Moreover, the pain relief produced by stimulation presents a significant confound to BP changes when comparing ON vs OFF conditions. In the present study, we investigated the relationship between simulation frequency and acute changes in BP. We hypothesised that maximal analgesic and haemodynamic responses to stimulation would occur at differing frequencies.  


Materials and Methods

Nine chronic pain patients with thoracolumbar DRGS participated in a single-session within-patient crossover study. All patients had been previously established on 20Hz stimulation. Six experiment conditions were tested in a random order: OFF-4Hz-10Hz-20Hz-40Hz-80Hz, at the participant’s normal therapeutic pulse width and amplitude. A 10-minute period elapsed between each setting change to limit carryover effects.5 For each condition, 5 minutes of continuous BP was recorded via finger plethysmography, with pain scores recorded using the visual analog scale (VAS). A linear mixed model analysis was performed, with pain and condition order as confound variables. 



Compared to the OFF condition, acute 4Hz stimulation (data available for 6 of 9 participants) produced a 7.1mmHg reduction in SBP (95% CI -13.7 – -0.5 mmHg) and a 6.7 mmHg reduction in DBP (95% CI -11.0 – -2.4mmHg), when adjusted for condition order and pain. Similar mean values were observed for SBP (-7.0mmHg) and DBP (-6.6mmHg) without adjusting for confounds. All other frequencies were non-significant. However, 20Hz stimulation provided the greatest analgesic effect compared to OFF stimulation (mean change -16.7mm, 95% CI -22.2 – -12.3 mm), with several participants reporting worsened pain at higher frequencies.  Post-hoc pairwise comparisons revealed a 7.2mmHg reduction in DBP with 4Hz stimulation compared to 20Hz (95% CI -14.42 – -2.1mmHg, p=0.003, Bonferroni-corrected).  Absolute blood pressure values for all participants by frequency are shown in Figure 1, whereas changes compared to the OFF condition are shown in Figure 2 (mean ± 95% CI). N.B. Mean Arterial Pressure is derived from SBP and DBP (1/3*SBP + 2/3*DBP).




Our study provides preliminary supporting for very-low frequency DRGS (VLF-DRGS) in autonomic neuromodulation, showing greater haemodynamic effects at 4Hz, with greater pain relief at 20Hz. More robust reductions in DBP vs SBP were observed across subjects, supporting our previous findings and suggesting a reduction in sympathetically-mediated vascular tone may underlie acute stimulation effects. In the DRGS pain literature, differential somatosensory fibre recruitment is a likely mechanism for the analgesic effects of VLF-DRGS.6 However, there may also be an increased effect on autonomic fibres, which supports findings in conditions such as diabetic neuropathy.7 There has been increasing interest in DRGS to treat sympathetic overactivity, such as ventricular arrhythmiasand hypertension. However, most experimental protocols utilise either high-frequency (1KHz) or low-frequency (~20Hz) DRGS.8 Our results warrant further investigation of VLF-DRGS in pre-clinical and clinical settings. Important limitations include sample size and the need to corroborate acute findings with long-term data. These are the subject of ongoing work.

Amir Puyan DIVANBEIGHI ZAND (Oxford, United Kingdom), Alexander Laurence GREEN
14:25 - 14:30 #36034 - OP120 Dorsal root ganglion stimulation for intractable chest pain through nerve root foramen after spinal surgery.
OP120 Dorsal root ganglion stimulation for intractable chest pain through nerve root foramen after spinal surgery.

Background: Nowadays, the efficacy of Dorsal root ganglion (DRG) stimulation for intractable pain which Spinal Cord Stimulation (SCS ) is ineffective has been suggested. In addition, the availability of radiofrequency lesioning (RF) and pulsed radiofrequency (PRF) has become common especially for the pain due to nerve root. This time, we report the case which has severe chest and back pain intractable for normal SCS, RF, and PRF then treated with DRG stimulation through nerve root foramen.

 Case 43 male. He suffered from severe chest and back pain located in Th4 and 5 area after operation of decompression for spinal canal stenosis from C7 to Th8. SCS was performed and it was effective in early period. However, the effect disappeared, and the devise was removed. Then, RF and PRF for nerve roots were performed. The patient felt paresthesia at painful area in his body but the pain itself was not relieved. Because he felt the paresthesia was comfortable, we thought that continuous stimulation may be effective for pain. So, leads were inserted through nerve root foramen targeting for nerve roots and DRG, and a pulse generator was also implanted. With continuous stimulation for nerve roots and DRG, he felt less pain than SCS. However, the right lead was dislocated 3 months after operation. The effect of the left side has sustained more than 4 years.

 Discussion: The mechanism of DRG stimulation has not been identified yet. However, there are some reports about priority of DRGS to SCS in the effect for pain due to nerve roots.There are some devices for DRGS, which is inserted through translaminar approach same as SCS. The method we tried this time could stimulate nerve roots and DRG more directly. Conventional RF and PRF is performed with the same procedure, and they could be used as the trial of DRGS. This procedure may be reasonable after spinal surgery because SCS is sometimes difficult due to scar of spinal canal. On the other hand, dislocation of leads is a problem of this procedure.

Conclusion: DRG stimulation through nerve root foramen may be effective for the pain due to nerve roots especially after spinal surgery.

Nobuhiko TAKEDA (Tokyo, Japan), Kaname ITO, Hirofumi HIYAMA
14:30 - 14:35 #36045 - OP121 Decompression of the Greater Occipital Nerve for Occipital Neuralgia and Chronic Occipital Headache Caused by Entrapment of the Greater Occipital Nerve.
OP121 Decompression of the Greater Occipital Nerve for Occipital Neuralgia and Chronic Occipital Headache Caused by Entrapment of the Greater Occipital Nerve.

Background Chronic entrapment of the greater occipital nerve (GON) can not only

manifest in typical stabbing pain of occipital neuralgia (ON) but also lead to continuous

ache and pressure-like pain in the occipital and temporal areas. However, the effect of

GON decompression on these symptoms has yet to be established. We report the

follow-up results of GON decompression in typical cases of ON and chronic occipital

headache due to GON entrapment (COHGONE).

Methods A 1-year follow-up study of GON decompression was conducted on 11

patients with typical ON and 39 COHGONE patients with GON entrapment. The degree

of pain reduction was analyzed using the numerical rating scale-11 (NRS-11) score and

percent pain relief before and 1 year after surgery. A success was defined by at least a

50% reduction in pain measured via NRS-11 during the 12-month follow-up. To assess

the degree of subjective satisfaction, a 10-point Likert scale was used. Postoperative

outcome was also evaluated using the Barrow Neurological Institute (BNI) pain

intensity score. The difference in GON decompression between the patients with

typical ON and those with COHGONE was studied.

Results GON decompression was successful in 43 of 50 patients (86.0%) and percent

pain relief was 72.9925.53. Subjective improvement based on a 10-point Likert scale

was 7.92.42 and the BNI grade was 2.061.04. It was effective in both the ON and

COHGONE groups, but the success rate was higher in the ON group (90.9%) than in the

COHGONE group (84.6%), showing statistically significant differences in the results

based on average NRS-11 score, percent pain relief, subjective improvement, and BNI

grades (p<0.05, independent t-test).

Conclusion GON decompression is effective in chronic occipital headache and in ON

symptoms induced by GON entrapment.

Yunoh HWANG (Seoul, Korea), Son BYUNG-CHUL
14:35 - 14:40 #36046 - OP122 Long-Term Changes in Thecal Sac Compression and Decreased Cerebrospinal Fluid Space Following Paddle Lead Spinal Cord Stimulation at T9: A Long-Term Follow-Up via Three-Dimensional Myelographic Computed Tomography.
OP122 Long-Term Changes in Thecal Sac Compression and Decreased Cerebrospinal Fluid Space Following Paddle Lead Spinal Cord Stimulation at T9: A Long-Term Follow-Up via Three-Dimensional Myelographic Computed Tomography.

Objectives: To investigate the long-term changes in thecal sac compression following T9 paddle lead spinal cord stimulation (SCS) using three-dimensional myelographic computed tomography (CT).

Materials and Methods (Table 1): Seventeen patients with five-column paddle lead SCS at T9 underwent three-dimensional myelographic CT scans preoperatively, immediately after surgery, and after an average of 11 months. The cross-sectional areas of thecal sac and spinal cord and the widths of anterior and posterior cerebrospinal fluid (CSF) spaces were repeatedly measured and compared. The contact angle of the lead with long-term pain relief was assessed.

Results (Table 5): The cross-sectional areas of thecal sac and spinal cord decreased significantly after lead placement (30.47 ± 9.21% and 4.71 ± 9.84%, respectively). Even after 11 months, a significant reduction was found with the preoperative values (17.97 ± 12.32% and 2.88 ± 7.09%). The widths of anterior and posterior CSF spaces decreased significantly after surgery (43.53 ± 13.17% and 57.13 ± 13.17%, respectively) and the severe decrease persisted long-term (29.13 ± 21.54% and 50.99 ± 16.07%). The average pain relief was 42.27 ± 17.50% with no correlation between the rate of reduction in cross-sectional areas of thecal sac and the widths of CSF spaces.

Conclusions: Significant early reduction and late partial restoration occurred in the thecal sac and spinal cord and the width of the anterior and posterior CSF spaces in the T9 5-column paddle lead SCS. Thecal sac compromise was expected to some extent after paddle lead implantation, but the degree is significant, and the cross-sectional area of the spinal cord as well as the thecal sac is affected. Fortunately, these anatomical changes did not cause any clinical problems except for intercostal root irritation. The shape and flat contours of the five-column paddle leads clearly affected the results.

Jun-Yong CHA (Seoul, Korea), Byung-Chul SON
14:40 - 14:45 #36061 - OP123 Treatment of chronic migraine with gamma knife targeting the pterygopalatine ganglion.
OP123 Treatment of chronic migraine with gamma knife targeting the pterygopalatine ganglion.

Introduction: Radiosurgical treatment of trigeminal autonomic cephalalgias (Sluder's neuralgia and cluster headache) using irradiation of the pterygopalatine ganglion has been described. However, this experience is not well-known in the treatment of migraines. Here, we present a small sample of patients suffering from migraine headaches.

Patients and method: We treated 7 patients  (F:M=5:2, age range 43-66 yrs, median 49 yrs, follow-up 12 -163 months, median 54 months) suffering from chronic migraine with gamma knife radiosurgery (GKS).Two of them suffered from bilateral migraine.  All patients had received conservative treatment in specialized clinics for headache prior to radiation. The radiation was targeted to the area of the pterygopalatine fossa at  the level of the canal for the great petrosal nerve. Two shots (4 mm /weight 1/ and 8 mm /weight 0.5/) with identical coordinates were used for radiation application. The maximum dose was 90 Gy. In the patients with bilateral migraine the both pterygopalatine ganglions were irradiated.  In total, 9 pterygopalatine ganglions was irradiated  in 7 patients. Pain relief was evaluated by patients in terms of the percentage of residual pain and also using the BNI score. A residual pain of up to 50%, BNI score III, and sustained relief for at least 1 year have been considered successful treatment outcomes.

Results: Successful treatment was achieved in 6 patients: 4 patients with unilateral migraine on the corresponding side of the head, 1 patient with bilateral migraine on both sides of the head, and 1 patient with bilateral migraine on only one side of the head. In 1 patient we were unsuccessful - the relief lasted only 8 months. Overall, a favorable response to GKS irradiation was observed in 7 out of 9 pterygopalatine ganglions. Five patients were headache free.  The treatment effect occurred within 1 week - 3 months, median 3 months. Recurrence occurred in 3 patients after 12,24 and 108 months. We repeated the radiation with the same dose for pain relief in 1 patient again with good effect.  We did not observe any side effects of the treatment.

Conclusion: Patients with migraine responded well to gamma knife treatment. We achieved pain relief in 7 cases (6 patients). We have not observed any side effects. GKS in migraine targeting the pterygopalatine ganglion is another treatment option for these difficulties with minimal risk. In case of failure, GKS does not exclude other types of treatment such as biological treatment or neuromodulation.                                                                                                                                                                                                                                                                                  This study was supported by the  Ministry of Health, Czech Republic – conceptual development of research organization (NHH, 00023884, IG221201).


Dusan URGOSIK (Prague, Czech Republic), Jaromir MAY, Roman LISCAK
14:45 - 14:50 #36071 - OP124 New way of use spinal cord stimulation to prevent postcardiac surgery atrial fibrillation.
OP124 New way of use spinal cord stimulation to prevent postcardiac surgery atrial fibrillation.

Introduction. Spinal cord stimulation (SCS) is effective in the treatment of chronic pain and intractable angina pectoris. Recently, animal studies have showed that SCS can also suppress atrial fibrillation (AF). Our study aimed to test the safety and efficacy of temporary SCS to prevent the occurrence of AF in the early postoperative period in patients undergoing elective coronary artery bypass grafting (CABG).

Methods and Materials. Fifty-two patients with indications for CABG and history of paroxysmal AF were randomized to 2 groups: CABG plus standard medical therapy (MED) with beta-blockers (n=26, Control group) and CABG plus MED plus the percutaneous lead placement for temporary SCS (n=26, SCS group). In the SCS group under local anesthesia and with fluoroscopic guidance, temporary leads were placed at C7-T4 level according to the patient’s sense of paresthesia and connected to a trial stimulator. Temporary SCS was begun 3 days before elective CABG, deactivated during surgery, reactivated in the intensive care unit after CABG, and continued for 7 days at which time the leads were removed. Continuous external ECG monitoring was performed for 30 days after CABG in all patients. These primary objectives were tested over the 30-day postoperative period: 1) occurrence of adverse events, including death, stroke or TIA, myocardial infarction and kidney injury; and 2) occurrence of AF or any atrial tachyarrhythmia lasting over 30 seconds.

Results. Percutaneous lead placement for temporary SCS was successfully performed in all 26 patients before CABG with no complications. There were no adverse events related to temporary SCS in any patient throughout the follow-up. There were no significant differences in CKMB and creatinine levels between groups (p=0.1 and 0.2, respectively) as well as other typical CABG-related complications (p>0.05). Postoperative AF occurred in 8 (30.7%) of 26 patients in the Control group versus only 1 (3.8%) of 26 patients in the SCS group (p=0.012, log-rank test).

Discussion. Though SCS is a minimally invasive procedure, it could have complications, but in our study, we avoid them. We use conventional SCS in these patients with paresthesia feelings in the chest; hence, the effect of SCS with other types of stimulation (burst or high frequency/density) is the other direction of exploration in this question.

Conclusions. Temporary SCS was effective in suppressing postoperative AF after CABG, with no adverse events in this study. Further studies of SCS with larger samples are indicated to test its clinical value as a perioperative intervention.

Vladimir MURTAZIN (Novosibirsk, Russia), Roman KISELEV, Alexander ROMANOV, Martin KILCHUKOV, Alexander CHERNYAVSKIY
14:50 - 15:00 #36073 - OP125 Persisting Improvement of Deep Brain Stimulation in Neuropathic Pain Syndromes.
OP125 Persisting Improvement of Deep Brain Stimulation in Neuropathic Pain Syndromes.

In comparison to the enormous effect of basal ganglia circuit neuromodulation in movement disorders proves neuromodulation against neuropathic pain being almost ineffective. I started 15 years ago with implantation of two electrodes per cerebral hemisphere. The posterior limp of the internal capsule and the sensory thalamic region were my target structure. Our goal was to alleviate the severe burning pain including allodynia, dysesthesia, hyperpathia associated by sensory deficits following damage of the nervous system by stimulating of the sensory thalamic nuclei and the posterior limp of the internal capsule.

Material and Methodes: From 2008 until 2023 we treated more than 70 patients by stereotactic DBS against neuropathic pain. Out of these 12 Patients suffered from atypical facial pain (4 x analgesia dolorosa), 9 cluster headache, 3 patients had a complete paraplegia, 7 patients had more than 2 cervical root avulsions, 10 times ischemic thalamic post stroke pain, 17 times hemorrhagic thalamic post stroke pain, 4 times peripheral nerve injury following surgery are the pathologic specimen. The average age of the patient at the time for surgery was 51.9 years with a range from 38 to 68 years. 34 patients were female. The average pain disease time was 116.6 months until surgery (10 months – 336 months). As target for stimulation we choose our modified approach in combination of sensory thalamic and posterior limp of the internal capsule. Beside of quantitative sensory testing we utilized in all patients a questionnaire consisting of EQ-5D-German Version, Oswestry Questionaire – German Version, Mc.Gill Pain Questionaire short form German Version, SF-36 Standard German Version 1.0, Eisner VAS Body Region Questionaire.

Results: A combined stimulation of the sensory thalamic region and the posterior limp of the internal capsule revealed a stable pain reduction of more than 60% in all our patients with exception of our posthaemorrhagic central stroke patients and the complete paraplegic patients. Allodynia, dysesthesia and hyperpathia were reduced dramatically in our patients with more than 80 % pain reduction proofen by quantitative sensory testing.

Discussion: A modified approach and the combination of two electrodes per hemisphere is revealing better results in deep brain stimulation against the most severe pain syndromes in humans since 15 years in comparison to the international literature.

Wilhelm EISNER (Innsbruck, Austria), Johannes KERSCHBAUMER, Wolfgang LÖSCHER, Julia WANSCHITZ, Sweta BAJAJ
15:15 - 15:25 #36165 - OP128 Optimization of radiofrequency needle placement in percutaneous cordotomy using electromyography in the deeply sedated patient.
OP128 Optimization of radiofrequency needle placement in percutaneous cordotomy using electromyography in the deeply sedated patient.

Background: Cordotomy, the selective disconnection of the nociceptive fibers in the spinothalamic tract (STT), is used to provide pain palliation to oncological patients suffering from intractable cancer-related pain. Cordotomies are commonly performed using a cervical (C1-2) percutaneous approach under imaging guidance and require patients’ cooperation to functionally localize the STT. This, can be challenging in patients suffering from extreme pain. It has recently been demonstrated that intraoperative neurophysiology monitoring by electromyography may aid in safe lesion positioning.


Objective: The aim of this study is to evaluate the role of compound muscle action potential (CMAP) in deeply sedated patients undergoing percutaneous cervical cordotomy (PCC).  


Methods: A multi-center, retrospective analysis was conducted of all patients who underwent percutaneous cordotomy while deeply sedated between January 2019 and November 2022. The operative report, neuromonitoring logs, and clinical medical records were evaluated.


Results: 11 patients underwent PCC under deep sedation. In all patients, the final motor assessment prior to ablation was done using the electrophysiological criterion alone. The median threshold for evoking CMAP activity at the lesion site was 0.9V ranging between 0.5 and 1.5V (average 1V ± 0.34V SD). An immediate, substantial decrease in pain was observed in 9 patients. Median pain scores (NRS) decreased from 10 preoperatively (range 8-10) to a median 0 (range 0-10) immediately following surgery. None of our patients developed motor deficits.


Conclusion: CMAP-guided PCC may be feasible in deeply sedated patients without added risk to postoperative motor function. This technique should be considered in a group of patients who are not able to undergo awake PCC.

Segev GABAY, Segev GABAY, Sapir YECHIAM, Akiva KORN, Hochberg URI, Tellem ROTEM, Zegerman ALEX, E Brogan SHANE, Rahimpour SHERVIN, Shofty BEN, Strauss IDO STRAUSS (Tel Aviv, Israel)
15:25 - 15:30 #36179 - OP129 Effect of Low-Frequency Dorsal Root Ganglion Stimulation in the Treatment of Neuropathic and Nociceptive Pain.
OP129 Effect of Low-Frequency Dorsal Root Ganglion Stimulation in the Treatment of Neuropathic and Nociceptive Pain.


The role of stimulation parameters in dorsal root ganglion stimulation (DRG-S), especially of stimulation frequency, is not well understood. Previous studies documented higher effectiveness for frequencies as low as 20 Hz, but there is evidence that even lower values could lead to better outcomes. In this study, we investigate the influence of low-frequency DRG-S.



We report on the results of a randomized double-blind clinical trial with crossover design. Patients with an already implanted DRG-S system were included and randomly tested with 4 Hz, 20 Hz, 60 Hz and sham stimulation. Amplitude was adjusted to subthreshold values for each frequency. Each frequency was tested for 5 days, followed by a 2-day wash-out period. Patients were assessed using VAS, McGill Pain Questionnaire, EQ-5D-5L and Beck Depression Inventory.



17 patients were included. Time between inclusion in this study and primary implant was 32.8 months. Baseline stimulation frequency was 20 Hz in all patients. Mean baseline pain intensity was VAS 3.2 (SD 2.2). With 4 Hz stimulation, VAS was 3.8 (SD 1.9), with 20 Hz VAS 4.2 (SD 2.0) and with 60 Hz VAS 4.6 (SD 2.7). Worst pain control was seen with sham stimulation with a VAS of 5.3 (SD 3.0). Stimulation with 4 Hz achieved lower VAS scores, but this was only statistically significant when compared to sham (p = 0.001). A similar trend favoring 4 Hz stimulation was seen using the Beck Depression Inventory, but in this case no statistical significance was found. Outcomes of McGill Pain Questionnaire and EQ-5D-5L favored 20 Hz stimulation, but again without statistical significance.



Low-frequency stimulation might be most effective in dorsal root ganglion stimulation for chronic neuropathic pain. Longer wash-out and observational periods might be necessary to show clear differences in frequency response.

Philipp SLOTTY, Jan VESPER (Duesseldorf, Germany), Phyllis MCPHILLIPS, Zarela KRAUSE MOLLE

"Friday 29 September"

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13:30 - 15:30


Moderators: Krassimir MINKIN (Head of Center of Functional Neurosrgery) (Sofia, Bulgaria), Jordi RUMIÀ ARBOIX (Consultant. Stereotactic and Functional Neurosurgery.) (Barcelona, Spain), Takaomi TAIRA (Professor) (Tokyo, Japan)
13:30 - 13:40 #33941 - OP130 Stereo-electroencephalography guided interstitial laser therapy (LITT) in neocortical epilepsy.
OP130 Stereo-electroencephalography guided interstitial laser therapy (LITT) in neocortical epilepsy.

Stereoelectroencephalography (SEEG) can be applied to delineate EZ and guide LITT. By definition, in order to achieve seizure freedom, one needs to resect or disrupt the EZ. As the anatomical reach of ablation effect from the current LITT systems is restricted up to approximately 1 cm radius from the center of the probe, LITT might be ideal for well-defined and restricted EZ. To date, there is no consensus on SEEG electrophysiologic patterns that would precisely identify EZ to guide and predict seizure outcomes after LITT. An EZ electrophysiologic biomarker, “EZ fingerprint”, has been recently described using time-frequency analysis and validated in focal epilepsies.  This study aims to investigate seizure outcomes in patients with drug-resistant epilepsy (DRE) who underwent SEEG guided LITT by correlating the extent of laser ablation to seizure onset zone (SOZ) based on conventional analysis and predicted epileptogenic zone (PEZ) estimated by time-frequency electrophysiologic pattern.

We retrospectively analyzed 16 consecutive DRE patients. SOZ contacts were analyzed from the conclusion made during multidisciplinary patient management conferences and confirmed by two epileptologists independently. SOZs were further divided into localized, lobar and multilobar, and nonlocalized onset patterns. PEZ contacts were identified using “EZ fingerprint” pipeline. The completeness of the ablation of PEZ and SOZ was analyzed. 

Out of 16 patients, only 11 patients had PEZ identified. Two localized lobar SOZ patients with complete ablation of PEZ achieved seizure freedom (SF) at the last follow-up (40 and 46-month). One patient with localized lobar and five with localized multilobar SOZ had partially ablated PEZ and achieved a mean 22.4-month SF with subsequent seizure recurrence. One patient with localized multilobar and two with nonlocalized SOZ had ablation performed outside of the PEZ, and seizures recurred within 1 month. 

Only complete ablation of limited PEZ leads to seizure freedom, whereas partial ablation of slightly broader restricted PEZ may lead to long-term seizure freedom with eventual seizure recurrence. Failure to identify PEZ and ablation limited to the conventional SOZ led to early seizure recurrence in most cases.

13:40 - 13:50 #34732 - OP131 Magnetic resonance imaging-guided laser instertitial thermal therapy (MRIgLITT) for refractory epilepsy in pediatric patients: 4 years single-center experience.
OP131 Magnetic resonance imaging-guided laser instertitial thermal therapy (MRIgLITT) for refractory epilepsy in pediatric patients: 4 years single-center experience.


To describe our initial experience with magnetic resonance imaging-guided laser instertitial thermal therapy (MRIgLITT) for the treatment of epilepsy in our pediatric institution.


We have collected prospectively all cases treated with MRIgLITT in our institution. We have registered the cause of epilepsy, the epilepsy outcome and complications.


We have performed 51 procedures (49 patients and 2 high realistic simulations): 26 surgeries for hypothalamic hamartomas, 11 to complete disconnective surgeries (hemispherotomies or posterior quadrant disconnections), 10 for focal lesions (5 tumors and 5 focal cortical dysplasias), an amigdalohipocampotomy, and an entire posterior quadrant disconnection. Patient average age was 9 years, being the youngest patient 15 months old.

14 patients with hypothalamic hamartomas were seizure free after the first procedure, five required a reintervention and 1 of them still presents seizures after 4 surgeries. Disconnective surgery completion was effective in all but two patients. Three patients required to be reintervened through MRgLITT and 2 through open surgery (one failed after completing an anatomic hemispherectomy and we suspect a contralateral epileptogenic focus). Patients operated on the other focal lesions and the TPO are all Engel 1/ILAE 1. The maximum follow up is of 4 years. We have also started to collect biopsy material through the same trajectory.

Complications appeared only in the hypothalamic hamartomas group: short-term memory impairment in 5 patients, fever in 3, trajectory ablation due to insufficient water cooling in 2 initial cases, transient oculomotor iii paresis in 2, hyperphagia and somnolence due to hypothalamic injury in a type IV HH and, recently, diabetes insipidus in one.

Complications with hypothalamic hamartomas have decreased significantly as the team has gained experience with the technique. The other indications were extremely safe.


MRgLITT has been an effective and relatively safe procedure for HH in pediatric patients, and it has also been useful in disconnective surgery, LGG and FCD. The amigdalohipocampotomy is also feasible in children. Biopsy material can be obtained prior to the ablation.

This treatment seems highly effective, although further follow-up is required.

Santiago CANDELA-CANTÓ (Barcelona, Spain), Jordi MUCHART, Alia RAMÍREZ, Jana DOMÍNGUEZ, Anna WINTER, Diego CULEBRAS, Mariana ALAMAR, Victoria BECERRA, María HERNÁNDEZ, Javier APARICIO, Jordi RUMIÀ
13:50 - 13:55 #35031 - OP132 Triggered seizures for ictal SPECT imaging: a feasibility study.
OP132 Triggered seizures for ictal SPECT imaging: a feasibility study.

Single-Photon Emission Computed Tomography (SPECT) of seizures is an informative technique to plan epilepsy surgery. However, the image quality crucially relies on capturing the onset of a seizure, the precise timing of which is unpredictable. As a result, neurology and nuclear medicine departments invest considerable amounts of time and money in hope of obtaining high-quality SPECT images. To reduce the involved resources, we aimed at imaging planned seizures that were triggered using direct electrical stimulation of the epileptic network in epilepsy patients undergoing invasive exploration.

A prospective case series of three adult patients with left temporal epilepsy was conducted between February and November 2022. During presurgical epilepsy evaluation with stereotaxic electroencephalography (sEEG), grey matter sEEG contacts were screened to determine sites of stimulation able to trigger patient-typical seizures. On the following day, seizure triggering was repeated once and a ready-to-inject radiotracer (Technetium-99m-HMPAO) was administered within seconds of seizure onset confirmation. The primary outcome was the feasibility of obtaining timely ictal SPECTs from triggered patient-typical seizures, as a way to complement discrete sEEG sampling with spatially-continuous imaging of seizure networks. Measures included areas of hyperperfusion (i.e. voxels of SPECT deviation map with z-value ≥2.25), time from seizure onset to radiotracer injection, electrodes showing seizure activity over the first 60 seconds and adverse events.

In all three patients, an ictal SPECT was successfully obtained within 12 seconds of triggered seizure onset without any adverse event. In two out of three, the SPECT revealed areas of hyperperfusion in eloquent cortex that were not sampled by sEEG but corroborated patient-typical semiology (peri-ictal aphasia). In this feasibility study, triggered ictal SPECT constituted a safe and easy-to-use method for imaging early seizure propagation networks, which complements invasive electrophysiological exploration. Our study revives the interest in imaging seizures to guide resective epilepsy surgery, as it is readily implementable at specialized epilepsy centers.

Sabry BARLATEY (Bern, Switzerland), Camille MIGNARDOT, Cecilia FRIEDRICHS-MAEDER, Kaspar SCHINDLER, Roland WIEST, Andreas NOWACKI, Matthias HAENGGI, Werner Z’GRAGGEN, Claudio POLLO, Axel ROMINGER, Thomas PYKA, Maxime BAUD
13:55 - 14:00 #35508 - OP133 MRI-guided laser interstitial thermal therapy for treating drug-resistant epilepsy associated with TSC in children: preliminary experience in 2 cases and technical considerations.
OP133 MRI-guided laser interstitial thermal therapy for treating drug-resistant epilepsy associated with TSC in children: preliminary experience in 2 cases and technical considerations.

Background : Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder that affects multiple systems and is associated with refractory early-onset epilepsy. Seizures are often the earliestclinical manifestation of TSC, leading to epilepsy in over 80% of patients, and most seizures have a focal onset. Recent surgical technological advances have broadened the definition of surgical candidacy, with the goals of surgery shifting towards quality of life and maximizing neurodevelopmental potential in patients unable to obtain seizure freedom.Laser interstitial thermal therapy (LITT) has been used as a surgical option for the treatment of TSC-related epilepsy due to its minimally invasive nature, real-time monitoring capabilities, smaller incision, shorter hospital stay, reduced blood loss, and reduced postoperative pain. 

Methods We report our experience of two  cases of drug resistant TSC-associated epilepsy treated by MRgLITT (Visualase, Medtronic)

Results : All patients had drug-resitant TSC - related epilepsy. Targets were chosen based on clinical , radiological and neurophisiological data (EEG, vEEG, MRI , ASL-MRI ) and after multidisciplinary discussion.  We ablated tubers in one patients, and 6 tubers in the other patient ( in two different surgical procedures). Both patients were discharged after 24 hours without complications. Both patients at 1 year follow-up are seizure free.

Conclusions : In our two cases, MrgLITT has been shown to effectively target multiple epileptogenic tubers in a single procedure, resulting in a significant reduction in seizure frequency. This is in contrast to traditional open surgery, which is often limited to the resection of a single tuber at a time. Overall, the ability of MrgLITT to hit multiple targets in one single procedure has significant implications in children.  Not only does it reduce the need for multiple surgeries, but it also reduces recovery time for patients. Furthermore, the ability to monitor the ablation in real-time along with the functionality of adding thermal limits allows surgeons to minimize unintended ablation of structures outside the target zone and the risk of complications. 

Giuseppe MIRONE (NAPOLI, Italy), Claudio RUGGIERO, Bernardo PIA, Domenico CICALA, Giuseppe CINALLI
14:00 - 14:05 #35655 - OP134 Laser interstitial thermal therapy for focal epilepsy : a single preliminary single center experience.
OP134 Laser interstitial thermal therapy for focal epilepsy : a single preliminary single center experience.

Background: Laser interstitial thermal therapy (LITT) is an emerging option for treating deep brain tumors or focal epilepsy. A laser catheter is implanted stereotactically into the selected brain tissue after accurately planning the trajectory for the treatment. The patient is then transferred into an MRI suite where a thermal lesion is performed by heating the selected tissue to temperatures high enough. Continuous MRI sequencing allows real time visualization of tissue destruction. Selected patients with epileptogenic foci have been successfully treated with LITT both in single treatment or in addition to open surgery. We describe our preliminary experience with LITT for epilepsy surgery.


Methods: We retrospectively reviewed all patients treated for focal epilepsy with LITT at the Neurosurgical Department of the ULSS 8 Berica in Vicenza, Italy since 2020. We collected both clinical and radiological data from the presurgical workup such as site and supposed type of lesion, seizure history, kind and number of antiepileptic drugs. Available data concerning seizure control were described using Engel and ILAE classifications.


Results: Eleven patients aged 19-76 years (median 34,2) were treated in 12 treatment sessions. The site of ablation was: the temporal lobe in 6 patients who underwent amygdalohippocampectomy for hippocampal sclerosis; extratemporal in the other 6 patients (3 insular, 1 frontal, 1 cingular, 1 parietal) with radiological signs of Focal Cortical Displasia (FCD).  

Three patients underwent pre-operative SEEG study and two had a previous resective surgery. One patient underwent resective surgery after LITT due to unsatisfactory seizure control.

At last available follow up (median 5,9 months, range 1-38 months,) 5 patients showed a good seizure control (Engel Class 1, ILAE class 1 or 2), two had a significant reduction of seizures (Engel Class 2, ILAE 2/3) and three a slight reduction (Engel Class 3, ILAE class 4) No patients developed a surgical complication


Conclusions: LITT shows satisfactory results in terms of seizure control in our series of patients even though postoperative follow up is rather limited. Patients with well-defined and focal lesions on the MR imaging seem to have a better response.

LITT is a safe and repeatable procedure that can be used as an add on treatment to surgery in more complex cases and favors the reduction of both the number and intensity of seizures.

Some limitations are the high costs of the procedure, occupation of multiple time slots in the MRI suite and the treatment of irregular or more diffused lesions, because of low conformational flexibility.

Massimo PIACENTINO (Vicenza, Italy), Cristiano PARISI, Valerio VITALE, Raffaella SCOTTO OPIPARI, Federica RANZATO, Paolo BONANNI, Lara ZORDAN, Fabio RANERI
14:05 - 14:15 #35664 - OP135 Radiofrequency ablation of the centromedian thalamic nucleus in the treatment of drug-resistant epilepsy; long-term follow-up and results.
OP135 Radiofrequency ablation of the centromedian thalamic nucleus in the treatment of drug-resistant epilepsy; long-term follow-up and results.

Objective: To determine the usefulness and efficacy of radiofrequency ablations (RFA) of the Centromedian thalamic nucleus (CMN) to control primarily generalized or multifocal seizures in refractory epilepsy.
Methods: Twelve patients with clinical diagnosis of multifocal or primarily generalized drug-resistant epilepsy were included. Bilateral RFA of the CMN was performed through a monopolar 1.8 mm. tip electrode with a temperature of 80 Celsius degrees during 90 seconds. Patients were followed in every 3 months visit for 6 to 60  months and kept a monthly seizure count calendar. We also compared maximal paroxysmal electroencephalogram (EEG) activity and neuropsychological evaluation pre and 6 months postoperatively. Results: A significant reduction in the number of generalized seizures was observed in all subjects in the range of 60–98%, starting the first post-operative month. Although focal aware seizures remained unchanged throughout follow-up, there was an important reduction on paroxysmal activity between the pre and postoperative EEG. No major changes on cognitive status were detected. There was post- operative dysphagia and odynophagia lasting one week and there was no mortality in this group of patients. Conclusion: Preliminary results of CMN RFA suggest safety and a trend toward reduction of some seizure types, it may reduce the seizure frequency like other palliative procedures since the first post-operative month, but a larger, controlled study would be needed to establish the value of this therapy.

Gustavo AGUADO CARRILLO (Mexico City, Mexico), Francisco VELASCO CAMPOS, Ana Luisa VELASCO MONROY, Jose Luis NAVARRO OLVERA, Stephani Dalila HERES BECERRIL
14:15 - 14:25 #35667 - OP136 Stereoelectroencephalograhy-guided radiofrequency thermocoagulation in paediatric patients with refractory epilepsy : A single-center prospective cohort.
OP136 Stereoelectroencephalograhy-guided radiofrequency thermocoagulation in paediatric patients with refractory epilepsy : A single-center prospective cohort.


Since 2015 the authors have performed thermocoagulation in  pediatric patients with refractory epilepsy, after multidisciplinary committee evaluation, at Sant Joan de Déu Barcelona Children's Hospital. The aim of this study was to determine the factors favoring thermocoagulation indication in drug resistant pediatric epilepsy patients in our center, the morbidity and outcomes for post- stereoelectroencephalograhy themocoagulation in these patients.


Data were collected from 35 patients with stereoelectroencephalograhy implanted in out center from 2015 to 2022 , Dixi Medical platinum/iridium microdeep electrodes were placed according to the Talairach technique targeting the hypothesized epileptogenic zone.  Following stereoelectroencephalograhy, the epileptic zone was treated with thermocoagulation and/or resective surgery. Outcomes were evaluated based on ILAE outcome scale. 



Thermocoagulation was performed in 9 patients. Patients with increased tendency towards thermocoagulation indication were males, with a family history of epilepsy, no significant cognitive impairment, later age at epilepsy onset, nocturnal predominance. A statistically significant tendency towards thermocoagulation indication was also found with increased stereoelectroencephalograhy experience (P=0.0006) and epilepsy origin hypothesis outside of the temporal lobe (p= 0.002).

Three patients had no significant improvement (Less than 50% seizure reduction), these patients received surgery in the following months (mean of 190 days). The 6 responding patients have been observed for a mean of 462 days.

ILAE after thermocoagulation was evenly spread with 2 patients in class 1, 2  in class 2, 2 in class 3, 1 in class 4 and 2 in class 5. No significant increase in complications was detected (22% in the thermocoagulated, 19.23% in non thermocoagulated patients). Even in patients who after thermocoagulation required surgery, there was tendency towards lower ILAE class (2 patients in class 1 , 1 in class 3) compared to the overall cohort.

A statistically significant reduction in surgery indication was detected in patients receiving thermocoagulation (33%) in comparison with patients who underwent only stereoelectroencephalography (77.22%, p=0.006).

14:25 - 14:30 #35725 - OP137 Microendoscopic transventricular deep brain stimulation of the anterior nucleus of the thalamus as a safe treatment in intractable epilepsy: A feasibility study.
OP137 Microendoscopic transventricular deep brain stimulation of the anterior nucleus of the thalamus as a safe treatment in intractable epilepsy: A feasibility study.

Introduction: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is proposed in patients with severe intractable epilepsy. When used, the transventricular approach increases the risk of bleeding due the anatomy around the entry point in the thalamus. To avoid such a complication, we used a transventricular microendoscopic technique.

Methods: We performed a retrospective study of nine adult patients who were surgically treated for refractory epilepsy between 2010 and 2019 by DBS of the anterior thalamic nucleus.

Results: Endoscopy provides a direct visual control of the entry point of the lead in the thalamus through the ventricle by avoiding ependymal vessels. No hemorrhage was recorded and accuracy was systematically checked by intraoperative stereotactic MRI. We reported a responder rate improvement in 88.9% of patients at 1 year and in 87.5% at 2 years. We showed a significant decrease in global seizure count per month one year after DBS (68.1%; P=0.013) leading to an overall improvement in quality of life. No major adverse effect was recorded during the follow-up. ANT DBS showed a prominent significant effect with a decrease of the number of generalized seizures.

Conclusion: We aimed at a better ANT/lead collimation using a vertical transventricular approach under microendoscopic monitoring. This technique permitted to demonstrate the safety and the accuracy of the procedure.

14:30 - 14:35 #35740 - OP138 One-year seizure-free after Forel-H-tomy for drug-resistant epilepsy: a case report.
OP138 One-year seizure-free after Forel-H-tomy for drug-resistant epilepsy: a case report.

The patient, a 62-year-old woman, suffered from an extensive cerebral contusion to the left fronto-temporal lobe due to an acute subdural hematoma at the age of 44. Six months after the injury, she developed epileptic seizures. The seizures were generalized seizures with right cervical rotation and fencing posture. Despite prescriptions for four antiepileptic drugs, partial seizures occurred several times a month and a focal to bilateral to tonic-clonic seizure once every two months. Video-EEG showed epileptic discharges of left frontal lobe. The patient was referred to our department for palliative surgery. The patient underwent left Forel-H-tomy. Muscle hypotonia in the right upper and lower limbs appeared after the surgery and resolved spontaneously within the 6 months. The prescription of antiepileptic drugs was not changed, and partial seizures and a focal to bilateral tonic clonic seizure have not appeared for 1 year.

Shiro HORISAWA (Shinjyuku, Japan), Takaomi TAIRA
14:35 - 14:45 #35770 - OP139 Cerebellar connections contribute to seizure control in patients with generalized drug-resistant epilepsy after neuromodulation of the centromedian nucleus of the thalamus.
OP139 Cerebellar connections contribute to seizure control in patients with generalized drug-resistant epilepsy after neuromodulation of the centromedian nucleus of the thalamus.

Introduction: Epilepsy is a widespread neurologic disorder and almost one-third of patients suffer from drug-resistant epilepsy (DRE). For patients with generalized DRE who are not surgical candidates, neuromodulation targeting the centromedian nucleus of the thalamus (CM) has been showing promising results. Recently, a less clinically beneficial “cold-spot” and a more clinically beneficial “sweet-spot” were suggested by the authors of the ESTEL trial, the first monocentric randomized-controlled study investigating CM-DBS (deep brain stimulation) in DRE patients. Interestingly, this sweet-spot extended beyond the borders of CM proper and covered part of the ventrolateral nucleus. Nonetheless, it remains unclear which structural connections may contribute to the anti-seizure effect of the stimulation. 

Objective: In the this tractography study, we investigated the differences in structural connectivity among CM, the sweet-spot and the cold-spot. We also tried to validate our results in a cohort of DRE patients who underwent CM-DBS or CM-RNS (responsive neurostimulation). 

Methods: FSL probabilistic tractography was performed on 100 subjects from the Human Connectome Project to investigate the structural connectivity of the whole CM, the sweet-spot and the cold-spot to 45 cortical and subcortical areas. Using the number of streamlines that reached the latter target areas, the probability of connectivity with all the targets was calculated and compared among the three seeds with MANOVA. Similarly, the structural connectivity of VTAs (volumes of tissue activated) from 8 DRE patients was investigated. Patients were divided into responders and non-responders based on the degree of reduction in seizure frequency (>50%) and the mean probabilities of connectivity were similarly compared between the two groups.

Results: The sweet-spot demonstrated a significantly higher probability of connectivity (p<0.001) with the precentral gyrus, superior frontal gyrus and the cerebellum than the whole CM and the cold-spot.  Responder patients displayed a higher probability of connectivity with both ipsilateral (p=0.021) and contralateral cerebellum (p=0.041) than the non-responders.

Conclusion: The sweet-spot shared a similar structural connectivity pattern with responder patients, implying higher structural connectivity with frontal and prefrontal areas and the cerebellum. However, the only statistically significant difference between responder and non-responder patients resulted with the cerebellar connections. Therefore, we hypothesize that the interplay between CM and the cerebellum may underlie the beneficial effects of neuromodulation in patients with drug-resistant generalized epilepsy.

Luigi Gianmaria REMORE (Milan, Italy), Ziad RIFI, Hiroki NARIAI, Dawn ELIASHIV, Aria FALLAH, Benjamin EDMONDS, Joyce MATSUMOTO, Noriko SALAMON, Meskerem TOLOSSA, Wenxin WEI, Marco LOCATELLI, Evangelia TSOLAKI, Ausaf BARI
14:45 - 14:50 #35776 - OP140 Robot-assisted insertion and low-temperature ablation Interstitial laser thermocoagulation (LITT) : an effective method for the management of hypothalamic hamartomas.
OP140 Robot-assisted insertion and low-temperature ablation Interstitial laser thermocoagulation (LITT) : an effective method for the management of hypothalamic hamartomas.


Hypothalamic hamartoma (HH) manifests with a variety of symptoms including drug-resistant epilepsy warranting surgical management. Interstitial laser thermotherapy (LiTT) is an increasingly used technique for the treatment of HH. In addition to real-time temperature monitoring during ablation, we believe that the combination of robotic-assisted insertion to optimise probe placement within the lesion and low-temperature ablation to avoid even transient exposure of adjacent structures to cytotoxic temperatures could  contribute to reducing the morbidity of the procedure, without altering the clinical efficacy of the ablation

 Material and method: We report our experience of a series of 8 patients managed at the university hospital of Amiens between 2019 and 2023 for the surgical treatment of a HH using this methodology.  For each patient, one or two fibres were positioned under robotic assistance using the Rosa@ robot. Ablation was performed with the VISUALASE device (Medtronic) at low temperature, i.e. ensuring that the organs (hypothalamus, trigone, mamillary body, optic tract, etc.) immediatly adjacent receive a temperature of less than 45° throughout the ablation process. The completeness of the ablation was checked peroperatively by using diffusion and Flair sequences immediately at the end of the procedure.

 Results: The mean age of the population was 13.5 years (3 - 35 years). 2F/6H. 2 patients had been operated twice before the procedure. According to the modified Delalande classification, 2 patients were classify class IIa, 1 as class IIc, 1 as class IIIa, 2 as class IIIb and 2 as class IV. No bleeding or infectious complications. Ablation was complete in 7 patients (87.5%) and greater than 95% in 1 patient. 87.5% improved and according to ILAE classification, 5 (62.5%) class 1, 1 class 2, 1 class 4 and 1 class 5. No postoperative neuro-cognitive or behavioural complications. 6 (75%) showed cognitive and/or behavioural improvement. 2 patients presented a postoperative endocrine complication: thyroid insufficiency (n=1) and bulimia with loss of satiety without weight gain at follow-up (n=1).

Conclusion: Our initial experience confirms the interest of LITT in the management of HH. Robotic assistance associated with "low temperature" ablation could contribute to decrease the morbidity of these procedures.

14:50 - 15:00 #35849 - OP141 How wrong can we be? Overcoming errors in indirect targeting of the Centromedian nucleus by incorporating third ventricular anatomy.
OP141 How wrong can we be? Overcoming errors in indirect targeting of the Centromedian nucleus by incorporating third ventricular anatomy.


Deep brain stimulation (DBS) of the thalamic centromedian nucleus (CM) is a promising therapy for patients with diverse brain diseases, including epilepsy, Tourette syndrome, and disorders of consciousness. However, the CM is challenging to visualize on routine MRI. For this reason, many surgeons use an “indirect” targeting method based on established stereotactic coordinates. In a meta-analysis by Ilyas et-al.; all 47-patients who underwent DBS, CM was targeted based on the Schaltenbrand atlas, which defined the target as a point 10mm lateral to the midline at the posterior commissure (PC). Note that this target marks the endpoint (position of the lowermost DBS contact) of the trajectory. In the literature, this was the most commonly used coordinate to target the CM, however, the accuracy of this approach is unknown. We aimed to quantify the likelihood of DBS electrodes being positioned within the CM using this indirect targeting coordinate. 


Materials and Methods: 

We used 100 T1-weighted MRI scans from a dataset of healthy adults (Human Connectome Project). Indirect targeting of CM was manually performed per hemisphere. The resulting stereotactic coordinates were warped to a common template space (MNI-ICBM-152). These coordinates indicate the intended endpoint of a lead trajectory. To estimate positions of DBS contacts along this trajectory, we developed a Probable Electrode Location (PEL) mask representing the range of likely trajectory angles between the cortical entry- and thalamic end-points (Fig1). Euclidean distance between the centroid of the PEL mask and the centroid of an atlas-based definition of the CM was measured per subject and defined as “error”.



Average Euclidean error was 5.5±1.0mm 5.3±1.0mm on left and right sides, respectively (Fig2), and predominantly due to medial-lateral deviations, i.e. along the x-axis (Fig3). Strong correlations were observed between the width and volume of the third ventricle and Euclidean error (Fig4).



Standard indirect coordinates do not provide optimal targeting within the CM. To minimize this variability, we propose an alternative indirect targeting approach: using the posterio-lateral corner of the third ventricle as an anatomical anchor, and a point 6.5mm lateral to this anchor would define the new target (Fig5). Using this new approach, the average Euclidean error was reduced to 1.5±0.2mm (left CM) and 1.2±0.7mm (right CM). Therefore, excluding the variability of the width of the third ventricle from the indirect targeting approach by using the posterio-lateral corner of the third ventricle as an anchor, instead of the center of the PC, improved the overall accuracy. 


Hargunbir SINGH (Boston, USA), Michaela STAMM, Aaron WARREN, John ROLSTON
15:00 - 15:05 #35995 - OP142 A phase 1 open-label trial of focused ultrasound unilateral anterior thalamotomy in focal onset epilepsy.
OP142 A phase 1 open-label trial of focused ultrasound unilateral anterior thalamotomy in focal onset epilepsy.

Objective: Focused ultrasound ablation (FUSA) is an emerging treatment for neurological and psychiatric diseases. We describe the initial experience from a pilot, open–label, single–center, clinical trial of unilateral anterior nucleus of the thalamus (ANT) FUSA in subjects with treatment-refractory epilepsy. 


Methods: Two adult subjects with treatment-refractory, focal-onset epilepsy were recruited. The subjects received ANT FUSA using the Exablate Neuro (Insightec, Inc.) system. We determined the safety and feasibility (primary outcomes), and changes in seizure frequency (secondary outcome) at 3, 6, and 12-months. Safety was assessed by the absence of side effects, i.e., new-onset neurological deficits or performance deterioration on neuropsychological testing. Feasibility was defined as the ability to create a lesion within the anterior nucleus. The monthly seizure frequency was compared between baseline and post thalamotomy.


Results: Both subjects tolerated the procedure well without neurological deficits or serious adverse events. One t experienced a decline in verbal fluency, attention/working memory, and immediate verbal memory. Seizure frequency reduced significantly in both: one subject was seizure free at 12-months, and in the second subject, the frequency reduced from 90-100 seizures per month to 3-6 seizures per month. 


Conclusion: This is the first known clinical trial to assess the safety, feasibility, and preliminary efficacy of ANT FUSA in adult subjects with treatment-refractory focal-onset epilepsy.

Vibhor KRISHNA, Jesse MINDEL, Francesco SAMMARTINO (Columbus, USA), Cady BLOCK, Alok DWIVEDI, Jamie VAN GOMPLE, Nathan FOUNTAIN, Robert FISHER
15:05 - 15:15 #36001 - OP143 Deep brain stimulation for epilepsy: meta-analysis of outcomes and connectomic underpinnings.
OP143 Deep brain stimulation for epilepsy: meta-analysis of outcomes and connectomic underpinnings.

Objective: The precise mechanism of neuromodulation in epilepsy is unknown and biomarkers are needed for optimizing treatment. The primary goal of the systematic review and meta-analysis is to describe recent advancements in the field of DBS for epilepsy, to compare the results of published trials, and to clarify the clinical utility of DBS in DRE. The secondary objective was to identify the neural network associated with deep brain stimulation (DBS) targets for epilepsy and to explore its application as a novel biomarker for neuromodulation.

Methods: A systematic literature search was performed by two independent authors. Forty-four articles were included in the meta-analysis (23 for anterior thalamic nucleus (ANT), 8 for centromedian thalamic nucleus (CMT), and 13 for hippocampus) with a total of 527 patients. 

Using functional connectivity maps weighted by seizure outcomes, brain areas associated with stimulation were identified in normative functional resting state scans of 1000 individuals. To pinpoint specific regions in the normative epilepsy DBS network, we examined overlapping areas of connectivity between the anterior thalamic nucleus (ANT), centromedian thalamic nucleus, hippocampus, and less studied epilepsy targets. We also retrospectively used MRI-derived brain morphological measures to examine preexisting neuroanatomical differences (n-15) and longitudinal changes (n=7) associated with successful treatment using deformation-based (DBM) analyses in long-term DBS of the ANT.

Results: The mean seizure reduction after stimulation of the ANT, CMT, and hippocampus in our meta-analysis was 60.8%, 73.4%, and 67.8%, respectively. DBS is an effective and safe therapy in patients with DRE. Based on the results of randomized controlled trials and larger clinical series, the best evidence exists for DBS of the anterior thalamic nucleus 

Cortical nodes identified in the normative epilepsy DBS network were in the anterior and posterior cingulate, medial frontal and sensorimotor cortices, frontal operculum and bilateral insulae. Subcortical nodes of the network were in the basal ganglia, mesencephalon, basal forebrain, and cerebellum. The ANT was identified as a central hub in the network with the highest betweenness and closeness values. The caudate nucleus and mammillothalamic tract also displayed high centrality values. The anterior cingulate cortex was identified as an important cortical hub associated with the effect of DBS in epilepsy. Two cortical clusters identified in the epilepsy DBS network included regions corresponding to physiological resting state networks, mainly the default mode and salience networks. The DBM analysis revealed volumetric changes in multiple cortical regions corresponding to the normative network of neuromodulation in epilepsy. Additionally, a smaller preoperative local volume of the amygdala was associated with better long-term response to DBS. The neural network of the DBS targets shared hubs with known epileptic networks and brain regions involved in seizure propagation and generalization. 

Conclusion: Recent studies confirm the satisfactory results of the anterior thalamic nucleus (ANT) deep brain stimulation (DBS) and hippocampal neuromodulation in drug-resistant epilepsy (DRE), including responsive neurostimulation (RNS). We described a brain network common to epilepsy neuromodulation based on normative functional connectivity. The cortico-subcortical network might underpin the mechanisms of epilepsy pathophysiology and effect of neuromodulation. In the future, DBS treatment could be tailored to individual patients and disease-specific networks.

Artur VETKAS (Toronto, Canada), Alexandre BOUTET, Sarica CAN, Nardin SAMUEL, Brendan SANTYR, Jürgen GERMANN, Kalia SUNEIL, Andres M LOZANO
15:15 - 15:20 #36047 - OP144 Stereotactic EEG using Leksell frame – safety, accuracy and speed in 100 consecutive implantations.
OP144 Stereotactic EEG using Leksell frame – safety, accuracy and speed in 100 consecutive implantations.


Stereotactic EEG (SEEG) was introduced by Talairach and Bancud in Paris in 1957. This technique for investigation of the epileptogenic zone has progressively spread from France through Italy to the rest of the world and nowadays is the most widely used technique for invasive EEG recording. The technical development and the introduction of computed tomography, magnetic resonance imaging, different angiographic studies and stereotactic frames improve the safety and the accuracy of the SEEG. The recent introduction of robotic stereotactic systems claims to add accuracy and speed to the classical stereotactic systems. The aim of our study is to evaluate the safety, accuracy and speed using our technique with magnetic resonance angiography and Leksell frame and to compare these parameters with the recent robotic SEEG series.

Matherial and Methods

Our study included our series of 100 consecutive SEEG implantations between January 2013 -and December 2022. Theavascular trajectory planning was based on a specific magnetic resonance angiography. The SEEG was carried out using Dixi electrodes, the Leksell G Frame, Surgiplan software (Elekta) and a frameless preoperative MRI with MR angiography fused with a stereotactic preoperative CT. We consider a safe avascular window on the entry point if the distance between the closest vessel and the center of the electrode is at least 2.5 mm.


Our series of 100 implantations including 31 SEEGs in children. The mean number of implanted electrodes was 16 (range: 12-18). We did not observe any postoperative complication in this consecutive series of 100 implantations (1586 electrodes). The accuracy on the pial surface was 0.85 mm ( range: 0.2-2.3 mm; standard deviation: 0.45mm). The accuracy on the target was 1.81 mm, range 0.3-3.5 mm (standard deviation: 0.91). The average speed was 10 minutes per electrode. 


The classical technique of frame based SEEG with avascular planning using MR angiography is fast, safe and accurate. The new frameless or frame based robotic systems have to look at least for the same results.

Krasimir MINKIN (Sofia, Bulgaria), Kaloyan GABROVSKI, Petar KARAZAPRYANOV, Velislav PAVLOV, Yoana MILENOVA, Petya DIMOVA
15:20 - 15:25 #36150 - OP145 Intraoperative microelectrode recording in deep brain stimulation for epilepsy: benefits and caveats. Experience of 28 ANT DBS patients.
OP145 Intraoperative microelectrode recording in deep brain stimulation for epilepsy: benefits and caveats. Experience of 28 ANT DBS patients.

Background: Surgical accuracy is crucial for successful deep brain stimulation therapy. Microelectrode recording (MER) is commonly used in movement disorder surgery to verify target nucleus intraoperatively based on its electrophysiological characteristics. The localizing value of MER for targeting ANT in patients with refractory epilepsy has not been studied in detail.

Objective: We compared the surgical targeting accuracy of 28 patients with refractory epilepsy by constructing three-dimensional models of MER samples along the actual lead trajectory through each individual patient’s thalamus.

Methods: 16 patients were operated under MER guidance (6 trajectories out of 32 were extraventricular) and 12 patients without MER. The deviation from planned trajectory, success rate of placing contacts in ANT and seizure reduction at 6 months compared to baseline were evaluated. Three dimensional models were created using Medtronic Suretune III software. Transventricular and extraventricular trajectories were also compared in relation to surgical targeting accuracy.

Results: MER signal characteristics correlated with imaging data in 85% of samples (neuronal firing in gray matter or no firing in white matter). Surgical accuracy was acceptable in both methods: deviation from planned trajectory was 1.2±1.2mm and 1.2±0.7 in non-MER and MER trajectories, respectively. Intraoperative MER did not increase success rate of placing contacts in ANT. In most of the cases with final electrode placement outside ANT, MER signals started markedly below the expected level, resulting in incorrect implantation depth (too deep). Extraventricular trajectory led to significantly more misplacements (83%) of the lead than transventricular (12%) trajectory, regardless of whether MER was used (p<0.001, Pearson Chi-Square test). MER had no significant effect on outcome as measured by seizure reduction.

Discussion: MER is relatively effective in differentiating white matter from gray matter. Early neuronal firing above the target suggests trajectory through ANT while later appearance of neuronal firing suggests lateral trajectory first through external medullary lamina followed by firing of neurons at the level of ventral anterior nucleus. Neuronal firing markedly below target level may arise from dorsomedial nucleus.

Conclusions: Transventricular implantation was surprisingly accurate even without the preliminary path performed by MER electrode. MER signal characteristics provide relatively reliable information about target tissue type. The level of first detected neuronal firing in relation to target level has localizing value, but information should be interpreted with caution. We recommend not to modify planned lead depth based on MER.

15:25 - 15:30 #36157 - OP146 High angular resolution diffusion weighted imaging and higher order tractography of the white matter tracts in the anterior thalamic area: Insights into DBS targeting in epilepsy.
OP146 High angular resolution diffusion weighted imaging and higher order tractography of the white matter tracts in the anterior thalamic area: Insights into DBS targeting in epilepsy.

Background: Deep brain stimulation of anterior nucleus of thalamus (ANT) is recently EU/US approved form of therapy for refractory focal epilepsy. It’s mechanism of action is not yet fully understood, and patient outcomes appear less consistent compared to movement disorders. Furthermore, very little anatomy -based information, such as tractography of relevant fiber systems, exists guiding DBS therapy at this moment. Objective: We aim to demonstrate ANT -related fiber systems based on histology in vivo using sophisticated 3T high angular resolution diffusion weighted imaging (HARDI) and multi-shell / multi-tissue constrained spherical deconvolution (MSMT-CSD) based deterministic and probabilistic tractography in healthy volunteers. Method: HARDI data was acquired from five healthy volunteers using 3 T Siemens MAGNETOM Skyra machine using multiple b-values (1000, 2000 and 3000) and 64 directions and further preprocessed for tractography. MSMT-CSD based deterministic and probabilistic tractography was performed from selected fiber systems based on existing literature. Results: Several fiber systems were identified: Anterior thalamic radiation, thalamo-cingulate tract, inferior thalamic peduncle (with remote termination areas in amygdala, ventral tegmental area and occipital cortex) and mammillothalamic tract. In addition, we observed three parallel connections to hippocampus (via cingulum bundle, fornix and tempro-pulvinar pathway). Interestingly, different seed areas in ANT complex mimicking DBS contact locations resulted in different predominant fiber systems in a systematic manner: (1) anterior deep seed location showed prominent inferior thalamic peduncle and its remote connections; (2) inferior aspect of ANT showed strongest anterior thalamic radiation and mamillo-thalamic tract connections; and (3) all seeds in ANT (but less at inferior aspect of ANT) were strongly connected to hippocampus via temporo-pulvinar pathway. Discussion: The connections of ANT are complex and different stimulation sites are likely to affect different networks depending on lead locations and the selection of the active contact. Conclusion: In depth understanding of the network of anatomical structures related ANT is likely to influence therapy outcomes. A hypothetical model is proposed for image guided DBS surgery and a clinical decision making to optimize therapy outcomes.



"Friday 29 September"

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15:30 - 16:00

Flash Poster Session 4 - Screen 1

Moderator: Oystein TVEITEN (Neurosurgeon) (Bergen, Norway)
15:40 - 15:45 #35720 - PF31 Spinal cord stimulation for the treatment of intractable, chronic pain in pediatric patients: a presentation of two cases.
PF31 Spinal cord stimulation for the treatment of intractable, chronic pain in pediatric patients: a presentation of two cases.

Background: Chronic pain in the pediatric population is a complex condition with an estimated prevalence as high as 10%. If untreated, it can adversely affect the psychological well being of children and lead to morbidity, opioid dependence and even mortality. Spinal cord stimulation (SCS) is a neuromodulation method approved by the FDA for pediatric use in 1989, with still limited data on its use - a recent systematic review by Karri et al. found 17 pediatric patients who received SCS implantation for chronic pain.


Methods: We retrospectively analyzed clinical data of pediatric patients who underwent SCS

implantation at the University Hospital Center Zagreb. Patients with chronic, intractable pain who failed conservative treatment were considered candidates for SCS implantation.


Results: A 14-year-old female patient with complex regional pain syndrome (CRPS) suffered from bouts of intractable pain (VAS 10/10) in her right wrist since the age of 8, accompanied by restricted range of motion in the radiocarpal joint. Similar symptoms occurred in her left foot at the age of 14. Due to failure of conservative treatment SCS was implanted for both pain regions (C2-C7 and Th10-L1). The patient was completely pain-free postoperatively, with improved range of motion of the affected joints.

A 15-year-old male patient with chronic demyelinating polineuropathy and neurogenic bladder reported intermittent intractable pain in both legs (VAS 9/10) since the age of 9. Upon failure of conservative treatment, SCS was implanted in the Th8-Th12 region. An excellent postoperative outcome was achieved, the pain resolved (VAS 3/10) and an improvement of bladder control was noted.


Conclusion: SCS in the treatment of intractable, chronic pain is an effective, albeit underutilized method in the pediatric population. Prospective, randomized studies should further evaluate the safety and efficacy of this method in a large pediatric cohort.

Jakob NEMIR (Zagreb, Croatia), Nina BARIŠIĆ, Niko NJIRIĆ, Barbara SITAŠ, Ervina BILIĆ, Zdravko HEINRICH, Goran MRAK
15:45 - 15:50 #35749 - PF32 Microsurgical challenges in the management of trigeminal neuralgia caused by vertebrobasilar dolichoectasia.
PF32 Microsurgical challenges in the management of trigeminal neuralgia caused by vertebrobasilar dolichoectasia.

Aims: Vertebrobasilar dolichoectasia (VBD) causing trigeminal neuralgia is rare. We discuss the clinical presentation and the techniques and challenges in microsurgical vascular decompression of the trigeminal nerve in patients with VBD.

Material and methods: We report 2 patients with medically refractory trigeminal neuralgia due to vertebrobasilar dolichoectasia who underwent microsurgical vascular decompression of the trigeminal nerve. We highlight their clinical presentation, neuroimaging, and intra-operative findings, and discuss the microsurgical techniques employed in managing these patients.

Results: Both of our patients were males, aged 53 and 61 years. Both were normotensives, with one patient having diabetes mellitus. Both had relatively shorter duration of symptoms- 3 years and 1 year. Neuroimaging in both these patients showed a tortuous and ectatic vertebrobasilar artery abutting the trigeminal nerve which was confirmed during surgery. Both patients underwent microsurgical vascular decompression. While it was possible to separate and keep the dolichoectatic vessel away using Teflon sheets in one patient, the other patient required a sling-clip technique to achieve and maintain satisfactory decompression. Both patients had immediate relief in pain with no recurrence on follow -up (3 months and 1 year).

Discussion: Vertebrobasilar dolichoectasia (VBD) is characterised by dilatation and elongation of the vertebrobasilar arteries. VBD causing Trigeminal Neuralgia is an extremely rare condition with an incidence of 0.05%.  Although VBD is known to be associated with hypertension, both of our patients were normotensives. Both patients had a relatively short duration of symptoms indicating the severity of facial pain and relative resistance to medical management. Microsurgical vascular decompression is technically challenging in these patients – mobilizing the ectatic arteries in the narrow working spaces between the cranial nerves, futility of arachnoidal dissection and shredded Teflon alone to keep the artery away, being conscious of the branches and perforators arising from the vertebrobasilar artery during mobilization, and to work around the variations in petrous bone anatomy. In-order to achieve and maintain the decompression from the trigeminal nerve we used different techniques in these patients. In one patient, we used Teflon sheets instead of shredded Teflon (Teflon wedge technique). In the other patient, we used a Teflon sling and gently pulled the artery away from the trigeminal nerve and anchored it to the petrous dura and secured it with an aneurysm clip (sling-clip technique). Both patients had good, sustained relief in their symptoms.

Conclusion: Microsurgical vascular decompression is an effective treatment option in trigeminal neuralgia caused by vertebrobasilar dolichoectasia. This procedure can be tailored based on the intra-operative neurovascular relationship, the bony and the vascular anatomy.

Sathwik SHETTY (BANGALORE, INDIA, India), Bopanna K M, Praveen GANIGI, Paritosh PANDEY
15:50 - 15:55 #35969 - PF33 Spinal cord stimulation in chronic, neuropathic pain after spinal cord injury – a single center case series.
PF33 Spinal cord stimulation in chronic, neuropathic pain after spinal cord injury – a single center case series.


Neuropathic pain after spinal cord injury (SCI) is one of the most challenging types of pain to treat. Up to 70 % of patients after SCI experience chronic central neuropathic pain (CNP). Spinal cord stimulation (SCS) can by applied in chronic neuropathic pain in Persistent Spinal Pain Syndrome (PSPS) and in Complex Regional Pain Syndrome (CRPS) but in CNP after SCI effectiveness of SCS is limited.

The aim of our study was to evaluate SCS use in patient with severe chronic neuropathic pain after SCI.


Among 112 patients treated due to neuropathic pain of a different origin mostly in the course of PSPS and CRPS in our department from 2019 to 2022, we selected 8 individuals (4 males and 4 females) with CNP caused by SCI. In 6 patients pathophysiology of pain was associated with traumatic SCI, in other two with stroke. In 4 cases electrode leads were implanted in cervical area and in 4 other cases in thoracic area.

We have assessed the effects of SCS in patients with CNS caused by SCI using NRS score Oswestry Inventory, the EQ-5D quality of life scale with follow-up to 1 year.


In follow-up of 1 year only in 2 individuals, the SCS proved to be effective with the reduction of pain over 50%, while in 6 it did not. 


Our results correspond with the findings in the literature. SCS in CNP after SCI has limited efficacy. Nevertheless, results of its treatment can be satisfactory in selected patients, when motor and sensory function is preserved.


Paweł SOKAL, Damian PALUS (Bydgoszcz, Poland), Oskar PUK, Magdalena JABŁOŃSKA, Sara KIEROŃSKA

"Friday 29 September"

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15:30 - 16:00

Flash Poster Session 4 - Screen 2

Moderator: Giorgio SPATOLA (Neurosurgeon) (Brescia, Italy)
15:40 - 15:45 #35693 - PF34 Association of anatomical navigation and microelectrode recordings to improve intraoperative targeting in deep brain stimulation surgery.
PF34 Association of anatomical navigation and microelectrode recordings to improve intraoperative targeting in deep brain stimulation surgery.

Introduction: Microelectrode Recording (MER) is considered a crucial feature of Deep Brain Stimulation (DBS). During asleep DBS, general anesthesia interferes with MERs, which are less straightforward to interpret in an intraoperative setting. Therefore, huge expertise is required to be able to base intraoperative lead localisation on MERs alone, risking sub-optimal final electrode placement. This study aims to investigate whether anatomical navigation during asleep DBS surgery is a reliable and useful additional tool. The intraoperative association of anatomical (imaging studies and 3D reconstructions) and electrophysiological (microelectrode recordings) information would in fact permit a facilitated surgical procedure.


Methods/Materials: This study is carried out on patients undergoing asleep DBS in the Pediatric and Functional Neurosurgery Department of Padova. During surgery, intraoperative MERs are integrated with deterministic anatomical imaging of the structures crossed by the trajectory, obtained using a dedicated software. This allows to visualize exact anatomical relationships of each point along the trajectory of the lead with the 3D reconstructed areas of interest. For Subthalamic Nucleus (STN) DBS these areas include the thalamus, the zona incerta, the STN and the substantia nigra, whereas for Globus Pallidus Internus (GPi) DBS these include the striatum, GPe, GPi, and the optic tract. To investigate whether this feature of anatomical navigation is a reliable and helpful additional factor in the decision-making for the placement of the definitive electrode, we compare the intraoperatively planned electrode placement with the postoperatively reconstructed electrode position.


Results: Preliminary results suggest that the mean distance between the intraoperatively planned target and the postoperatively reconstructed target is

Discussion: The study suggests that the association of intraoperative anatomical navigation to MERs significantly facilitates the evaluation of the optimal lead placement, given that there seems to be no relevant difference between the intraoperatively planned electrode placement and the postoperatively reconstructed electrode position.

Conclusion: Preliminary results suggest that the anatomical navigation is a useful and reliable tool to significantly facilitate the interpretation of intraoperative MERs.

Aldo SPOLAORE (Padova, Italy), Giulia Melinda FURLANIS, Luca SARTORI, Alessandro GRECO, Nicola BRESOLIN, Feifei WU, Valentina D'ONOFRIO, Alberto D'AMICO, Luca DENARO, Angelo ANTONINI, Andrea LANDI
15:45 - 15:50 #35711 - PF35 Long-term follow-up of bilateral pallidal stimulation for the treatment of genetically-proven myoclonus-dystonia syndrome in three individuals of a large family.
PF35 Long-term follow-up of bilateral pallidal stimulation for the treatment of genetically-proven myoclonus-dystonia syndrome in three individuals of a large family.


Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective and well-tolerated treatment for generalized dystonia. Rare reports confirm the clinical efficacy of bilateral GPi DBS for the treatment of myoclonus-dystonia syndrome.


We present a large family with genetically proven myoclonus-dystonia syndrome whose 3 members underwent bilateral GPi DBS. The study includes 1 woman and 2 men. The formal objective dystonia assessment included Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) its motor and disability parts. Myoclonus was assessed using the rest and action subscores of the Unified Myoclonus Rating Scale (UMRS). The patients were followed at regular ambulatory visits at 6 months, 1, 2 and 3 years after surgery. The baseline scores for myoclonus and dystonia were compared to postoperative scores in the stimulation on condition.



At the last follow-up visit (3 years after surgery), the rest and action parts of UMRS were improved by 98.5 %, and 90.5 % respectively when compared to baseline scores. The motor and disability scales of BFMDRS were improved by 85 % and 60 % at the last follow-up visit compared to baseline BFMRDS scores. There were no hardware or stimulation induced complications over follow-up period. The stimulation settings were relatively low when compared to another dystonic syndromes treated by DBS. Positive social adjustment allowed 2 patients to regain their jobs and 1 patient continued his education.


Bilateral GPi DBS is safe and highly efficacious method for treatment of intractable myoclonus-dystonia syndrome. In our observations, the effect of GPi DBS is recognized after 1 month of stimulation and is excellent for additional 3 years of continues stimulation. GPi DBS should be regarded as an valuable option for patients with severe, disabling, drug-resistance form of myoclonus-dystonia syndrome.  


Michał SOBSTYL (Warsaw, Poland), Jacek ZAREMBA, Angelika STAPIŃSKA-SYNIEC
15:50 - 15:55 #36008 - PF36 Pallidal deep brain stimulation improves HPCA-linked (DYT 2) dystonia.
PF36 Pallidal deep brain stimulation improves HPCA-linked (DYT 2) dystonia.

Dystonia is a movement disorder characterized by involuntary muscle contractions leading to repetitive movements or abnormal postures. Deep brain stimulation (DBS) is an effective option in medically refractory forms of idiopathic dystonia, and the target is usually the globus pallidus internus (GPi) bilaterally. Mutations in hippocalcin (HPCA) - DYT2 have been reported to cause a rare autosomal-recessive (AR) form of dystonia in a few cases with different phenotypes and treatment responses. To our knowledge, there is no report about DBS in dystonia patients with HPCA mutation. Here, we will present a dystonia case with an HPCA mutation who underwent bilateral GPi DBS. A 20-year-old male patient was admitted to the outpatient clinic with mild difficulties in walking and speech starting at the age of 8 years. His complaints increased over time, and he developed dystonia of the lower limbs at the age of 17 years. The dystonia spread to the upper extremities, trunk, and cervical and facial muscles within two years. He had jerky generalized dystonia in his neurological examination, mainly including trunk, arms, legs, neck, face, bulbar and laryngeal muscles, and also had mild dysphagia for both solids and liquids. HPCA:c.G28del-C; (p.P10PfsTer80) compound heterozygous mutation was detected in the molecular analysis. Biperiden treatment was started, and his posture partially improved with 12 mg/day. Botulinum toxin treatment was performed for his segmental dystonia. On the follow-up, his symptoms worsened, and oral medication and botulinum toxin treatment response decreased. He could not eat and drink independently and had difficulty sitting and walking because of jerky movements and generalized dystonia. He started to need assistance with activities of daily living. The patient underwent bilateral GPi DBS surgery at the age of 28 years. After DBS surgery, the jerky movements and upper limb dystonia decreased on the third day. He was able to eat and drink independently.   In the first year after the surgery, he could walk and sit independently and had no dysphagia. There were no jerky movements, and he was independent with the activity of daily living with the following stimulation parameters: right GPi, -2 +C, 3.3 mA, 60 msn, 130 Hz; left GPi, -3 +C, 2,8 mA, 60 msn, 130 Hz. The preoperative BFMDRS score was 80 and decreased to 39 in the postoperative period. He also had favorable impairment in all subdomains of SF-36.  The biperiden dose was reduced to 4 mg/daily. There are a few case reports in the literature about dystonia patients with HPCA mutations. However, to our knowledge, there has been no report of DBS in these patients yet, and this is the first report. For patients with HPCA-linked dystonia, pallidal DBS can be a treatment option. It is important to note that DBS is not a cure for genetic dystonia, and there are still many unanswered questions about the long-term effectiveness of the treatment. However, in cases where medication and other therapies have failed to provide relief, DBS is a valuable option for improving symptoms and quality of life for both patient and caregiver. 

Bedia SAMANCI, Erdi SAHIN, Yavuz SAMANCI (Istanbul, Turkey), Burcu ATASU, Ebba LOHMANN, Basar BILGIC, Selçuk PEKER, Hasmet HANAGASI

"Friday 29 September"

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15:30 - 16:00

Flash Poster Session 4 - Screen 3

Moderator: Kuan Hua KHO (Neurosurgeon) (Enschede, The Netherlands)
15:40 - 15:45 #35629 - PF37 Novel positioning system for Vantage stereotactical frame enabling accurate and two hands frame placement.
PF37 Novel positioning system for Vantage stereotactical frame enabling accurate and two hands frame placement.

Worldwide up to 100,000 radiosurgical procedures and around 25,000 DBS implantations are carried out yearly using a stereotactic frame. Moreover, intracranial lesion biopsies and stereotactic EEG electrode placement are also done using a frame-based technique. Appropriate frame positioning on the patient’s head is mandatory for optimal and error-free stereotactical MRI imaging. The stereotactic frame must be accurately placed on the patient’s head to ensure the images align correctly with the treatment plan. Incorrect placement can lead to final target coordinates calculation errors.

Conventional Leksell G and Vantage frame mounting methods are based on the usage of ear bars [1], over-the-head Velcro or mounted bar [2], additional plates for supine placement [3, 4], or bite bars [5]. Most of these methods are suitable for the Leksell G frame but not for a Vantage frame, presented a few years ago [6]. The Vantage frame was designed to be more comfortable for patients and surgeons, and its composition improved imaging capabilities. It is attached manually to provide initial stability using adhesive straps, and then the frame is finally fixed with titanium studs to the skull bone. Its fixation now requires at least two medical staff for optimal angles and alignment. The attachment process is inconvenient and impractical, and the fixation time is long and stressful for patients. Daily clinical practice shows that an attachment could be more precise and straightforward.

This research aims to design and investigate a novel, universal 3D positioning system of a stereotactic frame suitable for use with Leksell Vantage frame. The principal scheme of such a system is presented in Figure 1.

The proposed positioning system consists of two or four inflatables, soft silicone bladders, two hand pumps with discharge valves, two adjustable air distributors, and adhesive ("velcro" type) straps for additional fixation if needed for a specific size of the patient head.

The stereotactic frame positioning system prototype was evaluated with actual patients in The Hospital of Lithuanian University of Health Sciences Kauno Klinikos.

Due to the convenient design of the stereotacic frame positioning system prototype, intuitive usability and simply manipulated fixation system, the procedure time is shortened. The standard procedure took an average of 15min 44s ± 1.24 (SD) and the prototype frame positioning system took an average of 10min 40s ± 0.62 (SD). Due to the shorter procedure time and more convenient use, less stress was found for patients and the doctor.

Obtained results showed that it is possible to use a novel 3D positioning system, presented above – the number of personnel to perform the procedure is reduced, and the procedure is performed faster due to shorter preparation and procedure time, especially if the patient is restless or has uncontrolled movements.


This research was supported by the interinstitutional project StereoUp funded by Kaunas University of Technology and the Lithuanian University of Health Sciences.

Andrius RADZIUNAS (Kaunas, Lithuania), Sarunas TAMASAUSKAS, Arimantas TAMASAUSKAS, Darius EIDUKYNAS, Vytautas JURENAS, Vytautas OSTASEVICIUS
15:45 - 15:50 #35640 - PF38 Deep Brain stimulation and structural brain MRI changes in Parkinsons disease – preliminary study.
PF38 Deep Brain stimulation and structural brain MRI changes in Parkinsons disease – preliminary study.

Introduction: Deep Brain Stimulation (DBS) is established as effective therapy for advanced Parkinson's disease (PD). Despite significant symptom improvements with the use of DBS, the exact mechanism of DBS functioning as well as its effect on the central nervous system remains unknown. Furthermore, many issues are unresolved; what is the mechanism of DBS in PD, does DBS induce structural changes in basal ganglia due to stimulation or is it possible to quantify the reorganization of brain structures in PD patients? The aim of this study is to determine the structural changes caused by DBS in patients with PD using volumetric and tractographic analysis of magnetic resonance imagining (MRI).

Methods: In this study 10 patients with PD will perform preoperative and postoperative MRIs, which will, with the use of computer programs for volumetric analysis alongside tractographic analysis, provide insight into DBS effect on CNS structures. Ten PD patients underwent bilateral STN DBS electrode implantation. Brain MRI scans were done prior to the procedure, in a week after the procedure, and approximately two years after the electrode implementation. In depth and detailed volumetric analysis was done using automated, observer independent volumetric software, while tractographic analysis was done using TrackVis program.

Results: Structural changes have been showed using volumetric analysis at third measuring point, while tractographic parameters also showed altered data in both second and third measuring point.

Conclusion: The result of this study enables a better understanding of DBS activity in PD patients and provide data on potential structural brain changes in patients with PD and to provide a good starting point for further research.

Petar MARCINKOVIC, Marina RAGUŽ, Darko ORESKOVIC, Andelo KASTELANCIC, Marin LAKIC (Zagreb, Croatia), Nataša KATAVIĆ, Igor FUCKAN, Vladimira VULETIC, Darko CHUDY
15:50 - 15:55 #35679 - PF38b Monitoring of heart rate and activity for severity assessment in the unilateral and bilateral 6-OHDA rat Parkinson model.
PF38b Monitoring of heart rate and activity for severity assessment in the unilateral and bilateral 6-OHDA rat Parkinson model.

Introduction: In animal experimentation, welfare and severity assessments of all procedures applied to animals are necessary to meet legal and ethical requirements, as well as public interests. Injection of 6-hydroxydopamine (6-OHDA) into the nigrostriatal system of rats is used as a model for Parkinson's disease (PD) to investigate the pathophysiological background and treatment. The classical method of unilateral intranigral infusion of 6-OHDA leads to a massive destruction of nigrostriatal dopaminergic neurons and concomitant motor disturbances. After daily injection of Levodopa, these rats develop dyskinesias, a devastating side effect after long-term treatment in PD patients. In the bilateral model, 6-OHDA infused into the striatum, leads to slow and incomplete retrograde degeneration of dopaminergic neurons. This model can be used to study the development of PD or cognitive function. For severity assessment, we here quantitatively measured weight, heart rate and activity in the unilateral and bilateral 6-OHDA model, as well as during 21 days of Levodopa injection.

Methods:  In male Sprague Dawley (SD) rats (n=16) a telemetric device was subcutaneously implanted under general anesthesia and perioperative pain management. After recovery for four weeks, rats received either unilateral stereotaxic injection of 6-OHDA into the substantia nigra (n=8) or bilateral injection into the striatum (n=8). Four weeks after unilateral 6-OHDA injection, rats were subcutaneously injected with Levodopa (10 mg/kg) for 21 days. Perioperatively and during 21 days of Levodopa injection we measured weight, heart rate and activity during the first two hours after light on and light off, as well as directly before and after Levodopa injection.

Results: Striatal bilateral injection of 6-OHDA led to weight loss for the first four postoperative days (two rats nearly 20% of their preoperative weight; p<0.05), while unilateral 6-OHDA injection had no effect. Heart rate was enhanced for the first postoperative three days in both models, while activity measures were not affected after surgery.  Levodopa injection for 21 days in the unilateral 6-OHDA model had no effect on weight and heart rate, but enhanced activity measures assessed via the subcutaneous telemetric device.

Conclusion: The results indicate that perioperatively rats` wellbeing is more affected by bilateral injection of 6-OHDA with incomplete loss of nigral dopamine, although heart rate measures also indicate disturbed wellbeing after unilateral injection of 6-OHDA. The development of dyskinesias, however, has only mild and transient effects on rat`s wellbeing.

Marcel Roland OELERICH (Hanover, Germany), Ann-Kristin RIEDESEL, Mesbah ALAM, Joachim K. KRAUSS, Kerstin SCHWABE
15:55 - 16:00 #36106 - PF39 Focused Ultrasound Thalamotomy for Parkinsonian Tremor in the Setting of a Ventricular Shunt: Technical Report.
PF39 Focused Ultrasound Thalamotomy for Parkinsonian Tremor in the Setting of a Ventricular Shunt: Technical Report.

Background: To date, only one case report (1) of magnetic resonance imaging (MRI)-guided focused ultrasound (FUS) for essential tremor (ET) has demonstrated safety and efficacy of the procedure in a patient with a ventricular shunt.

Objective: To demonstrate the feasibility of FUS thalamotomy in patients with ventriculo-peritoneal shunts and tremor-dominant Parkinson's disease, provided careful planing and the strict observation of safety measures.

Methods: A 80-yr-old right-handed male with medically refractory tremor-dominant Parkinson's disease, more prominent on his right hand, and a right-sided ventricular shunt for normal pressure hydrocephalus, underwent FUS to the left ventro-intermedius (VIM) nucleus. The VIM nucleus was targeted using indirect targeting based on AC PC, refined with deterministic tractography. Clinical outcomes were measured using on-medication Clinical Rating Scale for Tremor A+B on the treated hand, with a follow-up of seven months.

Results: Shunt components required 7% of the total ultrasound transducer elements to be shut off. Nine therapeutic sonications were delivered, (maximum temperature, 69°), with constant checking of cavitation and/or defocusing. The procedure led to a 80% improvement in hand tremor and a 90% improvement in functional disability at the 7-mo follow-up. No complications were noted.

Conclusion: This is the second case reported of FUS thalamotomy in a patient with a ventricular shunt, and the first on a case of tremor-dominant Parkinson's disease. Achievement of therapeutic temperatures without cavitation and thermal spot distortion is feasible in this subset of patients.

(1) Yang AI, Chaibainou H, Wang S, Hitti FL, McShane BJ, Tilden D, Korn M, Blanke A, Dayan M, Wolf RL, Baltuch GH. Focused Ultrasound Thalamotomy for Essential Tremor in the Setting of a Ventricular Shunt: Technical Report. Oper Neurosurg (Hagerstown). 2019 Oct 1;17(4):376-381. doi: 10.1093/ons/opz013. PMID: 30888021.

Jordi RUMIÀ ARBOIX (Barcelona, Spain), Francesc VALLDEORIOLA, Javier TERCERO, Meritxell AZANUY, Gabriel SALAZAR

"Friday 29 September"

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16:00 - 17:00

Imaging & Neuronavigation

Moderators: Harith AKRAM (Associate Professor) (London, United Kingdom), Rene MARQUEZ-FRANCO (Researcher fellow / PhD Candidate) (Cologne, Mexico)
16:00 - 16:10 #34710 - OP147 Seven years of 7-tesla in deep brain stimulation for parkinson’s disease: pinpointing the dorsolateral stn.
OP147 Seven years of 7-tesla in deep brain stimulation for parkinson’s disease: pinpointing the dorsolateral stn.

Background: Identifying the dorsolateral subthalamic nucleus (STN)  for deep brain stimulation (DBS) in Parkinson’s disease (PD) can be challenging due to the small size and double-oblique orientation of this nucleus. Since 2015 we implemented 7-Tesla T2 weighted magnetic resonance imaging (7T T2) for improving visualization and targeting of the dorsolateral STN. Here we describe the changes in surgical planning and outcome since the implementation of 7T T2 for DBS in PD.

Methods: By comparing two time periods (2007-2014 and 2015-2022), we evaluate the influence of 7T T2 on STN target planning, the number of microelectrode recording (MER) trajectories, length of STN activity and the 6 months postoperative motor (UPDRS) improvement.

Results: From February 2007 to January 2014, in 76 PD patients, representing 146 STNs, 1.5 and 3-Tesla T2 guided STN DBS was performed. Three simultaneous MER channels were performed in all and the central trajectory was chosen for implantation in 39%. Average length of STN activity for the definite electrode was 3.9 ± 1.5 mm. From January 2015 to January 2022, in 182 PD patients, representing 360 STNs, 7T T2 and MER guided STN DBS was performed. The central trajectory was chosen for implantation in 81%, and used MER decreased from 3 trajectories to 1. The average length of STN activity was 5.1 ± 1.3 mm and the distance from target to dorsolateral border showed an increase (2015 2 mm to 2021 5 mm). The average total UPDRS improvement was comparable (46% and 48%, respectively).

Conclusion: Implementation of 7T T2 for STN DBS enabled aligning trajectories to dorsolateral STN and resulted in longer electrophysiological recordings; representing a refinement in targeting and surgical efficiency. Combining classical DBS targeting tools (MRI landmarks) with dorsolateral STN alignment may be used to directly determine the optimal DBS trajectory. Considering the improvement in dorsolateral STN visualization, an increase in UPDRS improvement is expected by adding probabilistic subthalamic connectivity.

Lisa VERLAAT (Amsterdam, The Netherlands), Niels RIJKS, Jose DILAI, Marjolein ADMIRAAL, Martijn BEUDEL, Rob DE BIE, Wietske VAN DER ZWAAG, Rick SCHUURMAN, Pepijn VAN DEN MUNCKHOF, Maarten BOT
16:10 - 16:20 #35754 - OP148 Segmentation of the subthalamic nucleus from clinical MRI: combining registration and deep learning.
OP148 Segmentation of the subthalamic nucleus from clinical MRI: combining registration and deep learning.

Precise segmentation of the subthalamic nucleus (STN) is crucial for accurate deep brain stimulation (DBS), where adverse outcomes can often be attributed to sub-optimal lead placement. The gold-standard of manual segmentation remains time-consuming and introduces human bias. As a result, large population studies that use manual segmentations as ground truth remain resource-expensive, hindering the progress of group comparisons to identify optimal lead placement, or morphological studies for disease progression.

Atlas registration methods fail to fully consider individual variability. This limitation is accentuated in the STN, where morphological changes depend on Parkinson’s disease progression. Furthermore, previously developed automatic segmentation algorithms have struggled with the close topographical relationship between the STN and neighbouring deep brain structures of similar contrast.

We present Auto-STN, a robust, accurate, and fully automated neural network to segment the STN on clinical T1w and T2w magnetic resonance imaging (MRI). The goal is to minimise variability in STN targeting and eliminate human biases, through standardising pipelines across MR protocols. Auto-STN incorporates subject-specific STN probability priors, so that spatial context and anatomical variability are fully considered.

Our dataset consists of 120 T1w and T2w scans from STN-DBS patients, acquired at 1.5, 3, and 7 T magnetic field strengths. Auto-STN was trained with a randomised 60:10:30 split of training, validation, and test subjects. We compare the performance of Auto-STN with the leading academic and industry algorithms, DBSegment (Baniasadi et al., 2023) and Brainlab Elements (Release 4.0; Brainlab AG, Germany).

We achieve an average Dice score similarity (DSC) of 0.92 across unseen clinical test scans, significantly higher compared to DBSegment (0.71) and Brainlab (0.38) (P < 0.0001). Notably, we report no statistical significance of Auto-STN performance between left and right STNs, in contrast to significant bilateral discrepancies in DBSegment and Brainlab predictions. We further measure Hausdorff distance (HD), a surrogate marker of border accuracy. The mean HD of 1.78 mm from Auto-STN approaches the margin of error threshold of 1.5 mm, beyond which we would relocate implanted leads at the National Hospital for Neurology and Neurosurgery. In contrast, HD from Brainlab and DBSegment generally exceed 4.5 mm. Our framework also demonstrated robust adaptability to unseen sequences. When trained only on 1.5 and 3 T scans, Auto-STN successfully generalised to unseen 7 T scans.

Taken together, Auto-STN helps eliminate human biases associated with manual segmentation, standardise protocols for planning and programming, and facilitate large cohort studies with improved automatic segmentation of the STN.

Tsi-Lok HO (London, Hong Kong), Francisca FERREIRA, Mikael BRUDFORS, Maarten BOT, John ASHBURNER, Harith AKRAM
16:20 - 16:30 #35759 - OP149 Structural connectivity of the ansa lenticularis using the stereotaxic “tenth” method.
OP149 Structural connectivity of the ansa lenticularis using the stereotaxic “tenth” method.


Radiofrequency lesioning in the Forel Fields (campotomy) has been used to treat movement disorders. Deep brain stimulation (DBS) targeting white matter regions has proven more effective at improving certain symptoms than targeting nuclei. However, the structural connectivity of these regions in humans remains inadequately described. Identifying the Ansa Lenticularis (AL) for surgical planning could potentially enhance symptom-specific surgeries for patients with movement disorders.


The objective of the study was to characterize the structural connectivity using probabilistic tractography of the AL, a white matter tract connecting the ventrolateral thalamus and globus pallidus.


We retrospectively evaluated 16 patients with Parkinson's Disease (PD) and 16 healthy subjects, matched by age and gender, using 3T diffusion-weighted magnetic resonance imaging (dMRI). We performed constrained spherical deconvolution and anatomically constrained probabilistic tractography, defining the structural connectivity of the AL in a quantitative connectivity matrix. To define the stereotactic location of the AL, we measured distances “x”, “y”, and “z” of the coordinates taken in mm from the Schaltenbrand and Wahren (S&W) Atlas and standardized distances by dividing the AC-PC line distance into ten equal parts. Thereafter, we assessed specific structural connectivity, using four cortical and subcortical brain atlases: the ATAG_basal_ganglia, HCP842_tractography, FreeSurferDKT_Cortical, and Subcortical. They were used for brain parcellations, and quantitative connectivity matrices were calculated using the count of the connecting tracks between anatomical regions of the brain.


The study found that AL structural connectivity was consistently observed in both groups, with fibers connecting to various brain regions involved in the motor circuit, cortico-striatal pathway, and frontopontine tracts. Both the "mm" and "tenth" methods demonstrated structural connectivity with the striatum, globus pallidus internus, and externus; however, the "tenth" method provided a more specific representation of the AL and its structural connectivity across different atlases.


Structural connectivity of the AL was consistent between patients and controls, with some regions showing statistically significant differences in connectivity between the two groups. The specificity of the "tenth" method in each individual suggests that using this approach could improve the accuracy of surgical planning for localizing the AL and other white matter tracts. This method could potentially target white matter tracts at the point of maximum connectivity of fibers, offering a more efficient and precise strategy to plan white matter tract locations for optimizing stereotactic surgery in the future. Further studies with larger cohorts are needed to confirm these findings.

Francisco VELASCO, Rene MARQUEZ-FRANCO (Cologne, Mexico), Jose CARRILLO, Luis CONCHA
16:30 - 16:35 #36012 - OP150 MR Imaging and proton MR Spectroscopy follow-up of LITT-treated hypothalamic hamartomas.
OP150 MR Imaging and proton MR Spectroscopy follow-up of LITT-treated hypothalamic hamartomas.

Introduction: Hypothalamic hamartomas (HH) can cause pharmacoresistant epilepsy and may be treated by Laser Interstitial Thermal Therapy (LITT), a minimally invasive Magnetic Resonance Imaging (MRI)-guided neurosurgical procedure. To our knowledge, no previous studies dealing with spectroscopic and metabolic patterns of treated HH by LITT have been published.

Purpose:  The aim of this study was to characterize the evolution of MRI and Magnetic Resonance Spectroscopy (MRS) patterns during a follow-up of LITT-treated HH.

Methods: 7patients (5/7 patients under 20 years old) underwent MRI (T1, T2 FLAIR, T2*, Diffusion, Perfusion and 3DT1 post-Gadolinium) and proton MRS (PRESS sequence with 3 Echo Times of 35 ms, 144 ms and 288 ms) exams on 1.5T GE MRI scanner. MRI and MRS data were collected pre-operatively, at immediate post-operative, at D3/D5 post-operative, at M3 and M6 post-operative.

Results: Clinical LITT efficiency was based on the reduction of the number of epilepsy crises and the improvement of electroencephalogram patterns. MRI results revealed that the lesion volume decreased of about 30 – 50 % during follow-up. Post-surgical edema volume measured on FLAIR sequences was maximal at D3/5 after LITT procedure and then continuously decreased during the follow up. An increased peripheral diffusion hypersignal volume was measured at immediate post-operative and at D3/D5 post-operative, which then tended to normalize starting from M3 postoperative control. MRS results, based on ratios metabolites quantification [metabolites: Creatine (Cr), N-acetyl-aspartate (NAA), Choline (Cho), Myo-inositol (mI), lactate (lac)], depicted a decreased NAA/Cr ratio (6/7 patients) in the treated tissue at D3/D5 postoperative, an increased Cho/Cr ratio and increased quantities of lactate (increase of the lac/Cr ratio) at immediate postoperative and at D3/D5 post-operative controls, which improved over time.  Moreover, SRM depicted a glial reaction (as measured by an increase of the mI/Cr ratio) during the LITT procedure in the treated tissue in 5/7 patients, that was normalized at D3/D5.

Discussion and conclusion: The present results, although preliminary, provide an overview of the MRI, spectroscopic and metabolic features evolution of the LITT-treated HH. From our experience, the study of these changes evolution was relevant to better assess LIIT efficiency on pharmacoresistant epilepsy and we expect that may help in the future for the early detection of potential recurrence of HH. Further investigations with a larger data follow-up, as well as an evaluation of the effect of LITT- treated HH on distant brain regions will be carried out. Relations between MRI/MRS features and clinical data will be studied in order to improve the analysis, interpretation, and monitoring of this clinically recognized innovative minimally invasive neurosurgery procedure.

16:35 - 16:40 #36059 - OP151 3-Tesla Diffusion weighted MRI: from Intraoperative to Anatomical Evaluation of the Corticospinal Tract in Deep Brain Stimulation.
OP151 3-Tesla Diffusion weighted MRI: from Intraoperative to Anatomical Evaluation of the Corticospinal Tract in Deep Brain Stimulation.

Background: Deep brain stimulation (DBS) for Parkinson’s disease (PD) is increasingly being performed under general anesthesia (asleep DBS). As a result, the possibility of intraoperative evaluation for side effects is lost. Diffusion weighted imaging (DWI) can be used for depicting the corticospinal tract (CST); serving as anatomical substitute.


Methods: CST depiction by 3.0-Tesla (3T) DWI MRI was compared with the CST localisation during test-stimulation in patients undergoing DBS for PD. Depiction of the CST was done using deterministic tractography in DBS planning software. Stimulation threshold for involuntary contractions during awake DBS and distance to respective microelectrode track were used for comparison. Electrode localization was done using intraoperative cone beam CT.


Results: A total of 191 test stimulation sites in 75 microelectrode tracks were evaluated. Correlation between electrode distance to CST and occurrence of intraoperative involuntary contractions was strong and significant (r = .6, p= <.02). For 4.3 mm distance or more no involuntary contractions occurred; for less than 2.0 mm involuntary contractions always occurred. From 2.0 to 4.3 mm in 11% involuntary contractions were seen.



The occurrence of involuntary contractions during test-stimulation and the distance to CST depiction using deterministic tractography correlated well. Construction of the CST was done using regions of interests in motor cortex and cerebral peduncle. This method provides a readily implementable technique for CST depiction and a safety margin; a distance of 2.0 mm from electrode to the corticospinal tract depiction can be considered sufficient during STN DBS planning.

Niels RIJKS (Amsterdam, The Netherlands), José BILAI, Richard SCHUURMAN, Pepijn VAN DEN MUNCKHOF, Rob M.a. DE BIE, Martijn BEUDEL, Maarten BOT
16:40 - 16:50 #36113 - OP152 Improvement in motor functioning and quality of life following deep brain stimulation in Parkinson’s disease visualized by 7-Tesla MRI subthalamic network analysis.
OP152 Improvement in motor functioning and quality of life following deep brain stimulation in Parkinson’s disease visualized by 7-Tesla MRI subthalamic network analysis.

Background: Although many Parkinsonian patients benefit from subthalamic nucleus deep brain stimulation (STN-DBS), improvement in motor functioning and quality of life after DBS highly varies between individual patients. Average reported improvement has not increased in the past 10 years. The effect of DBS relies on the modulation of malfunctioning brain networks by delivering electrical pulses within the STN. By visualizing these networks using 7-Tesla MRI, insight in active contact location, improvement and subthalamic network modulation can be obtained; possibly enabling patient-specific network-guided-DBS.

Methods: All patients underwent 7-Tesla (7T) MRI with diffusion-weighted sequences. Three major STN projections (networks) were identified and masked: one from STN to primary and supplementary motor cortex (motor), a second to the prefrontal cortex (associative) and a third to the basofrontal cortex (limbic). For each active contact, the total connectivity per network was expressed as a percentage (range 0-100%), by using the total connectivity of the respective STN (network connectivity divided by the total connectivity; connectivity numbers calculated using the probabilistic segmentation software). As a result, the 7T MRI network analysis visualized for each active electrode contact; 1) in which segment (subdivision) of the STN it was located and 2) the surrounding projections per network (the connectivity per network, expressed as a percentage). Hemi-body motor improvement (Movement Disorder Society Unified Parkinson’s Disease Rating Scale Motor Section, MDS-UPDRS III), apathy (Starkstein Apathy Scale) and quality of life (QoL, Parkinson's disease questionnaire-39 item version, PDQ-39) were assessed at baseline and after a 6 month follow-up. Outcome scores were readily available from our advanced electronic DBS database.

Results: Sixty-five patients (18 women, age [mean ± SD]: 61.8 ± 8.9 years) who underwent bilateral STN-DBS were included in the study. Electrode contacts surrounded by a high density of motor projections resulted in more motor improvement (77% vs. 44% MDS-UPDRS III improvement, p<0.001). Electrode contacts surrounded by a high density of associative projections resulted in less motor improvement (39% vs. 61%, p=0.003) and QoL (3.5 vs. 12.5 points, p=0.015). Occurrence of apathy was seen in electrode contacts surrounded by a high density of associative and limbic projections, and a low density of motor projections.

Conclusions: Patient-specific subthalamic 7T MRI network analysis visualized an anatomical connectivity substrate for motor improvement, quality of life and apathy in DBS. After six months of DBS, active electrode contacts surrounded by a high density of motor projections and low density of associative/limbic projections resulted in more motor improvement and QoL. By using 7T MRI network analysis, DBS-electrode placement and activation can be individualized, which will likely further improve motor functioning and quality of life.

Naomi KREMER (Amsterdam, The Netherlands), Teus VAN LAAR, Marc VAN DIJK, Katalin TAMASI, Varvara MATHIOPOULOU, Niels RIJKS, Yarit WIGGERTS, Martijn BEUDEL, Rob DE BIE, Pepijn VAN DEN MUNCKHOF, Rick SCHUURMAN, Maarten BOT
16:50 - 16:55 #36117 - OP153 Applications of augmented reality for intraoperative targeting.
OP153 Applications of augmented reality for intraoperative targeting.

Introduction: Augmented reality (AR) is a technological megatrend that is increasingly being applied in many areas. The availability of this technology increasingly prompts the question of meaningful applications in clinical practice. Since the available AR glasses are not yet approved as medical devices for intraoperative use, we tested various use cases in phantom experiments.

Methods: With the use of AR glasses (Magic Leap 1) in combination with planning software (Elements, Brainlab, Munich), various use cases were systematically investigated. For this purpose, we examined the placement accuracies on phantoms and compared them with the respective standard methods:

1.  In order to compare the placement of bleeding drains in intracranial haemorrhage, 5 surgeons performed a total of 60 operations on a phantom. They used either a free-hand, a stereotactic frame-based or an AR-guided method.

2. Percutaneous placement of a cannula into the foramen ovale was investigated for the treatment of trigeminal neuralgia. Four subjects performed 64 placements (AR compared to standard landmark-based method).

3. To puncture a defined peridural target in the lumbar spine, 4 physicians placed a cannula 40 times with AR and 40 times hands-free. 

All punctures were performed in randomised order. Placement accuracies were determined using computer tomography of the phantoms.

Results: AR was significantly more accurate compared to freehand in all cases studied (p<0.001 for bleeding drains, p<0.01 for gasserian ganglion and p<0.0001 spinal). Even though frame-based stereotactic placement of bleeding drains had a higher accuracy (median deviation 1.95mm), the accuracy achieved with AR was still within acceptable limits for an emergency bedside procedure (median 3mm, p=0.023), in contrast to freehand puncture (median 11.1mm, p<0.001).

Discussion: For applications that are currently performed landmark-based in clinical practice (e.g. foramen ovale puncture or spinal puncture) or where the procedure must be performed quickly and directly at the patient's bedside due to emergency (e.g. bleeding or external ventricular drain), AR is an interesting technological enhancement. It has the potential to improve various puncture procedures in the future and to support the education and training of physicians.

Peter C. REINACHER (Freiburg, Germany), Roland ROELZ, Amin STANICKI, Nils SCHALLNER, Volker A. COENEN, Theo DEMERATH
16:55 - 17:00 #36133 - OP154 Accuracy verification of thalamic auto-segmentation by intraoperative microelectrode recording.
OP154 Accuracy verification of thalamic auto-segmentation by intraoperative microelectrode recording.

Background: Most surgical techniques for tremor control target the ventral intermediate nucleus of the thalamus (Vim nucleus), but it has been difficult to visualize the subnucleus of the thalamus. Recently, very accurate anatomical mapping has become available and is beginning to be utilized in surgery, but its accuracy is unknown. We compared intraoperative microelectrode recording (MER) with anatomical mapping on image analysis tools to verify its accuracy. 

Methods: Five patients (one with Parkinsons disease and four with essential tremor) who underwent Vim DBS at our institution were included. Th