Friday 10 September

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
08:30 - 10:00

Plenary Session 4

Moderators: Raphaëlle RICHIERI (marseille, France), Rick SCHUURMAN (neurosurgeon) (Amsterdam, The Netherlands), Veerle VISSER-VANDEWALLE (Head of Dep. of Ster. and Funct. NS) (Cologne, Germany)
08:30 - 08:50 Dementia and nucleus basalis of meynert. Ludvic ZRINZO (Professor of Neurosurgery) (London, UK, United Kingdom)
08:50 - 09:10 OCD. Rick SCHUURMAN (neurosurgeon) (Amsterdam, The Netherlands)
09:10 - 09:30 #24089 - Surgery for addiction: animal models suggest to target the subthalamic nucleus.
Surgery for addiction: animal models suggest to target the subthalamic nucleus.

Addiction remains a public health issue with few options for treatment. With the development of deep brain stimulation (DBS) for psychiatric disorders such as treatment-resistant depression, obsessive compulsive disorders, a few groups have started to consider DBS as a possible treatment for addiction. Most of them have suggested that the Nucleus Accumbens (NAc) could be the target. However, manipulating the activity of the NAc may reduce the motivation to take drugs but may also reduce any form of motivation. In contrast, lesion or DBS of the subthalamic nucleus (STN) can reduce motivation for cocaine without reducing motivation for food reward in both rats and monkeys. STN DBS has been shown to be beneficial on various criteria of addiction (loss of control over drug intake, compulsive drug seeking) in rats and these effects can be generalized for cocaine, but also heroin and alcohol. STN DBS seems thus to be an interesting strategy to treat addiction.

Christelle BAUNEZ (Marseille)
09:30 - 09:50 Novelty in Psychiatric Surgery. Volker COENEN (Head of Department) (Freiburg, Germany)
09:50 - 10:00 Discussion.
Grand Amphithéâtre

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
10:30 - 12:00

Plenary Session 5
Brain Prediction

Moderators: Linda ACKERMANS (Neurosurgeon) (Maastricht, The Netherlands), Lorand EROSS (Director of the institute) (Solymar, Hungary), Maxime GUYE (Neurologist) (Marseille, France), Viktor JIRSA (Director INS) (Marseille, France)
10:30 - 10:50 Predicting surgery outcome using patient-specfic virtual brain models in epilepsy. Viktor JIRSA (Director INS) (Marseille, France)
10:50 - 11:10 Augmenting diagnosis, inferring mechanisms, and predicting intervention outcomes in neurodegenerative disease through personalized Virtual Brain Cloud simulations. Petra RITTER (Berlin, Germany)
11:10 - 11:30 Diagnosis and prognosis of epilepsy using predictive mathematical models. John TERRY (London, United Kingdom)
11:30 - 11:55 Mapping brain response patterns to DBS with fMRi. Andres LOZANO (Tasker Chair in Functional Neurosurgery, University of Toronto) (Toronto, Canada)
11:55 - 12:00 Discussion.
Grand Amphithéâtre

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
10:30 - 12:00

Parallel Session 9b
Movement disorders

Moderators: Nicolas REYNS (Professor of Neurosurgery) (LILLE, France), Giorgio SPATOLA (Neurosurgeon) (Brescia, Italy), Pepijn VAN DEN MUNCKHOF (Neurosurgeon) (Amsterdam, The Netherlands)
10:30 - 10:35 #23973 - Evaluating and optimizing Dentato-Rubro-Thalamic-Tract Deterministic Tractography in DBS for Essential Tremor.
Evaluating and optimizing Dentato-Rubro-Thalamic-Tract Deterministic Tractography in DBS for Essential Tremor.

Background: Dentato-rubro-thalamic tract (DRT) deep brain stimulation  (DBS) suppresses tremor in essential tremor (ET) patients. However, DRT depiction through tractography can vary depending on the included brain regions. Moreover, it is unclear which section of the DRT is optimal for DBS.

Objective: Evaluating  deterministic DRT tractography and tremor control in DBS for ET.

Methods: After DBS surgery, DRT tractography was conducted in 37 trajectories (20 ET patients). Per trajectory, 5 different DRT depictions with various regions of interest (ROI) were constructed. Comparison resulted in an DRT depiction with highest correspondence to intraoperative tremor control. This DRT depiction was subsequently used for evaluation of short term postoperative adverse and beneficial effects.

Results: Postoperative optimized DRT tractography employing the ROIs motor cortex, posterior subthalamic area and ipsilateral superior cerebellar peduncle and dentate nucleus best corresponded with intraoperative trajectories (92%) and active DBS contacts (93%) showing optimal tremor control. DRT tractography employing a red nucleus or ventral intermediate nucleus of the thalamus ROI often resulted in a more medial course. Optimal stimulation was located in the section between VIM and PSA.

Conclusion: This optimized deterministic DRT tractography determination strongly correlates with optimal tremor control and shows limited side-effects. This technique is readily implementable for DBS target planning in ET. 

Figure legend

The panels A to G show the different possible depictions of DRTs which are used for comparison. The above panel shows an axial, the bottom a coronal view on a 3-Tesla T2 MRI of the thalamic and subthalamic area (commissural aligned imaging). The green DRT is depicted with ROIs in the ipsilateral motor area, ipsilateral PSA, ipsilateral cerebellar peduncle and dentate nucleus (DRT-PSA). The DRT-VIM (purple) is depicted after adding VIM (depicted by the software) as a ROI. The DRT-RN (orange) is depicted with ROIs in ipsilateral motor area, ipsilateral red nucleus, ipsilateral cerebellar peduncle and dentate nucleus (DRT-RN). The crossing DRT-RN (red) crosses the midline at the level of the red nucleus, and is depicted with ROIs in the ipsilateral motor area, and RN, contralateral cerebellar peduncle and dentate nucleus. The definite DBS electrode (yellow) is displayed. Panel A is located 2 mm above the commissural line, panel B at the commissural line, panel C is located 2 mm below the commissural line, panel D is located 4 mm below, panel E is located 6 mm below, panel F is located 8 mm below and panel G is located 10 mm below.

Maarten BOT (Amsterdam, The Netherlands), Fleur ROOTSELAAR, Vincent ODEKERKEN, Joke DIJK, Rob DE BIE, Pepijn VAN DEN MUNCKHOF, Rick SCHUURMAN
10:40 - 10:45 #23983 - Utilising 7-Tesla Subthalamic Nucleus Connectivity in Deep Brain Stimulation for Parkinson’s Disease.
Utilising 7-Tesla Subthalamic Nucleus Connectivity in Deep Brain Stimulation for Parkinson’s Disease.

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a highly effective surgical treatment for patients with advanced Parkinson’s disease (PD). Combining 7.0-Tesla (7T)  T2 and diffusion weighted (DWI) sequences allows for segmenting the motor part of the STN and possible optimisation of DBS.


Methods: 7T T2 and DWI sequences were obtained and probabilistic segmentation of motor, associative and limbic STN subdivisions was performed. Left and right sided motor outcome (MDS-UPDRS) scores were used for evaluating the correspondence between segmented location of stimulation and DBS effect. The Bejjani line was reviewed for crossing of segments.


Results: A total of 50 STNs were segmented in 25 patients. Due to the high resolution of the sequences, segmentation was well feasible using 7T T2 and DWI. Although the highest density of motor connections was situated in the dorsolateral STN for all, exact partitioning of subdivisions differed considerably. For all the active electrode contacts situated within the predominantly motor-connected segment of the STN, the average hemi-body UPDRS motor improvement was 80%, outside this segment 52%. The Bejjani line was situated in the motor segment for 32 STNs.  


Conclusion: The implementation of 7T T2 and DWI for STN segmentation in DBS for PD is feasible and offers insight in location of the motor segment. Segment guided electrode placement, instead of classical targeting, is likely to further improve motor response in DBS for PD. However, for full exploitation commercially available DBS software would have to allow for post-processing imaging.  


Varvara MATHIOPOULOU, Niels RIJKS, Matthan CAAN, Luka LIEBRAND, Rob DE BIE, Pepijn VAN DEN MUNCKHOF, Richard SCHUURMAN, Maarten BOT (Amsterdam, The Netherlands)
10:45 - 10:50 #23989 - Conventional and directional stimulation of subthalamic nucleus in Parkinson’s disease.
Conventional and directional stimulation of subthalamic nucleus in Parkinson’s disease.

Background: Subthalamic deep brain stimulation (DBS STN) became established as an effective treatment for advanced Parkinson's disease (PD). A new era in DBS appeared to be the introduction of segmented electrodes, which allow steering electric field in a certain direction horizontally. In view of ongoing discussion about the optimal stimulation spot within the STN in individual patients, directionality seems to be particularly relevant. Experimental modeling of directional stimulation suggests a possibility to increase the therapeutic window, reduce the appearance of stimulation-induced side effects, and enhance the efficiency of DBS. However, growing complexity of postoperative programming and patient management should be considered. There is still insufficient clinical data on eventual benefits of using segmented electrodes for outcome.

Objective: To assess efficacy and programming features of DBS STN using segmented directional electrodes compared to conventional omnidirectional leads in PD-patients with motor fluctuations.

Patients and methods: The study included 40 patients with advanced PD who underwent bilateral DBS STN surgery at our center in the last 3 years. In 20 patients (40 DBS-leads), segmented 8-contact electrodes were implanted (mean age at surgery 54.9±9.5 years, disease duration 13.2±4.3 years, Hoehn&Yahr stage 3.2±0.5). In the other 20 patients operated in the same timeframe (40 leads implanted), conventional 4-contact electrodes were used (mean age at surgery 57.4±9.0 years, disease duration 11.4±4.7 years, Hoehn&Yahr stage 3.2 ± 0.5). Groups did not differ significantly in baseline characteristics. All patients were operated by the same surgeon according to the uniform surgical technique including intraoperative microelectrode recording of neural activity (MER) and test stimulation. Neurological examination was standardized and performed preoperatively and at the 6-month follow-up in OFF- and ON-medication conditions (UPDRS, Schwab&England scale, PDQ39, levodopa equivalent daily doze/LEDD scoring). We analyzed intraoperative strategy, primary and following adjustments of the settings, and clinical outcome in each patient.

Results: Final trajectory of electrode implantation confirmed by MER and intraoperative stimulation coincided with central image-calculated trajectory in 67.5% of cases. In 32.5% of electrodes, correction of trajectory was performed (mainly in the medial direction). For MER, 1 to 3 microelectrodes were used (mean 1.5).

At the time of 6 months following continuous DBS STN, all patients experienced amelioration of parkinsonian symptoms and daily life activity in OFF-medication state with no significant difference between two groups. In patients with segmented leads implanted, mean OFF-state UPDRS-3 decreased from 51.3 to 16.7 points (66.3%) and UPDRS-2 from 23.0 to 8.7 (59.8%) compared to from 50.5 to 12.3 (73.9%) and from 22.9 to 9.8 (55.7%), respectively, in patients with conventional electrodes. In both groups, motor symptoms in ON-state also improved (mean UPDRS-3 changed from 13.0 to 7.9). Mean LEDD reduced from 1700 to 735 mg and from 1759 to 581 mg, respectively (p>0.05). Quality of life improvement comprised 19.3% for the whole group.

During initial setup, all leads were carefully screened for the best stimulation level, and then segmented ones were checked for the best direction of stimulation. Directional stimulation was preferentially used if better efficacy or minimization of DBS-induced side effects could be achieved. At the 3-month follow-up, in patients with segmented electrodes, directionality was employed in 9 patients (45%, 15 leads), To the 6-month follow-up, 14 leads were programmed directionally (9 patients). In 7 cases (17.5%), the most efficient electrode contact appeared to be outside the segmented level.

Conclusion: According to our data, efficacy of DBS STN via segmented electrodes is comparable to traditional omnipolar stimulation in short-term follow-up. Directional stimulation provides additional possibilities for programming and optimizing the clinical outcome of DBS STN. At the same time, high precision electrode placement is still required. Considering the increased complexity and time of selecting individual stimulation settings, systematic approach and development of new automated programming algorithms are desirable. We need studies in a larger patient population with long-term follow-up in order to evaluate potential benefits of directional DBS STN.

Alexey TOMSKIY, Anna GAMALEYA (Moscow, Russia), Svetlana ASRIANTS, Valentin POPOV, Anna PODDUBSKAYA, Sabina OMAROVA, Alexey SEDOV
10:50 - 10:55 #23998 - Power demand and battery longevity: 5-year results from a multi-center global registry.
Power demand and battery longevity: 5-year results from a multi-center global registry.

Objective: To characterize electrical features of long-term DBS settings for PD and ET patients, and how these features impact primary cell internal pulse generator (IPG) longevity derived from a global, multi-center registry.

Background: Several recent articles have been published on the impact of programmed settings and impedance on total electrical energy delivered (TEED) and consequently, battery longevity in DBS patients implanted with Activa PC have been compared with predecessor Kinetra IPGs.1-2 However, Activa PC contains hardware and programming capabilities that expand features beyond those available with Kinetra to provide physicians with more choices and greater flexibility in managing patient symptoms. The difference in battery longevity between Activa PC and Kinetra may be due to a number of design improvements which include size reduction for patient comfort and additional device features valuable in therapy optimization. In addition, sample size, diagnosis and duration of disease, stimulation settings including longitudinal impedance changes, and length of follow-up vary widely in these studies. The effect of these electrical parameters is better understood when a standardized approach across diverse centers and patient populations is used, such as a global registry.

Methods: The Product Surveillance Registry (PSR) was established in 2009, as a prospective long-term, multi-center global registry to monitor the reliability and safety of DBS systems. The stimulation settings were analyzed for 612 patients at 35 centers in 11 countries; 452 were first-time implanted IPGs and 215 were replacement IPGs. Electrical parameters were noted after stable programmed settings were achieved (6 months in de novo patients, 1 month in replacement patients). IPG longevity was estimated as the time to replacement due to battery depletion.  TEED (µJ) per lead was estimated from the actual device reported stimulation parameters and impedances over the lifetime of the battery. Statistical analysis was completed using Cox Proportional Hazards regression and Kaplan-Meier methods. 

Results:  The median IPG longevity for first-time implanted devices was 4.7 and 4.5 years, in PD and ET patients, respectively and device longevity was significantly longer in the first-time implanted group compared to the IPG replacement group. The IPG replacement group had higher TEED per lead for both PD and ET patients resulting in reduced battery life (Table 1), likely due to higher stimulation settings. Therapy impedance was significantly higher in first-time IPG devices compared to replacement devices in PD patients (p<0.0001); but not in ET patients (p=0.174).  Also, monopolar stimulation was used more frequently (78 % in PD vs 70% in ET) and 82% of devices had lead placed in STN target site in PD patients. The analysis of different stimulation targets revealed significant reduction of TEED in STN-DBS compared to GPi-DBS in first-time implanted PD patients (p<0.0001).

TEED increased significantly over time in PD patients (p<0.0001 in first-time implanted IPGs, but change was not significant in ET patients (p=0.386). With respect to therapy impedance, there was  evidence of significant downward trend in first-time implanted  PD and ET patients (p<0.0001, Figure 1). Overall, a significant inverse correlation was observed between IPG longevity and TEED in both PD (HR=1.009, p<0.0001) and ET (HR=1.011, p<0.0001) patients. 

Conclusion: The present analyses represent battery longevity from a real-world global patient population and reflect standard practice patterns at most DBS centers without protocol constraints regarding the management of these patients.  IPG longevity was quite similar in PD and ET patients but shorter in replacement IPGs, likely due to  higher energy demand in replacement IPGs compared to first-time implanted systems. The increase in TEED over time and higher TEED in replacement IPG may reflect changes in stimulation settings, usage patterns, or local tissue impedance fluctuations. Overall this analysis demonstrated the expected performance of 3-5 years of primary cell battery longevity for DBS therapy from a multi-center global registry in PD and ET patients.


1.              Helmers AK, Lubbing I, Deuschl G, et al. Neuromodulation. 2018;21(6):593-596.

2.              Niemann M, Schneider GH, Kuhn A, Vajkoczy P, Faust K. Neuromodulation. 2018;21(6):597-603.

Stephane PALFI (PARIS), Joachim K. KRAUSS, Peter KONRAD, George PLOTKIN, Emmanuel CUNY, Jean-Philippe AZULAY, Thomas WITT, Tom THEYS, Yesin TEMEL, Gayle JOHNSON, Kulwant BHATIA, Todd WEAVER
10:55 - 11:00 #24003 - Comparison of clinical outcomes and accuracy of electrode placement between robot-assisted and conventional deep brain stimulation of the subthalamic nucleus: a single-center study.
Comparison of clinical outcomes and accuracy of electrode placement between robot-assisted and conventional deep brain stimulation of the subthalamic nucleus: a single-center study.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has demonstrated major improvement of motor and non-motor manifestations and quality of life in Parkinson"s disease (PD) despite various surgical approaches. This single-center study aims to compare clinical outcomes and electrode placement accuracy in patients who underwent robot-assisted versus conventional frame-based stereotactic STN DBS surgery for PD.


This retrospective study included 48 PD patients, enrolled between October 2016 and December 2018 in the University hospital of Neurology and Neurosurgery of Lyon. They underwent either robot-assisted surgery (RAS) (Neuromate®, Renishaw) (n=20) or conventional frame-based stereotactic surgery (FSS) (n=28) with the same principles of STN targeting on MRI. ES performed RAS surgery, while GP performed FSS. Patients were evaluated before and 1 year after surgery. Electrode contacts within the STN was determined using merge of post-operative CT- and pre-op MRI with Brainlab® GUIDE™ XT software (Fig1).


Median age at surgery was the same (62.5 years old) in both groups. 1 year after surgery, with stimulation on and pharmaceutical treatment, there was no difference in the evolution of MDS-UPDRS III (p=0.29) and IV (p=0,80) between groups, the evolution of the quality of life (p=0.25), the evolution of levodopa treatment (p=0.94). The rate of complications was not different between both groups (p=0.99). Surgery duration was significantly longer in the RAS group (479 min, Q1-Q3: 460— 490) cmpared to the FSS group (351 min, Q1-Q3 317-392) (p=0.0001). There was no difference in electrode placement accuracy in both groups (table1).


This is the first study comparing clinical outcomes between robot-assisted and conventional surgery for DBS in PD in the same surgical center. We showed no difference in motor results, quality of life improvement, evolution of Levodopa treatment, complications of the surgery or electrode placement accuracy. The duration of surgery was increased in the RAS group. Prospective randomized study including a larger sample is required to determine best surgical approach, keeping in mind that the most important remains surgeon’s experience with the technique used.

Fig.1 : electrode placement accuracy 

Table 1: Results 

Shams RIBAULT, Emile SIMON (Lyon), Julien BERTHILLER, Gustavo POLO, Patrick MERTENS, Teodor DANAILA, Stéphane THOBOIS, Chloe LAURENCIN
11:00 - 11:05 #24020 - Optimization of the stimulation parameters settings of directional leads with a patient-specific imaging software in implanted parkinsonian patients.
Optimization of the stimulation parameters settings of directional leads with a patient-specific imaging software in implanted parkinsonian patients.

Optimization of the stimulation parameters settings of directional leads with a patient-specific imaging software in implanted parkinsonian patients

Gustavo Touzet MD3, Anne-Sophie Rolland PhD 1, Nicolas Carrière MD2, Bastien Gouges3, Luc Defebvre MD PhD2, David Devos MD PhD1,2, Caroline Moreau MD PhD2, Nicolas Reyns MD PhD3

1Department of Medical Pharmacology, Lille University, INSERM UMRS_1171, University Hospital Center, LICEND COEN Center, Lille, France; 2Department of Neurology, Lille University, INSERM UMRS_1171, University Hospital Center, LICEND COEN Center, Lille, France; 3Department of Neurosurgery, CHU LILLE University Hospital, France

Objectives: Deep brain stimulation in the subthalamic nucleus (STN) is routinely proposed to parkinsonian patients. Introduction of directional leads offers more flexibility for programming but may also increase the complexity and duration of the procedure. Here we assess whether Guide XTR, a new patient-specific imaging software, is helpful to refine stimulation parameters and to simplify the time consuming programming process.


Background: Clinical examination of the stimulation effect for each contact is the empirical method to set up stimulation parameters. Guide XTR models the volume of activated tissue and provides semi-automatic lead localization and segmentation of deep brain structures in order to visualize leads position and anatomical structures relative to putative stimulation fields.


Methods: We evaluated all parkinsonian patients who were implanted with bilateral directional leads in the STN. After surgery, patients were programmed and followed by the neurological team while blinded from anatomical data. All parameters were reviewed (ring or directional mode) and optimized based on standard clinical evaluation. After surgery, Guide XT was used to analyze imaging data by the neurosurgical team to choose the best stimulation configuration and parameters blinded from clinical data. Clinically determined parameters were then compared to imaging-based parameters.


Results: Twenty-eight patients were included in the study (19 males, 9 females, 59.1 ± 5.5 years old, disease duration 12.3 ± 7.4 years). The stimulation depth was similar between imaging and clinical settings in 75% of cases. Stimulation direction was similar between imaging and clinical settings in 18.75% of cases. Ring mode was selected in 62.5% with the clinical procedure and in 25% with the imaging procedure.


Conclusion: Predicted depth of stimulation using imaging data and empirically determined stimulation using clinical effects showed good concordance. Clinician used mainly ring mode stimulation despite imaging data suggesting a potentially better stimulation configuration using directional mode, possibly due to the complexity of the clinical evaluation. Imaging-guided parameters settings refined with clinical evaluation could therefore help to optimize parameters and limit non-motor side effects and need to be further evaluated.


Keywords: Parkinson’s disease, stimulation parameters, directional leads


Gustavo TOUZET (LILLE), Anne Sophie ROLLAND, Nicolas CARRIERE, Bastien GOUGES, Luc DEFEBVRE, David DEVOS, Caroline MOREAU, Nicolas REYNS
11:05 - 11:10 #25903 - Effects of unilateral stimulation in Parkinson’s disease: a randomized double-blind crossover trial.
Effects of unilateral stimulation in Parkinson’s disease: a randomized double-blind crossover trial.

Trials based on individual parallel designs have demonstrated that deep brain stimulation (DBS) treatments targeting either the subthalamic nucleus (STN) or globus pallidus interna (GPi) are both effective for the motor symptoms of Parkinson’s disease. However, few studies have compared the motor effects of STN and GPi DBS in individual patients. We compared the acute effects of unilateral STN and unilateral GPi DBS on motor function in individual patients with Parkinson’s disease treated with continuous DBS of both unilateral targets.

This prospective, double-blind, randomized crossover study assessed eight patients with idiopathic Parkinson’s disease who had been treated with continuous DBS of the unilateral STN and contralateral GPi for 2 years. Motor symptom severity, quantified by the Movement Disorder Society-Unified Parkinson Disease Rating Scale part III (MDS UPDRS-III), was assessed preoperatively and at 2-year follow-up in four randomized, double-blinded conditions: 1) Med−STN+GPi−, 2) Med−STN−GPi+, 3) Med+STN+GPi−, and 4) Med+STN−GPi+. The MDS UPDRS-III total score and subscale scores, including scores for axial and bilateral limb symptoms, served as the dependent variables.

Of the eight participants, seven completed the assessments in all four conditions, while one missed two postsurgical Med+ conditions. At the 2-year follow-up, compared with the preoperative Med− state, in the Med−STN+GPi− condition, the cardinal symptoms in both limbs were all improved, although the axial symptoms had deteriorated, except in the context of arising from a chair. In the Med−STN−GPi+ state, symptoms of the GPi-stim limb were improved significantly, while only tremor was improved on the ipsilateral side. The axial symptoms in the Med−STN−GPi+ state significantly worsened, and all sub-scores showed aggravation. Compared with the preoperative Med+ state, in the Med+STN+GPi− state, cardinal symptoms were improved on both sides, except for the tremor on the STN-stim side. The axial symptoms were more serious and the only improved axial symptom was arising from a chair. In the Med+STN−GPi+ state, the overall motor symptoms were aggravated, and the treatment effect was only reflected in the symptoms of tremor and rigidity on the GPi-stim side. The axial symptoms of the Med+ states were all worsened, except in the context of arising from a chair.

In conclusion, improvement of motor symptoms was significantly increased in all sub-scores favoring STN, except for the worsening degree of gait, in which Med+STN−GPi+ was slightly lower than Med+STN+GPi−. We also noted the effects of STN+ acting on both limbs, in contrast to the effects of GPi+, which mainly acted on the contralateral side. 

Zhitong ZENG, Linbin WANG, Weikun SHI, Lu XU, Zhengyu LIN, Xinmeng XU, Peng HUANG, Yixin PAN, Zhonglue CHEN, Yun LING, Kang REN, Bomin SUN, Dianyou LI, Chengcheng ZHANG (Shanghai, China)
11:10 - 11:15 #26047 - Biphasic anode-first pulses increase the therapeutic window.
Biphasic anode-first pulses increase the therapeutic window.

Objective – To investigate the use of biphasic anode-first pulses on the therapeutic window in essential tremor (ET) patients treated with ventral intermediate nucleus deep brain stimulation (DBS). Figure 1.

Background – Since the inception of DBS, cathodic pulses have been used1. Modelling studies suggest that biphasic pulses may influence the therapeutic window2.

Methods – Stimulation was delivered on the most ventral contact, unless this elicited unbearable paresthesias. In that case, one level more dorsally was stimulated. The non-tested hemisphere was turned OFF. Three thresholds were acutely defined for both cathodic and biphasic anode-first pulses: lowest amplitude inducing tremor arrest while performing a finger-to-nose test contralaterally (LowerTW),  lowest amplitude inducing upper limb ataxia contralaterally (AtaxicTW) and lowest amplitude causing non-transient stimulation-induced side effects contralaterally, other than limb ataxia (UpperTW). The thresholds were defined twice in all hemispheres and average results per hemisphere were analyzed. Wilcoxon signed rank test was used to compare the thresholds.

Results – Four ET patients (8 hemispheres) participated in this study. LowerTW was not significantly different between cathode versus biphasic pulse (1.82 ± 0.69 mA versus 2.11 ± 0.62 mA, p = 0.25). The amplitude that elicited limb ataxia was however significantly higher in the biphasic anode-first pulse (2.74 ± 0.96 mA versus 3.75 ± 1.41 mA, p = 0.0078). Also, non-ataxic side effect was only evoked at higher stimulation amplitudes when compared to biphasic pulses (3.69 ± 1.84 mA versus 4.78 ± 1.97 mA, p = 0.0078). Figure 2.

Conclusions – Biphasic pulses elicit stimulation-induced side effects at higher amplitudes, therefore increasing the therapeutic window. Further work is needed to determine if these pulses can bring clinical benefit compared to standard cathodic pulses.


1.          Benabid AL, Pollak P, Hoffmann D, et al. Long-term suppression of tremor by chronic stimulation of the ventral intermediate thalamic nucleus. Lancet. 1991;337(8738):403-406. doi:10.1016/0140-6736(91)91175-T

2.          Wongsarnpigoon A, Grill W. Energy-efficient waveform shapes for neural stimulation revealed with a genetic algorithm. J Neural Eng. 2010;7(4):1-20. doi:10.1088/1741-2560/7/4/046009.Energy-efficient

11:15 - 11:20 #26102 - Directional subthalamic deep brain stimulation in Parkinson’s disease: Better clinical results with directional stimulation.
Directional subthalamic deep brain stimulation in Parkinson’s disease: Better clinical results with directional stimulation.

Directional subthalamic nucleus deep brain stimulation in Parkinson’s disease allows for a better therapeutic window, with increased motor effects and less stimulation side effects. In our study, we aimed to determine the preferred type of stimulation (omnidirectional or directional) on last-follow-up in patients who were all implanted with directional leads. We then correlated the results of choice of type of stimulation with the anatomical electrode position in the subthalamic nucleus.

From April 2018 to August 2020, 17 patients received directional leads (Boston Scientific) for severe Parkinson’s disease implanted bilaterally into the subthalamic nucleus. The neurologists of the team had all freedom to change the mode of stimulation, but were at that time blinded to the exact lead position of the contacts as revealed by the guide XT software. DBS stimulation status (omnidirectional vs directional) and its evolution was compared post-operatively (when the patient was discharged) and at last follow-up with at least 1 year of follow up.  This mode of stimulation was then correlated to the evolution of the MDS UPDRS scores, to the side effects and to the anatomical position of the implanted electrodes. 1 patient was followed in another centre and data were not available.

6 and 10 patients were stimulated with directional (37%) or omnidirectional mode (63%) respectively at discharge. At last follow up, 11 out of 16 (69%) had a directional mode of stimulation, 7 switching from omnidirectional to directional mode, and 2 switching from directional to omnidirectional mode. Reasons for change included better efficacy and the need to reduce the side-effects. Anatomical correlations will be discussed according to those findings.

In conclusion, there was a great tendency to stimulate preferentially a majority of patients using directional mode for different reasons discussed in the paper.

11:20 - 11:25 #26138 - Pedunculopontine and Cuneiform nuclei deep brain stimulation for severe gait and balance disorders in Parkinson’s disease: a randomised double-blind clinical trial.
Pedunculopontine and Cuneiform nuclei deep brain stimulation for severe gait and balance disorders in Parkinson’s disease: a randomised double-blind clinical trial.

Doparesistant Freezing of gait (FOG) and falls represent the dominant motor disabilities in advanced  Parkinson’s disease (PD). Their pathophysiology is poorly understood, but imaging and post-mortem studies suggest a causal role of cholinergic dysfunction within the pedunculopontine nucleus (PPN), located in the mesencephalic locomotor region (MLR), also including the cuneiform nucleus (CuN) dorsally. We herein investigate the effects of deep brain stimulation (DBS) of the PPN and CuN nuclei, for treating gait and balance disorders in Parkinson’s disease (PD) patients in a randomized double-blind cross-over clinical trial. Six PD patients with dopa-resistant freezing of gait (FOG) and/or falls were included and operated for bilateral MLR-DBS. Patients each received three DBS conditions, PPN, CuN or sham, in a randomized order for 2-months each, followed by an open-label phase. The primary outcome was the change in anteroposterior anticipatory postural adjustments (APAs) during gait initiation on a force platform at the end of each DBS condition. Secondary outcomes included safety and differences in gait kinetics, and clinical gait, cognitive and quality of life scales between DBS conditions. During the randomized period, we found that the anteroposterior APA were not significantly different between the DBS conditions (median displacement [1st_3rd quartile] of 3.07 [3.12_4.62] mm with sham-DBS, 1.95 [2.29_3.85] mm with PPN-DBS and 2.78 [1.66_4.04] mm with CuN-DBS; p=0.25). Step length and velocity were significantly higher with CuN-DBS vs both sham-DBS and PPN-DBS. Conversely, step length and velocity were lower with PPN-DBS vs sham-DBS, with greater double stance and gait initiation durations. One year after surgery, step length was significantly lower with PPN-DBS vs inclusion. We also found no significant differences in the clinical scales including  the parkinsonian disability, gait and balance scales, and assessment of cognition or psychiatric troubles. Lastly, we observed 3 serious adverse events with one electrode displacement in one patient, one patient had a subdural hematoma following recurrent falls that did not necessitated surgery. Our study suggests a better effect of CuN-DBS relative to PPN-DBS on walking ability in advanced PD patients. However, the absence of significant clinical benefit with 2 months of DBS with no aggravation in FOG or falls one year after surgery would suggest that optimized DBS and for longer period might be beneficial. Further research is needed to better understand the role of the MLR in gait and balance control in humans using new imaging or neurophysiological approaches.


11:25 - 11:30 #26181 - Deep brain stimulation (DBS) of Subthalamic nucleus and Substancia nigra (SN) for the treatment of gait affection in Parkinson´s disease.
Deep brain stimulation (DBS) of Subthalamic nucleus and Substancia nigra (SN) for the treatment of gait affection in Parkinson´s disease.


Deep brain stimulation (DBS) has been shown to be effective and safe for treating the cardinal symptoms of Parkinson's disease.

Some aspects of the disease, such as gait disorders, respond worse to DBS. Various publications suggest the efficacy of combined DBS in the subthalamic nucleus (STN) and the substantia nigra (SN) for refractory gait disorder in PD. The objectives of our study are to confirm these previous findings. Material and methods:We present data from our randomized, crossover, double-blind, single-center study conducted in 10 patients with advanced PD.
Octopolar deep brain stimulation electrodes were placed bilaterally at STN, leaving the most distal contacts at SN. To perform the quantitative gait analysis, the Step 32 system was used. Clinical and neurophysiological parameters were compared after 4 weeks of STN stimulation versus 4 weeks of combined STN and SN stimulation. Side effects and patient preferences were reported. Results:
There were no complications associated with surgery Postoperative improvement was observed in the cardinal symptoms of PD and in gait parameters. The number of normal gait cycles increased significantly after surgery in both forms of stimulation.
The greatest increase in normal gait cycles occurred in combined STN and SN stimulation (0.57 preoperative, 0.71 STN, 0.79 STN + SN). Coclusion: The combined STN and SN DBS is a safe and effective technique to improve the axial motor disorders of PD, such as gait blocks and postural instability. Studies with a larger number of patients and long-term follow-up would be very useful to confirm the evidence of our work.


11:30 - 11:35 #26193 - Unilateral delivery of autologous injury-activated peripheral nerve graft tissue to the substantia nigra in patients with Parkinson’s disease.
Unilateral delivery of autologous injury-activated peripheral nerve graft tissue to the substantia nigra in patients with Parkinson’s disease.

Background: Both the FDA, under 21 CFR 1271.15(b), and the EU, under Art 2§2(a) and Preamble 8 of Dir. 2004/23/EC, allow for a Same Surgical Procedure Exemption for the grafting of autologous tissue during a same surgical procedure. With a goal of providing support to sick or dying cells, we have previously used this Exemption to deliver autologous injury-activated peripheral nerve graft tissue (APNG) to the substantia nigra in patients with Parkinson’s disease who are undergoing deep brain stimulation (DBS) surgery (van Horne et al. 2018). Following injury, the peripheral nervous system, activates a reparative response that generates a host of neurotrophic and cell-survival factors.

Objective: As part of an open-label Phase I clinical trial (NCT02369003) to expand the utility of this approach and examine dose escalation, we unilaterally implanted APNG to the substantia nigra under two different dosing regimens: a single deployment of APNG or two deployments of APNG.

Methods: As part of the standard of care, participants underwent a two-staged DBS procedure. At the time of stage I, the sural nerve was transected and the incision was closed. Later (3 to 14 days later) at stage II, the injured sural nerve was identified, and an about 1 cm section was excised. The fascicles were identified, diced, and deposited in the substantia nigra with one deployment or a deployment both to the anterior and to the posterior substantia nigra. Participants were followed for 12 months and the motor component of the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) was used to assess for changes in Parkinson’s disease severity.

Results: Across our previous trial (van Horne et al. 2018) and this one, a total of 37 participants have received only unilateral grafts to the substantia nigra with a mean age of 62 years (95% Confidence Interval: 60 to 65 years). Adverse event profiles were comparable to standard DBS with the most common study-related events being paresthesias of the lateral foot distal to the sural nerve tissue harvest site.  For the single deployment, off-state motor MDS-UPDRS mean scores were 45.3 points (40.2 to 50.5; n=28) at screening and 36.6 points (30.5 to 42.7; n=24) at 12 months. For participants receiving two deployments: 42.8 points (30.7 to 54.9; n=9) at screening and 35.8 points (21.5 to 50.0; n=8) at 12 months. Overall for unilateral APNG delivery, pooling both groups, the mean decrease in scores at 12 months was -8.4 points (-4.1 to -12.6; n=32). When we analyzed the lateral components of the MDS-UPDRS, the mean difference in scores at 12 months for the body side contralateral to the APNG deployment was -4.6 points (-2.8 to -6.6) and for the side ipsilateral to the APNG deployment it was -0.8 (-2.0 to + 0.5).

Conclusions: Further examination of the approach is merited to further establish the safety profile for this procedure and to investigate the potential for this strategy for disease modification.

11:35 - 11:40 #26201 - Clinical outcome of magnetic resonance guided focused ultrasound thalamotomy for essential tremor: results at 6 months follow-up.
Clinical outcome of magnetic resonance guided focused ultrasound thalamotomy for essential tremor: results at 6 months follow-up.


Essential tremor (ET) is one of the most common neurological disorders with a prevalence of 4.6% in people aged 65 years or older. Medical management is generally initiated when the tremor begins to interfere with the patient’s ability to undertake daily activities, but the effectiveness of drugs for this disorder is limited.

Stereotactic radiofrequency (RF) thalamotomy and deep brain stimulation (DBS), targeted to the ventralis intermedius nucleus of the thalamus (Vim), have proven effective for treating ET and other tremors. These interventions, although highly effective, have risks associated with an open neurosurgical operation.  Radiosurgical Vim thalamotomy with Gamma Knife has been used as a non-invasive alternative treatment. However, the lack of immediate clinical improvement and the possibility of extension of the lesion beyond the initially targeted region over time inducing permanent neurological deficits have limited the use of this technique.1

For the last decade, MRgFUS has been raising a lot of interest, as an incisionless and low-risk therapeutic option. This type of treatment creates a coagulation lesion via high-intensity ultrasound beams that converge in a selected target, with great accuracy and with neither need of incising the skin nor opening the skull. Vim-MRgFUS has been used to treat tremor associated with Parkinson´s disease, Essential Tremor, Multiple Sclerosis and Fragile X-associated ataxia.

In the present study, the durability of tremor relief in patients followed for 6 months after MRgFUS thalamotomy was evaluated to confirm the durability of efficacy and safety of MRgFUS thalamotomy for the treatment of medically refractory ET.



One hundred twenty-three ET patients treated with unilateral MRgFUS VIM between 2018 and 2021 were evaluated using the Clinical Rating Scale for Tremor (CRST) score at month, three months, and 6 months. Lesion characteristics were assessed on routine MRI sequences at 6 months in 44 patients. Relationships between imaging appearance in Brainlab Sotware (BrainLAB AG, Munich, Alemania), details of thalamotomy procedure (Insightec Inc, Tirat Carmel, Israel) and clinical outcome were investigated.



Mean hand tremor score section A and B at baseline (20.77 ± 5.81; 123 patients) improved by 83.33% ± 22.10% (Section A), 73.51% ± 28.40% (Section B) and 75.74% ± 33.53% (Section C;) at 6 months. This improvements difference was significant (p= 0.05). Paresthesias and gait disturbances were the most common adverse effects at 1 months and at 6 months only 28% patients presented soft adverse effects.

On T2-weighted images the most lesion was hyperintense, the mean relative volume at 6 months was 0,037 ± 0.026cm3 (IQR 0.31– 0.058cm3), some lesions were no longer discernable in T2-weighted images. Mean AC-PC line length was 25.98 ± 1.87 mm (IQR 24.63– 27.45mm). Clinically determined centers of Vim lesion placement differed from the assumed position of the nucleus as suggested in the literature. On the right-left axis, mean lesion position was 14.33 ± 1.95 mm (range 13.37 – 14.93mm) from third wall and 6.75 ± 1.19mm (IQR 5.76 ± 7.45mm) distance from the posterior commissure on the AC-PC line, what represents 26.01 ± 4.21% (IQR 23.55- 27.76%) of AC-PC line. On the dorso- ventral axis, mean lesion position was 3.01 ± 1.21mm (IQR 2.13-3.75). The mean of III ventricle measured on T2-weighted images was 6.81 ± 2.02 mm (IQR 5.63 – 8.35mm). The median patient SDR was 0.52 (IQR 0.44 -0.57). MRgFUS thalamotomies were performed using a median of 3.4 ± 1.4 sonications over maximal mean temperature of 55°C (IQR 2-4), delivering a median of 16243 ± 8640 joules (IQR 8655- 24154). The median of seconds over 55° was 29.85 ± 12.5 seconds (IQR 21 -37.5 seconds). The median median maximal mean temperature of 58 ± 2.14°C (IQR 57-60°C). There was no significant correlation between lesion volume at 6 months and clinical improvement (p =0.13) for tremor reduction on the treated side. The technical parameters were no significant correlation with clinical improvement, nevertheless, III ventricle size was significant correlation with tremor reduction (p=0,046), the greater ventricular size the clinical improvement decrease. 


MRgFUS thalamotomy for ET is an effective and safe procedure that provides long-term tremor relief and improvement in quality of life even in patients with medication-resistant disabling tremor.

Alana ARCADI (Pamplona, Spain), Iciar AVILES, María GOROSPE, Lain GONZALEZ-QUARANTE, Antonio MARTIN, Laura ARMENGOU, María Cruz RODRÍGUEZ, Jorge GURIDI
11:40 - 11:45 #26288 - MRI-guided Laser Interstitial Thermal Therapy thalamotomy for essential tremor: a proof-of-concept study.
MRI-guided Laser Interstitial Thermal Therapy thalamotomy for essential tremor: a proof-of-concept study.


Management of drug-resistant essential tremor (ET) is a challenge for clinicians. Thalamic deep brain stimulation (DBS) has proven to be effective in ET patients with drug-resistant tremor. However, for various reasons some patients are not eligible or refuse these DBS procedures. For these reasons, less invasive neurosurgical procedures have emerged in these second-line indications to create thalamic lesions using radiation or MRI-guided focused ultrasound. Recently a new technology has emerged allowing realization of brain lesion by laser with real-time guided MRI imaging: MRI-guided Laser Interstitial Thermal Therapy (MRIg-LITT). MRIg-LITT is increasingly used in neurosurgery thanks to its promising clinical results in treatment of epilepsy and tumors. Here, we report early data of MRIg-LITT thalamotomy in drug-resistant ET patients.


Briefly, MRIg-LITT thalamotomy consisted of stereotaxically placing a laser probe (Medtronic) in the ventral intermediate (VIM) nucleus of the thalamus using the ROSA robot system (Zimmer Biomet) under general anesthesia. Targeting and trajectory planning were established on the dedicated ROSANA planning software (Zimmer Biomet) separate from the robotic platform, allowing automatic image fusion between preoperative MRI and CT scan images. Intraoperative guidance by CT scans obtained with the O-Arm system (Medtronic) and microelectrode recording (FHC) allowed assisted laser probe placement. Once the probe was in place, patient was transported to MRI still under general anesthesia. A single MRIg-LITT thalamotomy in a 1.5T MRI (GE Optima MR 450w) was performed using the Visualase system (Medtronic) equipped with a diode laser (max power of 15W and 985 nm wavelength). MRIg-LITT protocol was carried out in stepwise, increasing deliveries of 10%, 15%, 20%, and 25% laser power sessions. The overall heating time was 9 min 50 s, alternating with rest periods of 1-2 min (laser power range of 1-2.5W). Then, the laser probe was removed and patient was awakened.

Improvement of upper limb tremor contralateral to the thalamotomy on Fahn-Tolosa-Marin (FTM) scale was evaluated at 3 months postoperative blindly by video by an external expert neurologist. Quality of life was assessed on the Quality of Life in Essential Tremor Questionnaire (QUEST) at 3 months postoperative. All patients gave their consent for the study

Quantitative variables are presented with their mean and standard deviation, qualitative variables with their percentages and numbers. Comparisons of quantitative variables are made using a Wilcoxon test.


Unilateral MRIg-LITT thalamotomy was performed in 5 patients with ET drug-resistant tremor. Mean age was 73.00 (7.07) years, 3/5 were male, 4/5 were right handed and mean duration of the tremor was 441.60 (263.24) months. Preoperative mean FTM score of upper limb contralateral to the thalamotomy was 14.60 (0.89) (rest tremor 0.40 (0.55), postural tremor 3.00 (0.71), action tremor 2.20 (1.09), drawings and writing 9.00 (2.00)). Preoperative mean QUEST Summary Index was 49.55 (11.68). Postoperative mean FTM score of upper limb contralateral to the thalamotomy was 3.80 (1.09) (rest tremor 0 (0), postural tremor 0.20 (0.45), action tremor 0 (0), drawings and writing 3.60 (0.89)). Postoperative mean QUEST Summary Index was 21.77 (11.86). Postoperative mean FTM score of upper limb contralateral to the thalamotomy was improved by 73.98% (p=0.098) and QUEST Summary Index by 56.07% (p=0.043). No serious adverse events have been reported. 5/5 patients report only transient motor weakness and proprioceptive disorders on the upper limb contralateral to the thalamotomy during 1 to 2 weeks post procedure. Persistence of long-term efficacy is currently being assessed, as is cognitive security.


Unilateral MRIg-LITT thalamotomy seems to be an effective and safe technique to treat upper limb drug-resistant ET when thalamic DBS is impossible or refused by the patient. It could be an alternative to radiosurgery or MRI-guided focused ultrasound to perform stereotaxic VIM thalamotomy. However, other studies with a larger number of patients and a longer follow-up period are necessary to validate the use of this technique in current practice. To our knowledge, only one study involving 13 patients reports use of MRIg-LITT thalamotomy for drug-resistant tremors in the literature.

Mickael AUBIGNAT (Amiens), Melissa TIR, Felix POTTECHER, Salem BOUSSIDA, Jean-Marc CONSTANS, Michel LEFRANC
11:45 - 11:50 #26296 - Ipsilateral effects of unilateral Deep Brain Stimulation for Essential Tremor.
Ipsilateral effects of unilateral Deep Brain Stimulation for Essential Tremor.

Ipsilateral effects of unilateral Deep Brain Stimulation for Essential Tremor

Background: Essential tremor (ET) is the most common adult movement disorder. For the relatively large group of patients which do not respond adequately to pharmacological therapy, deep brain stimulation (DBS) might constitute an alternative. Most ET patients will have bilateral symptoms and many of them receive bilateral DBS. Even so, unilateral DBS is still the most common procedure and some papers suggest an ipsilateral effect in these patients. 

Objectives: To analyze if we could find an ipsilateral effect of DBS for essential tremor.

Method: We retrospectively analyzed our patient cohort with DBS surgery from 1996 to 2017, selecting patients with ET that underwent surgery with unilateral DBS without previous DBS or lesional surgery. A total number of 68 patients (39 males, 29 females) were identified. The patients were evaluated at a mean time of 12 and 49 months after surgery using Essential tremor rating scale (ETRS).

Results: Total ETRS score was reduced from 49.5 points at baseline before surgery to 20.2 (p<0.001) at short term and 28.3 (p<0.001) at long term follow up. Contralateral tremor was reduced from 6.1 to 0.4 (p<0.001) and 1.2 (p<0.001) respectively. Contralateral hand function was reduced from 11.5 to 2.6 (p<0.001) and 4.6 (p<0.001), respectively. Ipsilateral hand function was reduced from 9 to 8.3 (p<0.05) but this was not maintained at long term follow up (9.4. p>0.05). Ipsilateral tremor was reduced from 4.0 at baseline to 3.7 (p<0.05) but not maintained at long term follow up (4.3. p>0.05).


In this study, we found a small but significant improvement on ipsilateral hand function (items 11-14 on the ETRS) and hand tremor (item 5/6) on short term follow up. But the effect was lost on long term follow up. Although we could see a larger improvement in a few of our study objects, on the group level this improvement was very modest (8% improvement). Furthermore, the effect was not maintained on the long-term evaluation.The situation is similar in the literature. Often a minor reduction is seen regarding hand tremor (item 5/6) which sometimes reaches significance. However, at the group level the improvement is always modest. It has been suggested that ipsilateral effects are caused by ipsilateral connections in this are . However, it is possible that other factors might contribute.


We observed a significant improvement on ipsilateral hand function and tremor in our material, but the effect was small and transient. Hence, we consider this question to merit limited consideration regarding decision making or patient counseling on DBS for ET.

Erik ÖSTERLUND (Stockholm Sweden, Sweden), Patric BLOMSTEDT, Anders FYTAGORIDIS
11:50 - 11:55 #26304 - Further refinement of the stimulation hotspot in subthalamic deep brain stimulation for parkinson’s disease.
Further refinement of the stimulation hotspot in subthalamic deep brain stimulation for parkinson’s disease.

INTRODUCTION: Individual improvement in motor symptoms can vary considerably after subthalamic deep brain stimulation (STN DBS). Through evaluating this, we have been able to define an optimal theoretic location for STN DBS by introducing a patient-specific reference point: the medial STN border. We aimed to evaluate the implementation of the medial STN border as a patient-specific reference point and its consistency for correlation with lateralized motor improvement using a larger and more recent cohort of PD patients who underwent STN DBS surgery at our institution. METHODS: Patients were selected from a single-center randomized controlled trial comparing bilateral STN DBS surgery under general versus local anesthesia, that included PD patients between May 2016 and November 2018. Body-sides were categorized into three groups, based on percentual MDS-UPDRS-III improvement: (1) non-responding (<30%), (2) responding (between 30% and 70%) and (3) optimally responding (>70%). A theoretic ‘hotspot’ was calculated by averaging X, Y, and Z coordinates of the ‘optimally responding’ group, relative to the medial STN border as well as to the MCP. The Euclidean distance from each active contact to both defined hotspots were calculated separately. RESULTS: 218 DBS electrodes were implanted in 109 patients with PD. Thirty-seven corresponding body-sides were categorized as non-responding body-sides (18%), whereas 108 as responding body-sides (51%) and 67 as optimally responding body-sides (32%). Average percentual UPDRS change of the non-responding body-side group were significantly higher in the current study population compared to the previous population (Bot et al. 2018; independent T(52) = 2.14, P = 0.037), whereas the responding body-side group had less average percentual UPDRS change in the current population (independent T(136) = 2.74, P = 0.007). Using the medial STN border as a patient-specific reference point, difference in mean Euclidean distances between non-responders and responders were statistically significant (independent t(143) = 2.25, P = 0.026), as well as between non-responders and optimal responders (independent t(102) = 3.22, P = 0.002). We found a significant negative correlation (Pearson’s correlation -0.23; P = 0.001) between percentage MDS-UPDRS-III Lateralized scores change and Euclidean distance from active contact to the refined ‘hotspot’ defined relative to the medial STN border. CONCLUSION: We evaluated the implementation of the medial STN border as a patient-specific reference point and its consistency for correlation with lateralized motor improvement using a larger and more recent cohort of PD patients who underwent STN DBS surgery at our institution. We reaffirmed the significance of the medial STN border as patient-specific reference point for DBS location and motor improvement in patients with PD in a larger and highly recent cohort. This refined optimal location for DBS in PD can be used for optimizing lateralized motor outcome scores and was defined at 2.8 mm lateral, 1.1 mm anterior, and 2.2 mm superior to the medial STN border.

Erik BOLIER (Amsterdam, The Netherlands), Maarten BOT, Pepijn VAN DEN MUNCKHOF, Rick SCHUURMAN
Salle Major

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
12:00 - 13:30

ESSFN Executive Committee meeting

Salle 50

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
13:30 - 14:30

Plenary Session 6
Epilepsy Surgery

Moderators: Hans CLUSMANN (Department of Neurosurgery) (Aachen, Germany), Michel LEFRANC (MEDECIN) (AMIENS, France), István VALÁLIK (head of department) (Budapest, Hungary)
13:30 - 14:00 Refractory epilepsies: strategies for the surgical management. Antonio GONÇALVES FERREIRA (Head of the Stereotactic and Functional Division) (LISBON, Portugal)
14:00 - 14:30 LITT achievement in Epilepsy Surgery. Robert GROSS (Neurosurgeon, MD/PhD Dir, eNTICE Chair, SOM Faculty) (Atlanta, USA)
Grand Amphithéâtre

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
15:00 - 17:00

Parallel Session 11
Movement disorders

Moderators: Alexandre EUSEBIO (Professor) (Marseille, France), Miroslav GALANDA (Kosice, Slovakia), Claudio POLLO (Deputy Chief Doctor) (Bern, Switzerland)
15:00 - 15:10 #26104 - Pallido-putaminal connectivity predicts outcomes of deep brain stimulation for cervical dystonia.
Pallido-putaminal connectivity predicts outcomes of deep brain stimulation for cervical dystonia.


Cervical dystonia is a non-degenerative movement disorder characterised by dysfunction of both motor and sensory cortico-basal ganglia networks. Deep brain stimulation targeted to the internal pallidum (GPi) is an established treatment, but its specific mechanisms remain elusive, and response to therapy is highly variable. Modulation of key dysfunctional networks via axonal connections is likely important.


Fifteen patients underwent pre-operative diffusion-MRI acquisitions and then progressed to bilateral DBS targeting the posterior GPi. Severity of disease was assessed pre-operatively and later at follow-up. Scans were used to generate tractography-derived connectivity estimates between the bilateral regions of stimulation and relevant structures, namely the thalamus, subthalamic nucleus, and the putamen.


Connectivity to the putamen correlated with clinical improvement, and a series of cortical connectivity-based putaminal parcellations identified the primary motor (M1) putamen as the key node (r=0.70, p=0.004). A forward regression model with this connectivity and electrode coordinates explained 68% of variance in outcomes (r= 0.83, p=0.001), with both as significant explanatory variables (connectivity: p=0.01, coordinates:  p=0.02).


We conclude that modulation of the M1 putamen – posterior GPi limb of the cortico-basal ganglia loop is characteristic of successful DBS treatment of cervical dystonia. Pre-operative diffusion imaging contains additional information that predicts outcomes, implying utility for patient selection and/or individualised targeting.  

Ashley RAGHU (Oxford, United Kingdom), John ERAIFEJ, John STEIN, Stephen PAYNE, Tipu AZIZ, Alex GREEN
15:10 - 15:20 #26119 - Clinical outcome after MRI-connectivity-guided radiofrequency thalamotomy for tremor.
Clinical outcome after MRI-connectivity-guided radiofrequency thalamotomy for tremor.

Clinical outcome after MRI-connectivity-guided radiofrequency thalamotomy for tremor

Thomas Wirth1, Ali Rajabian1, Viswas Dayal1, Abuhusain Hazem1, Nirosen Vijiaratnam1, Dilan Athauda1, Marwan Hariz1,2, Thomas Foltynie1, Patricia Limousin1, Harith Akram1*, Ludvic Zrinzo1*


1. Unit of Functional Neurosurgery, National Hospital for Neurology and Neurosurgery (UCLH) -Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, United Kingdom

2. Department of Clinical Science, Neuroscience, Umeå University, Umeå, Sweden


*These authors equally contributed and should be considered as co-supervising authors.


Background: Historic published outcome data for radiofrequency thalamotomy for severe tremor do not reflect advances in stereotactic targeting using MR connectivity guided surgery

Objective: To evaluate the efficacy and tolerability of contemporary unilateral radiofrequency-thalamotomy procedures in severe tremor.

Material and Methods: Twenty-one consecutive patients (14 essential tremor, 7 Parkinson’s disease) with severe, medically refractory tremor underwent awake radiofrequency thalamotomy procedures in a single institute between 2016 and 2019. Connectivity derived segmentation of the ventro-intermedial (Vim), the anterior ventrolateral (VL / Voa+Vop) and the ventroposterior (VPM/ VPL) nuclei was used to guide targeting. Changes in the Fahn-Tolosa-Martin rating scale (FTMRS) and tremor and disability scores were recorded in treated and non-treated hands as well as procedure related side effects

Results: Twenty-three thalamotomies were performed (with two patients receiving two interventions). The mean (SD) postoperative assessment timepoint was 14.1 (9.7) months. Treated-hand tremor scores improved by 63.8% whereas non-treated hand scores deteriorated by 10.13% (p<0.01). Treated hand tremor disability scores were also significantly lower at follow-up compared to baseline (7.55 vs 13; p<0.01) as were total FTMRS scores (34.7 vs 51.65; p=0.016). Baseline treated-hand tremor severity (r=0.786; p<0.01) and total FTMRS score (r=0.786; p<0.01) best correlated with tremor improvements. No significant correlation was noted between outcomes and gender, age at surgery, tremor etiology, lesion size and location, or previous Vim-DBS failure. 

The most reported side effect was mild, transient gait ataxia (38.1%). Other transient side effects included paresthesia (9.5%), mild dysarthria (19%), and mild motor or sensory deficits (4.7% each). Persistent side effects included mild gait ataxia (14.2%), mild sensory deficit (4.7%) and paresthesia (9.5%). No correlation was noted between lesion size or location and side effects.

Conclusion: Unilateral radiofrequency Vim thalamotomy guided by connectivity-derived segmentation is a safe and efficacious option for severe tremor in both PD and essential tremor

Thomas WIRTH, Ali RAJABIAN, Viswas DAYAL, Abuhusain HAZEM, Nirosen VIJIARATNAM, Dilan ATHAUDA, Marwan HARIZ, Tom FOLTYNIE, Patricia LIMOUSIN, Harith AKRAM (London, United Kingdom), Ludvic ZRINZO
15:20 - 15:30 #26126 - The effect of electric field weighting in improvement maps for deep brain stimulation.
The effect of electric field weighting in improvement maps for deep brain stimulation.


Electric field simulation is a common method to estimate the spatial extent of deep brain stimulation (DBS) effect. Recently, several studies have been focusing on establishing probabilistic improvement maps. These are often based on a volume of activated tissue estimated by an electric field threshold. This method generates a binary volume where voxels with electric field higher than the threshold is judged as activated and those with lower values are not activated. However, since higher magnitude of the electric field will increase the probability of stimulating more neurons, the electric field strength should be taken into consideration. In this study we present the impact of using the magnitude of the electric field as a weighting function to the improvement compared to using binary volume of activation.

Materials and Methods

This study includes clinical data from 87 patients with essential tremor (ET) with DBS lead 3389/3387 (Medtronic Inc, USA) implanted in the caudal Zona incerta (Ethics, Dnr 122-31). Parts of this dataset have previously been published [1]. Each patient underwent a monopolar review where the best improvement for each contact was noted based on the essential tremor rating scale item 5/6 and 11-14. Based on the review data, electric field simulations were performed for each patient and contact using the finite element method (FEM)(COMSOL Multiphysics 5.5, COMSOL AB Sweden) [2]. The simulation results were exported to a group constructed template space based on a nonlinear normalization of the patient’s brain images, similar to what was presented by Vogel et. al [3]. After the transform, the electric field was voxelized to template space resolution (0.5x0.5x0.5 mm) and thresholded at 0.2 V/mm since lower electric field values are judged to not impact the axons. For the total dataset, a mean improvement map weighted with the magnitude of the electric field in each voxel was created. Also, voxelwise statistics were computed comparing the weighted mean improvement in each voxel with the mean improvement in the cohort by using a t-test. Voxels with a p-value < 0.05 were judged as significant. After this, the electric field data was converted to binary label maps with 1 for all voxels above 0.2 V/mm and 0 elsewhere. For these binary volumes of activation, the mean improvement map and voxelwise statistics were repeated.


Comparing the mean improvement maps, they are similar and have corresponding trends of areas with higher or lower improvement. However, the generation of mean improvement maps are sensitive to low occurrence level, i.e. few volumes of activation overlapping in a voxel, which is more evident when created with a binary volume of activation. Comparing the methods shows that the estimated improvement in percentage differ by less than 10 percentage points in most voxels. When evaluating the voxels with higher deviation, it is clear that those voxels are mostly located near a DBS lead where the electric field is as highest. These voxels can deviate in estimated improvement up to 40 percentage points.

For the voxelwise statistics, the significant voxels are located in similar areas when using the electric field as weighting function as for using a binary volume of activation. However, the weighted test generates more significant voxels, which can be seen as larger clusters of significant voxels.


Weighting the improvement with the magnitude of the electric field gives similar results as for using binary volumes of activation. However, the weighted computation can be more sensitive to difference in the dataset especially at high electric field strengths and generate larger clusters of significant improvement.  

*Research supported by the Swedish Foundation for Strategic Research (BD15-0032) and Swedish Research Council (2016-03564)

[1] M. Åström et al., Prediction of Electrode Contacts for Clinically Effective Deep Brain Stimulation in Essential Tremor, Stereotactic and Functional Neurosurgery  (2018).

[2] M. Åström et al., Method for patient-specific finite element modeling and simulation of deep brain stimulation, Medical & Biological Engineering & Computing 47(1) (2009) 21-28.

[3] D. Vogel et al., Anatomical brain structures normalization for deep brain stimulation in movement disorders, NeuroImage: Clinical 27 (2020) 102271.

Teresa NORDIN (Linköping, Sweden), Dorian VOGEL, Erik ÖSTERLUND, Johannes JOHANSSON, Anders FYTAGORIDIS, Simone HEMM, Karin WÅRDELL
15:30 - 15:40 #26136 - Prefrontal network recruitment by STN-DBS is associated with freezing of gait after surgery in PD patients.
Prefrontal network recruitment by STN-DBS is associated with freezing of gait after surgery in PD patients.

Subthalamic deep brain stimulation (STN-DBS) is highly effective for treating dopasensitive motor symptoms of Parkinson’s disease (PD). The benefit of STN-DBS on gait disorders is variable and can result in worsened freezing of gait (FOG) in about 30% of PD patients. Factors contributing to this negative outcome are not understood. Here, we search for clinical and diffusion MRI factors that could predict this impairment. For this, we assessed the link between cortico-subthalamo-peduncolopontine tracts included in the volumes of activated tissue (VATs) by STN-DBS and the severity of gait disorders after STN-DBS at an individual level. Gait disorders were evaluated before (Off and On-dopa) and after STN-DBS using validated clinical scales (axial score, FOG-questionnaire, Gait and Balance scale) and gait recordings on a force platform in 19 PD patients (4F/15M; mean ± SD age: 59 ± 9 years; mean ± SD disease duration: 12 ± 4 years). For each patient, we localized the therapeutic DBS contacts and modeled the VAT using individual current settings [1]. 

In order to corelate cortico-subthalamo-peduncolopontine tracts included in STN-DBS VATs with the severity of gait disorders, we developed a whole brain tractography template [2] using diffusion weighted images (DWI) with 1.76 iso-voxel resolution from a cohort of preoperative PD patients (n=33) previously scanned in our center on a 3 Tesla MRI. An anatomical image template (0.9 iso-voxel resolution) was also reconstructed in the same space for the segmentation of the regions of interests. We segmented the cortex into 39 cortical Brodmann areas (BA) using MRIcro, adapting this segmentation to the cortical ribbon with Freesurfer. We visualized and segmented the pedonculopontine nucleus (PPN) using a 3D histological atlas containing a density map of cholinergic PPN neurons [3] and registered the PPN to the template space. Each individual VAT was registered to the template space as well. The cortical and PPN connectivity of each VAT was extracted from the whole brain tractography template. 

Correlations between connectivity of each VAT with the 39 Brodmann areas revealed that VAT connectivity grouped into two clusters: one prefrontal cluster (predominant connectivity with BA 8, 9, 10, 11, 32) and one sensorimotor cluster (predominant connectivity with BA 1-2-3, 4, 6) (Fig part A). We summed the connectivity for each VAT within these clusters, leaving connectivity with the PPN isolated as the only descending pathway. We then examined the correlations between the effects of STN-DBS on gait and the cortical and mesencephalic fibers contained in each individual VAT using linear regression t-test. In these 19 PD patients, we found that before surgery, gait disorders were significantly improved On-dopa (relative to Off-dopa) with a mean of 71% decrease in the axial score (range: 25-100%), and the presence of FOG Off dopa in 17 patients (mean [SD] FOG-Q: 17.5 [12.2]). With STN-DBS (Off-dopa), we observed various effects on gait ranging from a 100% improvement to a 135% worsening of the axial score, with a mean of 24% decrease in FOG severity (mean [SD] FOG-Q: 11.2 [8.4]). In this cohort, we found that FOG severity after surgery was significantly correlated with increased VAT connectivity with the right prefrontal cluster (p<0.05, Fig part B). By contrast, we observed a non-significant negative association between FOG-Q score after surgery and VAT connectivity with the sensorimotor cluster (p > 0.10, Fig part B). These data suggest that PD patients with post-operative FOG could benefit from avoiding the modulation of the prefrontal cortex-STN networks using individual DWI and directional leads, especially for the right hemisphere.


[1] Butson et al., Journal of Clinical Neurophysiology, 116.10, 2490-2500, 2005.

[2] Raffelt et al., Magnetic Resonance in Medicine, 67.3, 844-855, 2012.

[3] Sébille et al., Journal of Neuroscience Methods, 311, 222-234, 2019

Gizem TEMIZ (Paris), Angèle VAN HAMME, Claire OLIVIER, Antoine COLLOMB-CLERC, Sara FERNANDEZ-VIDAL, Elodie HAINQUE, Brian LAU, Carine KARACHI, Marie-Laure WELTER
15:50 - 16:00 #26298 - Could the individual cortico-subthalamic tractography improve surgical targeting in Parkinson's patients receiving deep brain stimulation?
Could the individual cortico-subthalamic tractography improve surgical targeting in Parkinson's patients receiving deep brain stimulation?

Deep brain stimulation of the subthalamic nucleus (STN-DBS) dramatically improves motor symptoms of patients with Parkinson's disease (PD). The mechanism of action of STN-DBS is not fully understood but the clinical effect is possibly due to both the inhibition of the STN cell bodies and the modulation of the cortico-subthalamic fibers that constitute the hyperdirect pathway. Axonal tracing in monkeys and recent studies using probabilistic tractography based on diffusion-weighted imaging (DWI) in humans showed that motor and premotor cortices provide the major input to the STN occupying mostly its posterolateral part. Conversely, limbic cortices projected to the antero-medial part of the STN whereas only few projections of associative cortices are found in between. Our aim was to determine whether mapping at an individual level the hyperdirect pathway could predict intraoperative outcomes in order to refine individual targeting.

Between December 2016 and January 2021, 30 patients with PD (18M/12F; mean age: 57± 11 years, disease duration: 10 years) and eligible for STN-DBS were prospectively included according to usual operability criteria and operated under sedation and local anesthesia. All patients had a severe parkinsonian motor disability with a mean of 71% improvement with levodopa (mean UPDRS part 3 scores Off/On- dopa: 48/13) and disabling levodopa-motor complications (mean UPDRS part 4 score: 10.3). Preoperative anatomical (0.9 iso-voxel resolution) and multi-shell DW (1.76 iso-voxel resolution) were acquired for each patient in a 3 Tesla MR. During surgery, motor disability was assessed using a simplified version of the MDS-UPDRS part 3 to assess rigidity, tremor and akinesia for the contralateral upper limb, including items 3.3 (rigidity), 3.4 (finger tapping), 3.5 and 3.6 (hand movements), and 3.15 (tremor) for each side during STN stimulation using 1 to 3 microelectrodes. We tested 3 different sites inside the STN to stimulate along 1, 2 or 3 different trajectories using 2 to 4 mAmp on each hemisphere, with 60 µs pulse width and 130 Hz pulse frequency. The benefit and side effects were noted for each stimulation site. We modeled the volume of activated tissue (VAT) for each stimulation site according to the amplitude and the impedance of each micro-electrode. We obtained a mean of 17 VATs (+/-5) for each patient. The intraoperative VATs were reconstructed in the pre-operative anatomical images space. On each patient MRI, we segmented the cortex into 39 Brodmann areas (BA) using MRIcro and performed a whole brain probabilistic tractography (with MRTrix) to constructed an individual whole brain tractogram. The streamlines between each BA and a total of 521 VATs were then extracted. We modeled the relationship between clinical changes ON stimulation and the connectivity of the VATs. Since multiple scores associated with different VATs were available for each patient, we used mixed-effects models to patient-level correlations. The repeated measure design also allowed us to separate between-patient effects from within-patient effects. 

We found that VAT connectivity with Brodmann areas 8 (frontal eye field), 9 (dorsal prefrontal cortex), and 32 (dorsal anterior cingulate cortex) were significantly associated with clinical changes (p < 0.05). Increased connectivity with BA9 was associated with clinical improvement, but only at the between-patient level. At the within-patient level, increased connectivity with BA8 was associated with clinical improvement, whereas increased connectivity with BA32 was associated with clinical worsening. Moreover, we found that patients for whom the cortico-subthalamic hyperdirect pathway deviates the most from the group contributed most to the within-patient results, suggesting that individual-level tractography can be effectively used to refine DBS electrode targeting of the STN for these patients.

Marie Des Neiges SANTIN (PARIS), Gizem TEMIZ, Sara FERNANDEZ VIDAL, Marie-Laure WELTER, Elodie HAINQUE, Eric BARDINET, Brian LAU, Carine KARACHI
16:00 - 16:10 #26308 - Structural covariance analysis to probe alterations in cortical thickness induced by essential tremor, and their renormalisation following stereotactic radiosurgical thalamotomy.
Structural covariance analysis to probe alterations in cortical thickness induced by essential tremor, and their renormalisation following stereotactic radiosurgical thalamotomy.

Essential Tremor (ET) is the most common movement disorder in the elderly, and its neurophysiological underpinnings remain to be fully elucidated. Here, we used structural magnetic resonance imaging to extract morphometric data reflective of regional cortical thickness, in right-sided drug-resistant patients suffering from ET (NET=34) and in matched healthy controls (HCs; NHC=29). Patients were scanned both before and after left unilateral stereotactic radiosurgical thalamotomy (SRS-T) of the ventral intermediate nucleus of the thalamus (see [1] for details).

Structural images were processed with Freesurfer [2] to extract values reflective of local cortical thickness, which were then averaged into the 68 parcels of the Desikan-Killiany anatomical atlas [3]. Eventually, the obtained measures were regressed out for age, gender, and total gray matter volume. From this data, we aimed at contrasting cortical thickness between (1) ET patients before surgery and matched healthy controls (to gain insight into the morphometric changes induced by ET), and (2) ET patients before and after surgery (to address the impact of SRS-T). 

For this purpose, we resorted to the computation of structural covariance (SC), in which Pearson's correlation coefficient between regional cortical thicknesses in a given pair of brain areas is computed across subjects, in group-wise fashion [4]. Structural covariance indicates to what extent two brain areas share similar morphometric properties, is influenced by genetic, cognitive and behavioral factors, and is tied to both structural and functional brain features. Group-wise SC computation yields a group difference statistic, which can be compared to a non-parametrically generated null distribution upon random shuffling of individual subjects across groups.

We considered a total of 2'278 individual edges (i.e., pairs of brain regions), and generated 100'000 null realizations. The multiple comparison problem was accounted for by a hard-thresholding screening-filtering approach that enables to take into account the positive dependence between different edges, thus strongly controlling for type I errors [5]. As this method requires an a priori classification of connections into sub-groups, we considered a sub-group as the set of connections between two given lateralised lobes of the brain, as defined in [6].

103 connections differed significantly between ET subjects before and after surgery, linking the left temporal and right frontal, left frontal and right parietal, and right parietal and right frontal lobes. The 5 most significant connections were (using the Desikan-Killiany atlas terminology, and reporting corrected p-values): R Precentral R Postcentral (p=0), L Inferior Temporal R Pars Orbitalis (p=2.35·10-4), R Inferior Parietal L Frontal Pole (p=2.51·10-4), R Supramarginal L Frontal Pole (p=4.58·10-4), and R Frontal Pole L Middle Temporal (p=6.57·10-4).

ET patients pre-surgically and HCs showed 284 significantly different connections, between the left temporal and left frontal, left and right temporal, left temporal and right frontal, left frontal and right temporal, left and right frontal lobes, and within the left frontal lobe. The top 5 most significant connections were: R Middle Temporal L Pars Orbitalis (p=4.19·10-5), R Superior Temporal L Pars Orbitalis (p=8.1·10-5), R Pars Opercularis - L Middle Temporal (p=8.94·10-5), R Superior Temporal - L Inferior Temporal (p=1.06·10-4), and R Banks STS - L Entorhinal (p=1.43·10-4).

In sum, our results point to marked group differences in the cross-regional dependence of cortical thickness. Compared to HCs, ET induced broad differences within, and across, the bilateral temporal and frontal lobes. SRS-T partly enabled the renormalisation of such interactions, while at the same time triggering additional readjustments involving parietal brain structures. Our results thus support the effectiveness of SRS-T to alleviate ET, and open up novel perspectives to comprehend its pathophysiology and its post-surgical evolution.



[1] Tuleasca C.*, Bolton T.A.W.* et al (2019) Journal of neurosurgery132(6), 1792-1801.

[2] Fischl B. (2012) Neuroimage62(2), 774-781.

[3] Desikan R.S. et al. (2006) Neuroimage31(3), 968-980.

[4] Alexander-Bloch A. et al. (2013) Nature Reviews Neuroscience14(5), 322-336.

[5] Meskaldji D. E. et al. (2015) NeuroImage108, 251-264. 

[6] Klein A. and Tourville J. (2012) Frontiers in neuroscience6, 171.

Thomas BOLTON (Lausanne, Switzerland), Dimitri VAN DE VILLE, Jean RÉGIS, Tatiana WITJAS, Nadine GIRARD, Marc LEVIVIER, Constantin TULEASCA
16:10 - 16:20 #23975 - Combining 7-Tesla T2 and 3T FGATIR Sequences for STN Identification.
Combining 7-Tesla T2 and 3T FGATIR Sequences for STN Identification.

Background: In deep-brain stimulation, new 3-Tesla (3T) and 7-Tesla (7T) MRI sequences could improve the visual identification of the borders of the subthalamic nucleus (STN).


Objective: To study the usefulness of 7T T2 MRI and 3T FGATIR MRI in identifying the borders of the STN in patients undergoing DBS for Parkinson’s disease.


Methods: STN borders identified by pre-operative 7T T2 and 3T FGATIR MRI were compared with STN-borders obtained intraoperatively by micro-electrode recording. Electrode localization was done using intraoperative cone beam CT.


Results: Sixty-four microelectrode tracks were evaluated, all but one showing activity typical for STN. The average difference between border determination on MRI and MER was 0.4 millimeter for the dorsal border and 0.2 millimeter for the ventral border.


Conclusion: Combining the 7T T2 and 3T FGATIR sequences provides an accurate representation of the electrophysiological STN activity as measured by MER, thereby providing reliable anatomical identification for surgical planning.



Figure legend

Overview of the mesencephalic area showing subthalamic nucleus and substantia nigra on 7T T2 and 3T FGATIR MR and corresponding MER.


Niels RIJKS (Amsterdam, The Netherlands), Wouter POTTERS, José BILAI, Rob DE BIE, Wietske VAN DER ZWAAG, Rick SCHUURMAN, Pepijn VAN DEN MUNCKHOF, Maarten BOT
16:25 - 16:30 #23823 - Turn’em off – to identify stimulation-induced cerebellar syndrome in VIM/DRT-DBS for essential tremor.
Turn’em off – to identify stimulation-induced cerebellar syndrome in VIM/DRT-DBS for essential tremor.


Up to 20 % of patients with DBS of the VIM/dentato-rubro-thalamic bundle (DRT) for essential tremor develop a stimulation-induced cerebellar syndrome, which is difficult to treat and has effects on the quality of life. It emerges gradually over years and is often difficult to detect in the early time course. While the exact cause is elusive, different theories have been discussed. Among them is the (supratherapeutic) co-stimulation of further cerebellar output pathways in addition to the DRT (Gropppa et al., Brain 2014) and antidromic stimulation of the cerebellum (Reich et al., Brain 2016). A thorough diagnostic work up was performed in affected patients and multi-modal data were retrospectively analyzed to identify common symptom patterns and potential causes.


In eight patients who complained about recurrent tremor and cerebellar symptoms after VIM/DRT-DBS a cerebral [18F]FDG PET, a tremor (accelerometer & EMG) and gait (video-based markerless motion capture system) analyses were performed with activated DBS (DBSON) and 72 hours after deactivation (DBSOFF_72h); gait and tremor were also analyzed directly after deactivation (DBSOFF). Exploratory PET analyses (categorical comparisons and correlations) were done with SPM.


Across all patients, we found a significantly increased metabolism of the thalamus and dentate nucleus and a decreased metabolism of the cerebellar hemispheres with DBSON (p < 0.01). Thalamic metabolism correlated positively with the metabolism of the dentate nucleus (both conditions pooled, p < 0.01). The coefficient of variation (CoV) of step length (a marker of gait ataxia) with DBSON correlated negatively with the change in metabolism of the right cerebellar hemisphere (DBSON – DBSOFF_72h; p < 0.01). The drop of frequency of postural tremor of the right hand upon deactivation of DBS (DBSOFF– DBSON) correlated with gait ataxia (CoVsteplength) with DBSON (p < 0.05).  The frequency of postural tremor on the right showed a differential course across patients.


We observed differential changes of neuronal activity in the dentate nucleus and cerebellar hemispheres according to stimulation state (DBSON vs. DBSOFF_72h). Increased neuronal activity of the thalamus with DBSON correlated positively with the increase of neuronal activity of the dentate nucleus, supporting the theory of antidromic stimulation, while reduced activity of the cerebellar hemispheres correlated with gait ataxia. The course of tremor frequency before and after deactivation of DBS may help to identify patients developing a stimulation induced cerebellar syndrome.

Bastian Elmar Alexander SAJONZ (Freiburg, Germany), Ganna BLAZHENETS, Marvin Lucas FROMMER, Isabelle WALZ, Johannes THUROW, Christoph MAURER, Michel RIJNTJES, Philipp Tobias MEYER, Volker Arnd COENEN
16:30 - 16:35 #23828 - Impaired movement-related beta band modulation precedes freezing episodes: hypothesis from upper limb freezing for novel STN sensing technology.
Impaired movement-related beta band modulation precedes freezing episodes: hypothesis from upper limb freezing for novel STN sensing technology.


Objective: Freezing phenomena in Parkinson’s disease (PD) constitute an important unaddressed therapeutic need. Changes in cortical neurophysiological signatures may precede a single freezing episode and indicate the evolution of abnormal motor network processes. Here, we hypothesized that the movement-related power modulation in the beta-band observed during regular finger tapping deteriorates in the transition period between regular tapping and upper limb freezing (ULF).

Methods: We analyzed a 36-channel EEG of 13 patients with idiopathic PD during self-paced repetitive tapping of the right index finger. In offline analysis, we identified ULF episodes and compared the period immediately before ULF (‘transition’) with regular tapping regarding movement-related cortical frequency domain activity and cortico-cortical phase synchronization.

Results: From time-frequency analyses, we observed that the tap cycle related beta-band power modulation over the contralateral sensorimotor area was diminished in the transition period before ULF. Furthermore, increased beta-band power was observed in the transition period compared to regular tapping centered over the contralateral centro-parietal and ipsilateral frontal areas.

Conclusion: Here, we demonstrate that impaired beta power modulation precedes freezing in upper limb movement. From this work, we generate the hypothesis that beta band related power modulations may also precede freezing of gait episodes. We will translate this finding to freezing of gait by analyzing local field potentials (LFPs) of the subthalamic nucleus in patients with next generation impulse generators with available sensing technology (Medtronic, Percept™ PC) Deterioration of beta power modulation prior to freezing has potential to evolve as biomarker in order to treat and prevent freezing of gait episodes with adaptive stimulation.

Significance: We demonstrate that impaired beta power modulation represents the transition phase from regular tapping to freezing of upper limb movement.

Maria-Sophie BREU, Marlieke SCHOLTEN, Alireza GHARABAGHI, Daniel WEIß (Tuebingen, Germany)
16:35 - 16:40 #23903 - The Multi Recharge Trial: A multicenter, open-label, controlled trial on acceptance, convenience, and complications of rechargeable internal pulse generators for deep brain stimulation.
The Multi Recharge Trial: A multicenter, open-label, controlled trial on acceptance, convenience, and complications of rechargeable internal pulse generators for deep brain stimulation.


Rechargeable neurostimulators for deep brain stimulation have been available since 2008, promising longer battery life and fewer replacement surgeries compared to non-rechargeable systems. Long-term data on how recharging affects movement disorder patients is sparse. This is the first multicenter, patient-focused, industry-independent study on rechargeable neurostimulators.



Four neurosurgical centers sent a questionnaire to all adult movement disorder patients with a rechargeable neurostimulator implanted at the time of the trial. The primary endpoint was the convenience of the recharging process rated on an ordinal scale from very hard (1) to very easy (5). Secondary endpoints were charge burden (time spent per week on recharging), user confidence, and complication rates. Endpoints were compared for several subgroups (age, type of movement disorder, type of IPG, timepoint of rechargeable IPG implantation, person performing the  recharging, user confidence, drivers).



Datasets of 195 movement disorder patients (66.1% of sent questionnaires) with Parkinson’s disease (PD), tremor, or dystonia were returned and included in the analysis. Patients had a mean age of 61.3 years and the device was implanted for a mean of 40.3 months. The overall convenience of recharging was rated as easy (4). The mean charge burden was 122 min/wk and showed a positive correlation with duration of therapy; 93.8% of users felt confident recharging the device. The rate of surgical revisions was 4.1%, and the infection rate was 2.1%. Failed recharges occurred in 8.7% of patients, and 3.6% of patients experienced an interruption of therapy because of a failed recharge. Convenience ratings by PD patients were significantly worse than ratings by dystonia patients. Caregivers recharged the device for the patient in 12.3% of cases. Patients who switched from a non-rechargeable to a rechargeable neurostimulator found recharging to be significantly less convenient at a higher charge burden than did patients whose primary implant was rechargeable. Age did not have a significant impact on any endpoint.



Patients with movement disorders rated recharging as easy, with low complication rates and acceptable charge burden.

Martin JAKOBS (Heidelberg, Germany), Ann-Kristin HELMERS, Philipp SLOTTY, Jürgen SCHLAIER, Karl KIENING, Andreas UNTERBERG
16:40 - 16:45 #23906 - Deep brain stimulation in patients with chronic antithrombotic or anticoagulation treatment: a series of 34 patients.
Deep brain stimulation in patients with chronic antithrombotic or anticoagulation treatment: a series of 34 patients.

Background:  In the aging society many patients with movement disorders, pain syndromes or psychiatric disorders who are candidates for deep brain stimulation (DBS) surgery suffer also from cardiovascular co-morbidities that require chronic antithrombotic or anticoagulation treatment. Because of a presumed increased risk of intracranial hemorrhage during or after surgery and limited knowledge about perioperative management chronic antithrombotic or anticoagulation treatment usually has been considered a contraindication for DBS.

Objective: To determine whether or not there is an increased risk for intracranial hemorrhage or for thromboembolic complications in patients under chronic antithrombotic or anticoagulation treatment (paused for surgery or bridged with subcutaneous heparin) as compared for those without.

Methods: Out of a series of 465 patients undergoing functional stereotactic neurosurgery, 34 patients were identified who were under chronic antithrombotic or anticoagulation treatment before and after receiving DBS. In patients with antiplatelet treatment medication was stopped in the perioperative period. In patients with vitamin K antagonists or NOACs, heparin was used for bridging. All patients had postoperative stereotactic CT scans, and were followed-up for 1 year after surgery.

Results: In patients with chronic antithrombotic or anticoagulation treatment intracranial hemorrhage occurred in 2/ 34 (5.9%) DBS surgeries whereas without the rate of intracranial hemorrhage was 15/ 431 (3.5%) which was statistically not significant. Implantable pulse generator pocket hematomas were seen in 2/ 34 (5.9%) surgeries in patients with chronic antithrombotic or anticoagulation treatment and in 4/ 426 (0.9%) without. There were only 2 instances of thromboembolic complications which both occurred in patients without chronic antithrombotic or anticoagulation treatment. There were no hemorrhagic complications during the follow-up for 1 year.

Conclusion: DBS surgery in patients with chronic antithrombotic or anticoagulation treatment is feasible. Appropriate patient selection and standardized perioperative management are necessary to reduce the risk of intracranial hemorrhage and thromboembolic complications. Furthermore, we could not identify an increased risk of hemorrhage in the first year of follow-up after DBS surgery.

Luisa CASSINI ASCENCAO, Joachim RUNGE (Hannover, Germany), Thomas KINFE, Christian BLAHAK, Christoph SCHRADER, Marc WOLF, Assel SARYYEVA, Joachim KRAUSS
16:45 - 16:50 #23932 - High frequency stimulation of the subthalamic nucleus restores sensorimotor and motor cortical oscillatory activity in a free-moving rat model of Parkinson's disease.
High frequency stimulation of the subthalamic nucleus restores sensorimotor and motor cortical oscillatory activity in a free-moving rat model of Parkinson's disease.

Background: Altered oscillatory activity in cortical-basal ganglia thalamic circuitries, especially enhanced activity in the beta band, have been linked to motor symptoms in Parkinson`s disease (PD). The subthalamic nucleus (STN) is targeted for deep brain stimulation (DBS) in PD and chronic stimulation has been shown to reduce beta band activity.

Objective: The effect of STN DBS on spectral power of oscillatory activity in the commonly used frequency bands in the motor cortex (MCtx) and sensorimotor cortex (SMCtx) was investigated by recording oscillatory activity via cortical electrode grids in free-moving 6-hydroxydopamine (6-OHDA) lesioned hemiparkinsonian (HP) rats and sham-lesioned controls.

Methods: Fifteen male Sprague Dawley rats (250-350g) were either rendered HP by unilateral injection of 6-OHDA (n=8), or by injection of saline (sham-lesioned; n=7) in the right medial forebrain bundle. After three weeks of surgical recovery, a DBS electrode was implanted in the STN, and an electrocortigram (ECoG) recording array was placed under the dura above the MCtx and SMCtx areas of the right hemisphere. All surgeries were performed under chloral hydrate (360 mg/kg; i.p.) anesthesia. Six days after surgery, free-moving rats were individually recorded in three conditions: (1) basal activity, (2) during STN DBS (130Hz, biphasic square pulse width of 80 µs, individual current intensity threshold (100 µA - 400 µA)), and (3) directly 300 seconds after STN DBS. Spectral power of oscillatory activity of theta (4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz) and gamma (30-100 Hz) were analyzed in the MCtx and SMCtx areas and compared between HP and sham-lesioned rats.

Results: In HP rats, the relative power of theta band activity was lower, and beta and gamma activity were higher in MCtx and SMCtx. This was reverted towards control level by STN DBS during stimulation and in the first 300 seconds after stimulation. No differences were found between MCtx and SMCtx.

Conclusion: Our results provide evidence that loss of nigrostriatal dopamine leads to increased beta and gamma, and reduced theta oscillatory activity in motor and sensorimotor cortical areas, which is compensated by STN stimulation both during and directly after stimulation.

Arif ABDULBAKI, Theodor DOLL, Joachim K. KRAUSS, Kerstin SCHWABE (Hannover, Germany), Mesbah ALAM
16:50 - 16:55 #23948 - Adoption of focused ultrasound thalamotomy for essential tremor: why so much fuss about FUS?
Adoption of focused ultrasound thalamotomy for essential tremor: why so much fuss about FUS?


Focused ultrasound (FUS) was approved as a new treatment modality for Essential Tremor (ET) in 2016. The goal of this study was to quantify FUS adoption for ET and understand its drivers.



The adoption of the various surgical options for ET was estimated using 3 measures: the number of presentations on the various surgical treatments for ET at specialized international meetings, the number of original papers published as identified by literature searches and the number of thalamotomy procedures performed worldwide for ET as provided by device manufacturers’ registries.   



First, we found that the number of presentations related to lesioning procedures are increasing relative to DBS at international meetings. Second, there are already more publications on FUS (93) than SRS (68) or radiofrequency (43) for ET, although they still lag behind DBS papers (750). Third, the number of annual FUS thalamotomies performed for ET (n > 1200 in 2019) in 44 centers, has surpassed the annual procedures across 342 GK units (n < 400, 2018) but is yet to reach the number of DBS cases for ET estimated at over 2400 per year. FUS adoption over GK cannot be explained by efficacy, safety, patient experience or cost factors. We hypothesize that the ability to perform intraoperative clinical assessments, the manufacturers’ interest in functional neurosurgery and functional neurosurgery’s key opinion leaders’ involvement in the technology are currently the real drivers of FUS uptake. 



FUS is being rapidly adopted for the treatment of ET.  We hypothesize that its minimally invasive nature coupled with the ability to perform intraoperative clinical assessments, its immediate effects and active marketing efforts are contributing factors. As lesioning modalities for the treatment of ET are reappraised, the superior popularity of FUS over SRS appears to arise for reasons other than differences in clinical outcomes.

Christian IORIO-MORIN (Sherbrooke, Canada, Canada), Mojgan HODAIE, Andres LOZANO
16:55 - 17:00 #23679 - Tremor and quality of life in patients with advanced essential tremor before and after replacing their standard deep brain stimulation with a directional system.
Tremor and quality of life in patients with advanced essential tremor before and after replacing their standard deep brain stimulation with a directional system.


Patients with essential tremor (ET) treated with thalamic deep brain stimulation (DBS) may experience increased tremor with the progression of their disease. Initially, this can be counteracted with increased stimulation. Eventually, however, this increased stimulation may cause unwanted side-effects as the circumferential effects of stimulation from a standard ring contact spreads into adjacent regions. Directional DBS leads may offer a solution to this clinical problem.


We compared the ability of a standard and a directional DBS system to reduce tremor without side-effects and to improve the quality of life for patients with advanced ET.


Six advanced ET patients with bilateral thalamic DBS had their standard DBS system replaced with a directional DBS system. Tremor rating scale scores were prospectively evaluated before and after the replacement surgery. Secondary analyses of quality of life related to tremor, voice, and general health were assessed.


There was a significantly greater reduction in tremor without side-effects (p=0.017) when using the directional DBS system compared to the standard system. There were improvements in tremor (p=0.031) and voice (p=0.037) related quality of life but not in general health for patients using optimized stimulation settings with the directional DBS system compared to the standard system.


In this cohort of advanced essential tremor patients who no longer had ideal tremor reduction with a standard DBS system, replacing their DBS with a directional system significantly improved their tremor and quality of life. Up-front implantation of directional DBS leads may provide better tremor control in those patients who progress at a later time point.


Marie T. KRÜGER (St.Gallen, Switzerland), Josue M. AVECILLAS-CHASIN, Mini K. SANDHU, Nancy E. POLYHRONOPOULOS, Natasha SARAI, Christopher R. HONEY
Grand Amphithéâtre

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
15:00 - 17:00

Parallel Session 12
Young Functional NS Session

Moderators: Attilio DELLA TORRE (Neurosurgeon) (CATANZARO, Italy), Emmanuel DE SCHLICHTING (PHC) (Grenoble, France)
15:00 - 15:10 #23792 - Development of Diffusion Tensor Imaging and Tractography for Spinal Cord.
Development of Diffusion Tensor Imaging and Tractography for Spinal Cord.

Introduction: In vivo spinal cord fiber tracts have never been described precisely in humans. Current knowledge corresponds to the results of animal dissections, cyto-histological findings and electrophysiological approaches. Advances in brain MRI have recently made it possible, via Diffusion Tensor Imaging (DTI), to highlight the tracts of the brain's white matter. To date, no study has been able to differentiate clearly spinal cord tracts using tractography.


Methods: 1) Using the MEDLINE database, a systematic review was carried out to try to define the optimal DTI parameters used until now for spinal cord tractography studies. 2) From MRI of the EMISEP (healthy subject cohort database), starting with the parameters previously defined, evaluate the effect of patient geometry (sagittal balance) and acquisition geometry on the quality of the tractography rendering, before and after distortion correction (with DSIStudio software). 3) From previous data, develop an original DTI protocol to distinguish different spinal tracts.


Results :

1)      Best DTI parameters coming from literature have been defined.

2)      Distortion corrections had a direct impact on the tractography according to the patient's sagittal balance. Moreover, the geometry of the acquisition had a direct impact on the quality of the tractography rendering, since adaptations had to be performed at each vertebral level.

3)      Performing a stitching process between encephalic and spinal cord DTI data, and a meticulous placement of region of interest are both keys to distinguish different fiber tracts inside the spinal cord. By performing these post-processing distorsions, the corticospinal tract, can be distinguish from the spinal cord disease (tumor for example) and allows new advances neuro-anatomy, and spinal cord neurosurgery.


Conclusion: The differentiation of spinal tracts with tractography seems to be possible. This imaging would be useful to improve human neuroanatomical and physiological knowledges. When will become usable in routine, spinal DTI will allow to analyze the consequences of intraspinal deseases on fiber tracts and could help the neurosurgeon to define their surgical approaches to intraspinal lesions.

Corentin DAULEAC (LYON), Patrick MERTENS, Carole FRINDEL, Francois COTTON
15:10 - 15:20 #23905 - SPECTRE - A dMRI visualization technique for the display of cerebral connectivity.
SPECTRE - A dMRI visualization technique for the display of cerebral connectivity.

Objective: The analysis and visualization of brain's white matter structures by diffusion magnetic resonance imaging (dMRI) is becoming an important prerequisite during planning of neurosurgical interventions (1). In this work, we propose a rather simple approach to visualize structural connectivity information in certain target regions (Spectre - Subject sPEcific brain Connectivity display in Target REgion). Our idea is closely related to track-weighted imaging (2), where dMRI streamlines are used to aggregate distal information, however we use normative geometric information as the underlying contrast for aggregation. For example, if we want to know whether a voxel in the brain is rather connected to the frontal or to the posterior region, we could just compute the mean of the y-coordinate (in MNI space) along each fiber emitted in this voxel. To realize this concept in a way, which is more suitable for visualization, we assigned cortical regions certain colors in a continuous fashion.

Methods: The concept is demonstrated on a group of subjects from the human connectome project (HCP). The used coloring scheme and target area is shown in Figure A. The rationale of the coloring scheme was developed in appreciation of deep brain stimulation (DBS) planning especially for the subthalamic nucleus (STN). STN anatomy typically is interpreted as follows: Medial and anterior parts of the nucleus are regarded as “limbic” and connect to prefrontal and frontopolar parts of the cortex. Adjacent and more posterior regions are the prefrontal association regions followed on the  posterior and lateral by motor parts (3). With this idea in mind the STN was color-coded in a ‘fronto-polar to motor’ gradient (green to blue) by its mere connectivity pattern.  For warping the coloring scheme to native space of the subject, SPM’s CAT12 is applied on the provided T1 images and the corresponding warping fields are used for warping.  For tract/fiber orientation distributions (FODs) were determined by (4). Then, ordinary probabilistic streamline tractography similar to FSL’s probtrax is used to generate the SPECTRE contrast. Seeds were placed in the area to be colored (here the midbrain) and during propagation of the streamlines the underlying coloring is accumulated. In every voxel (we use a supersolution of 0.5mm isotropic), 500 streamline were seeded to get a robust color value in each voxel.  We applied this procedure on 200 HCP subjects, normalized to group space (MNI) and averaged the SPECTRE maps. 

Results: In Figure B a transversal slice for an example subject together with outlines of deep nuclei is given, while in Figure C several transversal slices of the group average in MNI space are displayed. SPECTRE shows how the fronto-parietal-occipital cortical gradient experiences a twist by 90° while proceeding ventrally towards the midbrain, where the gradient becomes mostly medial-lateral with an interruption at the interface between RN and SNR. The interpretation of the fronto-parietal gradient as limbic-associative-sensori/motor is quite intuitive, in particular when focusing on the STN. In the tripartite descriptions (5) medial/anterior and inferior parts are regarded as limbic and connect prefrontally, especially to frontopolar and orbitofrontal regions. More posterior regions are the prefrontal association regions of the dorsolateral and prefrontal cortex followed laterally by motor parts (3). This agrees mostly with the segmentation used by Ewert et al (6). In Figure D Ewert’s STN subsegmentation is shown, in E the STN overlaid by the group SPECTRE maps. 

Discussion: With the aim of giving neuroscientists a comprehensive view of structural connectivity patterns we have proposed a novel imaging principle, which joins individual tractographic information with normative anatomical information.  SPECTRE allows us to appreciate the fronto-occipital connectivity gradient on the individual level and thereby helps to understand the amount of frontopolar contribution of connectivity to the STN and the region just adjacent to it. Preliminary experiments (not shown) suggest that robust and repeatable SPECTRE maps can be computed, even on clinically feasible dMRI data.

References: (1) Essayed et al. NeuroImage Clin. 2017;15:659–672.  (2) Calamante et al. Neuroimage. 2010;53(4):1233–1243. (3) Haynes et al. J Neurosci. 2013;33(11):4804–4814. (4) Alkemade et al. Brain Struct Funct. 2015;220(6):3075–3086. (5) Ewert et al. Neuroimage. 2018;170:271–282.

Marco REISERT, Christoph KALLER, Horst URBACH, Bastian SAJONZ (Freiburg, Germany), Marvin REUTER, Peter C. REINACHER, Volker Arnd COENEN
15:20 - 15:30 #23994 - Accuracy, precision and safety of stereotactic, frame-based, intraoperative MRI-guided and MRI-verified deep brain stimulation in 650 consecutive procedures.
Accuracy, precision and safety of stereotactic, frame-based, intraoperative MRI-guided and MRI-verified deep brain stimulation in 650 consecutive procedures.


Introduction and Aims

Ensuring a safe and accurate approach is fundamental in stereotactic functional neurosurgery. Reliance on anatomical targeting and dispensing with awake surgery is growing in popularity but can be vulnerable to suboptimal targeting. Despite the use of traditional techniques such as microelectrode recording (MER), suboptimal lead placement is currently one of the commonest indications for revision DBS procedures. This can be avoided by confirming lead placement in relation to the visible anatomical target with dedicated imaging during the procedure. Here, the accuracy, precision and safety of using intraoperative-MRI (iMRI) to both guide and verify lead placement during frame-based stereotactic surgery is examined.

Materials and methods

A 1.5 T MRI machine was installed in our surgical theatre in August 2011. Retrospective analysis of 1201 DBS leads implanted in 650 consecutive procedures over an 8-year period (Aug 2011 to Aug 2019) was performed for targeting accuracy, precision and perioperative complications. All patients underwent frame-based lead placement adjacent to the MRI machine with image verification before removing the stereotactic frame, allowing immediate lead re-implantation when necessary and systematic analysis of the targeting error. Fisher Exact test was used for statistical significance when relevant (p value set at 0.01)


Verification with stereotactic MRI was performed in 643 procedures and with stereotactic CT in 7.  The mean final targeting error was 0.85 mm, +/- 0.29 mm SD (range 0.05-2.29). Accuracy was submillimetre in 68 %, within the diameter of the implanted lead (1.27mm) in 80 % and within 1.5 mm in 92 % of analysed leads. Anatomically acceptable lead placement was achieved with a single brain-pass in 97% (n = 1164) of leads; immediate intraoperative relocation was performed in 37 of 1201 leads (3 %) to obtain satisfactory anatomical placement. General Anaesthesia was used in 91% (n=593) of procedures.

Four patients suffered a haemorrhage (0.6%), three presenting with transient neurological symptoms (0.4%), one associated with delayed cognitive decline [Figure]. We do not think that any of the haemorrhages led directly to long term deficits. Two of the bleeds coincided with immediate retargeting (2 of 37 leads, 5.4%). This contrasts with haemorrhage in 2 of 1164 leads implanted on first-pass. (0.17%) (p-value 0.0053)

Transient behavioural changes were noted in 27 patients (4.2%), while 2 suffered from moderate cognitive decline following surgery despite no radiological evidence of haemorrhage. Three patients had transient seizures in the postoperative period, two of which coincided with haemorrhage and one with immediate lead retargeting.

There were 21 infections leading to hardware removal (3.2% of patients), seven of which commenced cranially. Fourteen patients presenting with infection around the neurostimulator were initially treated by removal of the neurostimulator and cables plus appropriate antibiotic therapy; however, 12 of these ultimately progressed to total removal of hardware.

Delayed (>3 months) retargeting of 6 leads (0.5% of 1201) in four patients (0.6%) was performed following suboptimal stimulation benefit. Delayed distal maintenance procedures were performed in 20 patients (3.1%) due to hardware failure (n=10), discomfort or erosion (n=10). There were no MRI related hardware issues, no motor deficits and mortality was zero.


To our knowledge, this is the largest series reporting on the use of iMRI as a tool to both guide and verify lead location during DBS surgery. It demonstrates a high level of accuracy, precision and safety across targets, patients and surgeons. Although numbers are small, a significantly higher rate of haemorrhage was encountered when multiple brain passes were required for lead implantation. Thankfully, all of the haemorrhages were small and did not lead to permanent deficit. Nevertheless, this emphasises the importance of meticulous accuracy, perpetual audit and calibration to improve precision and maximise the safety of stereotactic functional neurosurgery.

Ali RAJABIAN (London Queen Square, United Kingdom), Saman VINKE, Joseph CANDELARIO, Catherine MILABO, Maricel SALAZAR, Karim NIZAM, Nadia SALLOUM, Jonathan HYAM, Harith AKRAM, Eileen JOYCE, Thomas FOLTYNIE, Patricia LIMOUSIN, Marwan HARIZ, Ludvic ZRINZO
15:35 - 15:40 #23902 - Portable magnetic resonance imaging for intensive care unit patients.
Portable magnetic resonance imaging for intensive care unit patients.


Patients in an intensive care unit (ICU) often require neuroimaging to rule out a wide variety of intracranial problems. Computed tomography (CT) may be available in the ICU itself, but magnetic resonance imaging (MRI) has greater sensitivity for many conditions that affect the brain. However, transporting patients who are on ventilators and other life-sustaining devices is a labor intensive process and involves placing the patient at risk for adverse events. This is the first report of portable MRI in a clinical setting. 


This is a prospective, non-randomized, observational study at one institution utilizing portable MRI in patients with laboratory confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Patients selected for imaging had any of the following: 1) unexplained encephalopathy or coma, 2) seizures, 3) focal neurologic deficit, 4) abnormal head CT. Imaging was performed in each patient’s ICU room with a portable, self-shielding, 0.064 Tesla (T) MRI.  


Among 19 patients, a total of 20 MRI scans in seven ICUs were acquired between April 20 and May 1, 2020. No adverse events to patients or staff from MRI acquisition were reported. In 12 patients, abnormal findings were seen, which included increased fluid attenuated inversion recovery (FLAIR) signal (n=12), hemorrhage (n=3), and diffusion-weighted imaging (DWI) positivity (n=3). Imaging led to a change in clinical management in 5 patients. 


Portable MRI is safe, feasible, and leads to changes in clinical management. This technique can be applied to any ICU patient whose care requires imaging of the brain. This novel technology offers a path towards new modalities for bedside stereotaxis and intraoperative imaging.

Justin TURPIN (New York City, USA), Prashin UNADKAT, Justin THOMAS, Nick KLEINER, Shahab KHAZANEHDARI, Sheshali WANCHOO, Kenia SAMUEL, Moclair BETSY, Karen BLACK, Amir DEHDASHTI, Raj NARAYAN, Richard TEMES, Michael SCHULDER
15:40 - 15:45 #23935 - Perfusion MRI findings in motor cortex and basal ganlions in Parkinson's disease patients resistant to medical treatment: single centre experiment.
Perfusion MRI findings in motor cortex and basal ganlions in Parkinson's disease patients resistant to medical treatment: single centre experiment.

Background: Parkinson's disease (PD), is a neurodegenerative disease characterized by, the loss of dopaminergic neurons in substantia nigra.

Objective: To contribute to the pathogenesis of the disease by comparing Diffusion tensor (DTI) and contrast perfusion MRI (PWI) findings in medical treatment resistant PD cases.

Material and Methods: 19 control and 18 medical treatment-resistant PD cases, who are candidates for deep brain stimulation, were included in our study. DTI and PWI examination were performed on all cases. Cerebral blood flow (rCBF), mean transit time (MTT) and fractional anisotropy (FA) values were measured in both hemispheres; on primary motor cortex (M1), supplementary motor cortex (SMA), putamen (P), external and internal globus pallidus (GPe / GPi), ventrolateral nucleus (T) of the thalamus, substantia nigra(SN).

Results: The average age of our control group cases was 59.2 ± 13.2 (31-79) and the median was 60 years. The average age of PD patient group was 56.7 ± 16 (42-77) and the median was 60.5 years. The duration of the disease was 12.4 ± 7.1 (5-30) years on average. In PD group, FA values were significantly lower (p ˂ 0.05) than the control group, in all regions. In the case group, rCBF-SMA values on both sides were significantly higher than the control group (p˂ 0.05). In the case group, MTT-GPi value on the left and MTT-M1, MTT-SMA, MTT-GPe and MTT-T values on both sides were significantly higher than the control group (p ˂ 0.05).

Conclusion: It is thought that decrease in FA compared to the control group in all regions except the motor cortex may be secondary to cell loss. In PWI, on the other hand, in medical treatment resistant PD cases, rCBF, increases in the supplementary motor and motor cortex. MTT, moreover, is prolonged in all regions, evident in left GPi. Perfusion differences may be due to increased blood brain barrier permeability, endothelial degeneration, and abnormal angiogenesis, and may contribute to dopa-resistant symptoms in PD cases. More research is needed to improve measurement techniques and standardize research protocols, not only to improve diagnostic accuracy, but also to monitor treatment effectiveness in clinical trials.

Halime CENKERI, Atilla YILMAZ (Istanbul, Turkey), Sadik Ahmet UYANIK, Eray ATLI, Umut OGUSLU, Birnur YILMAZ, Burçak GÜMÜŞ
15:45 - 15:50 #25834 - Feasibility of burr hole ultrasound to improve deep brain structure visualization for neuromodulation.
Feasibility of burr hole ultrasound to improve deep brain structure visualization for neuromodulation.


Deep brain stimulation (DBS) relies on precise electrode targeting and stimulation of small, deep structures within the brain to effectively treat various movement disorders. Target accuracy is contingent upon an assumed rigid alignment between the preoperative imaging data and intraoperative patient anatomy. However, this assumption can be compromised by intraoperative brain shift. Although gold-standard microelectrode recording (MER) effectively accounts for brain shift, it requires patients to remain unmedicated and awake in addition to potentially introducing intracranial bleeding due to multiple lead passes. Intraoperative magnetic resonance (MR) imaging is an effective alternative, but the associated image distortion from the implant as well as encumbrance and cost hinder widespread adoption. Considering that shift only occurs in approximately 10-20% of implants, we propose the use of low-cost burr hole ultrasound (US) during DBS to better visualize brain subsurface structures, and to potentially account for deleterious instances of brain shift during surgery. In this work, we aim to demonstrate initial feasibility of using burr hole US registered to preop MR as an additional intraoperative guidance tool for DBS.



A BK5000 ultrasound system and N11C5 burr hole transducer were used to acquire coronal and sagittal ultrasound images during N=6 DBS procedures. Ultrasound images were acquired prior to the placing of the stereotactic frame and implanting of electrodes for each case. The probe was sterilized prior to the start of each procedure. Corresponding MR slice views were selected using CRAVE-registered pre-op MR and post-op CT scans with lead placement confirmation. Regions of interest (ROIs) corresponding to the ventricles were manually generated on the US and MR slices using MATLAB. An iterative closest point (ICP) algorithm was used to map the US ROI to the MR ROI, and the corresponding transformation matrix was used to register the US image to the MR image. The percent of overlap between the US and MR ROIs was computed for each case and slice view. Additionally, a root mean square error (RMSE) was computed on the areas of the ROIs for each slice view.



The coronal and sagittal US ventricle ROIs resulted in 89.3% and 83.0% overlap, respectively, with the MR ventricle ROIs. The RMSE between the US and MR areas of the coronal and sagittal ROIs were 0.42cm2 and 1.77cm2, respectively. Fig. 1 shows example coronal US and MR ventricle ROIs before and after ICP registration.



The results in this work demonstrate that burr hole US can be used intraoperatively to better visualize deep brain structures that align well with preoperative imaging data. Although intraoperative US by itself can be difficult to interpret, we have demonstrated in this work that it has the potential to be an invaluable real-time guidance tool when registered to preoperative MR. Moreover, we hypothesize that, once optical tracking is incorporated, burr hole US can be used to drive biomechanical models of brain shift that normally rely on sparse intraoperative surface data, which is otherwise difficult to obtain within a small burr hole.

Jaime TIERNEY (Nashville, USA), Hamid SHAH, Michael MIGA
15:50 - 15:55 #25963 - Evaluating functional connectivity differences between DBS ON/OFF states in essential tremor patients.
Evaluating functional connectivity differences between DBS ON/OFF states in essential tremor patients.

Introduction: Essential tremor (ET) is a debilitating disease affecting millions. DBS targeting the ventral intermediate (Vim) nucleus of the thalamus has been an effective treatment modality for years. Yet, it is unclear which functional connections in the brain are most modulated by DBS to effect tremor control, and in fact, are most influential in tremor production.


Objective: We studied ET patients undergoing DBS of a major input/output tract of the Vim, the dentato-rubro-thalamic tract (DRTt), using resting state functional MRI (rsfMRI). By collecting rsfMRI scans with DBS ON at parameters for optimal tremor control, and then again with DBS OFF, our goal was to evaluate functional connectivity differences between the two states in the hopes of elucidating which regions connected to the motor cortex might be most involved in tremor regulation.


Methods: We enrolled five ET patients who had previously undergone DBS of the DRTt. Tremor severity using The Essential Tremor Rating and Assessment Scale (TETRAS) was scored with DBS ON at optimal stimulation parameters and with DBS OFF. Anatomical (gradient echo FFE 3D T1 sequence sagittal acquisition; voxel size = 1.2x0.94x0.94 mm3; TR 8.5 ms; TE 4.0 ms; Flip Angle 8) and functional (fMRI BOLD EPI sequence axial acquisition; voxel size 2x2x2 mm3; TR 3113 ms; TE 30 ms; 450 dynamics) 1.5T MRIs were acquired and replicated for the two DBS states; (scan time 24 minutes for each DBS state). Anatomical 3D T1 segmentation was performed using Freesurfer. Regions of interest (ROI) were pre-defined as the bilateral pre-central gyrus, superior and inferior parietal lobules (SPL/IPL), dentate nucleus (DN), and cerebellar nodule. fMRI data was preprocessed (slice timing, motion correction, despiking, linear detrending, nuisance regression, bandpass filtering (0.01-0.08 Hz) and smoothing were all performed). After the T1 data was registered with the fMRI data using FSL, these ROIs were transformed to fMRI space. All patients had their electrode-extension connections placed on the left parietal location; the EPI distortion and susceptibility artifact from these implants resulted in signal loss, to which a mask was applied to exclude from analysis. Timeseries for each ROI was extracted from the fMRI data; the Pearson correlation coefficient for each timeseries pair was calculated. A connectivity matrix was generated with threshold criteria to include only p-value < 0.05 and R-value > 0.40 for each DBS state. Comparison of DBS ON/OFF was then performed for each patient and a connectivity rank difference matrix was calculated with the following values for each cell: 1 = ON>OFF, 0 = ON=OFF, -1 = ON<OFF. Group analysis was performed by adding up the connectivity rank matrix per cell for all 5 patients.


Results: Of the five patients, 2 were male and 3 female; all were RH. Mean age was 74 years and disease duration was 28 years. Mean bilateral appendicular TETRAS with DBS ON was 1.3; DBS OFF was 6.5. Difference in tremor severity with DBS ON/OFF was highly significant (TETRAS p<0.001). The regions where most decreases in connectivity were seen between DBS OFF and ON  were the left and right IPL, right pre-central gyrus and right SPL, right pre-central gyrus and left SPL, and left and right SPL. Left and right SPL had the greatest connectivity differences relative to other regions, namely the left and right pre-central gyri, with decreased connectivity in the DBS ON state vs. DBS OFF. Group analysis revealed that overall, all ROIs except the left precentral gyrus had less connectivity with other ROIs when DBS was ON relative to OFF.  The cerebellar nodule had no significant connectivity. Please review Figure 1.


Conclusion: Stimulation of the DRTt and concordant improvement of tremor resulted in connectivity decreases seen in multiple regions thought to be involved with tremor pathology. The SPL and IPL were the ROIs displaying the greatest connectivity changes between DBS states. Parallel structural and electrophysiological connectivity analyses performed confirm that the SPL and IPL are critical regions that are involved in tremor modulation. Further work to characterize the correlation of clinical response to stimulation evoked functional changes could improve DBS for tremor. 

Albert FENOY (Houston, USA), Christopher CONNER, Z. David CHU, Stephen KRALIK
15:55 - 16:00 #26090 - The FGATIR sequence in DBS: Introducing the rubral wing for DRT depiction and tremor control.
The FGATIR sequence in DBS: Introducing the rubral wing for DRT depiction and tremor control.

Background: The dentato-rubro-thalamic tract (DRT) is currently considered as a potential target in Deep Brain Stimulation (DBS) for various types of tremor. However, tractography depiction can vary depending on the included brain regions. The Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR) sequence, with excellent delineation of grey and white matter, possibly provides anatomical identification of rubro-thalamic DRT fibers.

Objective: Evaluating the FGATIR sequence by comparison to DRT depiction, electrode localisation and effectiveness of DBS therapy. 

Methods: In patients with DBS therapy due to medication-refractory tremor, the FGATIR sequence was evaluated for depiction of thalamus, red nucleus (RN) and rubro-thalamic connections. Deterministic tractography of the DRT, electrode localisation and tremor control were compared. The Fahn-Tolosa-Marin Clinical Rating Scale for Tremor was used to assess (hand) tremor. Tremor control was considered successful when complete tremor suppression (grade 0) or almost complete suppression (grade 1) was observed. Stimulation-induced side effects, including dysarthria and gait ataxia, were categorized into moderate or severe.

Results: We retrospectively evaluated 14 patients; 12 essential tremor (ET), 1 tremor-dominant Parkinson's disease (PD), 1 multiple sclerosis (MS); representing 24 trajectories. Mean follow-up was 11.3 months (range 6-19 months). Two patients (PD and ET) were operated under general anesthesia. In all twelve awake electrode placements, a single trajectory was needed for complete intraoperative tremor control. The FGATIR sequence provided a clear delineation of the hyperintense thalamus in the hypointense surrounding internal capsule. A hypointense white matter tract within the thalamus, generally visible from the level of the posterior commissure, was distinguishable in both axial and coronal projections. In coronal plane this tract was most readily recognizable as a 'rubral wing', with the round RN as base and lateral triangular convergence. The deterministic DRT depiction was consistently situated within the rubral wing as visualized by the FGATIR sequence. The number of active contacts located within the DRT (and rubral wing) was 22 (92%), of which 16 (73%) showed successful tremor control. The two active contact points outside the DRT depiction were closely located at 0.5 (within rubral wing) and 2.0 (outside rubral wing) millimeters, and both showed good tremor control. The 6 active contact points located within the DRT with suboptimal tremor response represent 4 patients (1 MS, and 3 ET). Three patients (21%) experienced gait disturbances. Two patients (14%) experienced stimulation-induced dysarthria. 

Conclusion: The FGATIR sequence offers visualisation of rubro-thalamic connections which form the DRT, most readily recognizable as a 'rubral wing' in coronal plane. This sequence contributes to tractographic depiction of DRT and provides a direct anatomical DBS target area for tremor control. 

Maarten BOT, Rik PAUWELS (Amsterdam, The Netherlands), Pepijn VAN DEN MUNCKHOF, Maartje DE WIN, Vincent ODEKERKEN, Martijn BEUDEL, Joke DIJK, Rob DE BIE, Richard SCHUURMAN
16:00 - 16:05 #26149 - Distinguishing the motor subthalamic nucleus: a comparison between 7 Tesla MRI and intraoperative microelectrode recordings.
Distinguishing the motor subthalamic nucleus: a comparison between 7 Tesla MRI and intraoperative microelectrode recordings.

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a highly effective surgical treatment for patients with advanced Parkinson’s disease (PD). Combining 7.0-Tesla (7T) T2 and diffusion weighted (DWI) MRI sequences allows for segmenting the motor part of the STN. It is unclear whether STN microelectrode recordings (MER) differ in signal power depending on the location relative to the segmented motor part.


Methods: 7T T2 and DWI MRI sequences were obtained and probabilistic segmentation of motor STN subdivisions was performed in the postoperative phase in a total of 50 STNs in 25 PD patients, using FSL. A voxel connectivity threshold of 20% was applied, enabling visualising an area within 7T T2 STN representation with the highest density of connections to the motor cortices (motor and supplementary motor area). Intraoperative CT was used for DBS electrode localization and the coordinates of the center of the active electrode contact used for stimulation were determined. The active electrode contacts and corresponding MER were evaluated for being located inside (motor STN group) or outside (STN group) the segmented part with the highest density of motor connections. Subsequently, mean power and mean sigma (standard deviation) of the MER were compared between the two groups.


Results: There were no significant differences between motor STN and STN MER for mean signal power (p = 0.72) and mean signal variation (p = 0.72).


Conclusions: No differences between MER signal power inside or outside the segmented part with the highest density of motor connections were found. The MER signal power could not be used for distinguishing the motor part of the STN.

Naomi KREMER (Amsterdam, The Netherlands), Wouter POTTERS, José DILAI, Varvara MATHIOPOULOU, Rob DE BIE, Pepijn VAN DEN MUNCKHOF, Richard SCHUURMAN, Maarten BOT
16:05 - 16:10 #26180 - Additional imaging to guide surgical implantation of an electrode to relieve poststroke action tremor.
Additional imaging to guide surgical implantation of an electrode to relieve poststroke action tremor.

Introduction: We report the case of a now 49-year old woman who had an ischemic stroke in 2000. This caused right-sided low-frequency action tremor in the proximal upper limb, rigidity in the right shoulder and slight paresthesia and dysesthesia in the right hand. Cerebral imaging showed a thalamic cavity with a volume of approximately 154mm³.  Medication (Propranolol, Primidone, Gabapentin) did not alleviate the symptoms. Therefore, she requested deep brain stimulation (DBS).

Methods: To implant the DBS lead at an optimal target, an fMRI was performed comparing the resting state (upper arm supported; In this position there was no tremor) to a tremorous state, where the patient was asked to hold the right arm in a wing-beating position. Secondly, a fluorodeoxyglucose (F18) position emission tomography (FDG-PET) was acquired to investigate the metabolic state of the thalamic cavity. To evaluate the clinical effectiveness of DBS on the tremor, A Fahn-Tolosa-Marin (FTM) tremor rating scale (part A and B of the right upper extremity) was performed prior to surgery as a baseline, as well as one month after surgery with DBS off and on. Next, a randomized, double-blinded monopolar review was performed, where the therapeutic window (TW) of every individual DBS-contact was defined, as well as from the two directional levels as omnidirectional contact. Bottom of TW was defined as the lowest amplitude at which tremor arrest occurred in the right arm when performing a finger-to-nose test. Top of TW was defined as the lowest amplitude where non-transient stimulation-induced side effects appeared. To investigate a possible relationship between the distance from each DBS-contact to the fMRI activity to the TW, we first calculated the Euclidian distances between the center of each DBS-contact and the elevated fMRI signal. Thereafter, we correlated these distances to the TW calculated from each DBS-contact.

Results: Imaging (Fig. 1A) showed the cavity just anterior to the indirectly targeted ventral intermediate nucleus of the thalamus (VIM; targeted at 75% to posterior of the AC-PC line, at 14.26mm to lateral left, at the height of the AC-PC line), an increased fMRI signal during tremor anterior to the cavity and intersecting the dentatorubrothalamic (DRT) tract. Furthermore, the DRT on the affected side showed a decreased fiber density. Lastly, FDG-PET showed decreased tracer uptake at the left thalamus. Taken all of the above together, surgical planning proceeded with the hypothesis that the areas with increased fMRI signal on fMRI are expected to be most effective in reducing the tremor when electrically stimulated. For surgery, a directional lead was chosen. Fusion of the preoperative MRI scan to the postoperative CT scan showed that the lead was positioned immediately anterior to the cavity, where the most dorsal DBS-contacts were closest to the elevated fMRI signal and the largest part of the DBS lead intersected the DRT tract. When comparing the clinical measures, the FTM tremor rating scale indicated an 84.6% decrease in tremor before versus after surgery with DBS-on.

Conclusion: We report the case of a 49-year old woman in whom DBS was implanted due to a post-stroke low-frequency action tremor in her upper right arm. A single directional lead was implanted based on information gathered via diffusion MRI, fMRI and FDG-PET immediately anterior from the cavity, thereby intersecting the elevated BOLD signal and the DRT tract. After surgery, the tremor had disappeared, with only a minor tremorous trend when drawing a spiral. We propose that, in rare cases such as the one described here, additional imaging may provide the necessary information to guide the surgery, which could optimize the patients’ chances for a successful implantation.

Jana PEETERS (Leuven, Belgium), Evanthia THEODORU, Alexandra BOOGERS, Myles MC LAUGHLIN, Koen VAN LAERE, Stefan SUNAERT, Bart NUTTIN
16:10 - 16:15 #26273 - Using functional Ultrasound (fUS) for real-time functional and vascular delineation of brain structures with micrometer-millisecond precision: Towards a new, fully integrated, depth-resolved image-guided neurosurgical tool with multimodal potential.
Using functional Ultrasound (fUS) for real-time functional and vascular delineation of brain structures with micrometer-millisecond precision: Towards a new, fully integrated, depth-resolved image-guided neurosurgical tool with multimodal potential.


Neurosurgical practice still relies heavily on pre-operatively acquired images to guide intra-operative decision-making during procedures such as tumor resection and DBS electrode placement. This practice comes with inherent pitfalls such as registration inaccuracy due to brain shift, and lack of real-time functional or morphological feedback. Exploiting the opportunity for real-time imaging of the exposed brain can improve intra-operative decision-making, neurosurgical safety and patient outcomes. Previously, we described functional Ultrasound (fUS) as a high-resolution, depth-resolved imaging technique able to detect functional regions and vascular morphology during awake tumor resections [1]. Here, we describe our recent progress towards fUS as a fully integrated, MRI/CT-registered imaging modality in the Operating Room (OR) (Figure 1A).


Materials and Methods

fUS relies on high-frame-rate (HFR) ultrasound, making the technique sensitive to very small motions caused by vascular dynamics (µDoppler) and allowing measurements of changes in cerebral blood volume (CBV) with micrometer-millisecond precision. This opens up the possibility to 1) detect functional response, as CBV-changes reflect changes in metabolism of activated neurons through neurovascular coupling, and 2) visualize in-vivo vascular morphology of pathological and healthy tissue with high resolution at unprecedented depths. During a range of anesthetized and awake neurosurgical procedures we acquired images of brain and spinal cord using conventional linear ultrasound probes connected to a research acquisition system. The ultrasound probes were either handheld for dynamic scans of tissue volumes (Figure 1B) or stabilized over regions of interest using an intra-operative arm developed in-house (Figure 1C). During conventional awake craniotomy procedures, we asked patients to perform functional tasks to elicit cortical responses following the Electrocortical Stimulation Mapping (ESM)-procedure. During all procedures, our research system recorded real-time vital signs data of the patient (arterial pressure and EKG), which can be used to improve image quality in post-processing. Building on Brainlab’s Cranial Navigation and Intra-Operative Ultrasound modules, we co-registered our intra-operative Power Doppler Images (PDIs) to patient-registered MRI/CT-data in real-time. Using the IGTLink research interface, we were able to access and store real-time tracking data for informed volume reconstructions in post-processing.



Intra-operative fUS was registered to MRI/CT-images in real-time within the Brainlab interface, showing overlays of PDIs over the conventional neuro-navigation volume including pre-operatively drawn regions of interest and tumor borders (Brainlab Elements Smartbrush) (Figure 1D). During meningioma and glioma resections, these co-registered PDIs revealed fUS’ ability to visualize the tumor’s feeding vessels and surrounding vasculature, with a level of detail unprecedented by conventional MRI-sequences (Figure 1E-F). Using the intra-operatively recorded tracking data facilitated through the IGTLink, we made MRI-registered 3D-reconstructions of the 2D-PDIs post-operatively, which revealed unique vascular details such as the presumed middle cerebral artery originating from the circle of Willis (white arrow, Figure 1G). Imaging of deep brain nuclei (Figure 1H) reveals potential for vascular-guided DBS electrode placements, both in terms of improving morphological delineation as well as increasing safety by avoiding vital vascular structures during electrode implantation. During awake resections, fUS was able to detect distinct, ESM-confirmed functional areas as activated during conventional motor and language tasks (Figure 1I). In all cases, images were acquired with micrometer-millisecond (300 µm, 1.5-2.0 ms) precision at imaging depths exceeding 5 cm.



fUS is a new real-time, high-resolution and depth-resolved imaging technique, combining favorable imaging specifications with characteristics such as mobility and ease of use which are uniquely beneficial for a potential image-guided neurosurgical tool. The successful integration of fUS in the neurosurgical OR demonstrated by our team is an essential step towards clinical integration of fUS, as well as the technique’s validation against modalities such as MRI and CT.



[1] Soloukey, S. et al. Functional Ultrasound (fUS) During Awake Brain Surgery. Front. Neurosci. (2020)

Sadaf SOLOUKEY (Rotterdam, The Netherlands), Luuk VERHOEF, Frits MASTIK, Bastian GENEROWICZ, Eelke BOS, Joost SCHOUTEN, Biswadjiet HARHANGI, Ellen COLLÉE, Djaina SATOER, Marion SMITS, Clemens DIRVEN, Chris DE ZEEUW, Sebastiaan KOEKKOEK, Arnaud VINCENT, Pieter KRUIZINGA
16:15 - 16:20 #26281 - Structural changes in brains of patients with disorders of consciousness treated with deep brain stimulation.
Structural changes in brains of patients with disorders of consciousness treated with deep brain stimulation.


Aims: Disorders of consciousness (DOC) are one of the major consequences after anoxic or traumatic brain injury. So far, several studies have described the regaining of consciousness in DOC patients using

deep brain stimulation (DBS). However, these studies often lack detailed data on the structural and functional cerebral changes after such treatment. The aim of this study was to conduct a volumetric analysis of specific cortical and subcortical structures to determine the impact of DBS after functional recovery of DOC patients.

Methods: Five DOC patients underwent unilateral DBS electrode implantation into the centromedian parafascicular complex of the thalamic intralaminar nuclei. Consciousness recovery was confirmed using the Rappaport Disability Rating and the Coma/Near Coma scale. Brain MRI volumetric measurements were done prior to the procedure, then approximately a year after, and finally 7 years after the implementation of the electrode. The volumetric analysis included changes in regional cortical volumes and thickness, as well as in subcortical structures.

Results: Limbic cortices (parahippocampal and cingulate gyrus) and paralimbic cortices (insula) regions showed a significant volume increase and presented a trend of regional cortical thickness increase 1 and 7 years after DBS. The volumes of related subcortical structures, namely the caudate, the hippocampus as well as the amygdala, were significantly increased 1 and 7 years after DBS, while the putamen and nucleus accumbens presented with volume increase.

Conclusion: Volume increase after DBS could be a result of direct DBS effects, or a result of functional recovery. Our findings are in accordance with the results of very few human studies connecting DBS and brain volume increase. Which mechanisms are behind the observed brain changes and whether structural changes are caused by consciousness recovery or DBS in patients with DOC is still a matter of debate.

Marina RAGUŽ (Zagreb, Croatia), Nina PREDRIJEVAC, Domagoj DLAKA, Darko ORESKOVIC, Ante ROTIM, Dominik ROMIC, Fadi ALMAHARIQ, Petar MARCINKOVIC, Vedran DELETIS, Kostovic IVICA, Darko CHUDY
16:20 - 16:25 #26289 - Evaluation of the short- and long-term rotational stability of directional deep brain stimulation leads.
Evaluation of the short- and long-term rotational stability of directional deep brain stimulation leads.

Introduction: The two middle contacts of directional leads for deep brain stimulation are split into three segments, allowing current steering toward desired axial directions. To facilitate programming, their final orientation needs to be reliably determined. Moreover, the rotational stability of directional leads is a major prerequisite for sustained clinical effects. Thus, it is of major importance to determine if and for how long directional leads rotate after their implantation. We here aimed to evaluate the short- and long-term rotational stability of directional leads.

Methods: We retrospectively evaluated the orientation of directional leads in a consecutive series of 33 patients implanted with a total of 63 directional electrodes at different time points. In all cases a postoperative CT scan on the day of surgery (T1) and CT or rotational fluoroscopy at a second time point (T2) were available. In 32 directional leads, which had been implanted with an anterior intention (=0°) their intraoperative X-rays (T0) were evaluated.

Results: Sixty-three leads were evaluated. The mean follow-up between T1 and T2 was 409 (4–1171) days. The difference in rotation between T1 and T2 was 2.4° (0°-9.0°) indicating stable orientation. The difference between T0 and T1 was 155 minutes (108-189 minutes). In nine of the 32 d-leads with intraoperative X-ray, an iron-sight ( ISi; indicating 0° +/- 6° orientation) was visible at T0. In these electrodes median orientation was 1.5° (range 0.5-6.0°) at T1, confirming anterior orientation. In directional leads without ISi or where ISi was not evaluable, the median rotation was 15.5° (9.5–35.0°) and 26.5° (5.5-62.0°), respectively.

Conclusion: Directional lead orientation remains stable both in the short- or long-term. Postoperative images can thus be used at any postoperative time point to reliably determine their orientation. Intraoperative determination of lead orientation using marker-based X-ray alone is too imprecise, which explains the large deviations from the intended anterior (=0°) orientation at implantation in most leads; adding the ISi method can increase the accuracy and permits to define the orientation of directional leads intraoperatively.


Marie T. KRÜGER (St.Gallen, Switzerland), Fabian CAVALLONI, Yashar NASERI, Oliver BOZINOV, Georg KÄGI, Hägele-Link STEFAN, Florian BRUGGER
16:35 - 16:40 #23400 - Frameless robot-assisted stereotactic biopsies for lesions of the brainstem – a series of 106 consecutive cases.
Frameless robot-assisted stereotactic biopsies for lesions of the brainstem – a series of 106 consecutive cases.


Targeted treatment for lesions presenting with a brainstem location requires above all a precise histopathological diagnosis. In the current technological era, robot-assisted stereotactic biopsies represent an accurate and safe procedure for tissue diagnosis. We present our center’s experience in performing frameless robot-assisted biopsies for lesions of the brainstem. 

Material and methods

We performed a retrospective analysis of all patients benefitting from a frameless robot-guided stereotactic biopsy at the University Hospital in Lille (France), from 2001 to 2018. The NeuroMate robot (Renishaw, UK) was used in all cases. We report on lesion location, trajectory choice, histopathological diagnosis and follow-up. 


Our series encompasses 106 patients treated during an 18 years period, presenting with various anatomopathological diagnoses. Mean age at biopsy was 35.4 years (range 1-78). Most common location was pontine region (71.4%). A transcerebellar approach was used in 66 patients (62.2%). Various diagnoses are described, most commonly being diffuse glioma (65.7%), metastases (7.6%) and lymphoma (4.8%). Non conclusive diagnosis was found in 13 cases (12.6%). After second biopsy this decreased to 6 cases (5.8%). Transitory complications were recorded in 16% of cases (17 patients). The most common was oculomotor transitory disorder (5 patients). Permanent disability was seen in 5.6% (6 patients). Adjuvant targeted treatment was performed in 71% of patients. Surgery for debulking was possible in only 5 patients (after adjuvant therapy in two cases). Mean postoperative follow-up in the Neurosurgery Department was 2.2 years. 


Frameless robot-assisted stereotactic biopsies can provide the initial platform towards a safe and accurate management for brainstem lesions. To our best knowledge, we report on the largest case series for frameless robot-assisted stereotactic biopsies, with high diagnostic precision and low morbidity.    


Objective: Rapid and accurate diagnostic confirmation of brain tumor tissue during stereotactic biopsies is of major importance. Frozen section analysis is the gold standard, nevertheless in cases of multiple samples analysis it may be time consuming. Intraoperative flow cytometry is a novel technique that permits differentiation of low from high-grade tumors, brain tumor margins assessment and diagnosis of central nervous system lymphoma within 6 minutes. The technique is based on the evaluation of tumor’s cell cycle phases, ploidy status and cluster differentiation (CD) markers.  Major advantages of flow cytometry are the evaluation of multiple samples, minimal tissue requirements and there is no need to administer any substance to the patient.  In the present pilot study we assessed the value of intraoperative flow cytometry during brain tumor biopsies.

Material-Method: Four patients (3 males, 1 female, mean age 63.2 years) that underwent a stereotactic biopsy for a suspected neoplastic lesion were included in the study. Upon sample receipt fast flow cytometric analysis (Ioannina Protocol) was performed  and the results were compared to standard pathology.

Results: The final diagnosis were three glioblastoma cases and one case of metastatic cancer. Presence of neoplastic tissue was readily identified in all cases based on ploidy status, decreased G0/G1 and increased S and G2/M phase fractions. The exclusion of central nervous system lymphoma was performed within 6 minutes of sample receipt based on CD markers analysis. Histopathology verified the results in all cases.  

Conclusions: Intraoperative flow cytometry might be a novel promising technique for the rapid identification of neoplastic tissue during stereotactic brain lesion biopsies.


16:45 - 16:50 #23790 - Connectivity profile of deep brain stimulation targets in Tourette syndrome.
Connectivity profile of deep brain stimulation targets in Tourette syndrome.

Tourette syndrome (TS) is a neuropsychological disorder characterized by vocal and motoric tics, mainly affecting children and young adults. The pathophysiology of this disorder is not yet completely understood. Nevertheless, studies have shown a delayed neurodevelopment with abnormal connectivity patterns in the cortico-striatal-thalamic-cortical (CSTC) loops. While in most patients, symptoms either cease or considerably diminish in early adulthood, about 20% of the patients continue having symptoms their whole life, with the same or increased intensity. For adult patients with severe treatment-refractory TS, deep brain stimulation (DBS) is a safe and effective therapy option. So far numerous anatomical structures have been researched as DBS targets along the CSTC loops, including the centromedian nucleus- ventrooralis internus (CM-Voi), the CM-parafascicular complex (CM-Pf), the anteromedial (amGPi) and posteroventral globus pallidus internus (pvGPi), the globus pallidus externus (GPe) and the nucleus accumbens (Nacc). According to a recent review, the average improvement for all targets in the Yale Global Tic Severity Scale was about 47%, with none of them showing a greater benefit than the others. Studies on small cohorts showed that some patients responded better to stimulation of amGPi than CM-Pf while in others there was no significant difference. Furthermore, patients with additional obsessive-compulsive disorder seem to profit more from amGPi or Nacc DBS. The aim of this study is to correlate cortical connectivity patterns of patients stimulated in CM-Voi with clinical results, and to compare connectivity patterns of DBS targets for TS in order to elucidate if specific targets are better suited for patients with specific clinical phenotypes.

To establish relevant cortical areas in TS, we investigated diffusion tensor imaging (DTI) in seven Tourette patients who underwent CM-Voi DBS at our clinic. We analyzed the connectivity between the tissue activated by the electrodes and individual cortical areas. Connectivity profiles more specific to the motor cortex (M1, SMA, preSMA) were associated with a reduction of motor and vocal tics.  In poor responders the cortical connectivity was more widespread, mainly projecting to the prefrontal cortex.

Based on these results, we examined the connectivity profile of all DBS targets for TS namely CM, Voi, Pf, amGPi, pvGPi, GPe and Nacc, using a normative connectome. We compared the connectivity of each structure to the motor cortex (M1, SMA, preSMA), the primary sensory cortex, the amygdala and the hippocampus.

The connectivity profile of these targets was remarkably different. While pvGPi and GPe showed the strongest connection to the motor cortex, most fibers from Voi, CM, amGPi and Nacc connected to the prefrontal cortex, and Pf mainly to the amygdala. The connectivity profiles of the thalamic structures, Nacc and amGpi were more specific to single areas, while fiber tracts from pvGPi and GPe were more scattered.  Notably, neither CM nor Voi showed a particularly strong connection to the motor cortex, other than the individual tractography of our patients might have suggested.

In summary, we found that a better clinical outcome after TS DBS targeting CM-Voi correlated with a more specific connectivity of the tissue activated by the electrodes to the motor cortex based on individual tractography. Furthermore, the connectivity profiles of different TS DBS targets were highly variable based on the normative connectome. Further research is necessary to assess whether clinical outcome in TS patients with other DBS targets is also correlated with similar connectivity patterns.

Salle Major

Friday 10 September

Added to your list of favorites
Deleted from your list of favorites
15:00 - 17:00

Parallel Session 13

Moderators: Anne BALOSSIER (Dr) (Marseille, France), Ivano DONES (MILANO, Italy), Ioannis PANOURGIAS (DOCTOR) (ATHENS, Greece)
15:00 - 15:10 #26190 - Trigeminal microvascular decompression for refractory chronic short-lasting unilateral neuralgiform headache attacks.
Trigeminal microvascular decompression for refractory chronic short-lasting unilateral neuralgiform headache attacks.

BACKGROUNDA significant proportion of patients suffering from short-lasting unilateral neuralgiform headache attacks (SUNHA) are refractory to medical treatment. A recent structural neuroimaging study suggests a pivotal role of ipsilateral trigeminal neurovascular conflict (NVC) in their aetiology. Moreover, a small case series suggests that trigeminal microvascular decompression (MVD) may be an effective surgical treatment. We aimed to determine whether trigeminal MVD is a safe and effective surgical option for medically refractory chronic SUNHA patients in whom there is radiological evidence of NVC. 


DESIGN, SETTING AND PARTICIPANTS: An uncontrolled open-label prospective single centre study was conducted between Jan 2013 and Dec 2020. Consecutive patients with refractory chronic SUNHA and MRI evidence of trigeminal NVC ipsilateral to the pain side were enrolled in the study. 


INTERVENTION: All patients had high-resolution MRI sequences of the trigeminal nerves. Trigeminal MVD with the modified Jannetta technique was performed in this study.


MAIN OUTCOMES AND MEASURES: Responders were those who achieved 90-100% reduction in attack frequency (excellent response), or between 75% and 89% frequency reduction (“good response”), at final follow-up. Secondary efficacy and disability-related outcomes and surgical adverse events were collected.


RESULTS: The study included 47 chronic SUNHA patients: 31 with short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and 16 with short-lasting unilateral neuralgiform headache attacks with autonomic features (SUNA) (25 females, mean age 55.4 years ± 14.9). The vast majority of patients (89.4%) experienced both spontaneous and triggered attacks by cutaneous and/or intraoral stimulation. The mean number of medical treatments failed at the time of the surgery was 8.1(±2.7). Two patients also had an incomplete response to neuromodulation (occipital nerve or deep brain stimulation). At the time of surgery, all patients were taking preventive treatments. The mean baseline HIT-6 score was 67.7 (± 6.7); 38 patients (80.9%) had baseline HIT-6 scores within the severe disability range.


All patients had NVC ipsilateral to the pain side. Of 47 patients, 50 symptomatic nerves were analysed (three patients had side alternating attacks). Arterial conflict, by the superior cerebellar artery (SCA) (n=47), by the anterior inferior cerebellar artery (AICA) (n=2) or by both arteries (n=1) was found with all symptomatic nerves. NVC with morphological changes was found in 72% (n=36/50) and without in 28% (n=14/50) of symptomatic nerves. 


Post-operatively, 38 patients (80.8%) were responders. Of these, 34 (72.3%) obtained an excellent and four (8.5%) a good response. The majority of patients responded to MVD immediately (n=36, 94.7%), whereas two obtained an excellent response after three and four months respectively. Nine patients (19.1%, SUNCT=7, SUNA=2) reported no post-operative improvement. Mean follow-up was 49.0±25.7 months (range 7-96). At final follow-up, 32 patients (68.0%) remained excellent/good responders; six had recurrence of SUNHA symptoms (SUNCT=3, SUNA=3): two within the first six months, one within the first 12 months, two within the second year and one patient at month 38 post-surgery. Three of these patients obtained meaningful control of recurrent symptoms with lamotrigine and carbamazepine, two with occipital nerve stimulation and one with ventral tegmental area deep brain stimulation. All but one patient who obtained an immediate excellent response discontinued their preventive medications. Two patients underwent MVD on the other side due to worsening/onset of attacks on the contralateral side of the first operation. The outcome of the second MVD was similar to the first one. 


The HIT-6 score was reduced from 67.7 (± 6.7) at baseline to 45.0 (± 13.8) at final follow-up. Furthermore, the percentage of patients with severe disability was reduced from 80.9% (n=38) to 21.3% (n=10), with most patients’ HIT-6 scores showing no further impact of the headache condition in their life.


No serious surgical complications were noticed. Twenty-two post-surgery adverse events occurred in 18 patients. 


CONCLUSIONS: This study provides Class IV evidence that trigeminal MVD may be a safe and effective treatment for refractory chronic SUNHA patients.

Giorgio LAMBRU, Susie LAGRATA, Sanjay CHEEMA, Andrew LEVY, Indran DAVAGNANAM, Neil KITCHEN, Manjit MATHARU, Ludvic ZRINZO (London, UK, United Kingdom)
15:10 - 15:20 #26252 - Prospective Quality-of-Life Assessment and Meta-Analysis of Microvascular Decompression for Elderly Patients with Trigeminal Neuralgia.
Prospective Quality-of-Life Assessment and Meta-Analysis of Microvascular Decompression for Elderly Patients with Trigeminal Neuralgia.


Objective: The incidence of trigeminal neuralgia (TN) increases with age. Elderly patients with severe trigeminal neuralgia may choose microvascular decompression (MVD) for their treatment. This study aims to investigate the impact of MVD for trigeminal neuralgia on health-related quality of life (hr-QoL) in the elderly. Additionally, the authors update a systematic review and meta-analysis of age-stratified MVD outcomes for the trigeminal neuralgia.

Methods: The authors prospectively studied 40 consecutive patients who underwent MVD for the trigeminal neuralgia between 2018 and 2019. The hr-QoL of the elderly (65 years or older) and non-elderly (less than 65 years) patients was assessed using the 36-Item Short Form Health Survey (SF-36) before and 6 months after MVD. Preoperative and postoperative SF-36 score and pertinent clinical data were compared between elderly and non-elderly groups using paired t-tests and repeated-measures analysis of variance (ANOVA).

The authors also conducted a systematic review of the English literature providing age-stratified MVD outcomes for the trigeminal neuralgia. The search included articles published prior to December 2020 to update the previously published meta-analysis. Pooled data for the rates of excellent outcome, death, complication from stroke and thromboembolism, and recurrence were analyzed.

Results: The two cohorts were composed of 22 elderly (mean 76 years, range 65–89) and of 18 non-elderly patients (mean 57, range 38–64). SF-36 score of all domains improved significantly after the operation in both the age groups (p < 0.001). The physical functioning (PF) domain improved significantly less in the elderly compared to non-elderly patients (p = 0.018). In those 80 years or older, SF-36 score also improved significantly after the operation (p = 0.03), except for the PF and vitality domains.

Twenty-one studies met the inclusion criteria for the systematic review and meta-analysis. The updated meta-analysis demonstrated that the elderly had better pain control (risk ratio [RR], 1.05; 95% confidence interval [CI], 1.01–1.10; p = 0.02) and similar risk of recurrence (RR, 0.86; 95%CI 0.71–1.14, p = 0.12) compared to the non-elderly patients. A trend of declining risk of mortality and morbidity was illustrated in both the age group, although the preoperative comorbidity was commonly present in the elderly (RR, 2.90; 95%CI 1.75–4.79, p < 0.01).

Conclusions: MVD can improve the hr-QoL of the elderly with trigeminal neuralgia. Recent advances of perioperative management may control the morbidity and mortality risk. MVD can be a reasonable treatment of choice for the elderly with refractory trigeminal neuralgia.


Hiroki TODA (Osaka, Japan)
15:20 - 15:30 #23999 - Neuromodulation in treating complex regional pain syndrome.
Neuromodulation in treating complex regional pain syndrome.

Introduction: CRPS describes an array of painful conditions that are characterized by a continuing (spontaneous and/or evoked) regional pain that is disproportionate in time or degree to the usual course of any know lesion. The pain is regional (not in specific nerve territory or dermatome) and usually has a distal predominance of abnormal sensory, motor, sudomotor, vasomotor, and/or trophic findings. Neurostimulation is an intervention that has been studied extensively in a variety of pain syndromes, demonstrating both safety and efficacy. Spinal cord stimulation (SCS) an effective therapy in the management of patients with CRPS type I (Level A evidence) and type II (Level D evidence). Deep brain stimulation (DBS), motor cortex stimulation (MCS), peripheral nerve stimulation (PNS) and their combinations can use in treatment too. 

Methods: The study was conducted among 24 patients (10 male and 14 female, median age: 48), with an average 9-year history of severe intractable pain. Criteria for inclusion: CRPS I (n=5; 21%), II (n=17; 71%) and III (n=2; 8%); drug-resistant or inefficient medical therapy; ages ≥18. The patients were followed up by the VAS (Visual Analog Scale) and the PCS (Pain Catastrophizing Scale).

Preoperatively all patients had a VAS 6-10. Seven patients had pain attacks every month from 150 to 10000 (150 per hour). All patient have successful test (7 days), after which was implanting systems for chronic neurostimulation: SCS (n = 15; 62.5%), MCS (n = 2; 8.3%), DBS (n = 2; 8, 3%), PNS (n = 2; 8.3%), and also hybrid neurostimulation - SCS + MCS (1), MCS + PNFS (1) and DBS + PNS (1) - 12.6%.

Results: The catamnesis 6 years. The average VAS value decreased by 4.6. The average improvement PCS 2.76. The removal of the implanted system was seven patients (29,2%) for reasons: infection (2 – 28,6%), decrease in efficiency (3 - 42,8%), system breakdown (1 - 14,3%) and one of patients (14,3%) had a uncomfortable sensation in stimulation area. Although the removal of the implanted system, 2 patients have complete regression of attacks pain, 2 have 50% decrease intensity and frequency attacks of pain, 3 have 50% decrease in intensity pain.

Conclusions: In carefully selected patients neurostimulation can reduce pain and improve the health-related quality of life.

Emil ISAGULYAN (Moscow, Russia), Alexey TOMSKY, Elizaveta MAKASHOVA, Valentina MIKHAILOVA, Eugeny DOROCHOV, Ekaterina SALOVA
15:30 - 15:40 #23920 - Operative findings and outcome of microvascular decompression/ adhesiolysis for trigeminal neuralgia in multiple sclerosis.
Operative findings and outcome of microvascular decompression/ adhesiolysis for trigeminal neuralgia in multiple sclerosis.

Objective: Trigeminal neuralgia (TN) in multiple sclerosis (MS) poses several challenges for treatment. Although these patients often have typical attacks, they may not be considered as candidates for microvascular decompression (MVD). Optimal treatment in this group of patients is still unclear. Here we report on surgical findings and the results of MVD/ adhesiolysis in a series of patients with multiple sclerosis.


Methods: Fifteen patients with typical trigeminal neuralgia and MS underwent MVD. All patients had preoperative magnetic resonance imaging (MRI) to exclude mass lesion in cerebellopontine angle. The trigeminal neuralgia was refractory to the medication in all patients preoperatively.  All patients were available for follow-up. The outcome of intervention was graded according to the Barrow Neurological Institute (BNI) Pain intensity score. The 3, 12, 24 months follow-up and long-term follow-up (mean 41,2 months) were analysed.

Results: For the 15 patients, a total of 19 MVDs were performed. Intraoperative findings indicated scar tissue at the trigeminal entry zone (15/19 instances), arterial contact (8/19 instances) and vein contact (11/19 instances). A complete pain relief was achieved in all patients directly after surgery. From these 15 patients 4 patients underwent second MVD because of pain recurrence and on the 12 months follow-up all benefited from re-surgery. For 14 patients we were able to show 24 months follow up; 8 patients BNI I (complete pain relief), 2 patients BNI II (occasional pain, but no medications required), 2 patients BNI IIIa (no pain but continued taking medication for fear of stopping) and 2 patients BNI IV (limited benefit).


Conclusion: On the long-term follow-up, 13/15 patients had pain relief (including the patients who underwent a second MVD). These findings show that MVD provides good outcome for TN in patients with MS. These necessities, however, a careful patient selection and meticulous surgical decompression/ adhesiolysis.

Gökce HATIPOGLU MAJERNIK (Hannover, Germany), Shadi AL-AFIF, Hans E. HEISSLER, Joachim K. KRAUSS
15:40 - 15:45 #23879 - Sub-perception and supra-perception spinal cord stimulation in chronic pain syndrome: a randomised, semi-double-blind, crossover, placebo-controlled trial.
Sub-perception and supra-perception spinal cord stimulation in chronic pain syndrome: a randomised, semi-double-blind, crossover, placebo-controlled trial.

Objective: The introduction of modern sub-perception modalities has improved the efficacy of spinal cord stimulation (SCS) in refractory pain syndromes of the trunk and lower limbs. The objective of this study was to evaluate the effectiveness of low frequency, high frequency, and burst SCS among patients with chronic pain.

Material and methods: A randomised, semi-double-blind, placebo controlled, four period (4×2 weeks) crossover trial was conducted from August 2018 to January 2020. Eighteen patients with SCS due to failed back surgery syndrome and/or complex regional pain syndrome were randomised to four treatment arms without washout periods: (1) low frequency (40-60 Hz), (2) high frequency (1 kHz), (3) burst, and (4) sham SCS (i.e., placebo). The primary outcome was pain scores measured by visual analogue scale (VAS) preoperatively and during subsequent treatment arms. Results: Pain scores (VAS) reported during the preoperative period was M [SD] = 8.19 (0.98). There was a 49.67% reduction in pain reported in the low frequency treatment group (M [SD] = 4.18 [1.76]), a 38.32% reduction in the high frequency treatment group (M [SD] = 5.13 [1.36]), a 34.2% reduction in the burst settings group (M [SD] = 5.27 [1.33]), and a 36.23% reduction in the sham stimulation group (M [SD] = 5.23 [1.38]). The reduction in pain from the preoperative period to the treatment period was significant in each treatment group (p < 0.001). Overall, these reductions were of comparable magnitude between treatments, including the sham (placebo) treatment. Average pain did not significantly differ between treatment arms and was relatively stable across treatment periods. However, the modality most preferred by patients was low frequency (55% or 10 patients). 


One of the main advantages of this study was the double-blind setting in sub-perception modes and the placebo control. These settings were made possible by paraesthesia-free stimulation that was applied in this trial. No sensory perceptions were observed during the three allocated treatment arms (i.e., burst stimulation, 1 kHz stimulation, and sham stimulation). Furthermore, the crossover design allowed for each subject to be exposed to each modality, which allowed for individual subjects to serve as their own control. 

The primary goal of the study was to establish the type of stimulation was the most effective for relieving pain and to establish which type was the most preferred in long-term stimulation.  Patients were not aware of the type of stimulation that had been programmed and were not aware of whether the stimulation was on or off because they were informed that they could not perceive any sensations. There were no washout periods between subsequent treatment arms. The design of this cross-over study could be burdened by carry-over effects, but the analysis revealed that average pain was relatively stable through the entire study periods. In present study, average values of pain intensity after each type of stimulation were not shown to be superior to sub-perception stimulation. The observed reduction in pain was modest across all modalities. During the sham arm, devices showed that the IPG was on. LF tonic SCS had, however, the most robust analgesic effect of greater than 49.7%. At the end of the randomised phase, the majority of subjects (55%) chose tonic stimulation as their preferred mode for SCS. Further, we found that LF tonic SCS was associated with the highest level of relative pain relief and the lowest use of NSAIDs and anticonvulsants. 

In contrast to prior studies, we did not find burst stimulation to be superior to other forms of stimulation, although 3 people (14.7%) in the present study reported this modality to be the most satisfactory. In our study, we applied clustered tonic stimulation. We did not observe higher efficiency of HF stimulation as compared to other forms of stimulation. This observation is in agreement with conclusions drawn from a prior review of HF stimulation clinical trials, which showed a lack of high-quality evidence on the superiority of HF SCS. Conclusions: SCS was effective in pain relief. Sub-perception stimulation was not superior to supra-perception. SCS was characterised by a high degree of placebo effect. No carryover effect was observed between subsequent treatments with different frequencies. Contemporary neuromodulation procedures should be tailored to the individual preferences of patients.

Paweł SOKAL (Bydgoszcz, Poland), Sara KIEROŃSKA, Agnieszka MALUKIEWICZ, Marcin RUDAŚ, Marcin RUSINEK

What do you want to do ?
New mailCopy

Introduction: Somatotopic organization of the sensory thalamus has been described using intraoperative data from microelectrodes recordings, location or stimulation-induced paresthesias in patients treated by deep brain stimulation (DBS) for intractable pain. These data suggested a mediolateral somatotopic organization in the contralateral ventroposterior thalamus, the head and the inferior limb being represented respectively medially and laterally. The aim of our study was to explore the somatotopy of the sensory thalamus using the principle of directional DBS.

Methods: Four patients with chronic refractory neuropathic pain were included in a prospective study evaluating combined thalamic and anterior cingulate DBS. DBS directional leads (Infinity, Abbott) were implanted under local anesthesia in the sensory thalamic region corresponding to their contralateral pain. Orientation and location of the leads were assessed by postoperative 3D CT-scan and merged on Schaltenbrand and Wahren atlas according to their AC-PC coordinates. Three months after surgery, bipolar stimulation was delivered in each direction and correlated to location of stimulation-induced paresthesias.

The stimulation specificity was defined as the difference in mA between the stimulation threshold inducing paresthesias in the desired painful area and the threshold inducing paresthesias in undesired body areas.


Results: Stimulation-induced paresthesias were perceived in areas of the body that differed according to the stimulation direction, allowing to map the somatotopic organization of the sensory thalamus in each patient. The somatotopy re-constructed using directional DBS in the four patients will be displayed and was globally in accordance with the somatotopy based on previous data.. Compared to the omnidirectional stimulation, the specificity of directional stimulation was 43% wider and the intensity needed to produce paresthesias in the intended body area was 35% lower. There was no complication.

Conclusion: This preliminary study confirmed the somatotopic organization of the sensory thalamus and strengthens the concept and interest of directional DBS. More patients will be include in the study to confirm these findings.

15:50 - 15:55 #23916 - Spinal cord stimulation in the treatment of ischemic pain: Microcirculation and tissue perfusion improvement.
Spinal cord stimulation in the treatment of ischemic pain: Microcirculation and tissue perfusion improvement.

Introduction. Refractory angina pectoris (RAP) and peripheral vascular disease (PVD) is a chronic pain condition that affects a certain group of patients with systemic atherosclerosis. These diseases have bad control of neither by a combination of medical therapy nor by vascular surgery treatment (angioplasty or bypass surgery). The efficacy of SCS is supported by one placebo-controlled study, two larger randomized controlled trials, and several small controlled studies. According to systematic reviews, there is strong evidence that SCS gives rise to symptomatic benefits and improves functional status in patients with vascular diseases. Spinal cord stimulation (SCS) is an effective and safe treatment for these patients that has an excellent effect on pain relief and microcirculatory function’s improvement.

Methods. Two groups of patients with non-reconstructable RAP (n=22) and PVD (n=75) underwent SCS procedure in our facility. Preoperative and follow-up myocardium perfusion scintigraphy (MPS), transcutaneous oximetry (TCO), and laser-doppler flowmetry (LDF) were performed on admission and in 1 year after the procedure. The lead placement in the RAP group was C7-Th4, in the PVD group - Th11-L1. Pain relief was assessed by a visual analog scale (VAS) in all patients.

Results. The patients showed 8,56±0,13 marks according to VAS before the procedure and pain relief to 2,09±0,09 marks (p<0,01) in the 1-year follow-up. All the patients in the RAP group demonstrated the rise of tolerance to physical activity. MPS detected the decrement of perfusion's defect from 15,72±2,05 to 9,17±1,3 units (increase in coronary reserve up to 24%). TCO detected the microcirculatory improvement (n=75): tissue oxygenation increased from 7,5 to 43,1 mm Hg (p=0,045).

Discussion. The present study has some limitations: the follow-up period was relatively short, leading to a limited evaluation of the outcome of SCS. Measurements were not used to select patients for SCS since we intended to include this indicator as a factor that could potentially influence the clinical dynamics after this procedure. The duration of clinical manifestations of RAP and PVD is associated with the long-term results of SCS. Hence, the approaches to the treatment of these diseases need to be optimized to timely use of surgical and nonsurgical therapy, including SCS, to improve the clinical and cost-effectiveness of non-reconstructable vascular disease treatment.

Conclusions. In summary, patients with non-reconstructable RAP and PVD show a positive clinical dynamic 1 year after SCS. At the same time, the initially low peripheral tissue metabolism, and the significant disturbance of the functional status of peripheral microvasculature is associated with the negative clinical dynamics one year after SCS. Our experience also highlights the importance of preserving the microcirculatory reserve capacity (1), confirms that SCS can reduce the pain (2), and improve quality of life with vascular reserve enhancement (3) in patients with ischemic pain syndrome.

Vladimir MURTAZIN (Novosibirsk, Russia), Roman KISELEV, Martin KILCHUKOV, Asya KLIMKOVA, Kirill ORLOV
15:55 - 16:00 #24032 - Multimodality treatment for pain control in multiple sclerosis-related trigeminal neuralgia.
Multimodality treatment for pain control in multiple sclerosis-related trigeminal neuralgia.

Background: The best surgical choice for MS-related TN (MSrTN) remains controversial. Recent literature express poor pain control and high recurrence rates in surgical interventions of MSrTN compared to classical TN. Our aim was to evaluate the effects of microvascular decompression (MVD), radiofrequency thermocoagulation (RFT) and gamma-knife radiosurgery (GKRS) in patients with MSrTN. The primary outcome measure was the duration of pain-control; in other words, the time until the treatment failure and the factors that are predictive for outcome with different surgical modalities in the treatment of MSrTN.


Methods: A total of 31 patients underwent 65 surgical procedures to treat drug-resistant MSrTN in our department from 2003 to 2019. The patients’ demographic characteristics, pain severity scores, pain characteristics, initial symptom of MS, type of MS, the duration between MS and TN diagnosis, the interval between MS and the beginning of TN, location of MS plaques in MRI, duration of pain control after each procedure, and acute pain relief were evaluated. Pain control was determined as BNI scores that are ranging from I-IIIB. 


Results: Mann-Whitney U test was performed to analyze probable statistical differences in the duration of pain control (months) and decrease of VAS score between GKRS and RFT. Statistical analyses were not run for the MVD treatment group because of inadequate data. Distribution of the pain control duration and VAS score decrease were not similar, as by visual inspection. VAS scores decrease after RFT (Mean ± SD: 8.28 ±1.93) were statistically significantly higher than after GKRS (Mean ± SD: 5.18±3.71), U= 48.5, z=-2.31, p=0.020. 

Although comparison between pain control duration after RFT (Mean ± SD: 20.11 ±24.3)  and GKRS (Mean ± SD: 9.36±13.7) was not statistically significant, longer pain-free duration has been achieved with RF, U= 57.5, z=-1.88, p=0.061.


Conclusion: Pain control in MSrTN patients is challenging and requires multimodal surgical management generally. Patients with MS have a higher risk of disability and morbidity. Our results showed that RFT is a safe and effective surgical procedure for decreasing pain with a favorable longer duration of pain control without adding any morbidity to MS patients



Şükrü AYKOL, Mesut Emre YAMAN (Ankara, Turkey), Burak KARAASLAN, Munibe Busra ERDEM, Enes KARA, Tolga TÜRKMEN
16:00 - 16:05 #24079 - Dorsal root ganglion stimulation, a salvage therapy in neuropathic pain syndromes.
Dorsal root ganglion stimulation, a salvage therapy in neuropathic pain syndromes.


Medically intractable neuropathic low back and leg pain became manageable in the last two decades since the wide availability of spinal cord stimulation systems. Recent developments of new SCS stimulators and leads, introduction of new waveforms provided a possibility to salvage even those patients, who were not responding to treatment or had residual pain in mainly the low back. Dorsal root ganglion stimulation however provides a possibility to treat even those patients suffering from monoradicular, monodermatomal, or low back pain, who were not responding to spinal cord stimulation therapy.



6 patients, who were implanted with Abbott Proclaim DRG systems were enrolled in this review. 3 patients were suffering from neuropathic low back pain, 2 of these patients were previously implanted with percutaneous SCS systems without any success in the low back area. 1 patient developed bilateral Th5 level after tumor resection, 1 patient was suffering from post-thoracotomy pain, and 1 patient experienced ilioinguinal pain after inguinal hernia surgery. Stimulation parameters were tailored according to postoperative VAS scores and sufficient dermatomal involvement.




Each patient completed the trial phase successfully lasting at most 3 weeks. Mean age was 57,83±8,93 years, years passed since age onset of symptoms was 9,83±7,03 years. Patients suffering from low back pain received bilateral Th12 Axium Slim Tip leads, the remaining 3 patients received DRG leads according to dermatomal involvement in the bilateral Th5, unilateral L1, and unilateral Th9 dermatomes. Frequency was set between 12-20 Hz, pulse width was in range between 200-340 microseconds, while amplitude showed a mean level 0,52±0,21 mA. Preoperative VAS scores were decreased and maintained from a mean of 7,83±1,17 to 1,50±1,05. No complication has been observed during implantation or follow-up.



Dorsal root ganglion stimulation provides a valuable option to treat medically intractable neuropathic low back or monoradicaluar, monodermatomal pain. Patients suffering from low back pain can benefit from bilateral Th12 level stimulation. Low amplitudes and frequencies provide an option to prolong battery life in the long run, but it also raises the possibility of the involvement of different underlying neural circuits and regulatory mechanisms in action to achieve pain relief.

László HALÁSZ (Budapest, Hungary), Loránd ERŐSS
16:05 - 16:10 #25933 - Gamma Knife radiosurgery for trigeminal autonomic cephalalgias: preliminary results of a single-center prospective study.
Gamma Knife radiosurgery for trigeminal autonomic cephalalgias: preliminary results of a single-center prospective study.

Background: Gamma Knife radiosurgery (GKRS) was considered as a potential treatment for trigeminal autonomic cephalalgias (TACs). However, it was abandoned after that some authors reported an excessive facial sensory morbidity following GKRS for cluster headache (CH) in small cohorts of patients. Today, data about its efficacy, specific indications and ideal treatment parameters are lacking.


Objective: To report on 4 patients who underwent combined GKRS ablation of the cisternal part of the trigeminal nerve and of the sphenopalatine ganglion for TACs.


Methods: We have prospectively assessed four patients with TACs who were treated with combined GKRS ablation of the cisternal part of the trigeminal nerve and of the sphenopalatine ganglion. We report on characteristics including facial pain distribution and autonomic features, changes in pain scores and complications. Post-treatment facial numbness was assessed with the Barrow neurological institute (BNI) facial hypesthesia scale.


Results: Two patients with short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and two patients with chronic cluster headache (CH) were treated with GKRS and followed-up for at least six months. Two patients with SUNCT and one patient with chronic CH had complete pain relief after GKRS and one had partial pain reduction. Two patients had non-bothersome facial numbness after GKRS (BNI facial hypesthesia score II). Three patients met classical criteria for responders (50% decrease in pain scores). Autonomic features