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Poster; International audience; Background: Deep brain stimulation (DBS) is a common neurosurgical treatment for the tremor of Parkinson’s disease, essential tremor, and tremor of other causes. The outcome depends on optimal placement of the permanently implanted electrode. Many centers perform DBS surgery under local anesthesia in order to confirm the therapeutic effect with intraoperative stimulation testing. Visual inspection—the method generally used to rate changes in tremor during stimulation testing – is subjective, and its accuracy depends on the evaluator’s experience. This study presents the results of quantitatively estimating improvement in tremor during intraoperative stimulation tests in 15 patients. In addition, its influence on identifying the final position of the permanently implanted electrode is described.Method: We designed a 3D acceleration sensor system that is attached to the patient’s forearm during surgery. During intraoperative stimulation tests, at each different position, accelerometric data are synchronously recorded with the changing stimulation current amplitude. The method was applied in 15 DBS procedures in 2 centers (University Hospital Bern, Switzerland & University Hospital Clermont-Ferrand, France); the data were analyzed offline to assess improvements in tremor and to identify tremor-suppressing stimulation current-amplitudes. For correlation analysis, the quantitatively and visually determined improvements in tremor were categorized into: no improvement, low improvement, average improvement, high improvement and tremor arrest. The quantitatively identified tremor-suppressing currentamplitudes were compared to those identified by visual inspection, in order to determine the influence these findings would have had on the position chosen for permanent electrode implantation if they had been used for intraoperative decision-making. As this was a purely observational study, the accelerometric measurements werenot, in fact, allowed to alter the surgical procedures in any way.Results: A total of 359 evaluations were available for a comparison of the improvement in tremor identified by accelerometry vs. visual inspection. Of these evaluations, 156 (43.5%) were assigned the same categorie by both methods; 296 (82.5%) fell in the same or neighboring categories; and 63 (17.5%) were at least 2 categories apart. The quantitatively identified tremor-suppressing current-amplitudes were significantly lower than the visually identified ones (1.13 ± 0.8 mA vs. 1.7 ± 0.8 mA [mean ± SD]). Of the 26 finally chosen positions for permanent lead implantation, 15would have been different had the accelerometric data been considered.Discussion and Conclusion: The improvement of tremor brought about by test stimulation was rated in the same category by visual inspection and by quantitative measurement (accelerometry) in only 43.5% of the evaluations that we made in this study. In some of the evaluations where there was only mild tremor at baseline, the stimulation-induced improvement in tremor was classified by visual inspection as tremor arrest, while accelerometry revealed a very mild residual tremor. This fact explains many of the instances in which the tremor ratings obtained by the two methods were only 1 category apart, but it cannot account for the 17.5% of evaluations that were 2 or more categories apart. The quantitative assessment of tremor as performed here yields different findings from assessment by visual inspection alone. The tremor-suppressing stimulation current-amplitudes are lower, and this, in turn, can often affect the chosen site for permanent electrode implantation. Thus, quantitative tremor assessment can affect, and perhaps improve, targeting in DBS without altering the routine surgical procedure. This tentative conclusion awaits confirmation by further studies. Moreover, aside from its potential direct clinical utility, quantitative tremor assessment DBS surgery might be a useful adjunct to the clinical testing of new types of DBS electrode.

National audience

Talk; International audience; Routine clinical practice of Deep Brain Stimulation (DBS) enters a new era where battery-related events are challenging. The important number of primary implantations and replacements pushed industrials to develop new generations of devices. We aimed to analyze the battery lifetime of different kinds of non-rechargeable devices, manufactured by a single company (Medtronic, USA): the first generation of 4-contact neurostimulator for one DBS-lead (1 channel; Soletra®) and 8-contact neurostimulator for two DBS-leads (two channels of 4 contacts; Kinetra®); the second generation of advanced programming neurostimulator (Activa® PC, two channels of 8 contacts, and SC, 1 channel of 8 contacts). We retrospectively reviewed 281 consecutive patients operated on in a single institution (from 1995 to 2016): 584 surgeries for primary implantation or replacement of neurostimulator (infection and traumatic etiologies of battery replacement were excluded). The battery lifetime was defined as the period between the surgical implantation and the removal at battery depletion. Two hundred and eighty eight battery-lifetimes were analyzed in 157 patients suffering of Parkinson disease (n=129), essential tremor (n=19), dystonia (n=9). Exclusion criteria were: battery related, still operational (n=217); patient related, died before battery depletion (n=50); missing follow-up (n=3); and other diseases treated by DBS (n=2). Battery lifetime was analyzed using survival methods (univariate, Log-Rank test; multivariate, marginal cox model; two-sided tests) accounting for the following parameters: gender, neurological disease, age at the primary implantation, the UPDRS-score before DBS surgery, the deep brain target, battery model, mean voltage (low < 2V; usual from 2V to 4V; high v> 4V), location of battery (abdominal or sub clavicular) and presence of an adapter for replacement of first generation (Kinetra or Soletra) by second generation model (Activa).Results: The battery lifetime was shorter in male (p=0.03) and young (p

International audience; Aims: We performed quantitative diffusion tensor imaging and brain tractography to distinguish clinical severity in a series of 35 patients with hypomyelinating PLP1-related disorders classified using the Motor Developmental Score according to the best motor function acquired before the age of 5 years and the gross motor function measure (GMFM) at the time of magnetic resonance imaging acquisition. Methods: We calculated fractional anisotropy and diffusivity values in 26 regions of interest and the numbers of fibers and volumes of hemisphere tractograms. Fiber bundles on tractograms were characterized according to 3 criteria: size, direction of main-stream fibers, and connectivity of bundles (extratelencephalic projections, commissural fibers, and intrahemispheric connections). Results: Age-adjusted multivariate analysis in 3 severity groups revealed increased isotropic diffusion in the superior cerebellar peduncle and grey matter in the most severe group, and larger tractogram volumes and increased numbers of fibers in the least severely affected group. Tractogram patterns showed preserved extratelencephalic projections and a main anterior-posterior aspect of intrahemispheric fibers in most patients, whereas interhemispheric connectivity was variable. The most severely affected and intermediate patients had less intrahemispheric connectivity, with a frequent predominant anterior-posterior direction of main-stream fibers. Interpretation: Diffusion tensor imaging and tractographic parameters can operate as biomarkers to distinguish clinical severity in PLP1-related disorders and could improve our understanding of hypomyelinating leukodystrophies.

International audience

Poster; International audience; Introduction: The outcome of deep brain stimulation (DBS) depends heavily on the position of the implanted lead. After a preoperative anatomical planning, most groups collect numerous intraoperative data such as therapeutic effects induced by stimulation tests. To choose the final implant position, physicians “mentally” visualise all available data. The aim of the present work was to develop a method visualising intraoperative stimulation test results, patient’s images, electric field (EF) simulations for the patient-specific stimulation conditions and the corresponding therapeutic effects quantitatively evaluated by accelerometry. The application to five essential tremor (ET) patients should give a first idea about the optimal target position. Methods: In Clermont-Ferrand University Hospital the anatomic target structure and the neighbouring structures were manually outlined, a target and a trajectory defined and two parallel trajectories per hemisphere intraoperatively evaluated. Stimulation tests were performed at 7 to 8 positions per trajectory and several stimulation current amplitudes. The therapeutic effect was evaluated using a previously published method based on accelerometry. Finite element models and simulations were performed for up to three stimulation amplitudes per position and EF isosurfaces (0.2V/mm) were extracted. For the 3D visualization of the numerous overlapping isosurfaces, we generated “improvement maps” by assigning to each voxel within the isosurfaces the highest tremor improvement. Those maps were visualized together with anatomical images, delineated structures and trajectories (Paraview, Kitware Inc). The method was applied to 5 ET patients implanted in the ventro-intermediate nucleus of the thalamus (VIM). Results were analysed by the neurosurgeon regarding the optimal implant position. Results: The clinical teams were able to identify the optimal implant position for all patients with more ease and in less time compared to the routine discussion using pen and paper. Additionally, for 7 of the 9 improvement maps, the highest improvement region was found to be in the posterior subthalamic area, inferior and posterior to the VIM. Conclusion: Improvement maps assist the clinicians in determining the optimal implant location of the chronic DBS lead. Results support findings of other studies that the fibre tracts in the posterior subthalamic area like prelemniscal radiations may be responsible for alleviating tremor in ET patients.