3D visualization of intraoperative stimulation test results in deep brain stimulation

PosterInternational audienceI. INTRODUCTIONDeep brain stimulation (DBS) is a treatment for movement disorders such as Essential Tremor (ET). The implant position of the electrode is crucial. After preoperative surgical planning and intraoperative tests, the collected data is only “mentally” visualized and analyzed by the physician to decide on the optimal implant position of the DBS lead. We propose a method to combine and visually present this multitude of data for surgical decision making using patient-specific simulations of the electric field (EF) distribution, intraoperative accelerometry based tremor evaluations and direct-targeting technique of DBS.II. METHODFive ET patients participating in a clinical study (Ref: 2011-A00774-37/AU905, CPP Sud-Est 6, Clermont-Ferrand, France; written informed consent) were included in the presented protocol in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 and 2008. Patients underwent routine stereotactic bilateral implantation of the DBS electrodes in the ventro-intermediate nucleus of the thalamus (VIM) [1].During planning, the target structure and the anatomical neighbours were outlined on patient images and an anatomical target was selected. Two microelectrodes were intraoperatively inserted per hemisphere on parallel trajectories. Stimulation tests were performed on 5 to 10 positions pertrajectory with several stimulation amplitudes per position to evaluate side effects and changes in tremor using an accelerometer fixed to the patient's wrist [2]. To estimate the extension of the stimulation, the EF was simulated using a finite-element model for several amplitudes per position related to different tremor improvements [3]. To identify the optimal implant position for chronic stimulation, we summarized all data in "Improvement Maps” by assigning to each voxel in the stimulation test region the highest improvement in tremor. Improvements were visualized on the patient-specific anatomical outlines using a green color scale and simulations of side-effects in red (Paraview, Kitware Inc). Postoperatively the optimal implant positions with the highest improvement were identified for the five patients.III. RESULTSThe clinical teams were able to identify the optimal implant positions with more ease and in less time compared to the routine discussion using pen and paper. Additionally, for 7 out of the 9 improvement maps, the highest improvement region was found to be in the posterior subthalamic area inferior and posterior to the surgical target, the VIM.IV. CONCLUSIONSVisual analysis of the results of intraoperative stimulation tests in form of improvement maps assists the clinicians in determining the optimal implant location of the chronic DBS lead and in comparing results between patients