title: Patient-Specific Electric Field Simulations and Acceleration Measurements for Objective Analysis of Intraoperative Stimulation Tests in the Thalamus.
abstract: Despite an increasing use of deep brain stimulation (DBS) the fundamental mechanisms of action remain largely unknown. Simulation of electric entities has previously been proposed for chronic DBS combined with subjective symptom evaluations, but not for intraoperative stimulation tests. The present paper introduces a method for an objective exploitation of intraoperative stimulation test data to identify the optimal implant position of the chronic DBS lead by relating the electric field (EF) simulations to the patient-specific anatomy and the clinical effects quantified by accelerometry. To illustrate the feasibility of this approach, it was applied to five patients with essential tremor bilaterally implanted in the ventral intermediate nucleus (VIM). The VIM and its neighborhood structures were preoperatively outlined in 3D on white matter attenuated inversion recovery MR images. Quantitative intraoperative clinical assessments were performed using accelerometry. EF simulations (n= 272) for intraoperative stimulation test data performed along two trajectories per side were set-up using the finite element method for 143 stimulation test positions. The resulting EF isosurface of 0.2 V/mm was superimposed to the outlined anatomical structures. The percentage of volume of each structure's overlap was calculated and related to the corresponding clinical improvement. The proposed concept has been successfully applied to the five patients. For higher clinical improvements, not only the VIM but as well other neighboring structures were covered by the EF isosurfaces. The percentage of the volumes of the VIM, of the nucleus intermediate lateral of the thalamus and the prelemniscal radiations within the prerubral field of Forel increased for clinical improvements higher than 50% compared to improvements lower than 50%. The presented new concept allows a detailed and objective analysis of a high amount of intraoperative data to identify the optimal stimulation target. First results indicate agreement with published data hypothesizing that the stimulation of other structures than the VIM might be responsible for good clinical effects in essential tremor. (Clinical trial reference number: Ref: 2011-A00774-37/AU905).
authors.affiliation: Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland FHNWMuttenz, Switzerland; Department of Biomedical Engineering, Linköping UniversityLinköping, Sweden.
authors.forename: Simone
authors.initials: S
authors.lastname: Hemm
authors.affiliation: Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland FHNW Muttenz, Switzerland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Pison
authors.affiliation: Department of Biomedical Engineering, Linköping University Linköping, Sweden.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Alonso
authors.affiliation: Institute for Medical and Analytical Technologies, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland FHNW Muttenz, Switzerland.
authors.forename: Ashesh
authors.initials: A
authors.lastname: Shah
authors.affiliation: Université Clermont Auvergne, Université d'Auvergne, EA 7282, Image Guided Clinical Neurosciences and Connectomics (IGCNC)Clermont-Ferrand, France; Service de Neurochirurgie, Hôpital Gabriel-Montpied, Centre Hospitalier Universitaire de Clermont-FerrandClermont-Ferrand, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Coste
authors.affiliation: Université Clermont Auvergne, Université d'Auvergne, EA 7282, Image Guided Clinical Neurosciences and Connectomics (IGCNC)Clermont-Ferrand, France; Service de Neurochirurgie, Hôpital Gabriel-Montpied, Centre Hospitalier Universitaire de Clermont-FerrandClermont-Ferrand, France.
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Lemaire
authors.affiliation: Department of Biomedical Engineering, Linköping University Linköping, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Wårdell
keywords: acceleration measurements; deep brain stimulation (DBS); essential tremor; finite element method (FEM) simulations; intraoperative stimulation tests; patient-specific brain maps; ventral intermediate nucleus (VIM)