title: Deep brain stimulation of the pallidum internum for Gilles de la Tourette syndrome: a patient-specific model-based simulation study of the electric field.
abstract: OBJECTIVE
  The aim of this study was to investigate the deep brain stimulation (DBS) electric field distribution in proton-density MRI scans visualizing the globus pallidus internus (GPi) of patients with Gilles de la Tourette syndrome (GTS), along with its relation to the anatomy.
  
  
  METHODS
  Patient-specific brain tissue models (n = 7) with bilateral DBS electrodes in the GPi were set up using the finite element method in five patients who had undergone stereotactic proton-density MRI-guided surgery and showed variable improvement with DBS. Simulations (n = 27) of the electric field were performed and the results visualized on the respective preoperative stereotactic MRI scans. The mean electric field volumes (n = 81) within the 0.1, 0.15, and 0.2 V/mm isosurfaces were calculated and compared with the anatomy.
  
  
  RESULTS
  Visualization of the simulated electric field confirmed that the anteromedial limbic GPi was the main stimulated target for four of the patients and the posteromedial sensorimotor GPi for one. Larger volumes extended asymmetrically, with parts of fields stretching into the lamina between GPi and globus pallidus externus and into the internal capsule. There was a high correlation (r = 0.994, n = 54) between volumes and brain sides, but with a systematic shift toward the right side, especially for the larger volumes. Simulations with homogeneous tissue models showed no differences.
  
  
  CONCLUSIONS
  Patient-specific DBS electric field simulations in the GPi as visualized on proton-density MR scans can be implemented in patients with GTS. Visualization of electric fields together with stereotactic thin-slice MRI can provide further support when predicting anatomical structures possibly influenced by DBS in this complex disorder.
authors.affiliation: Department of Biomedical Engineering, Linköping University, Linköping, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Wårdell
authors.forename: Zinovia
authors.initials: Z
authors.lastname: Kefalopoulou
authors.forename: Elin
authors.initials: E
authors.lastname: Diczfalusy
authors.forename: Mats
authors.initials: M
authors.lastname: Andersson
authors.forename: Mattias
authors.initials: M
authors.lastname: Åström
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.forename: Marwan
authors.initials: M
authors.lastname: Hariz
mesh_terms: D000328:Adult; D003198:Computer Simulation; D046690:Deep Brain Stimulation / Q000379:methods*; D005260:Female; D005917:Globus Pallidus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D005879:Tourette Syndrome / Q000628:therapy*; D016896:Treatment Outcome; D055815:Young Adult
keywords: Deep brain stimulation; Tourette syndrome; electric field simulation; globus pallidus internus; modeling and simulation