title: The combination of subdural and depth electrodes for intracranial EEG investigation of suspected insular (perisylvian) epilepsy.
abstract: OBJECTIVE
  We present two methods of implantation for the investigation of suspected insular and perisylvian epilepsy that combine depth and subdural electrodes to capitalize on the advantages of each technique.
  
  
  METHODS
  Retrospective study of all intracranial EEG studies that included insular electrodes from 2004-2010. Patients were divided according to the implantation scheme. The first method (type 1) consisted of a craniotomy, insertion of insular electrodes after microdissection of the sylvian fissure, orthogonal implantation of mesiotemporal structures with neuronavigation, and coverage of the adjacent lobes with subdural electrodes. The second method (type 2) consisted of magnetic resonance imaging (MRI)-stereotactic frame-guided depth electrode implantation into insula and hippocampus using sagittal axes, and insertion of subdural electrodes through burr holes to cover the adjacent lobes. The combined implantations were developed and performed by one neurosurgeon (AB).
  
  
  RESULTS
  Nineteen patients had an intracranial study that sampled the insula, among other regions. Sixteen patients were implanted using the first method, which allowed a mean of 4, 5, 20, 15, and 42 contacts per patient to be positioned into/over the insular, mesial temporal, neocortical temporal, parietal, and frontal areas, respectively. The second method (three patients) allowed a mean of 8, 7, 16, 6, and 9 contacts per patient to sample the same areas, respectively. The four patients in whom transient neurologic deficits occurred were investigated with use of type 1 implantation.
  
  
  CONCLUSIONS
  Combined depth and subdural electrodes can be used safely to investigate complex insular/perisylvian refractory epilepsy. Choice of implantation scheme should be individualized according to presurgical data and the need for functional localization.
authors.affiliation: Service de Neurochirurgie, Hôpital Notre-Dame du CHUM, Université de Montréal, Quebec, Canada.
authors.forename: Werner
authors.initials: W
authors.lastname: Surbeck
authors.forename: Alain
authors.initials: A
authors.lastname: Bouthillier
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Weil
authors.forename: Louis
authors.initials: L
authors.lastname: Crevier
authors.forename: Lionel
authors.initials: L
authors.lastname: Carmant
authors.forename: Anne
authors.initials: A
authors.lastname: Lortie
authors.forename: Philippe
authors.initials: P
authors.lastname: Major
authors.forename: Dang Khoa
authors.initials: DK
authors.lastname: Nguyen
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003399:Craniotomy; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D019305:Epilepsy, Rolandic / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D042282:Microdissection; D008991:Monitoring, Physiologic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013238:Stereotaxic Techniques; D013355:Subdural Space; D055815:Young Adult