title: The 3-dimensional grid: a novel approach to stereoelectroencephalography.
abstract: BACKGROUND
  Successful surgical treatment of epilepsy requires accurate definition of areas of ictal onset and eloquent brain. Although invasive monitoring can help, subdural grids cannot sample sulci or subcortical tissue; traditional stereoelectroencephalography depth electrodes are usually placed too far apart to provide sufficient resolution for mapping.
  
  
  OBJECTIVE
  To report a strategy of depth electrode placement in a dense array to allow precise anatomic localization of epileptic and eloquent cortex.
  
  
  METHODS
  Twenty patients with medically intractable epilepsy either poorly localized or found to arise adjacent to eloquent areas underwent placement of arrays of depth electrodes into and around the putative area of seizure onset with the use of framed stereotaxy. Each array consisted of a "grid" of parallel electrodes in a rectangular pattern with 1 cm between entry sites. In a subset of patients, a few electrodes were placed initially, with additional electrodes placed in a second stage. Trajectories were modified to avoid cortical vessels defined on magnetic resonance imaging. Patients were monitored for 4 to 21 days to establish the precise location of seizure onset. Stimulation was performed to map cortical and subcortical eloquent regions. Electrode locations were coregistered for frameless stereotaxy during subsequent resection of seizure focus.
  
  
  RESULTS
  Two hundred fifty-four electrodes were implanted. Discrete regions of seizure onset and functional cortex were identified, which were used during resection to remove epileptogenic tissue while preserving eloquent areas. There were no hemorrhagic or infectious complications; no patient suffered permanent neurological deficit.
  
  
  CONCLUSIONS
  The 3-dimensional intraparenchymal grid is useful for identifying the location and extent of epileptic and eloquent brain.
authors.affiliation: *Department of Neurological Surgery and ‡Neurology, University Hospitals Case Medical Center, Cleveland, Ohio.
authors.forename: Charles
authors.initials: C
authors.lastname: Munyon
authors.forename: Jennifer
authors.initials: J
authors.lastname: Sweet
authors.forename: Hans
authors.initials: H
authors.lastname: Luders
authors.forename: Samden
authors.initials: S
authors.lastname: Lhatoo
authors.forename: Jonathan
authors.initials: J
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000601:surgery*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000379:methods*; D011183:Postoperative Complications / Q000601:surgery