title: Diagnostic outcome of surgical revision of intracranial electrode placements for seizure localization.
abstract: OBJECTIVE
  We aimed to determine the yield of revising intracranially implanted electrodes and the factors contributing to the yield.
  
  
  METHODS
  Patients were identified from the Mayo Clinic Epilepsy Surgery Database between 1997 and 2010. Twenty patients had revision of intracranial electrode placements because initial implantation did not localize seizure onset adequately.
  
  
  RESULTS
  Seizures were captured in 18 of 20 patients who underwent intracranial electrode revision, of which 10 (55.6%) showed localized seizure onset that led to a surgical resection. Seizures were improved in 9 of 10 patients who underwent resection; of these, five were seizure free. The only factors found to be statistically significant in localizing ictal onset zone after revised implantation were prior focal scalp interictal discharges and an initial intracranial EEG showing ictal onset at the edge of the electrode grid. No permanent complication was associated with revised implantation, but one patient had transient apraxia of the right foot.
  
  
  CONCLUSIONS
  Revised implantation could be useful in selected patients with inadequate seizure localization on initial intracranial EEG. Resective surgery was performed in 50% of patients who underwent revision of intracranial electrodes with the majority of these patients experiencing an improvement in seizure control.
authors.affiliation: *Departments of Neurology and †Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, U.S.A.
authors.forename: Ricky W
authors.initials: RW
authors.lastname: Lee
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Worrell
authors.forename: W Richard
authors.initials: WR
authors.lastname: Marsh
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Cascino
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Wetjen
authors.forename: Fredric B
authors.initials: FB
authors.lastname: Meyer
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Wirrell
authors.forename: Elson L
authors.initials: EL
authors.lastname: So
mesh_terms: D000293:Adolescent; D000328:Adult; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome; D055815:Young Adult