title: Supplementary implantation of intracranial electrodes in the evaluation for epilepsy surgery.
abstract: OBJECTIVE
  In some patients, resective epilepsy surgery can be planned based on a non-invasive work-up. However, in many cases, invasive monitoring with intracranial electrodes is required prior to recommending a resective procedure. Although the results of intracranial recordings are usually conclusive, a small group of patients may require additional electrodes to better define the seizure onset or propagation.
  
  
  METHODS
  One hundred and seventy seven patients who underwent intracranial electrode insertion between January 2000 and June 2005 were reviewed. Twelve of these patients required a supplementary implantation prior to making a recommendation about resective surgery. We report the nature of implantation as well as the outcomes in these 12 patients.
  
  
  RESULTS
  The mean age of these patients was 35 years (7 males). An average of 2.5 additional strip electrodes were required resulting in a mean of 9 strip type electrodes per patient, for a mean total of an additional 20 days. For most patients (9/12) this subsequent procedure identified an area of epileptic cortex other than that originally hypothesized. Seven patients went on to surgery of which three experienced a significant improvement in seizure control.
  
  
  CONCLUSIONS
  The addition of supplementary electrodes to an ongoing invasive electrode investigation can be a useful means of clarifying a patient's suitability for a resective surgical procedure. While the surgical outcomes may not be as favorable as in patients in whom the investigations are simpler, a proportion of these patients do benefit from the eventual resective procedure. In cases where the supplementary electrodes lead to the conclusion that surgery is not indicated, these patients can be satisfied that the surgical option has been explored to the fullest extent possible.
authors.affiliation: Epilepsy Programme, Department of Clinical Neurological Sciences, University of Western Ontario, London, ON, Canada N6A 5A5.
authors.forename: Keith W
authors.initials: KW
authors.lastname: MacDougall
authors.forename: David A
authors.initials: DA
authors.lastname: Steven
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Parrent
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Burneo
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000601:surgery*; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011300:Preoperative Care / Q000379:methods*; D016896:Treatment Outcome