The role of intracranial electrode reevaluation in epilepsy patients afterfailed initial invasive monitoring

Purpose: Intracranial electrode recording often provides localization of th e site of seizure onset to allow epilepsy surgery. In patients whose invasi ve evaluation fails to localize seizure origin, the utility of further inva sive monitoring is unknown. This study was undertaker; to explore the hypot hesis that a second intracranial investigation is selected patients warrant s consideration and can lead to successful epilepsy surgery. Methods: A series of 110 consecutive patients with partial epilepsy who had undergone intracranial electrode evaluation (by subdural strip, subdural g rid, and/or depth electrodes) between February 1992 and October 1998 was re trospectively analyzed. Of these, failed localization of seizure origin was thought to be due to sampling error in 13 patients. Nine of these 13 patie nts underwent a second intracranial investigation. Results: Reevaluation with intracranial electrodes resulted in satisfactory seizure-onset localization in seven of nine patients, and these seven had epilepsy surgery. Three frontal, two temporal, and one occipital resection as well as one multiple subpial transection were performed. Six patients ha ve become seizure free, and one was not significantly improved. The mean fo llow-up is 2.8 years. There was no permanent morbidity. Conclusions: In selected patients in whom invasive monitoring fails to iden tify the site of seizure origin, reinvestigation with intracranial electrod es can achieve localization of the region of seizure onset and allow succes sful surgical treatment.