Abstracts

Rationale: Invasive intracranial electrodes (IE) are an important part of the workup in many patients being considered for epilepsy surgery. Because IE are usually reserved for cases where seizure localization is ambiguous, one might expect that the eventual outcome epilepsy surgery would be worse than in patients who did not require IE as part of their workup. The purpose of this study was to specifically examine those patients who underwent insertion of IE, to determine how many of these patients eventually underwent resective surgery and to assess the eventual outcome. Methods: All cases admitted for IE between January 2000 and June 2005 were reviewed. Surgical outcomes were reported using the Engel classification and a multivariate analysis was used to determine which factors were associated with successful surgery. Results: 177 IE implantations were performed in 172 patients. Of these, 130 patients went on to have surgery. In the 113 patients in whom 1-year follow-up was available, 47% were seizure free at 1 year. Age was a major predictor of outcome with only 21% of patients over age 40 becoming seizure free with surgery compared to 58% in patients aged under forty years (p=0.0004). Other predictors of an Engel I outcome included having a temporal lobectomy or supplementary motor area resection. Conclusions: Good results from eventual resective surgery can be achieved in patients needing invasive recordings. Younger patients with temporal lobe epilepsy seem to have the highest likelihood of seizure freedom. Poorer outcome in older patients supports the possibility of progressive epileptogenesis in complex epilepsy.