Abstracts

In many patients being considered for epilepsy surgery, a standard pre-surgical evaluation consisting of a scalp electroencephalogram (EEG), magnetic resonance imaging (MRI), functional neuro-imaging and a neuropsychological assessment is sufficient to identify the epileptogenic zone. When this evaluation cannot identify the epileptogenic focus, invasive intracranial electrodes are often required. Although there is considerable data about the outcome of patients undergoing epilepsy surgery, most of these investigations examine all patients (with and without invasive recordings) together. This purpose of this study was to specifically examine patients who underwent invasive EEG and to determine how many of these patients eventually underwent resective surgery. In those who had surgery, we wished to examine the eventual outcome., We retrospectively reviewed charts for all patients admitted to the London health Sciences Centre Epilepsy Monitoring Unit between January 2000 and July 2004 for intracranial electrode monitoring. Surgical outcomes were reported using the Engel classification. We used a multivariate analysis to determine which factors if any were associated with successful surgery., There were 103 subdural electrode implantations performed by our two epilepsy surgeons in 100 patients. Of these, 78 patients went on to have resective surgery. Temporal lobectomy was performed in 39 (50%) patients. One-year follow-up was available on 66 of the 78 patients (85%). Thirty patients (45%) realized an Engel I outcome at 1 year. An additional 20 (30%) had their seizure frequency significantly reduced. Predictors of an Engel I outcome included younger age (p[lt]0.0001) and having a temporal lobectomy (adjusted OR = 4.17; CI =1.12 - 12.8). Factors that did not significantly affect outcome included the duration, area, and location of electrode coverage, the presence of a pre-operative lesion or the final pathology., Excellent results from eventual resective surgery can be achieved in the subset of patients needing invasive recordings. Younger patients with temporal lobe epilepsy seem to have the highest likelihood of seizure freedom. The need for bilateral or multilobar electrodes did not negatively affect prognosis.,