Abstracts

Rationale: Temporal lobe epilepsy (TLE) is the commonest medically-intractable localization-related epilepsy. Many patients with TLE are able to proceed directly to surgery if the non-invasive investigations are concordant. However, in some cases the lateralization of the epileptogenic focus is not clear, even with advanced non-invasive investigations. In these cases, intracranial electrodes (IE) for further monitoring are often required. We assess the role of this evaluation in the pre-surgical work-up and the long-term outcome of patients undergoing anterior temporal lobectomy (ATL) for TLE, and discuss the clinical utility of invasive EEG in this group of patients.Methods: A retrospective review of all surgical resections from 1977 to 2006 at our center was performed. Cases who underwent surgery for TLE who had pre-operative temporal IE were included. Only patients with exclusively temporal IE were included. Seizure outcome was assessed at last known follow up. Outcome was stratified according to whether the MRI was normal or abnormal.Results: Of 1,067 patients that underwent resective epilepsy surgery for TLE, 174 (87 females) underwent IE placement exclusively in the temporal lobes. Mean age at seizure onset was 15.1 years (range: 1-46), and the mean age at surgery was 30.3 years (range: 3-61). Of the 174 cases, 136 underwent ATL and 38 did not have surgery. MRI scans were performed in 132 of the patients undergoing ATL. The mean duration of follow up was 14.9 months (range: 1-36 months). Outcome was as follows: 71 cases (52%) were seizure free, and of these 44/67 (66%) had abnormal MRI. All 4 patients without MRI scans were in this group. In the 65 (48%) of patients who were not seizure free, the MRI was abnormal in 44 cases(67%). Pathology revealed MTS in 36 cases (26%), other pathologies (dysplastic, neoplastic cortex) in 79 cases (58%), and no abnormality in 13 cases (9.5%). In 8 cases pathological results were not available. Conclusions: Good outcomes were noted in this subset of TLE patients requiring presurgical IE. The presence of an MRI abnormality did not influence outcome. Although predictors of outcome remain unclear, overall effect on seizure-free outcome is robust.