Abstracts

To investigate whether the absolute interictal spike frequency is of prognostic significance for postoperative outcome in patients with medically refractory mesial temporal lobe epilepsy (MTLE). We retrospectively studied 55 patients with medically refractory MTLE. All patients were evaluated with prolonged scalp video-EEG-monitoring including true anterior temporal and sphenoidal electrodes for an average of 5 days. EEG samples of 5 minutes were automatically stored every hour during the monitoring. Patients were classified according to their absolute interictal spike frequency, either in Group I ([ge]60 spikes/h) or in Group II ([lt]60 spikes/h) and according to the relative spike distribution in a unitemporal and a bitemporal group ([ge]90% respectively [lt]90% of spikes over the affected temporal lobe). All patients underwent first time epilepsy surgery, either selective amygdalohippocampectomy (47 patients) or anterior medial temporal resection (6 patients). In 2 patients a more extensive anterior temporal resection was performed. Postoperative follow-up was at least 12 months. The frequent spikes group ([ge]60 spikes/h) comprised 14 patients, the non-frequent spikes group ([lt]60 spikes/h) 41 patients, the unitemporal group 35 patients and the bitemporal group 20 patients. We found that the occurrence of frequent spikes during presurgical prolonged EEG-monitoring was significantly associated with unsatisfactory surgical outcome as compared to the occurence of infrequent spikes (p=0.001 for 1 year postoperative outcome; p=0.011 for 2 years postoperative outcome). The outcome was non-significantly different between the unitemporal and bitemporal group (p=0.282 for 1 year postoperative outcome; p=0.208 for 2 years postoperative outcome We conclude that the absolute interictal spike frequency is of prognostic significance for postoperative outcome in patients with medically refractory temporal lobe epilepsy.