Abstracts

Rationale: Temporal lobe epilepsy with amygdala enlargement (TLE-AE) has been discussed as a subtype of TLE without hippocampal sclerosis. Questions to TLE-AE are whether the epileptogenic zone is amygdala or not, and what pathological change exist in the enlarged amygdala. No report has assessed the actual epileptogenesis of TLE-AE. The purpose of this study was to clarify whether the amygdala is the epileptic focus or not. Methods: This study enrolled 11 TLE patients with MRI detectable AE, who underwent surgical treatment. We investigated clinical features including age of seizure onset,seizure frequency, seizure semiology, and the result of the Wechsler Memory Scale-Revised(WMS-R). Two independent reviewers diagnosed the seizure onset zone (SOZ) from visual detection on chronic electrocorticography (ECoG) (n=8).The epileptic focus was also estimated by evaluating interictal epileptic discharges (IEDs) on intraoperative ECoG (n=11).We evaluated the relationship among surgical procedures, seizure outcome and histological diagnosis. Results: A mean age at seizure onset was 29.9 years.A mean seizure frequency was nine times a month.All patients had focal impaired awareness seizures with behavior arrests. No patient revealed ictal fear as seizure symptoms.Preoperative mean verbal, visual, and delayed recall scores on WMS-R were 110, 104 and 101, respectively. In seven out of eight patients, chronic ECoG showed the hippocampus was involved in SOZ. Intraoperative ECoG presented IEDs from hippocampus in nine. Two patients underwent anterior temporal lobectomy (ATL) without hippocampal procedure. However, nine patients were performed ATL with hippocampal resection or transection. ILAE class 1 outcome was achieved in eight (73%), including 78% of class I outcome in patients with hippocampal procedures. The specimens of resected amygdala did not result any histological alteration. Conclusions: This study demonstrated the actual epileptic focus of TLE-AE was found to be hippocampus, not amygdala. Funding: None