Abstracts

Rationale: Hippocampal transection is a newly developed method for the treatment of left temporal lobe epilepsy (TLE) with full preservation of verbal memory. We applied this method to TLE patients with organic lesions and MRI-normal hippocampus. Methods: The study subjects were four patients with intractable TLE associated with three cavernous angiomas and one dysembryoplastic neuroepithelial tumor. Preoperative examination of each subject demonstrated TLE of the same side same as the organic lesion. MRI showed a normal hippocampus and FDG-PET revealed medial temporal hypometabolism on the side of the focus. After an initial lesionectomy and then, recording of intraoperative electrocorticography (ECoG) was commenced. Multiple transections of the pyramidal layer under the alveolus were performed until the epileptic discharges from the hippocampus were completely abolished. The patients respectively underwent two left-sided and two right-sided surgeries, and were followed up for more than 1 year. The amytal test confirmed left-sided memory dominance in two patients with left-sided lesions. Wechsler Memory Scale Revised (WMS-R) tests were performed at 2 weeks, 6-months, and 1-year after surgery. Results: 1) All four of the patients obtained seizure-free outcome. 2) Two patients with right-sided transection showed no change in visual memory, verbal memory, and delayed recall at 2 weeks, 6-months, and 1-year after surgery. 3) Two patients with left-sided transection showed marked deterioration of visual memory, verbal memory, and delayed recall at 2 weeks after surgery. All of those models of memory improved gradually and almost returned to preoperative levels by 1 year after surgery. Conclusions: The results from the present study suggest that hippocampal transection for TLE patients with organic lesions and MRI-normal hippocampus is a useful method for achieving seizure cessation and memory preservation.