Abstract
The author presents a new surgical technique of hippocampal transection which can preserve postoperative verbal memory, even in left temporal lobe epilepsy without hippocampal atrophy on preoperative MRI images. A small corticotomy is performed in the superior temporal gyrus along the sylvian veins. The temporal stem is accessed by aspirating the gray matter of the superior temporal gyrus along the arachnoid membrane of the sylvian fissure. After resection of the temporal stem, the hippocampus and amygdala are exposed. Intraoperative ECoG is recorded to determine the extent of hippocampal transection. After the tough membrane of the alveus is cut with microscissors, a ring transector with 2 mm diameter is inserted through the slit, and the horizontal connections of the stratum pyramidal are disconnected. The medial part of the hippocampus, composed of CA4 and dentate gyrus, and the lateral deep pyramidal cell layer descending to the subiculum are disconnected using a ring transector with 4 mm diameter. After hippocampal transection is completed, ECoG is repeated to confirm complete cessation of epileptic discharges. If epileptic discharges exist in the anterior temporal basal area, cortical excision is performed through the anterior wall of the inferior ventricle. Epileptic discharges of the surface areas are treated by ordinary multiple subpial transection(MST). Over more than 4 years, 28 patients with unilateral temporal lobe epilepsy(left 17, right 11) underwent hippocampal transection. Out of 20 patients with>1 year follow-up, 16(80%) are seizure-free, 2 have rare seizures, and 2 are significantly improved.
