Abstracts

Rationale: Although amygdalo-hippocampectomy is associated with good seizure outcome for the mesial temporal lobe epilepsy (MTLE), postoperative memory impairment has been a longstanding unresolved problem. Especially, in the case of MTLE without hippocampal atrophy or sclerosis, postoperative worsening of memory function is inevitable. To resolve this problem, hippocampal transection (HT) was developed and has conducted in some special institutions. In this report, we present the surgical indication, procedure and postoperative seizure and memory outcome of HT. Methods: Surgical indication of HT is determined considering following factors; (1) bilateral onset of seizures (2) lack of hippocampal atrophy or sclerosis in preoperative MRI (3) lack of memory score decline. From 2005 to 2012, we performed HT in 38 cases (aged from 9 to 63, 19 men and 19 women, 19 in dominant side and 19 in non-dominant side). Of 38 cases, seven cases were associated with other intracranial lesion (tumor, cavernoma or cortical dysplasia) HT was conducted with trans-sylvian approach aimed for less invasiveness. After approaching the hippocampal formation via temporal stem, we cut the alveus perpendicular to long axis of hippocampus in 5 mm interval and transect the pyramidal cell layer along to the incision of alveus. Seizure outcome was evaluated with Engel's classification. Memory outcome was evaluated with Wechsler Memory Scale-Revised (WMS-R) comparing pre and postoperative state. Results: There were no surgical complications. Engel's class I (free of disabling seizures) was achieved in 74% (28/38). In the non-dominant side group, all indices (verbal memory, non-verbal memory, general memory, delayed recall and attention/concentration) were preserved postoperatively. In the dominant side group, verbal memory and delayed recall were temporarily declined (one month postoperatively), but recovered in one year, while another indices including non-verbal memory were preserved postoperatively. Conclusions: Favorable seizure outcome and memory outcome were achieved with HT. We concluded that HT is an effective surgical procedure especially in temporal lobe epilepsy without hippocampal atrophy or sclerosis.