Abstracts

Rationale: The paradoxical temporal lobe epilepsy (PTLE) is defined as mesial temporal lobe epilepsy (MTLE) without hippocampal abnormality in magnetic resonance images. Surgical outcome of PTLE is worse than MTLE in the point of seizure control and memory impairment after the operation. We perform the hippocampal transection (HT) by transsylvian approach for PTLE to block the epileptic propagation without making memory decline. We present the operative procedure and preliminary outcome of HT for PTLE in our institute. Methods: This study presents 11 patients of PTLE including 5 men and 6 women underwent HT between February 2005 and May 2007. Follow-up period ranged from 12 to 39 months (mean 30.1 mo). To identify the epileptic focus, we performed video-electrocorticogram monitoring in all patients. The patients were classified into 3 groups according to epileptic focus; right side focus was found in 3 patients (group R), left side focus was found in 1 patient (group L), and bilateral foci were found in 7 patients (group B). We decided operation side of group B according to analysis of frequency of seizure onset and inter ictal spike count. In the group B, right side operation was performed in 4 patients (group BR) and left side operation was performed in 3 patients (group BL). The operative procedure is as follows; at first, we open the sylvian fissure widely and approach hippocampal formation via temporal stem. We decide the extent of transection according to findings of intraoperative electrocorticography over the hippocampus. We cut the alveus perpendicular to long axis of hippocampus in 5mm interval and transect the pyramidal cell layer along to the incision of alveus. Seizure outcome and memory function were investigated for each group. Results: Seizure outcome was scored according to the Engel’s classification; class 1 was recorded in 9 patients, class 2 was recorded in 2 patients of the group B. Memory function was assessed by Wechsler Memory Scale-Revised before and one year after the operation. In the unilateral focus groups and group BR, visual and verbal memory and delayed recall were improved after the operation. In the group BL, visual memory was improved, however verbal memory showed a tendency of deterioration after the operation. Conclusions: Though the patient groups are too small to fully compare outcome, from the viewpoint of seizure control, HT for PTLE may be not less effective than surgical treatment for typical MTLE. The verbal memory may be preserve in patients of unilateral focus or right side operation for bilateral foci patients. The left side operation for bilateral foci patients may lead to deterioration of verbal memory. It will be necessary for precise confirmation to accumulate of patients and long follow-up period.