173 Long-term Follow-up After Multiple Hippocampal Transection (MHT)

Abstract

INTRODUCTION: The conventional procedure of hippocampectomy can impair memory. Furthermore, the hippocampus is the main source of stem cells. On the other hand, multiple hippocampal transection (MHT) can disrupt seizure circuits without loss of function or stem cells. In this presentation therefore, the authors will present long term outcomes in patients who had MHT for unilateral temporal lobe epilepsy. METHODS: There were 15 patients with a male/female ratio of 2-to-1; follow-up of 24 to 60 months (median of 41 months); and ages between 25 and 60 years. Preoperative electrocorticography (ECoG) was done using subdural and depth electrodes. All patients had multiple subpial transection (MST) on the neocortex and MHT on the hippocampus. Access to the hippocampus was gained through the middle temporal gyrus. Transverse cuts were made in the hippocampus at 4 mm intervals. The fimbria and entorhinal cortex were left intact. Amygdala was removed if it was epileptogenic (10 patients). Intraoperative ECoG was then done. If recordings showed epileptogenic activity, transections were repeated. If this activity persisted, the involved neocortex was resected. RESULTS: Based on intraoperative ECoG, repeat transections were needed in every case; though the second pass was over a much smaller area. Resection of temporal tip (1-2.5 cm diameter) was needed in 11 patients. There were no permanent neurological complications. Fourteen patients (94.7%) are Seizure free (Engel's class I) and 1 (6%) has rare seizures (class II). Neuropsychological studies showed that verbal memory was preserved. CONCLUSION: Although the series is small the long-term follow-up is adequate to draw preliminary conclusions. The results show that the seizure outcome with MHT is better than those reported with standard temporal lobectomy. The study also shows that intraoperative ECoG is important in order to conclude adequacy of the procedure. These conclusions indicate that this procedure needs to be persued as an alternate to hippocampectomy.