Abstracts

Rationale: Mesial temporal lobectomy for drug resistant intractable mesial temporal lobe epilepsy (mTLE) can achieve favorable seizure outcome but may conduce to memory decline especially in the patients in whom hippocampal sclerosis is not apparent in verbal dominant side. Multiple hippocampal transection (MHT) is a novel surgical procedure to avoid memory decline after mesial temporal lobe surgery. The seizure outcome of MHT at one year after surgery is equivalent to that of mesial temporal lobectomy, and the memory indices were preserved at the preoperative level. However, the long-term outcome after MHT has not been clarified. In this study, we report long-term outcome of our patients after MHT in terms of seizure control and cognitive function, and discuss the significance of MHT in the surgical treatment for mTLE. Methods: 24 patients who underwent MHT for drug resistant intractable mTLE were followed for longer than 5 years, including 6 patients with hippocampal sclerosis, 5 with other lesions, and 13 without lesion in preoperative MRI. All patients underwent MRI, rCBF-SPECT, FDG-PET, and video EEG monitoring before surgery. When the side of epileptic focus could not be determined from noninvasive evaluations, intracranial electrodes were implanted bilaterally. Seizure outcome was evaluated using Engel's classification at one year after surgery and at the last visit. Cognitive functions were evaluated with Wechsler Memory Scale-Revised (WMS-R) and Wechsler Adult Intelligence Scale-III (WAIS-III) before surgery and one month, 6 months, and 5 years after surgery. Results: Mean follow-up period was 77 months. Seizure outcomes were Engel I/II/III in 71%/25%/4% of patients at one year, and 67%/21%/13% at the last visit. Four (23.5%) of 17 patients who were Engel I at one year had seizure recurrence at the last visit. Memory indices were at the preoperative level at 6 months after transient decline at one month postoperatively, and were kept at the level at 5 years after surgery. Conclusions: Long-term seizure outcome after MHT was considered slightly worse than that of temporal lobectomy, while cognitive function was well preserved even after dominant-sided MHT. MHT is a significant option for patients with mTLE in whom respective surgery carries a risk of postoperative cognitive decline.