Efficacy of Vagal Nerve Stimulation (VNS) after Multiple Subpial Transection (MST) for Extra-Temporal Seizure Foci (P01.056)

Abstract

Objective: To evaluate seizure outcome with vagal nerve stimulation after multiple subpial transection in patients with extra temporal seizure foci. Background Though there are reports on seizure outcome of vagal stimulation (VNS) following failed major resective surgeries there are no studies on its effect following multiple subpial transections (MST). Design/Methods: 24 patients between the ages of 10-55 years were followed up for 24-148 months (median of 115 months). Seizure foci were bilateral in 11 patients, multi-lobar (unilateral) in 12 patients and single-lobar(unilateral) in 1 patient. MST was performed over broad areas in and around the seizure foci. Minimal topectomies were done in areas in which intra-operative EEG recording showed epileptogenic activity after 2-3 MST passes. VNS implant was done when the response from first surgery was poor (2 patients) or there was recurrence of seizures (24 patients). The interval between MST and VNS was 1 month-3years (median of 2 years). Results: There were no complications from VNS implant. The seizure outcome after VNS implant is: 15/24(62.5%) Engle9s class I, 8/24 (33.3%) class II and 1/24 (4%) class III. Conclusions: The results show that VNS improves seizure outcome in patients who have previously had MST. Based on literature search these results are better than those reported in patients who had VNS implant alone (with a 50 % responder rate in 30-40 percent); or had VNS implant after major resective surgery (with no significant benefit) or those who had major resective surgery alone. This difference may be because MST is performed over a large area of the brain; so that satellite foci in distant areas also get treated. Furthermore, it is possible that the pruning of the inter-neuronal connections that occurs in MST makes VNS signals reaching the cortical neurons more intense (and therefore more effective) by reducing its peripheral spread. Disclosure: Dr. Patil has nothing to disclose. Dr. Antony has nothing to disclose. Dr. Andrews has nothing to disclose.