Abstracts

Rationale: Vagal nerve stimulation (VNS) is an adjunctive therapy for intractable epilepsy. Tuberous sclerosis complex (TSC) is a multisystem disorder associated with epilepsy in 60 to 90% of affected individuals. Our goal was to characterize the efficacy and safety of VNS in a population of TSC patients with intractable epilepsy.Methods: Sixteen (8 males, 8 females) TSC patients treated using VNS followed at the Herscot Center for TSC at Massachusetts General Hospital were retrospectively analyzed. VNS efficacy was measured according to a proposed new classification (Epilepsia 48(2): 375-378, 2007) that is modeled on the Engel classification, but adapted to VNS therapy.Results: Prior to VNS implantation, all patients had intractable epilepsy, 10 had a history of infantile spasms, and three had a diagnosis of autism. All patients had multiple tubers and subependymal nodules on brain MRI. The average age at seizure onset was 1 year (range: 0 to 7, SD: 1.7), average age at VNS implantation was 15 years (range: 2 to 44, SD: 12.5), average follow-up duration on VNS was 4 years (range: 0.5 to 8.6, SD: 2.3). Three (19%) patients had class I outcome (>80% seizure frequency reduction), 5 (31%) patients had class II (50-79% reduction), 2 (13%) patients had class III (<50% reduction), 1 (6%) had class IV (magnet benefit only) and 5 (31%) had class V (no improvement). Intermittent magnet use was effective to abort seizures in 8 patients. Five patients reported improved level of functioning after VNS implantation, including 4 patients with classes I and II outcomes and 1 patient with class V. One patient had an increase in self-stimulatory behaviors (class III). VNS reached end of battery life in 2 patients: 1 patient had her generator replaced 8.5 years after implantation, while a new generator was not replaced in the other patient 7 years after implantation due to excellent seizure control. Conclusions: After VNS implantation, half of the TSC patients had at least 50% seizure frequency reduction and around a third reported an improved level of functioning. VNS can often be an effective and safe therapy for TSC patients with intractable epilepsy.