Abstracts

Rationale: To examine the efficacy of vagus nerve stimulation (VNS) therapy in children and adolescents with medically refractory epilepsy. Methods: We reviewed the charts of all patients implanted with a VNS at a single center between December 1997 and March 2011. All patients with complete follow-up data at 6 and 12 months were included. Patients were divided into two groups according to the median seizure frequency at baseline. A Wilcoxon Rank sum test was performed to determine if there was significant seizure reduction from baseline to month 12 across various subgroups organized by baseline characteristics. Results: 252 patients were identified. Complete follow-up data was available for 69 patients (29 girls, mean implantation age 11.1 years, SD 5.3). Mean age of seizure onset was 28.6 months (SD 34.3). Ten patients had generalized epilepsy, 30 had focal epilepsy, and 29 had both generalized and focal features. Forty-seven and 44 subjects had reductions in seizure frequency at months 6 and 12, respectively. The overall median percentage change (seizures/month) from baseline was -50% [25%, 75% Quartiles: (-73%, 0%)] at 6 months (p=0.005) and -40% [25%, 75% Quartiles: (-75%, 25%)] at 12 months (p=0.058). 4 patients were seizure-free at 12 month follow-up. Patients with higher baseline seizure frequency (>45/month) experienced a greater percentage reduction in seizures, with a median reduction of 61% [25%, 75% Quartiles: (-94%, -50%)] (p<0.001) and 69% [25%, 75% Quartiles: (-96%, -30%)] (p<0.001) at 6 and 12 months, respectively. Patients with a lower baseline seizure frequency (≤45/month) experienced a median seizure reduction of 25% [25%, 75% Quartiles: (-50%, 50%)] at 6 months (p=0.94) and 0% [25%, 75% Quartiles: (-50%, 100%)] at 12 months (p=0.39). Of the excluded patients, 6 had treatment discontinued during the 12 month follow-up period. Reasons for discontinuation included infection (n=3), nausea (n=1), skin breakdown (n=1), and perceived lack of efficacy (n=1). Sixteen of the 69 patients experienced adverse effects which did not warrant discontinuation of therapy, including voice changes, coughing, throat tickle, difficulty sleeping, and pain over the VNS area. Outcomes were compared across multiple subgroups including gender, age at VNS implantation, seizure semiology, previous history of SE, number of medications at baseline, presence or absence of MRI lesion, and duration of epilepsy prior to implantation. There were no significant differences in outcome in any of these subgroups (p>