Abstracts

Rationale: To analyze the efficacy and safety of vagus nerve stimulation in a large series of consecutive adults and children with medically-refractory epilepsy. Methods: A retrospective review was performed on 507 consecutive patients with refractory epilepsy who underwent a total of 720 VNS-related procedures by the senior author between November 1997 and April 2008. Seventy-one patients were referred to NYU for either VNS revision (34) or removal (37). Outcome analysis was performed on 436 patients (220 females and 216 males) who underwent primary implantation at our center and had at least 1 year of follow-up since implantation. Mean age at time of VNS insertion was 29.0 years (median: 27.9; range: 1 to 76 years) and included 307 adults (≥ 18 years; 70.4%) and 129 children (29.6%). Determination of seizure frequency was obtained from the last documented visit with the epileptologist or from patient or family report. Results: Follow-up is available for 81% of patients and is on-going. Duration of VNS therapy varied from 1 week to 11.35 years (mean: 4.83 years). Seizure frequency significantly improved with VNS therapy (mean/median reduction: 58.9%/66.7%; p<0.0001) without a significant reduction in antiepileptic medication burden (p=0.133). At least 50% reduction in seizure frequency occurred in 66.7% of patients and 45.0% of patients experienced at least a 75% reduction. Permanent neurological complications occurred in 12 patients (2.75%), hoarseness being the most common (9). Non-neurological complications requiring removal or revision occurred in 10 patients (2.3%), infection being the most common (6). Seventy-one patients (16.3%) underwent removal of VNS, usually for planned craniotomy (27) or nonefficacy (30). A total of 155 revision surgeries were performed on 128 patients, usually for battery depletion (131) or lead fracture (17). Sub-group analysis revealed no significant differences in efficacy between adults and children or between patients with recurrent seizures following intracranial epilepsy surgery and those without history of prior craniotomy. Conclusions: In this large series of consecutive patients, VNS was a safe and effective treatment for medically-refractory epilepsy in adults and children. Almost 60% of patients experienced at least 50% reduction in seizure burden. Patients who had failed intracranial epilepsy procedures prior to VNS therapy had similar outcomes to those who did not have prior surgery.