Abstracts

Some patients continue to experience seizures after epilepsy surgery. It has been reported that patients with prior epilepsy surgery did not respond as favorably as other patients to vagus nerve stimulation (VNS). We examined the effectiveness of VNS after epilepsy surgery to see if this finding could be replicated. All patients who had vagus nerve stimulator implant after epilepsy surgery at Thomas Jefferson University Hospital in Philadelphia were registered prospectively in a database. Follow-up was conducted by office visit or phone contact. Patients who had at least one year of follow-up after VNS were included in this review. Patients had either partial or generalized epilepsy with persistent disabling seizures. The maximum current output of the stimulator and stimulation parameters were noted. Seizure frequency in the three months prior to epilepsy surgery was compared to frequency in the three months prior to VNS implant and nine to twelve months after VNS. The number of responders to VNS was determined, defining response as either [underline][gt][/underline] 50% or [underline][gt][/underline] 80% seizure reduction. Note was also made of any medication changes at any point during the 12 months of follow-up. 19 patients fit criteria and had adequate data. Surgery was performed bewtween the years of 1986 and 2004. 12 patients were male and 7 were female. The mean age was - years, range of 16-70 years.After epilepsy surgery, 8 patients had [underline][gt][/underline] 50% seizure reduction, 4 had [underline][gt][/underline] 80% seizure reduction, and the rest had [lt] 50% reduction. After VNS, 7 patients (37%) had a further [underline][gt][/underline] 50% seizure reduction. Of these seven patients, 1 had [underline][gt][/underline] 80% seizure reduction, and one was seizure free. Of these seven patients, five had localization-related epilepsy, and two had generalized epilepsy. Mean current intensity was 2.3 mcV (range: 1.25 - 3 mcV) with varying duty cycles. Five of the seven responders had no medication change within the year follow-up period after VNS, while two patients had one antiepileptic drug added within the follow-up period. Of the remaining 10 patients who did not respond to VNS, eight had localization-related epilepsy and two had generalized epilepsy. There were no significant differences in VNS parameters between the responders and non-responders. VNS offers benefit in patients with persistent seizures after epilepsy surgery. The response rate is similar to literature reports of patients who have had VNS implanted without having had epilepsy surgery.