Vagus nerve stimulation in drug-resistant epilepsy: the efficacy and adverse effects in a 5-year follow-up study in Iran

Abstract

Drug-resistant epilepsy seems like a different disease compared with easy to control epilepsy, and new strategies are needed to help these patients. Vagus nerve stimulation (VNS) therapy is the most frequently used neurostimulation modality for patients with drug-resistant epilepsy who are not eligible for seizure surgery. In this study, we aimed to evaluate the efficacy and adverse effects of VNS in patients with drug-resistant epilepsy in an open-label, prospective, long-term study in Iran. We selected 48 patients with partial-onset drug-resistant epilepsy. Implantations were performed in the neurosurgery department of Loghman Hospital, Tehran, Iran. Follow-up visits were done on monthly bases for 5 years. Forty-four patients completed the study. Mean age of patients was 24.4 years. Mean years of epilepsy history was 14 years. The mean number of anti-epileptic drugs did not significantly change over five years (p = 0.15). There was no exacerbation of epilepsy; however, one patient discontinued his therapy due to unsatisfactory results. Five patient had more than 50 %, and 26 patients (59 %) had 25-49 % reduction in the frequency of monthly seizures persistently. Overall mean frequency of monthly seizures decreased by 57.8, 59.6, 65, 65.9, and 67 %, in 1st, 2nd, 3rd, 4th, and 5th years of follow-up, respectively. Most common side effects were as follows: hoarseness (25 %) and throat discomfort (10 %). We found VNS as a safe and effective therapy for drug-resistant epilepsy, with an approximate long-term decrease in mean seizure frequency of 57.8-67 %. Thus, VNS is recommended for suitable patients in developing countries.

Keywords: Adverse effects; Drug-resistant epilepsy; Efficacy; Iran; Long-term study; VNS.