Vagus nerve stimulation for epilepsy, clinical efficacy of programmed and magnet stimulation

Vagus nerve stimulation (VNS) by intermittent and programmed electrical stimulation of the left vagus nerve in the neck, has become widely available. It is an effective treatment for patients with refractory epilepsy. Patients can be provided with a magnet that allows to deliver additional stimulation trains. Since earlier studies have demonstrated the persistence of a stimulation effect after discontinuation of the stimulation train, we evaluated the clinical efficacy of VNS both in the programmed intermittent stimulation mode and magnet stimulation mode.

A group of 30 patients (16 F, 14 M) with medically refractory partial epilepsy, who were unsuitable candidates for resective surgery, were included in the study. The patients, their companions and caregivers were instructed on how to administer additional stimulation trains using a hand-held magnet when an aura or a seizure onset occurred. Patients or caregivers could recognize habitual seizures and were able to evaluate sudden interruption of these seizures. Using seizure diaries, detailed accounts of magnet use and regular clinic follow-up visits, data on seizure frequency and severity and number of magnet applications were collected. Patients who provided unreliable information were excluded from the analysis.

Forty-seven percent of all patients had an improvement in seizure control with a reduction in seizure frequency of more than 50% during a mean follow-up of 33 months (range: 4-67 months). More than half of the patients used the magnet and provided reliable information. In 63% of patients who were able to self-administer or receive additional magnet stimulation, seizures could be interrupted, be it consistently or occasionally. More than half of the patients who reported a positive effect of magnet stimulation became responders. In most cases the magnet was applied by a caregiver.

To our knowledge, this study is the first to explore the efficacy of magnet-induced vagus nerve stimulation. Results suggest that the magnet is a useful tool that provides patients and mainly caregivers with an additional means of controlling refractory seizures. Additional controlled studies comparing programmed stimulation and magnet-induced stimulation in monitoring conditions are warranted.