Evolution in VNS therapy for refractory epilepsy, experience with Demipulse devices at Ghent University Hospital

Vagus nerve stimulation (VNS) is a frequently used treatment for patients with refractory epilepsy who are unsuitable candidates for epilepsy surgery. There has been a steady evolution in VNS technology, as generators' volumes have become smaller and battery life expectancy longer. This pilot study is an open-label retrospective study that describes our experience with the latest commercially available generator, i.e. the VNS Therapy Demipulse Model 103. Treatment efficacy and side effects, as well as technical and practical enhancements useful for the patient and for the medical staff are discussed in this study.

Twenty patients (11F/9M) with a mean age of 40 years (range 8-61), who were considered unsuitable candidates for resective surgery, were implanted with a VNS Therapy Demipulse Model 103. Mean monthly seizure frequency reduction and side effects were evaluated 1 year after implantation.

Mean monthly seizure frequency decreased significantly from 54 seizures/month (SEM 30; range 1-555) before treatment to 33 (SEM 24, range 0-445) following 12 months of treatment (p<0.05). Seven patients (39%) were considered responders with a reduction in seizure frequency of more than 50%. One of those seven patients became seizure free. Side effects were stimulation-related tingling sensation in the throat and/or hoarseness, a painful sensation in the left neck or ear region and a lead breakage In addition; one case of SUDEP was reported.

Patients treated with VNS Therapy Demipulse generators proved to have a significant decrease in seizure frequency. In this patient group, VNS was well tolerated. The main technical advances are the decrease in size and improved options for battery life follow-up.