Vagus nerve stimulation for refractory epilepsy: a Belgian multicenter study

Veerle De Herdt, Paul Boon, Berten Ceulemans, Henri Hauman, Lieven Lagae, Benjamin Legros, Bernard Sadzot, Patrick Van Bogaert, Kenou van Rijckevorsel, Helene Verhelst, Kristl Vonck
European Journal of Paediatric Neurology: EJPN 2007, 11 (5): 261-9

INTRODUCTION: Vagus nerve stimulation (VNS) is a symptomatic add-on treatment for patients with medically refractory epilepsy. It consists of continuous electrical stimulation of the left vagus nerve by means of a helical electrode and an implantable, programmable pulse generator. Currently, over 50,000 patients are treated with VNS worldwide.

AIM: This uncontrolled, open-label retrospective study evaluates long-term outcome in patients treated with VNS for refractory epilepsy in seven different epilepsy centres in Belgium.

METHODS: For the purpose of this study, a minimum of essential inclusion criteria were defined to collect relevant data. This limited the results to basic findings with regards to efficacy on the long term. Inclusion criteria were a follow-up of at least 12 months and a documented seizure diary before implantation and at maximum follow-up. Primary outcome measures were the reduction in mean monthly seizure frequency and the percentage of patients with a seizure reduction of at least 50% (responder rate).

RESULTS: About 138 patients (67M/71F) had a mean age of 30 years (range 4-59) at time of implantation and a mean post-implantation follow-up of 44 months (range 12-120). The mean number of AEDs before implantation was 3 (range 1-5). About 117/138 patients had focal epilepsy, 21 patients had symptomatic generalised epilepsy. About 117/138 patients were older than 16 years, 21 patients were 16 or younger. At maximum follow-up, mean stimulation output current was 1.84mA (range 0-3.25). Mean number of AEDs at maximum follow-up remained unchanged. The overall reduction in mean monthly seizure frequency was 51%. Mean seizure frequency before implantation was 41 seizures/month (SD=61; range 1-300), mean seizure frequency after implantation at maximum follow-up was 7 seizures/month (SD=25; range 0-120). Responder rate was 59%. 13% of patients had a seizure frequency decrease between 30% and 50%. About 28% had a seizure frequency decrease of<30%. Seizure freedom was obtained in 12/138 patients (9%).

CONCLUSIONS: The long-term experience with VNS in Belgium confirms that VNS is an efficacious adjunctive antiepileptic treatment for patients with refractory epilepsy.

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