Vagus nerve stimulation for refractory epilepsy: a Belgian multicenter study.
BACKGROUND
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.


OBJECTIVE
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.
De Herdt
Veerle
V
Reference Center for Refractory Epilepsy, Ghent University Hospital, Belgium. Veerle.Deherdt@UGent.be
Boon
Paul
P
Ceulemans
Berten
B
Hauman
Henri
H
Lagae
Lieven
L
Legros
Benjamin
B
Sadzot
Bernard
B
Van Bogaert
Patrick
P
van Rijckevorsel
Kenou
K
Verhelst
Helene
H
Vonck
Kristl
K
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001530:Belgium; D002648:Child; D002675:Child, Preschool; D004599:Electric Stimulation Therapy; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome; D014630:Vagus Nerve / Q000502:physiology*