Vagus nerve stimulation - Clinical experience in a large patient series

During the last decade, intermittent electrical stimulation of the left cer vical vagus nerve was established as a new add-on treatment of drug-resista nt seizures. Particularly in Europe, the acceptance of vagus nerve stimulat ion (VNS) was tentative in the beginning because of unknown mechanisms of a ction. We report the outcome in a sample of 95 adult patients with drug-res istant seizures who have received implants since 1998. The last available f ollow-up data are included. Unavoidable medication changes (e.g., intoxicat ion) were accepted to examine VNS under usual clinical conditions. Median p ercentage of reduction in seizure frequency as compared to baseline was 30% . The seizure responder rate (greater than or equal to 50% reduction) was 4 5%. Four patients experienced total release from seizures. Adverse effects were mild in general. Seizure outcome was positively correlated with VNS du ration. No potential clinical factor (e.g., syndrome, cause, or lesion) cou ld be identified as an indicator of favorable outcome. Patients with on sti mulation-on periods of 30 seconds (standard cycle) had a better outcome tha n patients with stimulation-on periods of 7 seconds (rapid cycle). During a n embedded, randomized, controlled trial, no evidence was found for a diffe rential outcome of initial standard cycle versus initial rapid cycle stimul ation conditions. Taking into account the good cost-benefit ratio as well a s positive effects on well-being, VNS has to be considered an appropriate s trategy for the add-on treatment of drug-resistant seizures, particularly i n cases not suitable for epilepsy surgery.