Vagus nerve stimulation

Vagus nerve stimulation (VNS) is a unique form of therapy that has recently been approved by the Food and Drug Administration (FDA). It appears to be useful in patients who have failed medical therapy, cannot tolerate medication, or are poor candidates for intracranial surgery. Vagus nerve stimulation is delivered by a programmable device implanted under the left clavicle; it is essentially an electrical stimulator attached to a wire. A stimulating electrode at the other end of the wire is tunneled under the skin to the neck, where the vagus nerve is exposed. The coils on the electrode are then wrapped around the nerve, and a current is passed through periodically, usually once every 5 to 10 minutes. To date, more than 1000 patients at 150 centers have been treated in this manner. In one multicenter study, patients in the treatment arm were stimulated with levels that were thought to be therapeutic, whereas those in the placebo arm received VNS at levels that were thought to be subtherapeutic. There was a 28% reduction in seizure frequency in the treatment: arm and a 15% reduction in the placebo arm after 3 months of treatment, which was a statistically significant reduction. Overall, the device was found to be very safe, resulting in no untoward cardiac events and very little serious morbidity. The most common side effect was a buzzing in the throat whenever a stimulus was delivered, which resulted in hoarseness and throat pain in some patients. Longer durations of VNS are also associated with an incremental reduction in seizure frequency. About half the patients who continued with VNS and were available for follow-up achieved a 30% to 40% decrease in seizure activity.