VAGUS NERVE-STIMULATION

Vagus nerve stimulation (VNS) is a unique form of therapy that has rec ently been approved by the Food and Drug Administration (FDA). It appe ars to be useful in patients who have failed medical therapy, cannot t olerate medication, or are poor candidates for intracranial surgery. V agus nerve stimulation is delivered by a programmable device implanted under the left clavicle; it is essentially an electrical stimulator a ttached to a wire. A stimulating electrode at the other end of the wir e is tunneled under the skin to the neck, where the vagus nerve is exp osed. The coils on the electrode are then wrapped around the nerve, an d a current is passed through periodically, usually once every 5 to 10 minutes. To date, more than 1000 patients at 150 centers have been tr eated in this manner. In one multicenter study, patients in the treatm ent arm were stimulated with levels that were thought to be therapeuti c, whereas those in the placebo arm received VNS at levels that were t hought to be subtherapeutic. There was a 28% reduction in seizure freq uency in the treatment: arm and a 15% reduction in the placebo arm aft er 3 months of treatment, which was a statistically significant reduct ion. Overall, the device was found to be very safe, resulting in no un toward cardiac events and very little serious morbidity. The most comm on side effect was a buzzing in the throat whenever a stimulus was del ivered, which resulted in hoarseness and throat pain in some patients. Longer durations of VNS are also associated with an incremental reduc tion 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.