AN INSTITUTIONAL EXPERIENCE WITH CERVICAL VAGUS NERVE TRUNK STIMULATION FOR MEDICALLY REFRACTORY EPILEPSY - RATIONALE, TECHNIQUE, AND OUTCOME

OBJECTIVE: Intermittent stimulation of the left cervical vagus nerve t runk is emerging as a novel adjunct in the treatment of medically refr actory seizures. We sought to evaluate theoretical and practical issue s attendant to this concept. We review the anatomic and physiological background arguing for clinical application of vagus nerve stimulation , discuss salient aspects of patient selection and the nuances of surg ical technique, and present our observations of and results from appli cation of the method. METHODS: Each of 18 patients with medically refr actory epilepsy and at least six complex partial or secondarily genera lized seizures per month underwent placement of a NeuroCybernetic Pros thesis pulse generator (Cyberonics, Webster, TX) in the chest, connect ed to helical platinum leads applied to the left cervical vagus nerve trunk. The patients were then randomized in a double-blinded fashion t o receive either high (presumably therapeutic) or low (presumably less therapeutic) levels of vagus nerve stimulation. Reduction in seizure frequency, global assessments of quality of life, physiological measur ements, and adverse events were recorded during a 3-month period. Pati ents in the low group were then crossed over to high-stimulation parad igms during a 15-month extension trial. RESULTS: All operations were s uccessful, uneventful, and without adverse postoperative sequelae. One patient was excluded from analysis because of inadequate seizure cale ndars. Of the seven patients initially assigned to high stimulation, t he mean reduction in seizure frequency was 71% at 3 months and 81% at 18 months. Five (72%) of these patients had a greater than 75% reducti on in seizure frequency, and one (14%) remained seizure-free after mor e than 1.5 years of follow-up. The mean reduction in seizure frequency among the low-stimulation group was only 6% at 3 months. No serious c omplications, device failures, or physiological perturbations occurred . CONCLUSION: In our experience, vagus nerve stimulation has proven to be a safe, feasible, and potentially effective method of reducing sei zures in select patient populations. However, the elements of strict d efinition for the application of the method require further study.