Vagus Nerve Stimulation

This chapter focuses on vagus nerve stimulation (VNS) delivered via the implantable Neurocybernetic Prosthesis (NCP) from Cyberonics, Inc. (Houston, TX), which is gaining increasing popularity and credibility as a treatment option for patients with intractable epilepsy. It has also emerged as a novel adjunct in the management of patients with refractory depression and potentially other disorders. Clinical experience with VNS began in 1988 with the first human implantation of the NCP system. Since then, more than 40,000 patients worldwide have received VNS therapy, and more than 100,000 patient-years of experience have been accrued. The NCP device delivers intermittent electrical stimulation to the left cervical vagus nerve trunk, which secondarily transmits rostral impulses to exert widespread effects on neuronal excitability throughout the central nervous system. The selection criteria for insertion of the NCP system remain in evolution and reflect current governmental standards as well as institutional biases and general guidelines from prior clinical trials. Patients with both idiopathic epilepsy and seizures of structural etiology are considered appropriate candidates. Insertion of the NCP device takes less than two hours and is typically performed under general anesthesia, thus minimizing the possibility that an intraoperative seizure might compromise the surgery. While it can be performed as an outpatient procedure, it may be desirable to observe patients overnight for vocal cord dysfunction, dysphagia, respiratory compromise, or seizures induced by anesthesia, even though these complications are rare. The most commonly observed surgical complication is infection and the site of the infection is either at the generator in the chest or near the leads in the neck. Transient vocal cord paralysis is the second most common surgical complication of VNS implantation although most of these cases resolve clinically.