Vagus Nerve Stimulation
What is vagus nerve stimulation (VNS) therapy?
Vagus nerve stimulation involves the implantation of a generator that stimulates the vagus nerve and thus reduces seizure activity. The vagus nerve is one of 12 pairs of cranial nerves (i.e., nerves that originate in the brain). It has motor functions in the larynx (voice box), diaphragm, stomach, and heart, and sensory functions in the ears and tongue. It has both motor and sensory functions in the pharynx (sinuses) and esophagus.
Stimulation of the vagus nerve is thought to affect some of its connections to areas in the brain that are prone to seizure activity.
Who benefits from the VNS therapy?
The VNS Therapy System is indicated for use as an adjunctive therapy in reducing the frequency of seizures in adults and adolescents over 12 years of age with partial onset seizures that are refractory to antiepileptic medications.
Patients who have medically refractory seizures are those who have tried two or more medications and are still not satisfied with seizure control, side effects, or their quality of life.
Patients who suffer from complex partial seizures or generalized seizures, and who do not respond to anticonvulsant medication, and patients who cannot undergo brain surgery are considered good candidates for vagus nerve stimulation therapy. It also may be recommended as a treatment for photosensitive epilepsy and epilepsy resulting from head injury.
What is the implantation procedure?
The procedure is performed under general anesthesia. A neurosurgeon implants the device, a generator about the size of a small tape measure, in the upper left area of the chest. A connecting wire is run under the skin from the device to the vagus nerve in the left side of the neck. Three small leads are then carefully attached to the nerve. Implantation is usually accomplished within 1 to 2 hours.
For a few days following the procedure, the generator is programmed to stimulate the vagus nerve at regular intervals (e.g., for 30 seconds every 5 minutes) at a frequency determined by the doctor and patient. The physician adjusts the frequency using a computer. If a seizure begins between intervals, the patient activates the stimulator by swiping a magnet over their chest at the location where the device is implanted.
What are the risks and complications of surgery?
They include possible surgical injury to the vagus nerve, carotid artery, and internal jugular vein. The complications include coughing, hoarseness, and swallowing difficulties resulting from injury to the vagus nerve. Infection, bleeding, and discomfort at the site can occur. There may be tingling in the neck, hoarseness, and a slight cough during nerve stimulation.
What are the results of VNS therapy?
Many patients experience 50% reduction in seizure frequency, and seizures are less severe. Vagus nerve stimulation eliminates seizures in approximately 15% of patients, according to some studies, and a small number experience no improvement.
What are the side effects of VNS therapy?
VNS Therapy has been proven in clinical studies to provide a safe and effective way to control seizures. The result for many people is an improvement in alertness and memory plus more energy and a better mood. And because it is not a drug, VNS Therapy has allowed many people to reduce the number or dosage of medications they take. VNS Therapy does not typically cause side effects like depression, dizziness, confusion, weight gain, fatigue, insomnia and low energy. The most common side effects include hoarseness, a prickling feeling on the skin, shortness of breath, and increased coughing. And these side effects diminish over
Model 101 NeuroCybernetic Prosthesis (NCP)
Generator, flexible lead, and cuff for attachment to the vagus nerve. Used with permission from Cyberonics, Inc.
Vagus nerve stimulation
The NeuroCybernetic Prosthesis (NCP) in place in the left chest wall and attached to left vagus nerve. Image courtesy of Cyberonics, Inc.
Implanted NCP generator
Chest x-ray of implanted NCP generator. Used with permission from Cyberonics, Inc.