Vagus Nerve Stimulation Can Help Thousands of Epilepsy Patients

About 1 in 3 adults with epilepsy cannot control their seizures with medications, the first line of treatment for seizures. For some of these patients, epilepsy surgery may be a viable option. However, for patients who are not good candidates for epilepsy surgery or those who choose not to pursue it, Vagus Nerve Stimulation (VNS) provides a third treatment option.

Since the mid 1990s, VNS has been available as a treatment for epilepsy that cannot be controlled by medication or surgery. The therapy involves implantation of an electrical pulse generator in the chest, linked to a stimulating lead wire that is attached to the left vagus nerve in the neck. Sending electrical pulses to the vagus nerve has been shown to reduce or block seizures, although it is not clearly understood how.

The Medical College of Wisconsin was one of five medical centers in the United States and Europe involved in some of the early studies of the device's effectiveness, safety, and tolerability in patients with epilepsy. In the years since the device was approved for the treatment of epilepsy by the Food and Drug Administration, well over 200 patients with poorly-controlled epilepsy have undergone VNS implantation at the Medical College of Wisconsin and affiliated hospitals.

Results of Early Studies Still Hold Up
"We continue to find VNS an effective choice when medications fail and epilepsy surgery is ruled out, although there is some variability in the degree of response among patients," says Manoj Raghavan, MD, PhD, Assistant Professor of Neurology and Neurosurgery at the Medical College of Wisconsin and Director of the Adult Comprehensive Epilepsy Program at Froedtert & the Medical College.

Unlike some surgical outcomes, he notes, VNS is not a cure for epilepsy. It can help reduce seizures only as long as the implanted device is active. So far, it does not appear that VNS has any anti-seizure effects that are permanent which persist after inactivating the device. But as clinical trials have demonstrated, the seizures in patients undergoing active VNS therapy may continue to diminish over the first year or more of therapy. "Some patients don't see benefits immediately, but for many patients, their epilepsy becomes better-managed, and possibly with fewer medications."

Dr. Raghavan describes the procedure used to implant the VNS device as involving relatively minor surgery compared to epilepsy surgery: "A pulse generator is implanted under the chest wall by the surgeon, and a wire is tracked under the skin to the left vagus nerve in the neck. The procedure is often done as a day surgery at some centers, but patients are typically observed overnight at our center."

After the device is implanted, the neurologist must program it. The battery-powered pulse generator can be programmed to stimulate the vagus nerve automatically at various time intervals and power levels that are adjusted to the optimal settings for each patient.

"Initially, patients will not tolerate high current pulses, but if raised in small steps over several weeks they tolerate it quite well," Dr. Raghavan says. "So, in the weeks after the implantation procedure, patients can expect to make frequent brief visits to the clinic to have their devices adjusted to the best tolerated and most effective settings."

"Some patients who experience 'auras' that forewarn them of an impending seizure may also trigger the device manually using a small magnet provided to them" Dr. Raghavan says. "This sends an extra train of pulses to the vagus nerve, which may sometimes terminate a seizure that is starting up, or make it less intense"

The batteries used in VNS devices last several years before they wear out, he says. When that occurs, patients return to the clinic for a battery replacement, which Dr. Raghavan describes as "a minor procedure, which can be performed under local anesthesia."

Minimal Side Effects
Several studies done in the 1990s have looked at the frequency of side effects with VNS. In one large study, only six patients out of more than 440 studied discontinued the therapy due to intolerable side effects. Of the remaining patients, 19.8% reported mild hoarseness, 4.5% reported headaches, and 3.2% reported shortness of breath. The percentage of patients who chose to continue with VNS therapy was 96.7% after the first year, 84.7% after two years and 72.1% beyond the third year.

VNS has been approved by the federal government for use in treating intractable epilepsy since 1997. In 2006, the Food and Drug Administration also approved the use of VNS for the treatment of depression, although this controversial ruling is under review.

Clinical experience over the past decade of VNS use in epilepsy has only confirmed its place as a useful adjunctive therapy to medications for both adults and children who experience frequent, sometimes disabling seizures that do not respond to other available options.

Barbara Abel
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.