"In the epilepsy field, it has been—give people a pill to take every day, or do brain surgery. The vagus nerve stimulator is part of an emerging field that is hard to fit into the context of other epilepsy treatment. It's a different kind of therapy, and it is really taking off."
– Dr. Eric Geller, St. Barnabas Epilepsy Center, New Jersey

Since its approval in 1997, the vagus nerve stimulator has been used to treat a broad spectrum of epilepsies in both adults and children. It was originally studied and released for adults with partial epilepsy, but it seems to bring outcomes that are as good or better for people with generalized epilepsy.

More than 20,000 people are using vagus nerve stimulation (also called VNS). The United States Food and Drug Administration (FDA) officially has approved vagus nerve stimulation for certain kinds of epilepsy in adults and children over the age of 12. This general approval allows doctors to use the device for other seizure conditions and for younger children. This is called "off-label use" and it is considered ethical and safe. Studies performed since the device was approved have shown it to be effective for many of these other uses. Cyberonics, the company that makes the vagus nerve stimulator, has studied the possibility that it also may be useful in treating depression.

So stay tuned. The research on vagus nerve stimulation and other types of "neurostimulation" promises to be important for countless neurological conditions.

Does it really work?

The effectiveness of vagus nerve stimulation is measured by looking at the average (mean) reduction in the number of each patient's seizures over a study period, usually around 3 months. Then researchers usually divide the patients into two groups: "responders" (who have had their seizures reduced by 50% or more) and the "non-responders," with less than a 50% reduction in seizures. The percentage of patients who are responders is called the "responder rate."

For comparison, let's see how the vagus nerve stimulator measures up to the "new" seizure medicines, those released since 1993 (Felbatol, Gabitril, Keppra, Lamictal, Neurontin, Topamax, Trileptal, and Zonegran). For these medications, the responder rate ranges from roughly 20% to as high as 45%, with an average of about 25% to 30%. In the initial studies of vagus nerve stimulation, the responder rate was between 31% and 39%. As doctors gain more experience in its use, this rate has gone up to between 40% and 60%. The rate also tends to be higher in studies that follow patients for longer periods, as many patients continue to improve for some time after the device is implanted.

"The vagus nerve stimulator works better," says Dr. Werner Doyle of the New York University Comprehensive Epilepsy Center. "This is such common knowledge—that it is the answer when other surgeries fail and medicines are not working, or the side effects are so bad that a patient cannot tolerate them."

Why isn't it used more often?

"There are misconceptions about the vagus nerve stimulator, but there are also 'no conceptions' because people don't think about it," explains Dr. Sandra Helmers of the Emory Epilepsy Center at the Emory University School of Medicine in Atlanta.

The device, which looks like a pacemaker, is surgically implanted in the chest wall and connected to the left vagus nerve in the neck by a wire tunneled under the skin. It prevents seizures by sending regular, mild pulses of electrical energy through the nerve to the brain, with the intent of conditioning the brain to react better to the interruptions in brain function that are common in epilepsy. Some patients can actually shorten or stop their own seizures by using a special magnet. According to Geller, the magnet works for about one-third of patients.

We can't explain why it works. . .

"It isn't obvious why the vagus nerve stimulator works; we haven't found a pattern. Many people feel that before you test it, you should have a reason, you should have a theory," says Geller. "A lot of doctors I've talked to say: 'I don't know why stimulating a nerve in the neck should stop seizures, so I'm not going to prescribe it.' I come back and say: 'Well, how does Dilantin work?'"

Dr. Helmers agrees: "If we knew more about how it worked, that would be an advantage—but that would be an advantage for anything. I don't consider not knowing a disadvantage."

Brain surgery is too scary

Some people may not explore vagus nerve stimulation as a treatment option because they're scared off by the idea of "brain surgery."

"People think about it as a surgery and not as a medication, but it does not come near the brain," says Helmers. "It's like a pacemaker and it takes 30 to 40 minutes to implant. At some centers, patients are in and out in a day. At other centers, they spend one night in the hospital."

It only works if you have auras, right?

Some patients believe that vagus nerve stimulation is not an option for them unless their seizures are preceded by warning symptoms called an aura. Not so, explains Geller: "A patient is still getting the stimulation off and on all the time, which may stop seizures. Parents in particular tell me the magnet helps stop the seizure as it is happening. This is much safer than letting a seizure continue uncontrolled, using a medication to stop the seizure, or taking the child to the emergency room."

It probably won't stop all my seizures, so why bother?

When a doctor treats a patient with epilepsy, the obvious goal is a reduction in seizures, but another important goal is to reduce the amount of medicine going into the body. Some people take three, four, or five medications and suffer from the side effects. Even if the vagus nerve stimulator does not eliminate seizures, it might allow the doctor to reduce the number of seizure medicines or lower the dosage.

Compared to seizure medicines, the side effects of vagus nerve stimulation are dramatically different. Medicines for epilepsy can cause allergic rashes in up to 10% of people. They can damage the liver or blood cells, can interfere with other medication for different conditions, and can cause sleepiness, memory problems, and behavior problems. They also may have long-term consequences like osteoporosis or damage to the nerves in the arms and legs.

Vagus nerve stimulation has none of these effects. In fact, many patients feel more alert and interactive, which is very valuable for impaired patients, particularly children who are lethargic.

"If the stimulator wakes a child up, they can do more in school, they can participate more, enjoy life more," says Helmers. "So it really does offer a lot of benefits to people. You can use the device to improve a patient's quality of life."

There must be some bad side effects!

The only common side effects of vagus nerve stimulation are in the throat area, because a branch of the nerve goes to the vocal cords. When the device stimulates, the person may feel a tickle in the throat, a bit of a cough, or a softening of the voice—but this is usually tolerable. Some other side effects, like pain or chronic hiccups, can be eliminated if the doctor adjusts the way the device is working.

Even if a patient has some of these side effects, there's an important difference between these and the side effects of seizure medicines. Medicine takes time to build up in the system, so if a doctor changes the dosage, the side effects may not be seen for a week or two. With the stimulator, most of the side effects are the worst they will be as soon as the doctor changes the settings, and then they'll get better over a period of hours or days. So the doctor can see right away what patients will go home with, and send them home in comfort. Less common side effects can occur - be sure to ask your doctor.

Topic Editor: Steven C. Schachter, M.D.
Last Reviewed:11/20/06