Vagal nerve stimulation is a treatment for epilepsy in which an electrode is implanted in the neck to deliver electrical impulses to the vagus nerve.
Vagal nerve stimulation is an alternative to medication or surgical removal of brain tissue in controlling epileptic seizures. The seizures of epilepsy are caused by uncontrolled electrical discharges spreading through the brain. Anti-seizure drugs interrupt this process by reducing the sensitivity of individual brain cells to stimulation. Brain surgery for epilepsy either removes the portion of the brain where seizures originate, or cuts nerve fibers to prevent the nerve impulses that occur during a seizure from spreading to other parts of the brain. Vagal nerve stimulation uses a different approach; it provides intermittent electrical stimulation to a nerve outside the brain—the vagus, or tenth cranial nerve, which influences certain patterns of brain activity.
The vagus nerve is a major connection between the brain and the rest of the body. It carries sensory information from the body to the brain, and motor commands from the brain to the body. The vagus is involved in complex control loops between these destinations; its precise pathways and mechanisms are still not fully understood. It is also not known how stimulation of the vagus nerve works to reduce seizure activity—it may stimulate inhibitory pathways that prevent the brain's electrical activity from getting out of control, interrupt some feedback loops that worsen seizures, or act in some other fashion.
Vagal nerve stimulation has been effective in reducing seizure frequency in patients whose seizures are not controlled by drugs, and who are either not candidates for other types of brain surgery or who have chosen not to undergo these procedures.
Epilepsy affects about 1% of people in the general worldwide population. Approximately 40% of patients do not respond well to medications, however, and so may be candidates for surgical treatment. Vagus nerve stimulation was first performed in the United States in 1988 and received final approval by the United States Food and Drug Administration (FDA) in July 1997. Approximately 10,000 people worldwide have had stimulators implanted as of 2003; about a fifth of these patients are children 12 years old and younger.
The vagal nerve stimulator has two parts: an electrode that wraps around the left vagus nerve in the neck; and a pulse generator, which is implanted under the skin below the collarbone. The two parts are connected by a wire. Stimulation is performed only on the left vagal nerve, as the right vagal nerve helps control the heartbeat.
Surgery to implant a VNS device takes about two hours. A neurosurgeon implants the electrode and generator while the patient is under general anesthesia. A vertical incision is made in the left side of the neck, and the helical electrode is attached to the nerve itself. A second incision is made on the left side of the chest below the collarbone, and the pulse generator (a disc about 2 in [5 cm] in diameter) is implanted under the skin. The connecting wire is threaded around the muscles and bones to join the electrode and generator. The generator makes a small bulge under the skin but is hidden by clothing after the operation.
Before the neurosurgeon closes the incisions, he or she tests the VNS device to make sure it is working, and programs it to deliver the lowest amount of stimulation. The device is usually timed to stimulate the vagus nerve for 30 seconds every five minutes.
A candidate for vagal nerve stimulation will have had many tests already to determine the focal point of seizure activity. Preoperative tests include neuroimaging as well as psychological tests to determine the patient's cognitive (thinking) strengths and weaknesses.
The patient must be fully informed about VNS—how it works, its advantages and disadvantages, what will happen during surgery—before the operation is scheduled. A video as well as written material about VNS is available to view and discuss with the doctor.
Implantation of the stimulator in an adult may be performed as either an outpatient or inpatient procedure. In the latter case, the patient will remain in the hospital overnight for monitoring of heart function and other vital signs . Children who are receiving a VNS are usually scheduled for an overnight stay. Pain medication is given as needed.
The stimulation parameters are adjustable, and the neurologist may require several visits to find the right settings. Settings are adjusted with a magnetic wand that delivers commands to the stimulator's computer chip. The patient may be taught how to use a magnet to temporarily increase stimulation, to prevent a seizure, or to abort it once it begins.
The VNS generator is powered by a battery that lasts several years. It is replaced during an outpatient procedure under local anesthesia.
The most common adverse effects from vagal nerve stimulation are a hoarse voice, cough, headache, and ear pain. These side effects can be reduced by adjusting the stimulation settings, and may subside on their own over time. Infection and device malfunction are possible though rare.
Patients who have had a VNS implanted must avoid strong magnets, which may affect the stimulator settings. Areas with warning signs posted regarding pacemakers should be avoided. The patient should consult with the neurologist and the neurosurgeon about other hazards.
Approximately half of all patients who have received vagal nerve stimulation experience about a 50% reduction in seizures. Another 9% of patients obtain complete relief from seizures. Most patients who continue to take antiseizure medications can reduce their dosage, however, which offers some relief from the side effects of these drugs.
Vagal nerve stimulation is a relatively safe procedure, with no deaths attributed to the stimulation as of 2003. Pilot studies of 300 patients that were done prior to FDA approval of VNS reported the following complication rates: hoarseness, 37% of patients; coughing, 14%; voice alteration, 13%; chest pain, 12%; and nausea, 2%.
Some candidates for vagal nerve stimulation are also likely to be candidates for a corpus callosotomy , temporal lobectomy, or other surgical procedures.
See also Hemispherectomy .
Devinsky, O. A Guide to Understanding and Living with Epilepsy. Philadelphia: E. A. Davis, 1994.
"Seizure Disorders." Section 14, Chapter 172 in The Merck Manual of Diagnosis and Therapy , edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.
Rielo, Diego, MD, and Selim R. Benbadis, MD. "Vagus Nerve Stimulation." eMedicine , April 12, 2002 [June 10, 2003]. http://www.emedicine.com/neuro/topic559.htm .
American Association of Neurological Surgeons (AANS). 5550 Meadowbrook Drive, Rolling Meadows, IL 60008. (847) 378-0500. http://www.neurosurgery.org .
Epilepsy Foundation. 4351 Garden City Drive, Landover, MD 20785-7223. (800) 332-1000. http://www.epilepsyfoundation.org .
Richard Robinson
The implanting of a VNS device is performed by a neurosurgeon in a hospital, in consultation with a neurologist.
Is there long term effects of this procedure-such as vagal nerve damage?
If it helps control the seizures does it continue to help seizures indefinitely or does the effect diminish with time as medications have?
Imitrex (which I take almost every other day), do takes care of the pain.
The only medicine that helped diminish the frequency of my migraines was Topamax, but one of the side effects, (really spaced out), was unbearable.
If an antiepileptic drug considerably helpes me reduce the migraines and at the same time I suffer from chronic depression wouldn´t the VNS be an option for me?
I am willing to try it regardless the lack of evidence or trials proving it´s effectiveness on migraines.
Thank you very much.
P.S. Does anyone here know of a surgeon that is willing to remove the whole VNS???
I have had a VNS for 6 years. Cyberonics has come out with new information that allowed me to have an MRI. It is called "passive MRI." The MRI machine is fitted with a coil of some kind. The VNS is turned off for the duration of the scan. I had this done about 6 months ago and my neurologist got the pictures he was looking for. Make sure you have your Cyberonics rep on hand to explain exactly what needs to be done.
write me
I have had a seizure dog for almost 10 years now. And before I had my VNS inplant I called the company cyberonics many times. I wanted to know if she would still be able to alert me before one happened. They told me they had never done a study on this before. Well I can tell you this she would always stay very close to me 24 hours before I had a grand mal. I debated over several months because she was my security and I did not want to lose her ability to warn me because of a machine. God only knows how these wonderful animals can OUT DO a machine. But she can and has not lost that sense even though I had a mechanical device put in. As for how many times you swipe the magnet over the device it does not matter. This is per my Neuro Surgeon and I have swiped as many as 6-7 times. I was having seizures 24-7 but they were small enough I didn't know it. It was found by a 3 day study. The grand mal's were 1-2 weekly. If I can answer any other questions for you please feel free to e-mail. God bless you for training these dogs. My next dog will be trained to swipe the magnet for me. The training school is out of Atlanta GA. I would cut the wrist band down to the size of the dogs mouth leaving just enough room for her to pick up the magnet which could be attached to the bottom of the ref so the dog would know to always run there,or I would try putting it on her collar so if the pt falls down the dog can just lay her neck right ontop of the patients chest (magnet implant)the dog will feel the two magnets connect and if the dog does not get a respond she can lay down over her chest again. The dog will not hurt her by just laying her neck ontop of the VNS by her weight. It also would work better on the collar when the patient leaves the house for outings. Believe me I would rather have a dog across my chest trying to stop a seizure then having nothing at all. God Bless you hope I have been helpful.
Just to be safe I would get in contact with the VNS manufacturer Cyberonics for the correct information. I have had the device for three years. When you swipe the magnet over the stimulator it raises the voltage of the "shock". I wouldn't keep repeating it unless you needed to. For one thing, if I'm a case it hurts some people. Also the VNS can affect the Heart Rate. The main use of the VNS magnet is to help interrupt the seizure. If the seizure is over it will do nothing. It does not revive a person from a seizure. Contact the experts Cyberonics.com 1-800-332-1375. I hope this helps. Cheryl
A note to Sal on the Topamax...don't stay on that drug for too long...it is referred to as Stupimax by physicians for a reason!! I am a 52 year old female with a history of grand mal seizures since age 14. I have been through a gamete of medications, and that was one of the worst! It caused side effects that I didn't even realize I was having until they took me off it and felt so much better!! I also take Onfi, and have had some good outcomes with that.
Ijust dont know.