A vagal nerve stimulator is a small implanted device that sends weak electrical signals along the vagus nerve to your brainstem, which then sends signals to certain areas in your brain. These signals help prevent the electrical bursts in the brain that cause seizures.
The vagus nerve is also known as the tenth cranial nerve and is part of the autonomic nervous system, which controls functions of the body that you cannot voluntarily control, such as heart rate and digestion. There is one vagus nerve on each side of your body, running from your brainstem through your neck to your chest and abdomen.
The Food and Drug Administration has approved vagal nerve stimulation to treat epilepsy in patients 12 and older who have refractory partial epilepsy, and when other treatments have not worked. In addition, the FDA has approved vagus nerve stimulation for the treatment of refractory depression in adults who meet some very narrow guidelines and it is being studied for conditions such as multiple sclerosis, migraine and Alzheimer's disease.
Before surgery, your doctor will do a physical examination. You may need blood tests or other tests to make sure you don't have any health concerns that might be a problem. You may need to stop taking certain medications ahead of time and you will be required not to eat the night before the surgery.
The surgery usually takes one to two hours and is done under general anesthesia. Most patients return home the day of surgery.
The surgery itself doesn't involve your brain. The surgery requires two incisions. The battery-powered pulse generator is implanted under the skin near your left collar bone. A wire is threaded under your skin connecting the device to the left vagus nerve in your neck. The device is meant to be a permanent implant, but can be removed if necessary.
The pulse generator is about the size of a stopwatch. A lead wire is connected to the pulse generator and guided under your skin from your chest up to your neck, where it's wrapped around the left vagus nerve through a second incision. The battery lasts for approximately five to 10 years, after which many patients choose to have repeat surgery to replace the battery.
Risks of Vagal Nerve Stimulation
Surgical complications with vagal nerve stimulation implant are rare and are similar to the dangers of having other types of surgery. They include:
- pain where the incision is made to implant the device
- infection and bleeding
- incision scarring
Vagal nerve stimulation is considered safe. Mild side effects occur in some people when the device stimulates the nerve, which is approximately 30 seconds. The most common side effects include:
- throat pain
- swallowing difficulty
- hoarseness or slight voice changes
- chest pain
- abdominal pain or nausea
- shortness of breath, especially during exercise
- tingling or prickling of skin
- in children, vagal nerve stimulation may cause increased hyperactivity
For most people, the side effects are tolerable. They may lessen over time, but some side effects may be bothersome for as long as you use vagal nerve stimulation. Adjusting the electrical impulses can help minimize these effects.
If side effects are intolerable, the device can be shut off temporarily or permanently.
After Vagal Nerve Stimulator Implant
After the vagal nerve stimulator is implanted, the battery powered device can be programmed from outside your body by your doctor. It will be programmed to deliver electrical impulses to the vagus nerve at various durations, frequencies and currents. You can also use a handheld magnet to turn the device on if you feel a seizure about to start, and turn it off if it is causing unpleasant side effects. It may also shorten a seizure already in progress.
The VNS is kept turned off for the first two weeks following implantation to allow for healing. After that time, it will be turned on and programmed. You may notice a slight bulge in the area under your collarbone where the device is implanted.
The stimulator does not detect seizure activity.
Vagal nerve stimulation is not a cure for epilepsy and it does not work for everyone. It does not replace the need for antiepileptic drugs, but many people will have fewer seizures, as many as 30 to 50 percent fewer. Seizure intensity may lessen as well.
It can take as long as two years of vagal nerve stimulation before you notice any significant reduction in the number of seizures. Vagal nerve stimulation may also shorten the recovery time after a seizure. People who have had vagal nerve stimulation to treat epilepsy generally have an improved quality of life.
Studies have shown that:
- about a third of patients have had the number of their seizures reduced by half or more within three to 12 months; up to 80 percent will have the number of seizures reduced by half or more within seven to 10 years as the benefits increase over time
- about a third of patients have shown benefit but have had their seizure frequency reduced by less than half
- about a third of patients have had no worthwhile benefit
- swiping the magnet at the time of seizure can end seizures in about 25 percent of patients
- the number of anti-seizure medications required decreases over time as the VNS takes effect, which can reduce potential side effects