What is vagus nerve stimulation

Vagus nerve stimulation  (VNS) involves the use of a device to stimulate the vagus nerve with electrical impulses. Vagus nerve stimulation is currently US Food and Drug Administration (FDA) approved to treat epilepsy and depression. Vagus nerve stimulation is a therapy that sends electric signals to the brain. Vagus nerve stimulation involves implanting a device is called a vagus nerve stimulator or pulse generator that generates pulses of electricity to stimulate the vagus nerve. The vagus nerve stimulator produces repeating, low-level pulses of electrical current. The pulse generator is connected to a wire that attaches to the vagus nerve. The vagus nerve is one of the 12 cranial nerves, the paired nerves that attach to the undersurface of the brain and relay information to and from the brain. Cranial nerve fibers conduct impulses between the brain and other parts of the brain and various body structures, mostly in the head and neck  including the larynx (voice box), lungs, heart and gastrointestinal tract. The vagus nerve – the longest of the cranial nerves – also extends to organs in the chest and abdomen. The word vagus comes from a Latin word for “wandering.’ The vagus nerve has many paths. One path goes from the neck up to the brain. Vagus nerve stimulation therapy uses this path to send electric signals to the brain. Weak evidence shows that these signals may lower the number of seizures.

The vagus nerve stimulator is programmed using a computer to generate pulses of electricity at regular intervals, depending on the patient’s tolerance. For example, the device may be programmed to stimulate the nerve for 30 seconds every five minutes. The settings on the device are adjustable, and the electrical current is gradually increased as the patient’s tolerance increases. Re-programming the vagus nerve stimulator can be done in the doctor’s office. The patient also is given a hand-held magnet, which when brought near the vagus nerve stimulator, can generate an immediate current of electricity to stop a seizure in progress or reduce the severity of the seizure.

In conventional vagus nerve stimulation, a device is surgically implanted under the skin on your chest, and a wire is threaded under your skin connecting the device to the left vagus nerve. When activated, the device sends electrical signals along the left vagus nerve to your brainstem, which then sends signals to certain areas in your brain. The right vagus nerve isn’t used because it’s more likely to carry fibers that supply nerves to the heart.

New, noninvasive vagus nerve stimulation devices, which don’t require surgical implantation, have been approved in Europe to treat epilepsy, depression and pain. A noninvasive device that stimulates the vagus nerve was recently approved by the Food and Drug Administration for the treatment of cluster headaches in the United States.

Vagus nerve stimulation is an add-on therapy (adjunctive therapy), which means it is used in addition to another type of treatment. Patients who undergo vagus nerve stimulation continue to take their seizure medications. In some cases, however, it may be possible to reduce the dosage of medication.

Adjunctive therapy is a therapy added to other forms of treatment. Vagus nerve stimulation is meant for use only when other therapies have not helped.

In epilepsy, depression and mood problems are common. There also is weak evidence that vagus nerve stimulation may help these problems in people with epilepsy.

There are different types of seizures. They happen because of sudden changes in the brain’s electric activity. Brain cells interact by electric signals. During a seizure, a surge of electric energy affects all or part of the brain. The surge interferes with normal brain activity. Some seizures can cause muscle jerking or stiffness that the person cannot control. In some cases, the person may lose consciousness. Sensation, speech, mood, and memory can be affected. Seizures typically last one or two minutes.

Doctors use certain therapies to prevent seizures. These include:

• Anti-seizure drugs known as antiepileptic drugs
• Certain diet changes
• Brain surgery

However, different people have different reactions to treatment. When drugs and other types of treatment are not helpful, vagus nerve stimulation therapy may be an option.

Some of the studies examined here looked at vagus nerve stimulation for treating certain types of epilepsy. These include:

• Partial epilepsy
• Generalized epilepsy
• Lennox-Gastaut syndrome

Partial epilepsy involves only part of the brain. Generalized epilepsy involves the entire brain. Both types cause seizures. Lennox-Gastaut syndrome is a rare and serious form of epilepsy. Weak evidence shows that vagus nerve stimulation may help as added therapy for people aged 12 and older with these epilepsy types.

Lennox-Gastaut syndrome is a rare and serious form of seizure disorder. Lennox-Gastaut syndrome usually affects children before age 4. Lennox-Gastaut syndrome causes many types of seizures in these children. Lennox-Gastaut syndrome also affects thinking and learning ability. Weak evidence shows vagus nerve stimulation may help as added treatment in people with Lennox-Gastaut syndrome.

I have epilepsy and my current therapy is not helping me. How can I know if vagus nerve stimulation is right for me?

It is important to talk with your doctor about therapies for treating seizures. Be sure you understand all the options available, including vagus nerve stimulation.

It’s important to carefully consider the pros and cons of implanted vagus nerve stimulation before deciding to have the procedure. Make sure you know what all of your other treatment choices are and that you and your doctor both feel that implanted vagus nerve stimulation is the best option for you. Ask your doctor exactly what you should expect during surgery and after the pulse generator is in place.

Can vagus nerve stimulation be adjusted to help my type of seizures?

Some studies looked at a certain feature of the vagus nerve stimulation device. The feature is a magnet that sends stronger current when seizure symptoms are setting in. These are called an aura. Weak evidence shows that the magnet may stop a seizure during an aura.

Other studies tried to determine the best device setting. There is not enough evidence to show which setting is best.

Can vagus nerve stimulation be used long term?

There is weak evidence that vagus nerve stimulation may be more helpful over time. This may help people when drug therapy has stopped working.

Vagus nerve stimulation therapy benefits

About one-third of people with epilepsy don’t fully respond to anti-seizure drugs. Vagus nerve stimulation may be an option to reduce the frequency of seizures in people who haven’t achieved control with medications.

Vagus nerve stimulation may also be helpful for people who haven’t responded to intensive depression treatments, such as antidepressant medications, psychological counseling (psychotherapy) and electroconvulsive therapy (ECT).

The US Food and Drug Administration (FDA) has approved vagus nerve stimulation as an adjunctive therapy for people who:

• Are 4 years old and older
• Have focal (partial) epilepsy
• Have seizures that aren’t well-controlled with antiepileptic drugs

The FDA has also approved vagus nerve stimulation for the treatment of depression in adults who:

• Adults (aged 18 and older) with depression that is not helped by other treatments
• Have chronic, hard-to-treat depression (treatment-resistant depression)
• Haven’t improved after trying four or more medications or electroconvulsive therapy (ECT), or both
• Continue standard depression treatments along with vagus nerve stimulation

Additionally, researchers are studying vagus nerve stimulation as a potential treatment for a variety of conditions, including headaches, rheumatoid arthritis, inflammatory bowel disease, bipolar disorder, obesity and Alzheimer’s disease.

How is vagus nerve stimulation done?

Surgery to implant the vagus nerve stimulation device can be done on an outpatient basis, though some surgeons recommend staying overnight.

The surgery usually takes an hour to an hour and a half. You may remain awake but have medication to numb the surgery area (local anesthesia), or you may be unconscious during the surgery (general anesthesia).

The surgery itself doesn’t involve your brain. Two incisions are made, one on your chest or in the armpit (axillary) region, and the other on the left side of the neck.

The pulse generator, which is about the size of a silver dollar, is surgically placed under the skin in the upper part of your chest. The device is meant to be a permanent implant, but it can be removed if necessary. A connecting wire is run under the skin from the vagus nerve stimulator to an electrode that is attached to the vagus nerve, which is accessible through a small incision (cut) in the neck.

The pulse generator is about the size of a silver dollar and runs on battery power. A lead wire is connected to the pulse generator. The lead wire is guided under your skin from your chest up to your neck, where it’s attached to the left vagus nerve through the second incision.

After the vagus nerve stimulator implant procedure

The pulse generator is turned on during a visit to your doctor’s office a few weeks after surgery. Then it can be programmed to deliver electrical impulses to the vagus nerve at various durations, frequencies and currents. Vagus nerve stimulation usually starts at a low level and is gradually increased, depending on your symptoms and side effects.

Stimulation is programmed to turn on and off in specific cycles — such as 30 seconds on, five minutes off. You may have some tingling sensations or slight pain in your neck and temporary hoarseness when the nerve stimulation is on.

The stimulator doesn’t detect seizure activity or depression symptoms. When it’s turned on, the stimulator turns on and off at the intervals selected by your doctor. You can use a hand-held magnet to initiate stimulation at a different time, for example, if you sense an impending seizure.

The magnet can also be used to temporarily turn off the vagus nerve stimulation, which may be necessary when you do certain activities such as public speaking, singing or exercising, or when you’re eating if you have swallowing problems.

You’ll need to visit your doctor periodically to make sure that the pulse generator is working correctly and that it hasn’t shifted out of position. Check with your doctor before having any medical tests, such as magnetic resonance imaging (MRI), which might interfere with your device.

Vagus nerve stimulation results

Implanted vagus nerve stimulation isn’t a cure for epilepsy. Most people with epilepsy won’t stop having seizures or taking epilepsy medication altogether after the procedure. But many will have fewer seizures, up to 20 to 50 percent fewer. Seizure intensity may lessen as well.

It can take months or even a year or longer of stimulation before you notice any significant reduction in seizures. Vagus nerve stimulation may also shorten the recovery time after a seizure. People who’ve had vagus nerve stimulation to treat epilepsy may also experience improvements in mood and quality of life.

Research is still mixed on the benefits of implanted vagus nerve stimulation for the treatment of depression. Some studies suggest the benefits of vagus nerve stimulation for depression accrue over time, and it may take at least several months of treatment before you notice any improvements in your depression symptoms. Implanted vagus nerve stimulation doesn’t work for everybody, and it isn’t intended to replace traditional treatments.

Additionally, some health insurance carriers may not pay for this procedure.

Studies of implanted vagus nerve stimulation as a treatment for conditions such as Alzheimer’s disease, headaches and rheumatoid arthritis have been too small to draw any definitive conclusions about how well it may work for those problems. More research is needed.

Vagus nerve stimulation side effects

For most people, vagus nerve stimulation is safe. But it does have some risks, both from the surgery to implant the device and from the brain stimulation.

Surgery risks:

Surgical complications with implanted vagus nerve stimulation are rare and are similar to the dangers of having other types of surgery. They include:

• Pain where the cut (incision) is made to implant the device
• Infection
• Difficulty swallowing
• Vocal cord paralysis, which is usually temporary, but can be permanent

Vagus nerve stimulation may cause side effects in some people. These include:

• Changes in voice
• Chest pain
• Coughing
• Difficulty swallowing
• Hoarseness or throat discomfort
• Neck pain
• Pain or infection where the device was implanted through the skin
• Shortness of breath
• Tingling skin
• Worsening of sleep apnea for people with the condition
• Insomnia
• Headaches

For most people, side effects are tolerable. They may lessen over time, but some side effects may remain bothersome for as long as you use implanted vagus 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.