Vagal Nerve Stimulator for Epilepsy Seizure Prevention

This device sends electrical signals to the vagus nerve

A vagal nerve stimulator (VNS) implant is a device that can control seizures for some people with epilepsy. Unlike other types of epilepsy surgery, which involve surgery on the brain or cutting an area of the brain, the VNS device uses electrical stimulation through the vagus nerve in the neck to reduce seizures.

It's been used as an option for treating epilepsy since 1997 and is approved for this use in adults and children over age 4.

What to Expect During VNS Implantation
Verywell / JR Bee


The VNS implant is indicated for people who have refractory epilepsy—that which does not improve with a tolerable dose of anti-seizure medication. An estimated 15 percent to 30 percent of people with epilepsy have refractory cases that cannot be completely controlled with medication.

In general, VNS is used for focal epilepsy, which is characterized by seizures that begin in one area of the brain. It has also been used with some success for generalized epilepsy, characterized by seizures that involve the whole brain.

However, not everyone who has refractory epilepsy is a good candidate for a VNS device placement. VNS is not considered safe for people who have heart disease or arrhythmias (heart rhythm abnormalities). If you have extensive lung disease or sleep apnea, you may not be able to have placement of the stimulator, as the stimulation may interfere with your breathing.

A VNS implant has not been found to be effective for non-epileptic seizures, which are seizures that are not correlated with corresponding EEG changes.

How VNS Works

Your vagus nerves are involved in modifying numerous functions of your body, including your heart rate, blood pressure, breathing rate, and digestion. You have a right vagus nerve and a left vagus nerve, but a VNS device can only be placed on the left side because the right side controls your heart rate.

Vagal nerve stimulation with a VNS device is believed to decrease seizures through the vagus nerve’s interaction with the brain, but the exact mechanism through which it reduces seizures is still not completely clear.

Alterations in electrical activity, blood flow, or neurotransmitters resulting from the stimulation have all been suggested as possible explanations for the decrease in seizures among people with epilepsy who have VNS implants.

The vagus nerve has both excitatory and inhibitory actions on the brain, and it is likely that the vagal nerve’s inhibitory actions could be responsible for decreasing the seizures.

If you have a VNS implant, you can temporarily increase the amount of electrical stimulation by sweeping a magnet (which will be provided to you) over the generator. In some instances, this can help prevent a seizure if you feel one coming on, or it can stop a seizure that's already happening.

Implantation Procedure

A VNS device is placed during a surgical procedure that takes between 1 to 2 hours. It's a complex technique because the vagus nerve is delicate and has a significant impact on several physiological functions.

The procedure is usually performed in an operating room or surgical suite. It requires general anesthesia and mechanical ventilation of your lungs.


Before getting a VNS implant, you'll need to have pre-surgical testing with brain imaging and electroencephalogram (EEG) studies. Brain imaging is an important part of diagnostic testing for epilepsy because seizures can be caused by a problem such as a brain tumor or an infection. An EEG is also necessary to determine whether your seizures are focal or generalized, epileptic or non-epileptic.

If you've already had this type of testing as part of your epilepsy diagnostic process, you may not need to have it again prior to surgery.

what to expect during an electroencephalogram
Verywell / Cindy Chung

The Surgery

The procedure itself is done on an outpatient basis, which means you can go home the same day.

A battery-powered stimulator—often referred to as a generator—is implanted in the upper part of the chest on the left side. A lead wire, which is attached to the stimulator, is threaded up to the left vagus nerve. Another incision is made in the neck so that an electrode coil can be wrapped around the left vagus nerve.

The stimulator delivers an electrical pulse to the vagus nerve, which triggers the natural process of the vagus nerve sending a nerve impulse to the cerebral cortex of your brain.


After a vagus nerve implant, you can expect a fast recovery. It should only take a few days for the wound to heal.

Programming and Adjustment

The generator is programmed by a computer to continuously deliver intermittent on/off electrical impulses. You may have your device programmed right after it's implanted or it may be programmed later. Either way, the device usually isn't turned on until a week after the procedure.

Your medical team will teach you how to adjust the rate of stimulation at home and will explain when you need to make adjustments. This is done with a handheld magnet that is provided to you. You can also use the magnet to deliver extra stimulation through your generator if you feel that a seizure is coming on.

If you're ever unsure of how to adjust the rate of stimulation, don't hesitate to reach out to your healthcare provider's office.


Your device will need battery replacement about every seven to 15 years. Sometimes, batteries may wear out faster and need to be replaced sooner. Some repairs can be done using a local anesthetic, but if they involve the vagus nerve, you may need to have general anesthesia.


Overall, a VNS implant can improve quality of life. Studies show that it can decrease seizure frequency, seizure severity, and improve recovery time. VNS also decreases the risk of sudden unexpected death in epilepsy (SUDEP).

Results of a large study showed that people who had a vagal nerve implant experienced a 60 percent improvement in their level of alertness throughout the day.

VNS therapy is generally used in addition to anti-seizure medications, not instead of them. However, if VNS therapy works, it is possible to reduce the dosing of epilepsy medications.

In general, about 5 percent of people who have a VNS implant are completely seizure-free, while about 65 percent report an improvement in their overall quality of life.

Side Effects

Side effects are possible with the VNS device, and they occur due to stimulation of the nerve or the cerebral cortex. Side effects may include:

  • Hoarse voice: The most common side effect of a VNS device is vocal cord impairment, which manifests as a hoarse voice. Sometimes, this improves on its own.
  • Drowsiness: VNS stimulation may cause drowsiness in some cases by affecting your breathing during sleep, which can lead to sleep interruption.

Device Malfunctioning

If you or your child has a VNS implant, you should learn to recognize the signs of an electrical malfunction, hardware malfunction, or another issue with the device:

  • Signs of electrical malfunction or a dying battery can include insomnia or tiredness, severe dizziness, sudden voice change, shortness of breath, or a sense that your heart is beating rapidly or irregularly.
  • A hardware malfunction, such as a dislodged battery, disconnected wires, or lead malfunction, can cause neck pain and may result in seizures due to discontinued electrical stimulation.
  • If you have an emergency that requires you to be treated with a defibrillator, your VNS device can malfunction as a result of the electrical shock. Be sure to let your healthcare providers know if you are treated with a defibrillator so that you can have an adjustment to your programming or possibly a repair to the device itself.

Other Uses

Several approved brands of VNS devices exist, and they have several uses besides epilepsy. VNS has been approved for treating depression and headaches. A newer, non-invasive VNS device has been approved for cluster headaches, a type of recurrent headache that can be difficult to treat with medication.

The side effects and contraindications may not be exactly the same when VNS is used for depression and headaches. For use in depression, the VNS device is contraindicated in people who have suicidal ideation.

A Word From Verywell

Overall, the procedure, which has been performed on over 75,000 people worldwide, is considered safe. Over the past 30 years, the procedure—and management of complications and side effects—has improved. A track record of results has emerged, making it easier for your healthcare providers to anticipate whether a VNS device can reduce your seizures. If you have more questions about your symptoms or concerns about the right treatment options, you can use our Healthcare Provider Discussion Guide below to help start that conversation with your healthcare provider.

Epilepsy Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Woman
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.