Vagus nerve stimulation (VNS) to treat epilepsy

Overview

Vagus nerve stimulation (VNS) is a treatment that sends mild electrical pulses along the vagus nerve to the brain. The vagus nerve is a major nerve in the body that carries signals between the brain and the heart, lungs and stomach.

You also may hear vagus nerve stimulation called vagal nerve stimulation. The implanted device may be called a vagus nerve stimulator.

For epilepsy, VNS is used along with antiseizure medicines to reduce seizures that are not controlled with medicines alone. This type of epilepsy is called drug-resistant epilepsy.

To treat epilepsy, a surgeon places a small VNS pulse generator under the skin in the upper chest. A wire from the generator wraps around the left vagus nerve in the neck. The device sends pulses through electrodes to the nerve at regular times.

VNS does not cure epilepsy. The goal is to reduce how often seizures happen or make seizures less severe. VNS also has been shown to reduce the risk of death from a seizure. This is called sudden unexplained death in epilepsy (SUDEP).

VNS also is used for other conditions. These may include treatment-resistant depression, stroke rehabilitation (experimental), irritable bowel syndrome and some headaches. The type of VNS and how it is used can differ by condition.

Why it's done

Vagus nerve stimulation (VNS) may be considered for people with drug-resistant epilepsy. Drug-resistant epilepsy means that seizures continue even after a person has tried antiseizure medicines, but they have not worked.

VNS may be an option for people with epilepsy who are age 4 and older and have seizures that aren't controlled with antiseizure medicines. Healthcare professionals may consider VNS for some people with focal or generalized seizures. Focal seizures start in one area on one side of the brain. Generalized seizures may start on both sides of the brain.

Generalized tonic-clonic seizures, sometimes called grand mal seizures, may improve with VNS. Absence seizures, sometimes called petit mal seizures, also may improve with VNS. How well VNS works varies by seizure type and from person to person.

Before deciding on VNS, your healthcare team reviews your seizure history, the medicines you have tried and the results of tests. Your care team uses this information to understand where and how your seizures begin. The team also considers whether epilepsy surgery or another treatment may be a better option.

How VNS fits with other epilepsy treatments

Antiseizure medicines are usually the first treatment for epilepsy. VNS does not replace these medicines. Most people continue taking antiseizure medicines after the VNS device is implanted. The treatment plan may change over time.

Some people with drug-resistant epilepsy can have surgery to remove or disconnect the area of the brain where seizures start. That type of surgery may offer a chance for seizure freedom when the seizure-causing area can be found and safely treated. The surgery to implant the VNS device does not remove brain tissue. It also does not require surgery on the brain.

VNS may be an option when:

• Brain surgery is not possible.
• Brain surgery is not the right choice.
• Seizures start in more than one area.
• Seizure-causing areas cannot be clearly located.

Other implanted epilepsy treatments may be options for some people as well. They may include:

• Deep brain stimulation, which delivers controlled pulses to a target in the brain that is part of a circuit involved in seizures.
• Responsive neurostimulation, which monitors brain waves to detect the likely onset of seizures and stop them before they cause symptoms.
• Polyneurostimulation, which combines vagus nerve stimulation with deep brain stimulation or responsive neurostimulation.

Risks

Vagus nerve stimulation (VNS) has risks related to the surgery and side effects related to electrical stimulation. Your care team checks the device, adjusts the stimulation settings and follows up with you after surgery to help manage issues.

Possible risks of implant surgery include:

• Infection.
• Bleeding or a collection of blood near the surgical area.
• Injury to the vagus nerve or nearby structures, which can affect the voice or swallowing.
• Heart rhythm changes during device testing. Serious heart rhythm issues are rare.

Side effects from stimulation often happen when the device is sending a pulse. They may improve as your body adjusts or after the settings are changed.

• Hoarse or changed voice.
• Cough or throat discomfort.
• Shortness of breath.
• Trouble swallowing.
• Sleep apnea, a condition in which breathing stops and starts during sleep or worsening of existing sleep apnea.

The generator, wire or battery can develop problems over time. A device may require reprogramming, battery replacement or another procedure.

What you can expect

Before the procedure

VNS device implantation usually is done with general anesthesia. This means you are asleep during the surgery. Your surgical team reviews the procedure with you and prepares the skin on your neck and upper chest. A breathing tube is placed while you're asleep to help you breathe during surgery.

During the procedure

The surgery itself doesn't involve the brain. The surgeon makes a small cut on the left side of the neck and another cut on the upper chest. The surgeon places an electrode around the left vagus nerve and passes a thin wire under the skin from the neck to the chest. The wire connects to the pulse generator.

The generator goes into a small space the surgeon makes under the skin below the collarbone. Before closing the cuts, the surgical team tests the system to make sure the device and wire work properly.

After the procedure

Most people leave the hospital on the day of surgery or the next morning. You may feel tingling or slight pain in your neck. Temporary changes in the voice or with swallowing can happen after surgery. These changes may happen because the vagus nerve and nearby tissues have been handled and because a breathing tube is used during the procedure.

What VNS stimulation feels like

When the VNS device sends a pulse, you may notice a change in your voice, a feeling in your throat, a cough or mild discomfort. These feelings happen during stimulation and may improve as your body adjusts or after the settings are changed. Tell your healthcare professional if the stimulation is uncomfortable.

Turning on and adjusting the device

Programming of the VNS device often happens about two weeks after it is implanted. Or it may be started at a low setting during surgery. The VNS device turns on and off in cycles, such as 30 seconds on and five minutes off.

The settings are adjusted from outside the body. At follow-up visits, a healthcare professional uses a hand-held programming wand that communicates with the implanted generator. The settings can be increased gradually based on seizure control and side effects.

Follow-up visits are needed to check the device, adjust stimulation and monitor the battery. Battery life varies depending on the device and how much stimulation it delivers. The generator is replaced when the battery is near the end of its service life. During follow-up visits, a healthcare professional uses the programming system to check the battery status.

Using the VNS magnet

You receive a special magnet for the VNS device. If you or a caregiver notice that a seizure is starting, swiping the magnet over the generator can give an extra burst of stimulation. For some people, this may stop a seizure or make it less severe.

The magnet also can stop stimulation temporarily when it is held over the generator. Your epilepsy team shows you and your caregiver how and when to use the magnet.

Some newer VNS devices can detect a fast rise in heart rate, which may happen with certain seizures, and automatically give extra stimulation. This feature does not apply to every person or every VNS device model.

If you need an MRI scan or other medical procedure, tell your healthcare team that you have a VNS device. The device requirements need to be checked before the scan or procedure.

Results

VNS usually reduces seizures rather than stopping them completely. Results vary from person to person. Some people have little change. Other people have a large reduction in seizures. A review of 28 studies showed that VNS reduced seizure frequency by at least half in 46% of people with drug-resistant epilepsy.

The benefits also may increase over time. Some people respond within the first few months. For others, improved response takes longer. Studies have reported continued improvement during the months and years after implantation.

Researchers have studied whether age, seizure type and other health factors are linked to VNS results. So far, there is no reliable way to tell how well VNS may work for each person.

Your epilepsy team looks at your seizure diary, seizure severity, side effects and quality of life when deciding how well VNS is working. The team may adjust the stimulation settings over time. Antiseizure medicines usually continue unless your healthcare professional recommends a change.

VNS is a long-term treatment. It requires regular follow-up to check the device and adjust the settings as needed. The battery can be replaced when needed.

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