Vagal Nerve Stimulator for Epilepsy Seizure Prevention

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A vagus 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 itself or cutting an area of the brain, the VNS device uses electrical stimulation through the vagus nerve in the neck as the means to reduce seizures.

It has been used as one of the options for treatment of epilepsy since 1997, and it is approved for this use for adults and children over the age of 4.

Indications

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

Yet not everyone who has refractory epilepsy is the right candidate for a VNS device placement. In general, it is used for focal epilepsy, which is epilepsy characterized by seizures that begin in one area of the brain. It has also been used for generalized epilepsy, characterized by seizures that involve the whole brain, with some success as well.

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.

Contraindications

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.

How the Implant 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 your right vagus nerve 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 placing the magnet that will be provided to you over the generator to increase the electrical impulses. In some instances, this can help prevent a seizure if you feel one coming on, or it can stop a seizure that is already ongoing.

The Importance of the Vagus Nerve

Procedure Overview

A VNS device is placed during a surgical procedure that takes between one to two hours. It is a complex technique because it involves the vagus nerve, a delicate nerve that has a significant impact on several physiological functions. The procedure is usually done in the operating room or in a surgical suite and requires general anesthesia and mechanical ventilation. 

Pre-Testing

If you will have a VNS implant, first you would 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.

If you have already had this type of testing, you may not need to have it again within a few weeks of your surgery. An EEG is necessary to determine whether your seizures are focal or generalized and whether you have epileptic or non-epileptic seizures.

The Surgery

The procedure itself is done as an outpatient. 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 thread 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. The vagus nerve then sends a nerve impulse to the cerebral cortex of the brain through the natural connections between the vagus nerve and the brain.

Recovery

If you have a vagus nerve implant, you can expect a fast recovery. It should only take a few days for the wound to heal. Generally, the device is not turned on immediately, even if it is programmed right away, until about a week after the procedure.

What to Expect

Programming

The generator is programmed with a computer to deliver intermittent on/off electrical impulses continuously. You may have your device programmed right after it is implanted or you may have it programmed later.

Once you have a VNS, you need to learn how to adjust the rate of stimulation with a handheld magnet that you will be provided with. You can also use the magnet to deliver extra stimulation through your generator if you feel that a seizure is coming on.

Your medical team will teach you how to adjust the rate of stimulation at home and will explain when you need to make adjustments. You can also call or see your doctor when you need help with adjustments.

Maintenance

You will need periodic battery replacements for your device, typically every seven to 15 years. Sometimes, batteries may wear out faster and need to be replaced sooner. Repairs may be done using a local anesthetic, but if repairs involve the vagus nerve, you may need to have general anesthesia.

Side Effects

There are several side effects of the VNS device, and they occur due to stimulation of the nerve or the cerebral cortex:

  • 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 patients' breathing during their sleep with consequent sleep interruption.

Complications

If you or your child has a VNS implant, you can learn to recognize the signs of electrical malfunction, hardware malfunction, or other complication:

  • Signs of malfunction of electrical activity 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.
  • You may also have a hardware malfunction, such as a dislodged battery, disconnected wires, or lead malfunction. A dislodged device or wire 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 doctors 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.

Quality of Life

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), one of the causes of mortality among people with epilepsy.

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.

If you have epilepsy, you can continue to take medication if you have a VNS implant. Some people with a VNS implant still need to take anti-seizure medications, but usually at a lower dose than prior to the implant.

In general, about 5 percent of people who have a VNS implant are completely seizure-free without the medication, while about 65 percent report an improvement in their overall quality of life.

Other Uses

There are several approved brands of VNS devices, as well as several uses besides epilepsy. VNS has been approved for treatment of depression and headaches. A newer, non-invasive VNS device has been approved for cluster headaches, a type of recurrent headache that is 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

Epilepsy surgery is among the options for the treatment of epileptic seizures, but VNS is not right for everyone. The device does require some maintenance and familiarity with side effects.

Overall, the procedure, which has been performed on over 75,000 people worldwide, is considered safe and without many complications. 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 doctors to anticipate whether a VNS device can reduce your seizures or not.

Living Your Best Life With Epilepsy
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Article Sources
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  • Englot DJ, Rolston JD, Wright CW, Hassnain KH, Chang EF. Rates and Predictors of Seizure Freedom With Vagus Nerve Stimulation for Intractable Epilepsy. Neurosurgery. 2016 Sep;79(3):345-53. DOI: 10.1227/NEU.0000000000001165.

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