What Is Vagus Nerve Stimulation (VNS)?

Vagus nerve

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What Is Vagus Nerve Stimulation?

Vagus Nerve Stimulation (VNS) is a treatment option for people with epilepsy and sometimes depression. It involves the use of a device to send mild electrical pulses to the brain through the vagus nerve.

The vagus nerve is responsible for controlling involuntary body functions. It is connected to motor functions in your stomach and diaphragm as well as sensory functions in your ears and tongue. 

Types

Vagus nerve stimulation can be done in two ways. Either through implantation of a pulse generator in your chest or making use of a noninvasive vagus nerve stimulation device.

  • Invasive device: A pulse generator is implanted in your chest and used to send pulse signals to your brain through the vagus nerve. This is the most traditional form of VNS and the procedure has been approved by the Food and Drug Administration (FDA), for treating drug-resistant epilepsy.
  • Non-invasive device: Non-invasive VNS devices could be an option for people who don't want a VNS device inserted into their bodies. However a lot more work needs to go into their development. These devices aren't currently approved in the United States for epilepsy treatment.

How VNS Is Performed

The vagus nerve runs on both sides of your body, from your brain, through your neck, chest, and stomach. A device known as a pulse generator is surgically implanted in the upper left side of your chest.

An incision is then made in your neck and the thin wires that connect the pulse generator to your vagus nerve are inserted. 

The procedure for inserting the VNS device is usually an outpatient one and is performed by a neurosurgeon.

This means that you won’t need to be kept in the hospital after your surgery. The surgery takes about 45 to 90 minutes and is typically performed using general anesthesia.

The pulse generator is turned on a few weeks after your surgery. The electrical impulses being delivered to your brain are typically started at a low level and then gradually increased.

After the pulse generator has been turned on you’ll be given a handheld magnet to control the stimulator yourself. When the magnet is brought near the stimulator, it releases electrical pulses that will either stop a seizure from happening or make it less severe. 

The generator is usually not switched on until two weeks after the surgery to give your body time to heal. The generator is battery powered and will start to run low between 3 to 8 years after it is first inserted. The battery is replaced or a new generator is put in with a small procedure that only involves an incision in your chest.

Benefits

Anti-epileptic drugs are usually prescribed for people with epilepsy to help manage their seizures. However, some people don’t respond to these drugs and others experience very severe side effects. VNS is a great treatment option for people who fall into these categories.

Treatment For Seizures and Depression

It is important to know that this treatment is recommended alongside anti-epileptic drugs and not instead of it. However in some cases, the dosage of the anti-epileptic drugs are reduced.

The treatment aims to reduce the frequency and severity of seizures for people with epilepsy. It may also reduce the time it takes to recover after a seizure. This therapy doesn’t work for everyone. If it has absolutely no effect on you then your doctor will recommend it’s taken out.

VNS is also beneficial for people living with chronic depression who don’t seem to be responding to antidepressants and therapy.

Epilepsy 

VNS can only reduce the frequency of seizures with epilepsy, it can’t cure it. The intensity of seizures when they do occur might also reduce.

It can take several months after the procedure is done before you notice a significant reduction in the frequency of your seizures.

VNS is often used alongside anti-epileptic drugs and is not intended to completely replace them. It is not completely understood how exactly VNS works to reduce epileptic seizures. Some research shows that it increases blood flow to key areas in the brain and raises the level of some neurotransmitters, which might help to control seizures. 

One study shows that VNS can decrease the frequency of seizures by as much as 50% in the first four months of treatment. In some cases swiping your magnet over your stimulator as you are having a seizure might end the episode. 

In some people who have epilepsy, an increase in heart rate could be a sign of an oncoming seizure. Newer models of VNS generators can detect an increase in heart rate and send pulses to the vagus nerve. This might prevent the seizure from happening.

Chronic Depression 

VNS helps to improve depression symptoms, by stimulating the production of certain neurotransmitters in the brain.

For those with depression many people report seeing benefits in their depressive symptoms many months after they begin VNS treatments. The treatment also doesn’t work for everybody.

Risks 

Vagus nerve stimulation is a relatively safe treatment for epilepsy and chronic depression. However, it is not without its risks, especially during surgery to insert the device.

Before the surgery, your doctor will conduct a thorough medical investigation which usually involves a couple of tests to make sure you don’t have any health problems that might complicate the procedure.

Surgical complications such as infections and vocal cord paralysis are very rare but could occur. Some people might also experience some side effects after the surgery, such as:

  • Increased coughing
  • Headaches 
  • Chest pain 
  • Voice change 
  • Shortness of breath
  • Indigestion 
  • Nausea and vomiting 
  • Insomnia 
  • Throat spasms

People with the following conditions are also typically not given VNS treatments:

  • Having only one vagus nerve
  • Lung disorders like asthma 
  • Heart arrhythmia 
  • Abnormal functioning of the autonomic nerve system
  • Ulcers
  • Insulin-dependent diabetes

The effectiveness of VNS therapy depends on which condition it's being used to treat.

Other Considerations

After a VNS procedure, you need to monitor your condition closely. If you experience any severe side effects as a result of the stimulator, such as difficulty breathing or swallowing, increased drowsiness, or a change in your heart rate, you should see a doctor as soon as you can.

It is also important to let your doctor know you have a VNS device in you if you are asked to undergo an MRI scan. The magnetic fields in an MRI machine can cause the wires connecting the pulse generator to your vagus nerve to overheat and cause burns to your skin. 

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Article Sources
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