There are 12 cranial nerves in the body. They come in pairs and help link the brain with other areas of the body, such as the head, neck, and torso.

Some send sensory information, including details about smells, sights, tastes, and sounds, to the brain. These nerves have sensory functions. Other cranial nerves control the movement of various muscles and the function of certain glands. These are known as motor functions.

While some cranial nerves have either sensory or motor functions, others have both. The vagus nerve is such a nerve. The cranial nerves are classified using Roman numerals based on their location. The vagus nerve is also called cranial nerve X.

Explore the interactive 3-D diagram below to learn more about parts of the body the vagus nerve affects.

What does the vagus nerve affect?

The vagus nerve also called the pneumogastric nerve, is responsible for various internal organ functions, including:

  • digestion
  • heart rate
  • breathing
  • cardiovascular activity
  • reflex actions, such as coughing, sneezing, swallowing, and vomiting

It plays a role in the autonomic nervous system, which controls actions people do unconsciously, such as breathing and digestion.

It may also form a link between the gut and the brain, playing a role in what scientists call the gut-brain axis. In recent years, experts have been studying the gut-brain axis to look for links between conditions such as obesity and depression.

The word “vagus” means wandering in Latin. This is a very appropriate name, as the vagus nerve is the longest cranial nerve. It runs from the brain stem to part of the colon.

The vagus nerve sensory functions are divided into two components:

  • Somatic components. These are sensations felt on the skin or in the muscles.
  • Visceral components. These are sensations felt in the organs of the body.

Sensory functions of the vagus nerve include:

  • providing somatic sensation information for the skin behind the ear, the external part of the ear canal, and certain parts of the throat
  • supplying visceral sensation information for the larynx, esophagus, lungs, trachea, heart, and most of the digestive tract
  • playing a small role in the sensation of taste near the root of the tongue

Motor functions of the vagus nerve include:

  • stimulating muscles in the pharynx, larynx, and the soft palate, which is the fleshy area near the back of the roof of the mouth
  • stimulating muscles in the heart, where it helps to lower resting heart rate
  • stimulating involuntary contractions in the digestive tract, including the esophagus, stomach, and most of the intestines, which allow food to move through the tract

To test the vagus nerve, a doctor may check the gag reflex. During this part of the examination, the doctor may use a soft cotton swab to tickle the back of the throat on both sides. This should cause the person to gag.

If the person does not gag, this may be due to a problem with the vagus nerve, which could indicate a problem with the brainstem function.

Doctors may also assess vagal nerve function when looking at cardiovascular disease, as discussed in recent research. Damage to the vagal nerve can lead to problems with the cardiovascular system.

Measuring heart rate, blood pressure, and cardiovascular response to exercise can provide clues as to how your vagal nerve performs in conjunction with your cardiovascular system, which is known as cardiovagal tone. It can offer clues to your cardiovascular health.

Nerve damage

Damage to the vagus nerve can result in a range of symptoms because the nerve is so long and affects many areas.

Potential symptoms of damage to the vagus nerve include:

  • difficulty speaking
  • loss or change of voice
  • difficulty swallowing
  • loss of the gag reflex
  • low blood pressure
  • slow heart rate
  • changes in the digestive process
  • nausea or vomiting
  • abdominal bloating or pain
  • depression and anxiety in people with breathing problems or heart disease

The symptoms someone might have depend on what part of the nerve is damaged.

Gastroparesis

Experts believe that damage to the vagus nerve may also cause a condition called gastroparesis. This condition affects the involuntary contractions of the digestive system, which prevents the stomach from properly emptying.

Symptoms of gastroparesis include:

  • nausea or vomiting, especially vomiting undigested food hours after eating
  • loss of appetite or feeling full shortly after starting a meal
  • acid reflux
  • abdominal pain or bloating
  • unexplained weight loss
  • fluctuations in blood sugar

Some people develop gastroparesis after undergoing a vagotomy procedure, which removes all or part of the vagus nerve.

A 2020 study looked at the impact of vagal nerve stimulation in people with mild to moderate gastroparesis without a known underlying cause. After 4 weeks, participants saw improvements in their symptoms, including their ability to empty the bowel, suggesting this could be a useful therapy for people with this condition.

Vasovagal syncope

The vagus nerve stimulates certain muscles in the heart that help to slow heart rate. When it overreacts, it can cause a sudden drop in heart rate and blood pressure, resulting in fainting. This is known as vasovagal syncope.

Factors that can trigger this include pregnancy, emotional stress, and pain, but there may be no clear cause.

Alongside this type of fainting, you may experience:

  • warmth
  • nausea
  • tunnel vision
  • ringing in the ears
  • excessive sweating
  • low blood pressure
  • slow or irregular heartbeat

If you experience fainting, it’s a good idea to see a doctor to rule out potential serious causes. To prevent it, a doctor may recommend drinking plenty of fluids or avoiding standing up quickly.

Vagus nerve stimulation (VNS) involves placing a device in the body that uses electrical impulses to stimulate the nerve. It’s used to treat some cases of epilepsy and depression that don’t respond to other treatments.

Experts believe the vagus nerve might form a link between depression, metabolic disease, and heart disease. If research can confirm this, researchers say VNS could help with a variety of health issues.

The device is usually placed under the skin of the chest, where a wire connects it to the left vagus nerve. Once the device is activated, it sends signals through the vagus nerve to your brainstem, transmitting information to your brain.

A neurologist usually programs the device, but people often receive a handheld magnet they can use to control the device on their own as well.

It’s thought that VNS could help treat a range of other conditions in the future, including multiple sclerosis, posterior autoimmune uveitis, Alzheimer’s disease, and cluster headaches.

Experts are keen to learn more about the vagus nerve, as it may hold clues to various health issues.

Mental health and well-being

If VNS can help manage depression, some people have been looking into various ways of stimulating the vagus nerve to boost mental well-being.

These include:

  • diaphragmatic breathing techniques
  • cold water immersion
  • the use of transcutaneous VNS devices
  • biofeedback
  • yoga

Vagal response reduces with age, according to research. People with a strong vagal tone may find it easier to relax after a stressful event, and their body may be better able to manage inflammation and gut issues. It may also be better equipped to manage blood sugar, according to research published in 2020.

However, there is not enough evidence to prove that all these devices and techniques are safe and effective for everyone. Always speak with a doctor before trying a new treatment strategy, as it may not be suitable for you.

Rheumatoid arthritis

There is some evidence that VNS can help reduce the severity of rheumatoid arthritis (RA), an anti-inflammatory condition that causes pain and swelling in the joints and other symptoms throughout the body.

In 2021, researchers published findings after measuring markers of inflammation in 30 people who used a VNS device to help manage RA for 12 weeks. They found evidence that they experienced “clinically meaningful” reductions in levels of DAS28-CRP, a sign of inflammation in the body.

While promising, more studies are needed to confirm that VNS can help manage RA safely and effectively in a wider population.

The vagus nerve plays a role in many bodily functions, and it may form a link between areas such as the brain and the gut. Treatments that focus on the vagus nerve have proved to help people with epilepsy and depression, and it shows promise for rheumatoid arthritis, too.

Some experts believe that further research may offer clues to managing diabetes, obesity, heart disease, and other conditions that involve inflammatory processes.