The vagus nerve is one of 12 pairs of cranial nerves in the body. It’s involved in various bodily functions, including digestion, heart rate, and breathing.

There are 12 cranial nerves in the body. They come in pairs and help with many functions throughout the body, including hearing, vision, blood pressure control, and some physical movements.

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.

Read on to learn more about the vagus nerve, including what it affects, anatomy and function, related problems, vagus nerve stimulation (VNS), more.

The vagus nerve, also called the pneumogastric nerve, is involved in 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 affect communication 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 longestTrusted Source 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 you feel on the skin or in the muscles.
  • Visceral components: These are sensations you feel 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

It’s impossible to test every single function of the vagus nerve, but there are some simple tests that can help assess some functions of the vagus nerve

To test the vagus nerve, a doctor may checkTrusted Source 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. 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.

Vagus nerve function can be disrupted by structural damage or due to alterations in the neurotransmitters that help your vagus nerve to function

Problems with the vagus nerve can cause a range of issues.

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 or fast 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.

Heart rate issues

Vagal nerve dysfunction can cause both slow and fast heart rates depending on the type of dysfunction.

For example, overactivity can lead to bradycardia, or slow heart rate, while insufficient activity of the vagus nerve can lead to tachycardia, or fast heart rate.

This can be further explained by management of some types of tachycardia that can includeTrusted Source vagal nerve maneuvers in order to try to stimulate more vagal nerve activity to slow the heart rate.

Gastroparesis

Experts believe that damage to the vagus nerve may causeTrusted Source 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 2019 studyTrusted Source 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 is disrupted by sudden stimulation, it can cause a sudden drop in heart rate and blood pressure, resulting in fainting. This is known asTrusted Source vasovagal syncope or a vasovagal episode.

Factors that can trigger this include emotional stress, pain, and sudden changes in heart function.

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

You need to contact a doctor right away if you experience fainting

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

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.

In recent years, VNS has also received Food and Drug Administration (FDA) approval for the treatment of cluster headaches and post-stroke motor rehabilitation.

It could help treat a range of other conditions in the future.

VNS is generally safe. However, some side effects may occur. If you receive VNS, your doctor will discuss the potential side effects, and give you guidance so you will know when to call about side effects or adverse effects.

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

Mental health and well-being

There are also noninvasive ways to help control action of your vagus nerve.

These include:

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

For some people, vagal response reduces with age. People with a strong vagal toneTrusted Source may have fewer inflammation and gut issues, and they may be able to manage blood sugar more efficently, 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 inflammatory condition that causes pain and swelling in the joints and other symptoms throughout the body.

In 2021Trusted Source, 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, heart disease, and other conditions that involve inflammatory processes.