Vagus Nerve Damage Testing

There are various ways in which the vagus nerve can be tested as it innervates and controls many functions in the body. Before we can talk about the vagus nerve damage test, we need to learn what the nervous system is and the functions of the vagus nerve.

The nervous system is the connecting network of our body. It transfers signals for us to move, breathe, secrete hormones, pump blood, think, feel, and even regenerate (1). It is the body’s electrical wiring. This system is what allows you experience your environment. It is divided into 2, the central nervous system (CNS) and the peripheral nervous system (PNS) (2). The peripheral nervous system is made up of nerves that innervate the glands, muscles, soft tissues, and organs of the body, while the central nervous system encloses the brain and spinal cord.

There are 12 cranial nerves in the body. They come in sets and help to link the other parts of the body such as the head, neck, and torso. A few of them send sensory information including details about sight, smell, sounds, and taste to the brain. The nerves are known to have sensory functions. Other nerves control the actions of different muscles and the function of certain glands. They are known as motor functions. Although some of the cranial nerves have either motor or sensory functions, the vagus nerve has both.

The vagus nerve is a very long nerve that moves from the brain stemto the colon. The vagus nerve is the 10th cranial nerve also known as the wandering nerve. It is the main parasympathetic nerve of the body providing blood innervation to the neck, thorax, lungs, and abdomen. The nerve carries information about pain, touch,  and temperature from the throat and other parts of the inner and outer ear. It also controls all involuntary body processes such as breathing speech, swallowing, hearing, etc, and receives sensory information from the internal organs in the chest, neck, and abdomen like the esophagus, digestive tract, and heart. The vagus nerve carries sensory information from the baroreceptors and chemoreceptors in the aorta. This detects changes in the blood pressure and chemoreceptors in the aorta that senses oxygenlevels in the blood.

The vagus nerve controls muscles in the pharynx, soft palate, and larynx as well as muscle in the tongue that plays a critical role in speaking and swallowing.

The vagus nerve is a functionally diverse nerve having various modalities of innervation. The nerve constitutes the major component of the parasympathetic nervous system that serves a long list of functions like digestion, mood control, immune response, orgasm, heart rate, mucus and saliva production, and skin and muscle sensations. It also helps in the management of fear as it does the opposite of the sympathetic nervous system.

Damage to the Vagus Nerve

The functioning of the vagus nerve can be impaired by stress, anxiety, abdominal surgery, poor lifestyles like smoking, drinking alcohol, viral infections, over-working, lack of exercise, sleep, and poor nutrition. If the vagus nerve gets damaged by any of these, either physical trauma or the growth of a tumor, it may cause the following symptoms of vagus Nerve Damage

1. Hoarseness or loss of voice
2. Difficulty in swallowing
3. Deficient gag reflex
4. Gastroparesis
5. Deviation of uvula away from the side of the damaged nerve
6. Cardiovascular disorders
7. Inflammatory disorders
8. Gastrointestinal problems
9. Obesity
10. Dizziness

The symptom one might experience depends on the part of the vagus nerve that was damaged. Let us note that vagal tone decreases with age. This means that a young person might find it easier to recover from stress, inflammations, and gastrointestinal problems than one who is older. Research has found vagus nerve stimulation as a wayto send electrical impulses to stimulate damaged nerves. It calms irregular electrical impulses in the body(4). This can help with many problems caused by this dysfunction, especially in the case of epilepsy and mental illness. Although there are certain lifestyle changes one can indulge in like  regular exercise, meditation, eating a healthy diet, avoiding a sedentary lifestyle, maintaining a healthy weight, etc. But how do we determine when a vagus nerve is damaged?

How To Test Vagus Damage

The vagus nerve is usually tested in combination with the glossopharyngeal nerve
because they often rely on each other. (3). In this article, we will discuss the various ways in which a damage to the vagus nervecan be tested.

Method 1

For this to be easily done, you will need a partner. This is a really powerful technique that can have an intense effect on how you address your body. Now follow these steps;

• Your partner gets a flashlight.
• Get in a comfortable position where your partner can view your mouth.
• Open your mouth widely. If you are not going to be able to hold it down for long, you can use your fingers or tongue depressor to hold it in place.
• Have your partner look at the uvula at the back of your mouth. The uvula is a soft
  flap of tissue hanging down your throat.
• Now, produce the “ah, ah, ah” sound.
• Your partner then uses a tongue depressor or fingers to push down your tongue sothe uvula can be more visible.
• The partner is going to look at the uvula to see if there is a deviation fromone
  side to the other.

What you’re looking for, specifically, is if there’s any deviation from one side to the other.

If you notice the uvula moves to one side, then what that means is ventral vagal nerve dysfunction. If there is a lesion, the uvula shifts away from the paralyzed side tothe normal side. If the soft palate moves up to one side and does not move up to the other side, then that would mean there’s a dysfunction at the pharyngeal division of the ventral vagal nerve.

Method 2

To test the vagus nerve, your physician may assess your gag reflex. Note that this procedure is uncomfortable. The gag reflex is a natural response in which the body strives to get rid of undesirable or foreign objects from the oral cavity, through contraction of the muscle at the baseof the pharyngeal wall and tongue inside the mouth. During this examination, your physician will use a tongue depressor put down the tongue, and use a soft cotton swab to touch the back of the throat on both sides. This action should cause the person to gag. If you do not gag, this may be because of a problem with the vagus nerve, which could cause an issue with the brainstem functions. The result of the procedure is noted down.

Method 3

The physician listens while the patient is talking to take note of any whispering, hoarseness, nasal speech, or regurgitation of liquid through the nose after the water has been swallowed. If any of this is noticed, that could be a sign that there is damageto the vagus nerve. This is because a properly functioning vagus nerve does not cause any speech impairment.

Method 4

One of the functions of the vagus nerve is slowing the heart rate. It is normal for a healthy heart rate to rise after exercise and then slow back after the exercise ends. Sometimes, this is not usually the case. You may experience heart racing even while sitting quietly. Therefore, any damage to the vagus nerve is said to affect the heart this way. When there’s a problem, it can lead to complications in the cardiovascular system. Measuring blood pressure, heart rate, and heart response to exercise can determine the cardio vagal tone. This can determine the extent of damage to the vagus nerve.

Method 5

Vagus Nerve Measurement
This entails using a high-resolution ultrasound to determine the diameter and length of the vagus nerve. When the vagus nerve is dying, it diminishes in cross-sectional areaand diameter. This way, physicians can know when there is a problemwith the vagus nerve and with proper treatment, the nerves can improve. (5).

References

1. Ingo R.Titze, Principals of Voice Production, 2nd ed. (Iowa City: National Center for Voice and Speech, 2000), 23 – 54.

2. Douglas B. Webster, Neuroscience of Communication, 2nd ed. (San Diego: Singular Publishing, 1998),

3. Erman AB, Kejner AE, Hogikyan ND, Feldman EL. Disorders of cranial nerves IX and X. Semin Neurol. 2009 Feb;29(1):85-92.