In previous posts we described the functions of the vagus nerve, how to care for it, how to stimulate and how it might get damaged. In this post we look in a bit more detail at some of the symptoms of vagus nerve damage and dysfunction.
If you haven’t already done so, you can take our vagal tone calculator questionnaire, which is another great way of assessing the health of your vagus nerve.
If you’re wondering whether you have some kind of vagus nerve dysfunction, this post will give you some idea of what you should be looking out for. None of this constitutes medical advice and even if something sounds like it fits, you should always talk to your doctor about it.
The vagus nerve is the longest of your cranial nerves. It exits the brain on the right and left of the brain stem which is situated in the middle of the back of your skull, slightly below the level of the ears.
It branches up to the ear and also down through your neck and all the way down to your intestines at the bottom of your torso. It visits all your major organs -- the heart, lungs and stomach -- as well as your throat and ears.
Because of the wide ranging reach of the vagus nerve, the symptoms you might experience from low vagal tone are very broad, affecting many parts of the body. Also, because over 70% of the vagus nerve fibres carry sensory information back to the brain, it’s activity can have strong psychological effects, driven greatly by the gut-brain connections.
We’ve tried to break up the symptoms we describe into broad categories affecting different parts of your body or mind.
Swallowing is one of those reflex actions that we usually take for granted, but it requires a complex coordination of several different muscles around your throat.
As you swallow a number of reflex actions occur which shut the nasal cavities and open the oral cavities, followed by movements of the tongue and esophageal contractions which push down into the stomach. The vagus nerve plays an important motor and sensory role in this process, working in concert with a number of other cranial nerves.
Disfunction in the vagus nerve can therefore make swallowing difficult and even dangerous. A small mistake can result in food passing into your lungs rather than your stomach. If this happens, impulses from the vagus nerve induce reflexive coughing to try to expel the food or drink from the lungs.
If you experience difficulty swallowing or a change in your gag reflex, these can be a sign of problems with your vagus nerve.
The motor division of the vagus nerve is responsible for the control of your vocal chords. If your voice changes inexplicably, especially if it becomes hoarse or strained, this can be a sign of vagus nerve damage. You may also experience difficulty talking or coordinating the movement of your tongue when you speak. It may or may not be accompanied by a general feeling of discomfort around the region of the throat.
The vagus nerve is one of three cranial nerves which communicate taste signals back to the brain. Studies have shown that stimulation of the signals in the vagus nerve induce salivation, which is necessary to keep our mouth moist and to protect our oesophagus from stomach acids.
If signals are not carried correctly by the vagus nerve this can result in an unusually persistent dry mouth and throat. And because the vagus nerve also helps control coughing, this can also translate into a persistent cough.
The rate at which your heart beats actually varies from beat to beat as the heart makes small adjustments depending on the body’s demands. The measure of how responsive the heart is to changing needs from the body is referred to as “heart rate variability” (HRV).
Nowadays, HRV is considered more important than straight forward resting heart rate in predicting or assessing your general health and fitness. If you don’t already know about this, you could read or longer post on the subject here .
HRV is also one of the best measures we have for the health of the vagus nerve (often referred to as vagal tone). Because HRV and vagal tone are so closely linked, HRV is one of the best early warning signs that there may be problems. Because the two are so closely linked, a poor vagal tone can also reduce your HRV because a poorly performing vagus nerve is less able to carry the messages to and from your brain that allow careful regulation of each heart beat.
In more severe cases, your heart may beat too slowly (bradycardia) or may experience severe disruptions in its beating (arrhythmia) and may be associated with chest pain. Such conditions should immediately be discussed with your doctor.
The vagus nerve also controls what is called the baroreflex, which is a rapid vascular response which helps the body maintain a near constant blood flow during other environmental and bodily changes. So if your heart rapidly increases, the baroreflex will dilate your blood vessels to reduce immediate blood pressure.
It’s hard to tell if your vagus nerve is allowing your blood pressure to get too high, but vagus nerve related cardiovascular problems may also result in low blood pressure, which can lead to feelings of dizziness; in extreme situations, if it allows your blood pressure to drop too far, it can result in fainting. If any of this happens frequently, it may indicate that there is something wrong with your vagus nerve.
The vagus nerve is the main nerve that connects your brain and your guts. The brain-gut connection is now understood by science to be crucial to many aspects of our health. If you are experiencing any problems with your digestion, this could be a result of low vagal tone. Symptoms may include indigestion, constipation, stomach cramps, acid reflux (from overproduction of stomach acids), or any of the symptoms associated with gastroparesis.
If problems persist, it could lead to further more serious problems, such as peptic ulcers.
None of these symptoms will necessarily only be caused by impairment of vagus nerve function, but if you experience them, your vagus nerve is one possible cause that you should consider.
In mild cases, you may be able to treat it with home remedies, changes in diet or lifestyle, and stimulation at home using a tVNS device such as the vagus net device, but in more serious cases, you should always do this in consultation with your doctor.
The inflammatory response is part of the body’s defense system. When you become injured or unwell, all or part of your body becomes inflamed as your body attempts to heal. However, the degree of inflammation must be carefully regulated by the body; otherwise, over-inflammation can become a problem.
A low vagal tone can result in nervous system balances which lead to such over-inflammation.
Chronic low-grade inflammation is now believed by scientists to be associated with almost all age-related illnesses. And this is further linked to a declining vagal tone as we age.
While this is strongly linked to age, it can begin to occur at any time in your life and may be triggered by stress or injury.
This can manifest itself in autoimmune conditions such as rheumatoid arthritis, the buildup of fluids in the parts of your body, particularly in the joints, causing redness, pain or loss of mobility or function.
In mild cases, you might experience fatigue or headaches; but in more serious chronic cases, you could develop conditions such as depression or irritable bowel syndrome (IBS).
Recently, studies have associated chronic illnesses such as long-Covid with residual inflammation in the body resulting from initial infection.
Inflammatory symptoms such as these are highly treatable in the early stages by changing your habits and using tVNS.
Mood is often greatly affected by the state of our body. Levels of hunger, fatigue, quality of sleep and mild chronic pain or inflammation can all weigh down on your mood.
The majority of messages that are carried by the vagus nerve are sensory information about the state of bodily organs, which is all relayed back to the brain. Sensory information from internal, visceral organs is often vague and imprecise, so it is not always apparent to us that something is wrong. There are good reasons why we are built like this -- for more information read one of our earlier posts, but the downside of this is that if there are any underlying issues with parts of your body, we cannot always pinpoint the source of the problem and it could instead have an indirect effect on our psychology.
If the vagus nerve is somehow damaged, it will have a negative effect on essential bodily functioning, exacerbated by low quality sensory feedback to the brain. Rather than being experienced directly as pain, this often translates into a shorter temper, feelings of anxiety or severe depression. If you notice such changes happening slowly, it could be a sign that something isn’t quite right with your vagus nerve, or with your autonomic nervous system in general.
This symptom of low vagal tone is the one that people find the most surprising. But as the vagal nerve enters the brain, it merges with a part of the brain stem, which is in turn linked to many cognitive networks in the brain. The exact flow of information through these networks is not fully understood by scientists, but by following activation levels in these networks, it is possible for scientists to gain some idea of the brain’s interconnected pathways. By testing human performance in specific tasks, scientists can build up a picture of how vagal nerve activity affects brain functions.
Low vagal tone has, in such a way, been linked to memory, learning and concentration. It is not clear if a decline in vagal tone directly causes this kind of cognitive decline in old age, but there does seem to be some link between the two.
Difficulty concentrating, poor memory or difficulties in learning have also been linked to low vagal tone in younger people, though this is less common.
The main take-away from this post is that because the vagus nerve is such an important nerve with wide ranging function in the body, the symptoms associated with low vagal tone can be broad and sometimes unclear. It should be stressed that many of the symptoms we have touched on may also have other root causes. Just because you recognise some of these symptoms does not automatically indicate that you have a problem with the function of your vagus nerve. That is why we designed our vagal tone calculator, which we would recommend as the first touch point if you are at all concerned.