In our posts so far we’ve tackled the functions of the vagus nerve, how to stimulate it and its anatomy. We also have a vagal tone calculator which will give you some idea of how healthy your vagus nerve is and the problems that can develop when you have low vagal tone.
But how do problems with the vagus nerve develop and what causes them? How does the vagus nerve become damaged? Here, we will address these questions as best we can and look at the kinds of things that can cause problems with your vagus nerve.
There is actually a great deal that scientists still don’t understand about exactly how the vagus nerve becomes damaged, or its functioning becomes, in some way, compromised. It can be difficult to pinpoint all the causal processes that might lead to the damage. But we do understand some of the surrounding conditions that lead to it.
The causes of vagus nerve damage fall into three categories. Direct physical trauma to the nerve (1 and 2); damage from illness or disease (3 and 4); and damage due to life circumstances or lifestyle behaviours (5 to 7).
The vagus nerve is one of twelve cranial nerves that exit the brain via the cranium, rather than along the spine. The nerve wanders freely through the body without being shielded by any bone structure. So it is susceptible to some damage from direct injury, either to it directly or injury to the surrounding tissue. If some injury anywhere near the vagus nerve results in swelling that then applies prolonged pressure to the nerve, this can result in longer term damage.
Similarly to (1) above, if you have surgery in any location near the passage of the vagus nerve, the nerve can experience direct unintentional trauma or pressure from inflammation in the surrounding tissue. The vagus nerve travels down the neck and visits the heart, lungs, stomach and intestines. If you have had operations on any of these organs, there is a risk that there may be inadvertent damage caused to the vagus nerve. All surgery carries some such risks, but the risks are relatively low and your doctor would be able to advise you on this.
Postviral vagal neuropathy (PVVN) was first described by scientists about 20 years ago, but is still not well understood. Certain viruses such as the herpes virus is known to cause long lasting chronic symptoms in other cranial nerves, but it is still not known if this is the root cause of PVVN.
Patients usually present clinically with chronic symptoms associated with vagus nerve dysfunction, such as persistent coughs, swallowing difficulty or digestive issues.
Some studies correlate the onset of symptoms with a recent history of viral infections, often in the upper respiratory tract. The recent Covid19 pandemic has brought some such concerns to the fore, but still not enough is known.
HIV is another potential viral cause of PVVN that has been suggested in some clinical reports.
Other than direct viral infection, chronic illness such as diabetes can lead to elevated blood sugar levels which lead to inflammation and significant damage to blood vessels and the nervous system. Many nerves can be affected including the vagus nerve. Depending on which nerves are affected, symptoms will vary. Vagus nerve damage would be diagnosed in a similar way to PVVN.
The body always attempts to maintain balance -- what scientists refer to as “homeostasis”. We have described in previous blog posts how the two halves of the nervous system -- the sympathetic and the parasympathetic -- constantly work together in concert; to speed you up and slow you down in response to internal biological processes and changes in your environment.
During periods of stress the sympathetic branch of the nervous system becomes dominant and the parasympathetic branch becomes inhibited. For brief periods this enables your body to respond to the demands of life, get work done or meet other daily challenges. But if such heightened levels of stress persist and are not counteracted by periods of parasympathetic dominance, the lesser activity of this half of the nervous system can lead to a chronic inhibition. We touched a little on this when we talked in a previous blog post about the importance of giving your vagus nerve a regular ‘workout’.
This isn't really the result of damage per se, but one of the major reasons for a decline in vagal tone is the natural aging process. As we age, the nervous system has a propensity to become imbalanced; the sympathetic branch of the nervous system tends to dominate and the parasympathetic branch becomes less active. Scientists believe this is one the major causes of increased susceptibility in old age to diseases, heart problems, anxiety, depression and a host of other age related illnesses.
The declining function of the vagus nerve leads to higher levels of inflammation throughout the body, which scientists increasingly believe is one of the root causes of a host of age related ailments.
Poor dietary practices or addictions such as alcoholism or other drug abuse can lead to damage to any of the cranial nerves, including the vagus nerve. Symptoms will often accumulate over time and will become increasingly hard to treat. If the underlying causes are addressed early enough, symptoms will usually subside, but may benefit from some direct treatment.
Symptoms of vagus nerve damage can be very broad. The nerve plays a key role in the control of many of the body's organs and crucially of the digestive process. Problems can therefore manifest in a broad range of different ways.
The vagus nerve’s role in salivation and swallowing can manifest as a persistently dry mouth or dry cough and with difficulty swallowing.
The nerve's role in heartbeat regulation can be an underlying cause of poor heart rate variability; which in turn can lead to difficulty in maintaining healthy levels of exercise and poor recovery from physical training.
It’s importance in the regulation of the digestive system can impact not only the digestive process but the body’s regulation of inflammation, the immune system response and can cause psychological issues due to the gut-brain link -- an important holistic connection the scientist are only beginning to uncover as crucial to long term health and well-beiing.
We will explore all the possible symptoms in future posts, so please look out for those. But in the meantime, you could take our vagal tone calculator questionnaire and signup to our mailing list at the bottom of this page so you will be notified of our upcoming posts.
Physical trauma or trauma from surgery are typically the hardest to treat; your doctor would be able to advise you about this.
All the other root causes are highly treatable using a combination of change in primary behaviour, employing natural remedies and using non-invasive electrical or electromagnetic stimulation.
Many of these conditions readily respond to controlled vagus nerve stimulation (VNS) and in particular to transcutaneous auricular Vagus Nerve Stimulation (tVNS or taVNS).