Everyone knows what "neuropathy" is. It is that sense of tingling/numbness/pins and needles that diabetics get in their feet. But there are other types of neuropathy, some of which are much more dangerous.
First, a little biology. The vagus nerve is a major player in the parasympathetic autonomic nervous system. This is the system that helps us relax, chill and digest our food. There is a parallel autonomic nervous system that is called the sympathetic which is more commonly known as the "fight or flight" nervous system which speeds up our heart and breathing and cuts down blood flow to "unnecessary" organs (like the digestive tract) in times of stress and increases our inflammatory response to threats such as infectious disease.
The vagus nerve is actually a pair of cranial nerves (meaning they emerge directly from the brain via holes in the skull rather than from the spine) These nerves are very long, reaching all the way from the brain to the abdomen and they are very important.
Vagal neuropathy can occur in diabetics, alcoholics, in those with vitamin deficiencies--and after some viral upper respiratory infections. The vagus nerve controls 1) heart rate (slows it down) 2) inflammation (suppresses it) 3) swallowing (keeps you from choking or aspirating food and liquids which can lead to pneumonia 4) speech (via the recurrent laryngeal nerve that controls the larynx or voice box and the palatoglossal muscle of the tongue which is necessary for swallowing and for fluent speech 5) digestion (stomach acid production, gallbladder contractions, colon peristalsis--except for the rectum that is controlled by the sacral parasympathetics) 6) sweating which regulates temperature.
What happens when your vagus nerve stops working? Depends. If only one of the two nerves crashes you will have trouble swallowing and speaking and a hoarse voice and maybe a nagging cough and aspiration. If both nerves fail at the same time, you will have unchecked sympathetic autonomic nervous system activity--which means racing heart, shakiness, insomnia, migraine headache exacerbation (if you suffer from migraines), dry mouth, loss of sweating and temperature regulation, increased inflammation throughout your body and especially in your lungs, fatigue since your heart is racing even when your are sedentary, poor perfusion in your extremities making your muscles feel weak and anxiety(which your doctor may write off as a bad case of "the nerves" not realizing exactly what "nerve" is acting up).
Now, I am going to get personal. I had a virus--actually four of them. Three bouts with influenza, the last a really bad case with two weeks of cough/fever/weakness and then another nasty little bug called metapneumonia virus--all in the space of four months. Every time I got one of these bugs, my mouth would get a little bit drier, my speech would become a little less fluent and my voice would become a little more hoarse. Each time I got over the influenza these symptoms would begin to get better---only to return with the next bout of flu (and yes, I had a flu vaccine, but they just do not work the way they used to maybe because we grow the virus in Tamiflu laden chicken eggs) Until the final virus, when I began to choke (aspirate) anything I ate, my resting pulse shot up to 120-140, my arms up to the elbows and legs up to knees and the anterior half of my tongue felt like blocks of ice. I also stopped sweating and having hot flashes, my seasonal allergies suddenly went away (the only good part of vagal neuropathy), I could not have a bowel movement even with laxatives. Finally, on day eight of the metapneumonia virus, my oxygen saturation dropped and I had pneumonia. Oh, and did I mention that I also lost my sense of smell? Since I did not know what I had I assumed the worst and went to the hospital where I was admitted and placed on the Covid Death Watch. However, I was lucky. I did not have COVID. I had metapneumonia virus. Which acts an awful lot like COVID in its symptoms but which does not (usually) have COVID's lethality.
The metapneumonia virus is long gone. Two months have passed. Buy my vagus nerves still have not returned to full function. Occasionally I can sweat and occasionally I have a hot flash. Sometimes my voice is not a frog croak and sometimes I can swallow liquids without choking. My pulse is kept at a nice steady 80 by beta blockers, prescription medications. I am doing exercise, external vagal stimulation, vagal breathing, mediation and imagery in an attempt to heal my vagus nerves. I use medical nicotine (I have never been a smoker but I have found that a combo of 7 mg nicotine patches supplemented with small doses of lozenges relieve the ice cold extremities and improve my muscle strength and digestion, and also, surprisingly my oxygen saturation which used to be 99% and then fell to 94-95% post metapneumonia virus but now is back to a nice healthy 98% possibly from the anti-inflammatory effects of nicotine which is a vagal agonist meaning it boosts the vagal nervous system). I have added Vit E and zinc to my usual regimen since they help with nerve growth. And I have found that extra potassium is a must--probably because unchecked adrenaline lowers blood potassium levels.
Why is understanding the vagus nerve important in time of COVID? The current best hypothesis about why COVID suddenly turns lethal in some people is that it weakens the vagus nerve (as some respiratory viruses can) which causes sudden increase in lung inflammation and fluid accumulation and stiffness and finally death. In experiments on rodents, if you sever both vagal nerves at the level of the neck, the animals quickly die from pulmonary inflammation and edema, even if the animals are not exposed to any respiratory pathogens. If you severe the nerves above the abdomen they develop inflammatory peritonitis and die. If you preload them with nicotine, they don't get the inflammatory peritonitis. (The last journal article was the reason I decided to try medical nicotine for myself)
What does this mean for folks out there who have not had COVID yet? Treasure your vagal nerves! Pamper them! Exercise every day (it boosts vagal tone). Practice yoga/meditation/vagal breathing (quick inhalation filling up the entire lung meaning the abdomen should swell followed by prolonged, slow, smooth exhalation.) If you have sleep apnea, make sure that it is controlled---nothing suppresses the vagal system and boosts the sympathetic system like having multiple spells of low oxygen and high adrenaline at night while you sleep. Control your diabetes. Don't drink to excess. Eat a balanced diet and if you have pernicious anemia (impaired ability to absorb Vitamin B12) take your supplements.
Oh, and of course practice social distancing, wear an effective mask (plus or minus a face shield depending upon your job), wash your hands. Because the best treatment for COVID is still prevention.
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