In a new study, researchers found that many of the symptoms connected to post-COVID syndrome (PCC, also known as long COVID) could be linked to the effect of the virus on the vagus nerve—one of the most important multi-functional nerves in the body.
The vagus nerve extends from the brain down into the torso and into the heart, lungs and intestines, as well as several muscles including those involved in swallowing.
As such, this nerve is responsible for a wide variety of bodily functions including controlling heart rate, speech, the gag reflex, transferring food from the mouth to the stomach, moving food through the intestines, sweating, and many others.
Long COVID is a potentially disabling syndrome affecting an estimated 10–15 percent of subjects who survive COVID-19.
In the study, the team proposes that SARS-CoV-2-mediated vagus nerve dysfunction (VND) could explain some long COVID symptoms, including dysphonia (persistent voice problems), dysphagia (difficulty in swallowing), dizziness, tachycardia (abnormally high heart rate), orthostatic hypotension (low blood pressure) and diarrhea.
The researchers tested 22 long COVID patients with symptoms suggestive of VND.
Almost all had at least three VND-related symptoms. The median prior duration of symptoms was 14 months.
Six of 22 patients (27 percent) displayed alteration of the vagus nerve in the neck shown by ultrasound—including both thickening of the nerve and increased ‘echogenicity’ which indicates mild inflammatory reactive changes.
Further tests showed flattened ‘diaphragmatic curves’ in 10 out of 22 (46 percent) patients (which translates to a decrease in diaphragmatic mobility during breathing, or more simply abnormal breathing).
A total of 10 of 16 (63 percent) assessed individuals showed reduced maximum inspiration pressures, showing the weakness of breathing muscles.
Eating and digestive function was also affected in some patients, with 13 of 18 assessed (72 percent) having a positive screen for self-perceived oropharyngeal dysphagia (trouble swallowing).
8 of 19 patients had their ability to deliver food to the stomach impaired, with two of these eight (25 percent) reporting difficulty in swallowing.
Gastroesophageal reflux (acid reflux) was observed in nine of 19 (47 percent) individuals.
The team says most long COVID subjects with vagus nerve dysfunction symptoms had a range of significant, clinically-relevant, structural and/or functional alterations in their vagus nerve, including nerve thickening, trouble swallowing, and symptoms of impaired breathing.
Our findings so far thus point at vagus nerve dysfunction as a central pathophysiological feature of long COVID.
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The study was presented at the European Congress of Clinical Microbiology and Infectious Diseases and was conducted by Dr. Gemma Lladós et al.
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