A new study sheds light on the symptoms of long Covid-19 – What researchers have to say about the pneumogastric nerve’s role in the novel chronic disease caused by the coronavirus.
Many of the symptoms associated with the post-COVID syndrome also known as long COVID may be linked to the virus’s influence on the vagus nerve, one of the body’s most essential multi-functional nerves, according to new research.
The vagus nerve runs from the brain to the torso, where it passes via the heart, lungs, and intestines, as well as various muscles, including those that control swallowing.
As a result, this nerve is in charge of a range of biological activities, including heart rate control, speaking, the gag reflex, food transfer from the mouth to the stomach, food movement through the intestines, perspiration, and more.
Long COVID is a potentially debilitating disease that affects an estimated 10-15% of COVID-19 survivors. The authors hypothesize that SARS-CoV-2-mediated vagus nerve dysfunction (VND) could explain some long-term COVID symptoms such as dysphonia (persistent voice problems), dysphagia (difficulty swallowing), dizziness, tachycardia (abnormally fast heart rate), orthostatic hypotension (low blood pressure), and diarrhoea.
The authors conducted a pilot, thorough morphological and functional examination of the vagus nerve including imaging and functional testing in a prospective observational cohort of long COVID participants with symptoms suggestive with VND. 228 (66%) of the 348 patients in the study showed at least one symptom suggestive of VND. Between March and June 2021, the current study was conducted on the first 22 people with VND symptoms (10% of the total) seen in the Long COVID Clinic of University Hospital Germans Trias I Pujol. The research is still ongoing, and patients are still being recruited.
20 (91 percent) of the 22 people studied were women, with a median age of 44. The most common VND-related symptoms were diarrhoea (73 percent), tachycardia (59 percent), dizziness, dysphagia, and dysphonia (45 percent each), and orthostatic hypotension (14 percent ). At least three VND-related symptoms were experienced by nearly all (19 participants, or 86 percent). Prior to diagnosis, the median duration of symptoms was 14 months. Ultrasound revealed thickness of the vagus nerve in the neck in six of 22 patients (27 percent), as well as enhanced ‘echogenicity,’ which signals moderate inflammatory reactive alterations.
A thoracic ultrasonography revealed flattened ‘diaphragmatic curves’ in 10 of the 22 individuals (46 percent) (which translates a decrease in diaphragmatic mobility during breathing, or more simply abnormal breathing). A total of 10 of the 16 people tested (63 percent) had lower maximal inspiration pressures, indicating that their breathing muscles were weak.
Some patients’ eating and digestive functions were also impacted, with 13 of 18 patients (72 percent) having a positive screen for self-perceived oropharyngeal dysphagia (trouble swallowing). An examination of gastric and bowel function in 19 patients found that 8 (42 percent) had difficulties delivering food to the stomach (through the oesophagus), with two of these 8 (25 percent) having trouble swallowing. Gastroesophageal reflux (acid reflux) was found in 9 of 19 (47 percent) people, with 4 of them (44 percent) having trouble delivering food to the stomach and 3 of them (33 percent) having hiatal hernia (when the upper section of the stomach bulges through the diaphragm into the chest cavity).
A Voice Handicap Index 30 test (a typical approach to measure voice function) was abnormal in 8 of the 17 patients (47 percent), with dysphonia in 7 of the 8 cases (88 percent).
According to the study which to be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2022, Lisbon, 23-26 April), “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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