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Thứ Ba, 15 tháng 2, 2022

US finds link between long COVID, viral effect on vagus nerve

By Amerigo Allegretto, AuntMinnie.com staff writer

February 15, 2022 -- Ultrasound found links between symptoms of long COVID-19 disease and the effects of the SARS-CoV-2 virus on the vagus nerve, according to research that will be presented at the European Congress of Clinical Microbiology & Infectious Diseases in April. A team led by Dr. Gemma Lladós from Germans Trias i Pujol Hospital in Badalona, Spain found that COVID-19 patients with symptoms of vagus nerve dysfunction mediated by SARS-CoV-2 also had nerve thickening, decreased esophageal and diaphragmatic mobility, and reduced maximum inspiratory pressures values.

"We need to improve our understanding of the mechanisms that may cause the persistence of symptoms to help patients and find interventions that can prevent and treat vagus nerve dysfunction," Lladós told AuntMinnie.com.

Stretching from the brain to the torso and into the heart, the vagus nerve plays an important role in bodily functions. These include controlling heart rate, speech, the gag reflex, transferring food from the mouth to the stomach, moving food through the intestines, and sweating, among others.

Post-COVID syndrome, also commonly known as long COVID, affects 10% to 15% of COVID-19 survivors, researchers wrote. Symptoms include persistent voice problems, difficulty in swallowing, dizziness, tachycardia, low blood pressure, and diarrhea.

Ultrasound images show longitudinal section of the left vagus at the cervical level
Spanish research has found possible links between long COVID and vagus nerve dysfunction in patients. Ultrasound images show (Above) longitudinal section of the left vagus at the cervical level, where there is a slight fusiform thickening, and (Below) an axial cut of left cervical vagus showing hyperechogenic perineural thickening. Images courtesy of Dr. Gemma Lladós et al.
an axial cut of left cervical vagus showing hyperechogenic perineural thickening

However, the researchers said the mechanism that causes long COVID is currently unknown. Therefore, Lladós et al wanted to determine the morphological and functional activities of the vagus nerve in their pilot study of long-COVID patients with dysfunction, using ultrasound and functional tests.

They looked at data from 22 patients who were selected from a cohort of 228 individuals who had at least one symptom suggestive of vagus nerve dysfunction. Patients had a median age of 44 years and presented between March and June 2021. Out of these, 20 were women.

Most common vagus nerve dysfunction symptoms in patients presenting with long COVID
Difficulty swallowing45%
Persistent voice problems45%

The study authors found that 19 patients had at least three dysfunction-related symptoms, and the median prior duration of symptoms was 14 months.

Six patients had mild vagus nerve thickening and higher echo on neck ultrasound scans. Thoracic ultrasound, meanwhile, showed flattened diaphragmatic curves in 10 patients. Ten out of 16 patients also showed reduced maximum inspiratory pressures.

"Radiologists may find by ultrasound in the lateral cervical area some images over the vagus nerve reflecting mild reactive inflammatory changes," Lladós said. "In addition, a flattened diaphragmatic curve visualized by chest ultrasound could translate into decreased diaphragmatic mobility during respiration."

The team also found eating and digestive dysfunction in patients, with 13 out of 18 having indication of trouble swallowing. Eight out of 19 patients also reported having their ability to deliver food to the stomach impaired, two of whom had difficulty swallowing. Acid reflux was also seen in nine of 19 patients, four of whom reported difficulty delivering food to the stomach and three having hiatal hernia.

The researchers also found abnormalities in voice function for eight out of 17 patients, seven of these reporting dysphonia, or persistent voice problems.

Lladós told AuntMinnie.com that the team wants to compare their results with healthy controls and with patients infected by SARS-CoV-2 without the persistence of symptoms. He said the aim is to know if there is more morphological and functional involvement of the vagus nerve in infected patients.

The team's findings will be presented at the European Congress of Clinical Microbiology & Infectious Diseases in Lisbon, Portugal, which will be held April 23-26.

expert reaction to conference abstract looking at long COVID and the vagus nerve 

A conference abstract presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) Annual Meeting looks at vagus  nerve dysfunction in long COVID.


Dr David Strain, Chair of BMA Board of Science and Clinical senior lecturer and honorary consultant, University of Exeter Medical School, said:

“This is a conference abstract. The full paper is not available and therefore it is not possible to properly critique the data. It has also not undergone peer-review.

“The study appears to add to a growing collection of data suggesting at least some of the symptoms of long COVID is mediated through a direct impact on the nervous system. There is a well-established knowledge base that associates the vagus nerve with some of the cardinal features of long COVID such as palpitations, night sweats and gastrointestinal disturbances. Establishing vagal nerve damage is useful information, as there are recognised, albeit not perfect, treatments for other causes of vagal nerve dysfunction that may be extrapolated to be beneficial for people with this type of Long COVID.

“It is important to caveat that not all symptoms of long Covid may be associated with the direct impact of vagal dysfunction and there are many other presentations that will need further investigation. Further, we must remember that association is not necessarily causation. The Vagus nerve (so named because of its vagrant nature as it wanders through the body) is one of the longest nerves in the body and the longest and most complex of the cranial nerves. It is entirely possible that people susceptibility to nerve damage are at the greatest risk of developing long Covid; in this case this observation tells us little more than  nerve damage is an result of COVID, this is greater in those with Long Covid, and the damage is easy to detect in a long, complex nerve. Indeed, it is unlikely that vagal nerve damage could account for many other symptoms such as brain fog or muscle aches and pains. 

“Treatment with agents that have been demonstrated to be efficacious against vagal nerve dysfunction may provide relief for patients, however are unlikely to treat the underlying diagnosis, and thus patients would be at risk of rebound symptoms once treatment stops. Randomised Controlled trials into a Long Covid treatments will soon be commencing considering treatments for both underlying causes and symptomatic control I’m sure we will be able to evaluate these agents will only know when we respectively start with the symptoms whether reversal of this damage.”



Conference abstract: ‘Vagus nerve dysfunction in post-COVID-19 condition’ by G. Lladós et al was presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) Annual Meeting to be held in Lisbon from 23-26 April.

The full study is not available and this research has not undergone peer-review. 



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