Jul 27, 2021 16:00:00

Research results show that people who suffer from coronavirus infection for a long time have 'nerve damage to the cornea'

The new coronavirus infection (COVID-19) may have various symptoms that persist for a long period of time, even if it is mild, and this is also called ' Long Covid'.

Research results have been reported that in the cornea of patients who experience such long COVID, abnormalities such as 'damaged nerve cells' and 'increased immune cells' are observed.

Corneal confocal microscopy identifies corneal nerve fibre loss and increased dendritic cells in patients with long COVID | British Journal of Ophthalmology
https://bjo.bmj.com/content/early/2021/07/08/bjophthalmol-2021-319450

Nerve damage in cornea could be sign of'long COVID,' study hints | Live Science
https://www.livescience.com/nerve-damage-cornea-long-covid.html

Something in Patients' Eyes Could Reveal The Presence of'Long COVID', Doctors Say
https://www.sciencealert.com/something-in-your-eyes-may-reveal-if-you-ve-got-long-covid-scientists-say

Many cases of long COVID have been reported , and it is said that there are many cases that interfere with daily life after discharge. In a study published in March 2021, patients with long COVID had neurological symptoms such as decreased thinking ability, headache, numbness, taste disorder, olfaction disorder, muscle pain, dizziness, blurred vision, and tinnitus. It was shown to appear in.

What are the symptoms that 85% of patients who have suffered from a new coronavirus infection for a long time experience? --GIGAZINE

Dr. Rayaz Malik of Weill Cornell Medicine-Qatar , a medical college in Qatar, thought that the symptoms of long COVID could be caused by 'damage to nerve fibers extending from the cell bodies of nerve cells.'

Malik and colleagues are studying the damage and loss of nerve fibers found in patients with neurodegenerative diseases such as multiple sclerosis and diabetes, and the symptoms reported by patients with long COVID are nerve fiber damage. It is similar to the patient. Damage to nerve fibers causes various symptoms because nerve fibers are important for transmitting sensory information such as pain and body temperature and for moving muscles.

To investigate the relationship between symptoms seen in patients with long COVID and nerve fiber damage, the research team conducted a non-invasive procedure called corneal confocal microscopy (CCM). The research team gathered 40 subjects who recovered from COVID-19 1 to 6 months before the study and 30 healthy subjects who had no history of COVID-19, and took snapshots of corneal neurons with CCM. I took a picture. Former COVID-19 patients also answered questions about long COVID symptoms, with 22 out of 40 reporting protracted symptoms such as headache, dizziness, and numbness, and 13 12 weeks after infection. He answered that the symptoms continued even after the lapse.

The research team examined the total number of nerve fibers in the cornea from a snapshot of the cornea and evaluated the length of the fibers and the degree of branching. When nerve fiber damage is seen in the cornea, similar damage is often seen in other parts of the body, Dr. Malik said, 'The cornea is very good at nerve damage elsewhere in the body. It's like a barometer. '

As a result of evaluating nerve fiber damage, patients with COVID-19 followed by long COVID symptoms had significantly more nerve fiber damage in the cornea than patients without long COVID symptoms. Turned out. In addition, the degree of nerve fiber damage is associated with the severity of long COVID, and the more severe the damage, the more severe the symptoms of long COVID.

In addition, when the cornea of a former patient with COVID-19 and a healthy subject was compared, it was found that the subjects who recovered from COVID-19 had a large number of immune cells called

dendritic cells existing in the cornea. Compared to healthy subjects, former COVID-19 patients who did not experience long COVID had twice as many dendritic cells, and subjects who experienced long COVID had five times as many dendritic cells.

Dendritic cells take up antigens such as viruses and bacteria and have the role of activating immune cells that fight the antigens that actually invaded. Therefore, the fact that a large amount of dendritic cells were confirmed in the cornea of subjects who experienced long COVID may indicate that nerve fibers were damaged by the runaway immune response as a result of the progress of the immune process even after infection with the new coronavirus. It suggests that there is.

This study is an observational study only, and it is unclear whether the immune response actually caused nerve fiber damage. but,

A preliminary report published in the medical journal PAIN in 2020 also suggests that long COVID is associated with nerve fiber damage. The report points out that there is existing evidence that COVID-19 nerve damage is not due to viral infections, but to inflammation caused by the immune response.

'Infection (of the new coronavirus) will accelerate the activity of immune cells to fight enemies and cause collateral damage,' said Dr. Anne Louise Oaklander of Harvard University, author of a report published in PAIN. He commented that nerve fiber damage could be caused by immune cells. The findings of Dr. Malik and colleagues provide new evidence for nerve fiber damage in long COVIDs and help understand causes and treatments.

The CCM used in this study is mainly used for research purposes, and it is unlikely that it will be used for the diagnosis of long COVID in general hospitals. Therefore, clinically, a method of taking a skin sample of the foot and comparing it with the result of the interview may become the standard.

Due to the small sample size of the subjects in this study, Dr. Malik acknowledged the need for a larger study and plans to do a similar study in a larger group in the future. In addition, the subjects will be followed up to see how the state of nerve cells in the cornea changes.