Nerve damage and accumulation Immunity Corneal cells can be a sign of “long COVID”. This is a long-term syndrome that appears in some people after COVID-19 infection.
Experts have told Live Science that these preliminary results need to be validated by a large number of people with long COVIDs or known long-haul carriers of COVID-19. However, the findings suggest something that scientists have already suspected: because of peripheral nerve damage, some symptoms of long COVID appear, she said.
Long-distance transporters of COVID-19 experience a variety of symptoms, often reporting neurological problems such as headaches, numbness, loss of smell and “brain fog”, and thought and concentration problems. I have. Live science previously reported.. This set of symptoms suggests that long COVIDs can result from partial injury. Nervous Dr. Rayaz Malik, a senior author and medical professor and consultant physician at Weill Cornell Medicine-Qatar in Doha, describes cells in the body.
Related: 20 of the worst fads and pandemics ever
In particular, Reserve evidence suggest Its long COVID can be accompanied by damage to small nerve fibers, thin wires that branch off from specific nerve cells in the body and convey sensory information such as pain, temperature, and itching to the central nervous system. Fibrous nerve cells also help control involuntary physical functions, such as: Heart rate And defecation; therefore, damage to these cells can cause a variety of symptoms.
Malik and his colleagues Diabetes Neurodegenerative diseases such as Multiple sclerosisThey found that people with long COVIDs seemed to share symptoms similar to those of these patients and decided to investigate their potential associations.
The team took a snapshot of the nerve cells in the cornea, the transparent layer of the cornea, using a technique called corneal confocal microscopy (CCM). Eye It covers the pupil and iris. The team used a non-invasive procedure to count the total number of fibrillar neurons in the cornea and at the same time assess the length and extent of branching of those fibers. In their study under other conditions, the team found that when they found damage to the fibrillar nerves of the cornea, it often indicated that there was similar damage elsewhere in the body. “It’s like a very good barometer of nerve damage elsewhere,” Malik explained.
On Monday (July 26), according to a new study British Journal of OfftalmologyPeople who develop neurological symptoms after COVID-19 infection show significant fibrillar nerve loss in the cornea compared to COVID-19 survivors who do not have prolonged neurological symptoms. In addition, the degree of nerve fiber damage correlates with the severity of the participant’s symptoms, meaning that the greater the nerve damage, the more pronounced the symptoms.
A small study included 40 individuals who recovered from COVID-19 1 to 6 months before evaluation. Of the total group, 29 recovered from COVID-19 at least 3 months ago. In addition to obtaining a corneal scan, each participant completed a study that included questions regarding the neurological symptoms of long COVID.
They also filled out a questionnaire about neuropathic pain. This can include numbness, a tingling sensation, a burning sensation, and weakness. UC Davis Health.. Another questionnaire helped researchers identify the location and severity of myalgia in participants. It also helped flag additional symptoms such as fatigue and bowel problems, the authors say.
Of the 40 participants, 22 showed prolonged neurological symptoms such as headache, dizziness, and numbness 4 weeks after recovery from the first COVID-19 infection. And 13 of the 29 people who recovered for at least 3 months reported showing neurological symptoms 12 weeks after infection. “Looking at the graph, it’s very clear … the number of people with neurological symptoms is definitely decreasing,” said Malik, although other participants are not.
The authors of the study also evaluated 30 healthy individuals with no history of COVID-19 infection for comparison. They found that all COVID-19 survivors had a large number of immune cells in the cornea compared to these 30 control participants. More specifically, an abnormally large number of immune cells, called dendritic cells, have emerged that help inform the immune system of foreign invaders.
Related: 11 amazing facts about the immune system
People with prolonged neurological symptoms showed about a 5-fold increase in these dendritic cells compared to healthy controls. Those without neurological symptoms showed an approximately 2-fold increase.
“So there’s obviously something, there’s still an ongoing immune process,” Malik said, even after the first COVID-19 infection was cleared. “So there is an immune trigger that is switched on and it may take some time for it to settle down,” he said. And in the meantime, this runaway immune response damages nerve cells.
New studies cannot prove that the immune response caused the observed nerve damage.However, this idea is that most neurological damage from COVID-19 inflammationAccording to the journal’s 2020 commentary, it is not due to a virus that directly infects nerve cells. pain..
“It’s not an infectious disease in itself, it’s an immune response,” said Dr. Anne Louise Oaklander, an associate professor of neurology at Harvard University School of Medicine and an assistant pathologist at Massachusetts General Hospital. study. “The infection spins immune cells to start firing, fighting enemies, and causing collateral damage,” she said. In this case, fibrillar neurons can be the victim of friendly fire.
Oaklander added that she is “excited” about the new study because the new study provides evidence of fibrillar nerve injury in long-term COVID patients. This data is useful for biomedical researchers like Oaklander who are trying to understand the causes of long COVIDs and how to treat the syndrome. But so far, she said, the study does not always provide a solution for patients.
In their treatise, Malik and his colleagues suggest that a corneal confocal microscope can be used as a diagnostic tool to help identify people with long COVIDs, especially those with neurological symptoms. However, the technology is currently used primarily for research and is not widely available in clinical practice, Oaklander said.
Gold standards for assessing fibrillar nerve damage include taking small ones skin A biopsy from the patient’s leg and measurement of nerve endings in it, she said. Doctors can screen for symptoms of nerve damage through written surveys and neurological examinations, but currently a skin biopsy is needed to confirm the diagnosis. For this reason, Oaklander suggests that future studies of long COVID patients would be helpful if they included these skin biopsies and a standard questionnaire used to screen for small fibrous sensory neuropathy. did. (“Neuropathy” refers to damage to nerves that pass through the body outside the brain and spinal cord.)
For now, Malik said his group will follow up with a group of the first 40 participants to see how corneal nerves and long COVID symptoms change over time. rice field. In addition, they plan to replicate their study with a larger group of patients to validate the results.
“People may say,’Well, 40 patients aren’t enough.’ I agree. We need a bigger study,” Malik said. Ultimately, assuming that results can be confirmed in a larger cohort, this series of studies may provide useful hints on how physicians can treat long COVIDs, he added. There are treatments for post-infection neuropathy. The question is whether it will work for COVID patients with long post-infection microfiber neuropathy, and if so, how optimally it can be applied.
Originally published in Live Science.
