Scientists have found no trace of SARS-CoV-2 in the brains of people with the infection. However, they observed vascular damage caused by the inflammatory response of the body in the postmortem brain of patients tested positive for COVID-19, suggesting that the virus may attack the organ indirectly.
The scientific advances that researchers have made over the past year have greatly helped to learn about the new coronavirus that first appeared in Wuhan, China.
Initially, COVID-19 was characterized by fever, sore throat, cough, and shortness of breath, all of which were manifestations of a respiratory illness.
However, a spectrum of other clinical manifestations, including headache, abdominal pain, diarrhea, and loss of taste and smell, have been reported. Researchers have also found evidence that the new coronavirus damages the heart, causes blood clots and causes gastrointestinal problems.
While the pandemic affects older adults and people with pre-existing health conditions disproportionately, younger adults are not immune.
Earlier this year, reports showed that younger adults who contracted the new coronavirus showed more neurological symptoms, including mental confusion, headaches, dizziness, uncoordinated muscle movements, seizures, and an increased risk of stroke.
These are just a few examples of how much we have learned and how much we still need to learn to fully understand the SARS-CoV-2 virus. New research suggests that the virus may also cause a brain vessel injury.
The research authors presented their findings as a correspondence article in the New England Journal of Medicine.
The study was conducted by researchers from the National Institute of Neurological Disorders and Stroke (NINDS) in Bethesda, MD, and other institutions across the United States.
They examined post-mortem brain tissue samples from 16 patients in New York City and from three patients in Iowa City who died between March and July 2020 and tested positive for COVID-19 before or after death.
Patients were between 5 and 73 years old, and their medical history usually showed pre-existing conditions, including obesity, heart disease, or high blood pressure and diabetes.
Before death, treatment was primarily aimed at respiratory infection, and only two patients showed inflammatory delirium.
The researchers also used MRI images to detect abnormalities in the brain tissue. This included the olfactory bulb, a brain region involved in the sense of smell, as odor loss is known to be one of the first symptoms of COVID-19.
Another brain region they examined was the brain stem, which is crucial to human survival. It regulates sleep and eating habits and controls the heart rate and the rate of respiration.
To assess the relevant brain tissue, the researchers used a staining method called immunohistochemistry, which allows the visualization of proteins in cells and tissues.
Of the 19 brain tissue samples, 13 were taken and 10 showed brain abnormalities. Further analysis showed blood vessels.
In nine patients, the presence of lesions suggested that they were brain vessel leaks. There were also signs of a leaking blood protein called fibrinogen in the brain. According to the authors, this is evidence of inflammation caused by an overreactive immune system that fights infection.
In ten patients, MRI images showed hip intensities corresponding to congested blood vessels and an accumulation of fibrinogen in the environment.
“Our results suggest that it may be caused by the body’s inflammatory response to the virus,” says Dr. Avindra Nath, clinical director of the NINDS at the National Institutes of Health (NIH) and the senior author of the study.
Interestingly, the SARS-CoV-2 virus was not found in any of the patients’ brain tissue. However, the authors write that there is no way to know if the virus was present at some point:
“It is possible that the virus was lifted at the time of death, or that the viral copy numbers below our detection level were lower.”
Looking more closely at the injury spots, the researchers found that immune cells, such as T cells, are present around the brain, further supporting evidence of an inflammatory response in the brain.
“We were completely surprised. Originally we expected to see damage caused by oxygen deficiencies, ”says Dr Nath. “Instead, we have seen multifocal areas of damage commonly associated with strokes and neuro-inflammatory diseases.”
Because the new coronavirus was not detected in the brain tissue of the deceased patients, the authors say it is too early to determine whether there is a link between the neurological effects associated with COVID-19 and the vascular injuries present in these study was observed.
“In the future, we plan to study how COVID-19 harms the blood vessels of the brain and whether it produces some of the short- and long-term symptoms we produce in patients,” says Dr. Nath.
As scientists continue to investigate all the effects of SARS-CoV-2 infection, it is important to slow down the spread of the virus.
The public can do their part to minimize the risk of transmission by wearing a face mask, doing social distance and staying home where possible.
Adherence to these guidelines is essential as vaccination efforts continue worldwide.
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