Since the start of the pandemic, researchers and clinicians have found that COVID-19 may start in the respiratory system, but it can affect many more parts of the body. The virus can affect people in very different ways, but in some individuals, it's known to cause blood clots throughout the circulatory system and can also damage organs like the kidneys, liver, pancreas, and spleen. It may also cause neurological problems like headache, dizziness, cognitive dysfunction, and notably, the loss of the sense of smell.
Scientists have been trying to learn more about whether the brain disruptions associated with COVID-19 infections are happening because the blood vessels in the brain are becoming inflamed or are experiencing clotting, or whether the virus is entering cells in the brain directly.
A new study by scientists at the National Institutes of Health (NIH) sought to assess that question by examining brain specimens from patients that died from COVID-19. Their findings indicated that the virus is not infecting the brain, but it is causing serious damage to blood vessels there.
"We found that the brains of patients who contract infection from SARS-CoV-2 may be susceptible to microvascular blood vessel damage. Our results suggest that this may be caused by the body's inflammatory response to the virus," said Avindra Nath, M.D., the clinical director at the NIH's National Institute of Neurological Disorders and Stroke (NINDS) and the senior author of the study reporting these findings in NEJM. "We hope these results will help doctors understand the full spectrum of problems patients may suffer so that we can come up with better treatments."
In this work, the researchers were able to examine samples of brain tissue from nineteen patients ranging in age from five to 73 years old. Some of them had died suddenly while others died at home or in the hospital. High-powered magnetic resonance imaging scans were taken first to identify areas of the brain tissue samples that warranted a closer look.
When they focused on those areas, they saw blood vessels that were abnormally thin, and in some cases, blood proteins were leaking out into the brain. There were bright spots, which is evidence of an immune response, potentially because of the leaking proteins. The investigators also identified dark spots that indicate bleeding. There were leaky blood vessels in these dark areas, but not an immune response.
"We were completely surprised. Originally, we expected to see damage that is caused by a lack of oxygen. Instead, we saw multifocal areas of damage that is usually associated with strokes and neuroinflammatory diseases," said Dr. Nath.
The scientists looked for evidence of SARS-CoV-2 infection in brain cells by using several different methods for identifying genetic material from the virus.
"So far, our results suggest that the damage we saw may not have been not caused by the SARS-CoV-2 virus directly infecting the brain," said Dr. Nath. "In the future, we plan to study how COVID-19 harms the brain's blood vessels and whether that produces some of the short- and long-term symptoms we see in patients."
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