Blood vessel damage and inflammation in the brains of deceased COVID-19 patients suggest the damage is not caused by the virus, but the body's immune response to it.
Researchers from the U.S. National Institutes of Health (NIH) consistently found signs of damage caused by thinning and leaky brain blood vessels in tissue samples from patients who died shortly after getting COVID-19.
The researchers saw no signs of the virus in the tissue samples, which they said may mean that the damage was not caused by the virus itself.
"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 Dr. Avindra Nath, clinical director at the NIH's National Institute of Neurological Disorders and Stroke.
"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," he explained in an NIH news release.
For the study, Nath and his team examined brain tissue from 19 patients who died after having COVID-19.
In 16 patients, the investigators found bright spots, which contained blood vessels that were thinner than normal and sometimes leaking blood proteins into the brain. The spots were surrounded by T cells — signs of an immune response.
In contrast, dark spots contained clotted and leaky blood vessels but no immune response.
"We were completely surprised," Nath said. "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."
The researchers, however, saw no signs of infection in the brain samples.
"So far, our results suggest that the damage we saw may not have been caused by the SARS-CoV-2 virus directly infecting the brain," Nath said. "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."
The findings were published Dec. 30 in the New England Journal of Medicine.