The virus may have been cleared by the time of death or viral copy numbers were below the level of detection.
In a recent study conducted by the National Institutes of Health, investigators routinely observed spotted hallmarks of damage caused by thinning and leaky brain blood vessels in tissue samples of patients who died quickly after contracting the coronavirus disease 2019 (COVID-19). However, they did not see any signs of an infection from the SARS-CoV-2 virus in the collected samples, potentially suggesting that the damage was not caused by a direct viral attack.
The findings, published in the New England Journal of Medicine, adds to the growing body of evidence that an infection from COVID-19 has some sort of neurological impact. There have been widespread reports of those with the virus experiencing symptoms such as delirium, fatigue, headaches and loss of sense of smell and taste. The disease has also caused patients to suffer other neuropathologies like strokes. While some evidence of the virus has been found, investigators are still attempting to understand how COVID-19 impacts the brain.
The team behind the study analyzed brain tissue samples of 19 patients who had died shortly after contracting the disease, with ages ranging from 5 to 73 years old. The time of death varied from a few hours after getting COVID-19 to 2 months. Many of the patients had one or more risk factors like obesity, diabetes and other cardiovascular issues.
Using a high-powered magnetic resonance imaging (MRI) scanner 4 to 10 times as sensitive as most common MRI scanners, the investigators examined the olfactory bulbs and brainstems of the tissue samples. They observed that both of the regions showed multiple bright and dark spots, which indicate inflammation and bleeding.
They then examined the samples under a microscope and found that the bright spots showed thinning blood vessels that were leaking proteins into the brain, triggering an immune reaction. They also saw that the dark spots had clotted, as well as leaky, blood vessels but no immune response. However, using several methods for detecting genetic material or proteins from SARS-CoV-2, they found no evidence of the virus in the tissue samples.
"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," Avindra Nath, senior author on the study said. "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."