The virus may have been removed by the time of death, or the number of viral copies was lower than the detection level.
In a recent study conducted by the National Institutes of Health, investigators regularly observed spotted features of damage caused by thinning and leaking cerebral blood vessels in tissue samples from patients who died quickly after contracting coronavirus 2019 (COVID-19) has. However, they did not see any signs of an infection of the SARS-CoV-2 virus in the collected samples, possibly indicating that the damage was not caused by a direct virus attack.
The findings, published in the New England Journal of Medicine, contributes to the growing body of evidence that a COVID-19 infection has a kind of neurological impact. There are widespread reports of people 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 have other neuropathologies such as strokes. While evidence of the virus has been found, investigators are still trying to understand how COVID-19 affects the brain.
The team behind the study analyzed brain tissue samples from 19 patients who died shortly after contracting the disease, ranging in age from 5 to 73 years old. The time of death ranged from a few hours after COVID-19 to 2 months. Many of the patients have one or more risk factors such as obesity, diabetes and other cardiovascular problems.
Using a strong magnetic resonance imaging (MRI) scanner 4 to 10 times as sensitive as most common MRI scanners, the researchers examined the olfactory bulbs and brainstems of the tissue samples. They noted that both regions displayed multiple bright and dark spots, indicating inflammation and bleeding.
They then examined the samples under a microscope and found that the clear spots showed thinner blood vessels leaking proteins into the brain, causing an immune response. They also saw that the dark spots clotted, as well as leaking blood vessels, but there was no immune response. However, using various methods to detect genetic material or proteins of SARS-CoV-2, they found no evidence of the virus in the tissue samples.
“We found that the brains of patients who contract SARS-CoV-2 infection may be susceptible to microvascular damage. Our results suggest that it may be caused by the body’s inflammatory response to the virus,” Avindra said. Nath, senior author about said the study. “We hope these results will help physicians understand the full spectrum of problems patients may experience, so that we can come up with better treatments.”