Brain damage not caused by direct attack of COVID-19, study says

In an in-depth study of how COVID-19 affects a patient’s brain, researchers at the National Institutes of Health have consistently spotted signs of damage from thinning and leaking brain blood vessels in samples tissue from patients who died shortly after contracting the disease.

Additionally, they saw no signs of SARS-CoV-2 in the tissue samples, suggesting the damage was not caused by a direct viral attack on the brain. The results were published as correspondence in the New England Journal of Medicine.

We have found that the brains of patients who acquire SARS-CoV-2 infection may be susceptible to microvascular damage to blood vessels. Our results suggest that this may be caused by the body’s inflammatory response to the virus. We hope these results will help physicians understand the full range of problems patients may experience so that we can provide better treatments.. “

Avindra Nath, MD, study lead author and clinical director, National Institute of Neurological Disorders and Stroke, NIH

Although COVID-19 is primarily a respiratory disease, patients often experience neurological issues such as headaches, delirium, cognitive dysfunction, dizziness, fatigue, and loss of smell. The disease can also cause strokes and other neuropathologies.

Several studies have shown that the disease can cause inflammation and damage to blood vessels. In one of these studies, researchers found evidence of small amounts of SARS-CoV-2 in the brains of some patients. Nevertheless, scientists are still trying to understand how the disease affects the brain.

In this study, the researchers conducted an in-depth examination of brain tissue samples from 19 patients who died after suffering from COVID-19 between March and July 2020. Samples from 16 of the patients were provided by the Medical Examiner’s Office in head of New York, while the other 3 cases were provided by the Department of Pathology at the University of Iowa College of Medicine, Iowa City.

The patients died at a wide variety of ages, from 5 to 73 years old. They died within hours to two months of reporting symptoms. Many patients had one or more risk factors, including diabetes, obesity, and cardiovascular disease. Eight of the patients were found dead at home or in public places. Three other patients collapsed and died suddenly.

Initially, the researchers used a special high-powered magnetic resonance imaging (MRI) scanner, 4 to 10 times more sensitive than most MRI scanners, to examine samples of scent bulbs and brainstem from each. patient. These regions are believed to be very susceptible to COVID-19. Olfactory bulbs control our sense of smell while the brainstem controls our breathing and heart rate. The scans found that both regions had an abundance of bright spots, called hyperintensities, which often indicate inflammation, and dark spots, called hypointensities, which represent bleeding.

The researchers then used the scans as a guide to take a closer look at the spots under a microscope. They found that the bright spots contained thinner-than-normal blood vessels and sometimes leaked blood proteins, like fibrinogen, into the brain.

It seems to trigger an immune reaction. The spots were surrounded by T cells from the blood and the brain’s own immune cells called microglia. In contrast, the dark spots contained both coagulated and leaky blood vessels, but no immune response.

“We were completely surprised. We originally expected to see damage from a lack of oxygen. Instead, we saw multifocal areas of damage typically associated with stroke and neuroinflammatory disease, ”Dr. Nath said.

Finally, the researchers saw no signs of infection in the brain tissue samples even though they used several methods to detect the genetic material or proteins of SARS-CoV-2.

“So far, our results suggest that the damage we have seen may not have been caused by the SARS-CoV-2 virus directly infecting the brain,” said Dr Nath. “Going forward, we plan to study how COVID-19 harms blood vessels in the brain and whether it produces some of the short- and long-term symptoms that we see in patients.