In an in-depth examination of how COVID-19 affects a patient's brain, National Institutes of Health researchers consistently spotted hallmarks of damage caused by thinning and leaky brain blood vessels in tissue samples from patients who died shortly after contracting the disease. 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 a correspondence in The New England Journal of Medicine.
Early results suggest this phenomenon may be caused by the body's inflammatory response to the coronavirus, and the discovery will likely lead to a refinement of treatments for the disease.
Although COVID-19 is primarily a respiratory disease, patients often experience neurological problems, including headaches, delirium, cognitive dysfunction, dizziness, fatigue, and loss of the sense of smell. The disease may also cause patients to suffer strokes and other neuropathologies.
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Several studies have shown that the disease can cause inflammation and blood vessel damage. In one of them, there was evidence of small amounts of SARS-CoV-2 in some patients' brains. Nevertheless, scientists are still trying to understand how the disease affects the brain.
WHAT'S THE IMPACT?
The new findings give frontline healthcare workers an insight into how their patients' may be affected by the virus, and could help to pave a road map for better and more effective treatments.
In this instance, the researchers conducted an in-depth examination of brain tissue samples from 19 patients who had died after experiencing COVID-19 between March and July. Samples from 16 of the patients were provided by the Office of the Chief Medical Examiner in New York City, while the other three cases were provided by the department of pathology at the University of Iowa College of Medicine, Iowa City.
The patients died at a wide range of ages, from 5 to 73, and died within a few hours to two months after 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 settings, while another three patients collapsed and died suddenly.
Initially, the researchers used a special, high-powered magnetic resonance imaging scanner that is four to 10 times more sensitive than most MRI scanners. This was to examine samples of the olfactory bulbs and brain stems from each patient. These regions are thought to be highly susceptible to the coronavirus.
Olfactory bulbs control the sense of smell while the brain stem controls breathing and heart rate. The scans revealed that both regions had an abundance of bright spots, called hyperintensities, that often indicate inflammation, and dark spots, called hypointensities, that represent bleeding.
The team then used the scans as a guide to examine the spots more closely under a microscope. They found that the bright spots contained blood vessels that were thinner than normal and sometimes leaked blood proteins, like fibrinogen, into the brain. This appeared 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 clotted and leaky blood vessels but no immune response.
With no signs of infection in brain tissue samples, the preliminary conclusion is that the virus doesn't affect the brain directly, but rather likely harms the blood vessels in the brain through other means.
THE LARGER TREND
The numbers of COVID-19 cases continue to bring grim news, especially in the U.S., which struggled early in the pandemic to secure testing capacity and necessary personal protective equipment for frontline healthcare workers.
As of Thursday, December 31, 2020, the Johns Hopkins University coronavirus tracker showed more than 19.7 million confirmed cases of the virus in the U.S., with the death toll climbing to over 342,000. Both figures lead the world. Second on the list is India (with 10,266,674 cases and 148,738 deaths), while Brazil comes in third (with 7,619,200 cases and 193,875 deaths).