In a new study, scientists at the National Institutes of Health performed in-depth brain scans of patients with COVID-19. They observed distinctive signs of damage caused by dilution and leakage of blood vessels in the brain in tissue samples from patients who died shortly after contracting the disease.
Surprisingly, there were no signs of SARS-CoV-2 in the tissue samples. This indicates that the damage was not caused by a direct viral attack on the brain.
The brains of patients who contract SARS-CoV-2 infection may be sensitive to damage to microvascular blood vessels. The results recommend that this be caused by the body’s inflammatory response to the virus.
Avindra Nath, MD, clinical director at the National Institute of Neurological Disorders and Stroke (NINDS) of the NIH and lead author of the study said: We hope that these results will help doctors understand the full range of problems that patients may suffer, so that we can come up with better treatments.
COVID-19 is mainly a respiratory disease, but it also affects the brain. Patients often experience neurological problems, including headaches, delirium, cognitive dysfunction, dizziness, fatigue, and loss of sense of smell. The disease can also cause patients to suffer strokes and other neuropathologies.
Several studies have shown that the disease can cause inflammation and damage to blood vessels. In one of these studies, scientists found evidence of small amounts of SARS-CoV-2 in the brains of some patients. However, scientists are still trying to understand how the disease affects the brain.
This new study was performed on brain tissue samples from 19 patients who died after experiencing COVID-19 between March and July 2020. Samples from 16 of the patients were provided by the New York Office of the Chief Medical Officer in while the pathology department provided the other 3 cases at the University of Iowa College of Medicine, Iowa City.
Patients died at a wide range of ages, from 5 to 73 years. They died within a few 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.
For the study, a special scanner for magnetic resonance imaging (MRI) was used. The scanner is 4 to 10 times more sensitive than most MRI scanners.
Using the scanner, the scientists examined samples of olfactory bulbs and brainstem from each patient. These regions are considered to be extremely sensitive to COVID-19. Scans showed that both regions had an abundance of light spots, called hyperintensities, which often indicate inflammation, and dark spots, called hypointensities, represent bleeding.
The scientists then used the scans as a guide to examine the spots more closely under a microscope. They found that the light spots contained thinner-than-normal blood vessels and sometimes leaked proteins from the blood, such as fibrinogen, into the brain.
This seems to trigger an immune reaction. The spots were surrounded by blood T cells and immune cells in the brain called microglia. Instead, the dark spots contained both clotted blood vessels and blood vessels, but did not respond immune.
Dr. Nath said: “It simply came to our notice then. Initially, we expected to see the damage caused by the lack of oxygen. Instead, we have seen multifocal areas of damage that are usually associated with stroke and neuroinflammatory disease. “
To date, our results suggest that the damage we have seen may not have been caused by the SARS-CoV-2 virus that directly infects the brain. In the future, we intend to study how COVID-19 damages the blood vessels of the brain and whether it produces some of the short- and long-term symptoms we see in patients. “
- Myoung-Hwa Lee et al., Microvascular lesions in the brains of patients with Covid-19, New England Journal of Medicine (2020). DOI: 10.1056 / NEJMc2033369