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Currently very little is known about the effect of severe COVID-19 on the brain. This case study suggests that the virus may harm small blood vessels in the brain. (Image: iStock)

Drs. Patrick Nicholson, Laila Alshafai and Timo Krings, neuroradiologists in the Joint Department of Medical Imaging at UHN and Sinai Health, recently revealed new details on how COVID-19 may affect the brains of certain individuals.

In a short preliminary case series, the research team observed evidence of internal bleeding and clotting in the blood vessels of the brain of four individuals with severe COVID-19.

"We believe that this could be, at least in part, related to an infection of the blood vessels by the virus, a so-called endotheliitis, where the virus doesn't stay in the lungs, but is able to travel into the blood, ultimately causing bleeds," says Dr. Krings, who is also a clinician scientist at the Krembil Brain Institute.

"Bigger picture, this may open a possibility to stabilize the endothelium early, especially in patients who are most vulnerable."

All four individuals included in the study were unable to breath on their own. One was on a mechanical ventilator, and three were on an extracorporeal membrane oxygenation (ECMO) machine – a device that delivers oxygen directly to the blood.

All of the patients displayed new symptoms such as weakness or drowsiness – this was the initial reason why brain imaging was carried out. Images of the brains of patients were taken using advanced techniques to reveal the detailed structure of blood vessels and soft tissues. These techniques included computerized tomography and magnetic resonance imaging (MRI).

Extra vigilance needed when screening individuals with COVID-19

The team identified a number of abnormal features in the brain scans, including small areas of localized bleeding. In other areas, they found evidence of clotting in small blood vessels in the brain. 

The researchers note that these abnormalities could point to a condition known as thrombotic microangiopathy. Other case studies have suggested that COVID-19 can infect and damage cells that line blood vessels, which may help explain the bleeding that was observed.

Certain limitations exist in this study. For example, the number of patients is very limited and the use of ECMO may also contribute to bleeding in the brain, which could confound results. Due to this, the researchers leading this study have teamed up with a larger group of neurologists, and ICU physicians to verify their findings in a larger cohort of patients.

In summarizing the implications, the team urges clinicians to be extra vigilant when screening individuals with COVID-19. 

"Use of medical imaging, such as MRI, for those with changes in behaviour or consciousness, may be key to the early detection and treatment of brain bleeds in those with COVID-19," Dr. Nicholson says.

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