The brains of nine people who died quickly after contracting Covid-19 were studied for this article published in the journal Brain.
The team of researchers from the American Institutes of Health (NIH) did not detect traces of the virus in the brain but, conversely, antibodies, causing damage to the walls of blood vessels which cause especially inflammation.
This discovery could explain some of the lasting effects of Covid-19, such as migraines, chronic fatigue, loss of taste and smell, sleep problems or even the feeling of "brain fog", a state of intellectual fatigue. .
It could also open up avenues for future treatments.
"Patients often develop neurological complications with Covid-19, but the associated pathophysiological process is not well understood," said Avindra Nath, the study's first author, in a statement.
"We had already shown the damage affecting blood vessels on the brains of patients during autopsies, but we did not understand what caused this", adds the researcher.
"I think with this article we have some new insights into this process."
The brains of the nine patients, aged 24 to 73, were compared with ten others from a control group.
The researchers observed neuronal inflammation and the immune response.
Antibodies produced in response to Covid-19, scientists have found, have mistakenly targeted the cells that make up the blood-brain barrier, a structure that surrounds blood vessels in the brain and tries to block foreign substances.
The degradation this causes can in turn lead to protein leaks, bleeding and blood clots, which increases the risk of stroke.
A leak can also trigger an immune response to repair damaged cells, which causes inflammation.
The biological functioning of these affected parts of the brain is thus disrupted.
“It is quite possible that the same immune response affects patients with +Covid long+, which causes brain injury,” said researcher Avindra Nath.
"These results therefore have very important therapeutic implications."
A treatment against these forms of long Covid could, for example, limit the production of the antibodies causing brain damage.
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