Dutch researchers at the Amsterdam UMC have discovered that corona is even more harmful than we already knew: it also affects the brain.

The disease can cause the immune system in the brain to run wild. The research is published today in the leading medical journal The Lancet Microbe.

Pathologist Paul van der Valk and his team extensively studied the brains of eleven patients who died of covid-19. He saw in ten of them that the disease had left clear marks in the brain. Immune cells (so-called T lymphocytes) have been discovered that do not belong in the brain.

He found these abnormalities in the entire brain and spinal cord in the deceased patients. “These are cells that are normally excluded from the brain,” says Van der Valk. “But in the covid-19 patients we saw that they had left the bloodstream and entered the brain tissue. Then I know as a pathologist: something is very wrong here.”

The virus itself was not found in the brains of the deceased. Van der Valk therefore sees strong indications that the immune cells, intended to fight covid-19, have mistakenly also attacked certain proteins in the brain. “That can happen if the protein somewhat resembles the virus. The own immune system then runs wild.”

Further research is needed to find out which body proteins in the brain are targeted by these immune cells. But the process could possibly explain why so many corona patients still suffer from fatigue and concentration problems for a long time, sometimes many months, says Van der Valk. “Immune-suppressing medication may be able to provide relief for this group. But this still needs to be investigated further.”

British neurologists already described this summer that corona can cause cerebral hemorrhage and nerve damage in some cases, even in people with relatively mild corona complaints.