A study published on Wednesday and carried by the French News Agency showed that the headaches, disorientation, and even delirium that some Covid-19 patients suffer from, may be the result of the emerging corona virus attacking the brain directly.
The research is still in its early stages, but it offers several new lines of evidence to support what was previously considered a mere hypothesis.
According to the study led by immunologist Akiko Iwasaki at Yale University, the virus is able to multiply inside the brain, and its presence deprives brain cells close to oxygen, but the extent of its spread is not yet clear.
The techniques used in the study were praised by S. Andrew Josephson, chair of the Department of Neurology at the University of California, San Francisco.
He said, "Understanding whether there is a direct effect of the virus in the brain is very important."
But he added that it would be best to be careful until the paper undergoes peer review.
Break through the barrier
It would not be completely shocking if it turns out that the new Corona virus (its scientific name SARS Cove 2) is able to penetrate the barrier between the blood and the brain, which is a structure that surrounds blood vessels in the brain and tries to prevent toxins and foreign substances in the blood from entering the brain.
For example, the Zika virus does the same, causing major damage to the brains of the fetus.
But doctors have so far believed that the neurological effects observed in about half of patients could instead be the result of an abnormal immune response known as a cytokine storm that causes encephalitis, rather than being invaded directly by the virus.
Unknown prevalence
Iwasaki and his colleagues decided to approach the question in three ways: by infecting small brains grown in the laboratory known as brain organelles, by infecting mice, and by examining brain tissue from patients who had died of Covid-19.
In the brain organelles, the research team found that the SARS-Cove 2 virus is able to infect nerve cells and then control the nerve cell to reproduce.
The affected cells in turn caused the death of the surrounding cells by suffocating the oxygen supply to them.
One of the main arguments against the direct brain invasion theory is that the brain lacks high levels of the protein called ACE2 (ACE2) that the Corona virus attaches to, and which is found in abundance in other organs such as the lungs.
But the team found that the organelles had enough "ACE2" protein to facilitate entry into the virus, and the proteins were also present in the brain tissue of the deceased patients.
Cerebral fluid
The researchers also examined the cerebrospinal fluid in a hospitalized patient with Covid-19 suffering from delirium, and found that he had equivalent (neutralizing) antibodies to the virus in the spinal fluid, which formed other evidence supporting their hypothesis.
Then the team studied two groups of mice, one that was genetically modified to contain ACE2 receptors in their lungs only, and the other in their brain only.
The mice infected in their lungs showed some signs of lung infection, while the brain-infected mice lost weight quickly and died quickly, indicating the possibility of a higher death rate upon entering the brain.
Finally, the researchers examined the brains of 3 patients who had died from serious complications linked to Covid-19, and found evidence of the virus in all, to varying degrees.
The study authors explained that they need more autopsies to find out the extent of the brain infection.