Scientists find probable causes of COVID-19 brain fog

A recent study using mice may have found the cause of this unpleasant symptom

Recent scientific breakthroughs may have found the cause of the “brain fog” that people who experienced COVID-19 have become all too familiar with.

Brain fog — confusion, forgetfulness, lack of clarity and general feeling of fuzziness — is a common symptom of COVID-19. Like many symptoms of COVID, it has puzzled scientists, and for many who had COVID-19, it lasted long after they had recovered from the illness and longer than the other symptoms.

Now, after conducting tests on rats, scientists have been able to better understand COVID-19′s effect on the brain and how brain fog came to exist.

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Published in the journal Cell, researchers Michelle Monje and Akiko Iwasaki, of Stanford and Yale universities respectively, discovered that the virus was able to disrupt the activity of several brain populations, and even left behind symptoms of inflammation in the brain.

Monje had spent years studying the causes of chemotherapy-induced brain disruptions, known as “chemo-fog,” and noticed the similarities between this affliction and the brain fog associated with COVID-19.

“The same symptoms of impaired attention, memory, speed of information processing, dis-executive function—it really clinically looks just like the ‘chemo fog’ that people experienced and that we’d been studying,” Monje said to WIRED.

In September of 2020, she reached out to Iwasaki, an immunologist, and together they began to study brain activity in mice after contaminating them with the virus. The scientists observed the cerebrospinal fluid, or liquid surrounding the brain, in the week after infection. Through this, they were able to see inflammation, as well as an increase in microglia reactivity in the brain tissue, which explained where some of the “fog” issues were coming from.

Microglia are essentially the immune cells of the central nervous system that clean up “debris.” However, when they experience an increase in reactivity, this can lead to them cleaning up more than they need to. This disrupts the homeostasis of the brain — essentially the steadiness of its functions. It can also impact the creation of new neurons, which are linked to the maintenance of a healthy memory.

At the end of the study, the scientists found “incredibly interesting” discrepancies in the brain health of the mice infected with the virus versus the mice in the control group.

While additional research is required to make a more conclusive explanation on brain fog, it seems as though science may have found the key to understanding the issue.

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