COVID-19 "Brain Fog" Is Real

New research is helping to clarify why it happens.

Posted Feb 24, 2021 | Reviewed by Gary Drevitch

Key Points:

  • COVID-19 patients have been reporting to their doctors that they are feeling mentally foggy or distracted.
  • New research reports that cells known as megakaryocytes, found in bone marrow, have been detected in the brains of some patients who died from COVID-19.
  • The cells, which could cause the fogginess effect, may reach the brain as part of the body's response to the virus.

A few months back I was chatting with a psychiatrist about the impact of the pandemic on our brains. I assumed our conversation would be dominated by accounts of increased anxiety and depression, but instead, she began talking about the overwhelming number of COVID-19 patients who had felt, or were still feeling, mentally foggy and distracted. 

Neurological symptoms—including “brain fog” but also general dysregulation of executive functions like behavior and emotion—have been reported in COVID-19 patients, but most studies have shown neither SARS-CoV-2 viral material in the brains nor the inflammation often associated with these neurological consequences.

Now, a team of researchers from Johns Hopkins and Brigham and Women’s Hospital has discovered something that provides a bit more clarity.

They analyzed brain tissue from 15 randomly selected patients (male and female, ranging in age from 40s to 80s) who had died from COVID-19. They compared their brains to the brains of two people who did not die of COVID-19. They found that one-third of the patients who died from COVID-19 had an accumulation of megakaryocytes in their brain blood vessels. 

Megakaryocytes are large cells, found in your bone marrow, that produce a bunch of different blood cell types, including the platelets that allow your blood to clot as you heal a wound.

Lukas Bieri/Pixabay
Source: Lukas Bieri/Pixabay

According to a news release from Johns Hopkins, this appears to be the first time that megakaryocytes have been found in human brain blood vessels. Researchers are hypothesizing that, in the case of COVID-19, there’s so much damage to the lungs that megakaryocytes travel there—from the bone marrow—to help out, and then move from the lungs to the brain. That being said, there’s a logistical challenge: To get to the brain, these large cells would need to make their way through tiny blood vessels in the lungs. 

Although how they get to the brain is still unclear, researchers predict that megakaryocyte accumulation could be impeding normal blood flow throughout the brain, altering how much blood is flowing to different regions, and the patterns in which it does. 

As an outsider, I’d be curious to see if a brain imaging technology might be sensitive enough to pick up on blood flow changes in people who have, or are recovering from, COVID-19 and are experiencing "brain fog."