The Link Between COVID-19 and Brain Fog

Source: Photo by Devin Justesen on Unsplash

Scientists are trying to understand how the coronavirus SARS-CoV-2 causes "brain fog" and other neurological symptoms. Brain fog includes confusion, mental fatigue, depression, and forgetfulness.

The most recent evidence suggests that the coronavirus’s attack on the brain is multifaceted. It currently appears as though the virus attacks some brain cells directly and reduces the blood flow to some others. As a consequence of its assault on glia cells, the levels of immune molecules increase dramatically; these molecules can then cause direct harm to other brain cells.

Exposure to the coronavirus SARS-CoV-2 can cause memory loss. My laboratory demonstrated that the elevated presence of immune molecules underlies problems with memory formation and other aspects of brain fog.

The current challenge is to understand how the coronavirus initiates these changes so that therapies can be designed to intervene and prevent or reduce long-term problems with brain function. To achieve this goal, scientists investigate where the virus is going and what it is doing once it gets into the brain. Solving this mystery is critical since neurological symptoms were observed in 80% of hospitalized people with COVID-19.

The grey matter of the cerebral cortex is greatly affected by the virus. Some areas of the cortex show significant loss of volume. The grey matter of the cortex contains neurons and their supporting cells, called glia. One type of glia is called astrocytes. Astrocytes provide neurons with nutrients and remove metabolites, and the debris neurons produce during their normal function. The second type of glia found in the cortex's grey matter is called microglia because of their small size. They have a tremendous job, however. Microglia produce and release immune molecules that can be both protective and harmful. The neurons are responsible for transmitting and processing information.

Interestingly, some recent studies suggest that the virus has difficulty getting past the brain’s main line of defense, the blood-brain barrier. So, how does the virus gain access to the brain? By going up through the nose.

Evidence suggests that the virus accesses the brain via the olfactory mucosa, which lines the upper nasal cavity, which borders the brain. Now you can understand why healthcare workers were testing for the presence of the virus by sticking a swab DEEP into your nose.

Once inside the brain, the virus infects astrocytes. There are ten times as many astrocytes as neurons inside the grey matter of the cortex. Indeed, recent studies indicate that the virus much prefers to infest astrocytes over other brain cells. Infected astrocytes are likely the cause of neurological symptoms, especially fatigue, depression, and brain fog. Interestingly, even when the brain no longer contains any virus, there is evidence for impaired astrocyte functioning that coincides with the brain fog symptoms.

The inflammatory molecules from astrocytes are not the only cause of neurological problems. Reduced blood flow and malfunction of the body’s immune system also contribute. In the coming months, many other mechanisms are likely to be uncovered. Treatment of brain fog will require targeting all of the tools initiated by the invasion of the virus. Because the consequences of the virus in the brain can be devastating and maybe long-term, the only intelligent thing to do is get vaccinated.