Why the Brain May Fog
The reasons for brain fog are not yet clear. Spudich believes the most likely cause relates to inflammation created by the body’s immune response rather than to the virus itself. She says an overactive immune response is similarly thought to be responsible for other symptoms of COVID-19, including the breathing problems that often cause hospitalization.
Spudich points to HIV/AIDS as another condition in which an out-of-control immune system inflames the brain, leading to mental lapses. If an immune response is to blame for brain fog, it may be that inflammation in the body becomes so widespread that it reaches the brain. Or it could be that immune cells “are going into the brain to chase a little virus there,” Spudich says, noting that all this is currently conjecture.
There is the possibility that the virus itself is in the brain, perhaps by traveling through the top part of the nose or by infecting cells known to cross the blood-brain barrier. Thus far examinations of spinal fluid (which comes from the brain) and autopsies have not demonstrated this for the vast majority of COVID-19 cases.
The good news is that physical damage to the brain is rare, as documented by MRI images in some people.
Cognitive Rehab and Brain Apps May Help
When patients complain of brain fog, Spudich says the first step is a thorough physical exam to rule out other medical causes, such as a stroke, which is known to occur from COVID-19. Patients may then be referred for cognitive rehabilitation (aka cog rehab).
“Cognitive rehabilitation is like physical therapy, but it’s for the brain,” explains Jennifer Wethe, PhD, a neuropsychologist who codirects the concussion program at Mayo Clinic Arizona and is an assistant professor of psychology at the Mayo Clinic School of Medicine, in Scottsdale.
The first steps are written and oral tests, usually conducted by a neuropsychologist, to identify the specific problems. Then the rehab would focus on strategies to improve certain functions, like concentration, as well as techniques to compensate for brain fog, Dr. Wethe says. Rehab occurs several times a week for a month or more.
If concentration is an issue, for instance, the therapist may present a deck of cards and ask you to recall the card placed facedown, then the one before that one, then two before, and so forth. Later you might be asked to recall cards after an interruption. In addition to neuropsychologists, some occupational therapists and speech pathologists are trained in these methods.
Therapists also help patients develop “metacognitive” strategies aimed at making the thinking process more visible. “If you’re working as an assistant and the phone rings, you can learn to mentally mark your place in your current task before picking up the phone,” she says.
Cognitive rehabilitation has been successful with traumatic brain injuries, strokes, and concussions, Wethe says. It is typically covered by insurance for some of these conditions; whether insurers will foot the bill for post-COVID complications is an open question.
Doctors cannot predict how long post-COVID brain fog will persist, but Spudich thinks in many cases the fog may disperse on its own. “With HIV, once the virus is controlled, the cognitive issues resolve. There’s a real chance that with COVID people may just get over this themselves,” she says.
Plus, she notes, “As we continue to learn more, we may find therapies we can give to people to help them improve even faster.”