BY JAMIE DUCHARME
GOOD QUESTION
EARLY IN THE COVID-19 PANDEMIC, doctors noticed that for what was originally described as a respiratory virus, SARS-CoV-2 seemed to have a strong effect on the brain, causing everything from loss of taste and smell and brain fog to, in serious cases, stroke. Years later, cognitive decline, changes in brain size and structure, depression and suicidal thinking, tremors, seizures, memory loss, and new or worsened dementia have also been linked to SARS-CoV-2 infections. In some cases, these longer-term problems occur even in patients who had mild COVID-19.
The question now is what, exactly, is going on in the brains of people infected by SARS-CoV-2—and whether the damage can be reversed.
Not long after the pandemic began, Dr. Avindra Nath, clinical director of the National Institute of Neurological Disorders and Stroke (NINDS), and his colleagues analyzed the brains of 13 people who died from COVID-19. They didn’t find SARS-CoV-2 in those brains—but they did find damage to the blood vessels there, which were coated with antibodies. It looked as if the body’s immune system had gone haywire, attacking its own blood vessels and setting off a cascade of effects that led to significant inflammation in the brain, potentially culminating in fatal damage to the part that controls breathing. In people who survive COVID-19, brain inflammation may also explain lasting symptoms like brain fog and memory loss, Nath says.
Dr. Lara Jehi, who researches COVID-19 and the brain at the Cleveland Clinic, also points to inflammation as a possible trigger. In a 2021 study, Jehi and her colleagues compared the brains of people with Long COVID and Alzheimer’s disease. “We found many areas of overlap between the two,” she says, centered on “inflammation in the brain and microscopic injuries to the blood vessels.”
Jehi’s team wanted to determine whether the SARS-CoV-2 virus was entering the brain and causing damage directly, or triggering an immune response that led to brain changes. Their findings pointed to the latter—but researchers still haven’t ruled out the possibility that the virus has direct effects on the brain.
INDEED, SINCE NATH’S brain-scanning project early in the pandemic, other researchers have found the virus in the brains of people who died from COVID-19. For a 2022 paper, researchers analyzed brain tissue from 11 people who had COVID-19 when they died. In all but one of those people, the researchers found the virus’ genetic material in central-nervous-system tissue—which, they wrote,
