A new global study is in progress to address the mystery of how SARS-CoV-2 may cause brain fog and other neurological symptoms in some people, Axios report.
Roughly 79 million Americans were infected with COVID-19 during the first two years of the outbreak. While most survived, many are grappling with long-term symptoms, or long COVID, that affect the brain and other body systems.
- “Neuro-long COVID is a very important problem in the U.S. It affects millions of people and leads to people not being able to work the way they used to, or to lose time from work,” Igor Koralnik, chief of neuro-infectious diseases and global neurology at Northwestern Memorial Hospital, informed Axios.
- In a January Science perspective, NIH’s Avindra Nath and Yale’s Serena Spudich wrote that research into the disorders and development of therapies is urgent.
- “It’s the third-most frequent neurological condition in the U.S. today,” says Koralnik, who has treated 1,200 patients in the COVID clinic since May 2020.
The process
Researchers are trying to answer some of the most important questions: how the virus penetrates the protective blood-brain barrier, if the effects are permanent, and if the virus is damaging the brain.
- The majority of the data gathered thus far is based on adults, so the effects of the virus on children and infants are less well known.
Accessing the brain: Although the blood-brain barrier usually prevents many germs from entering the brain, certain pathogens can pass through it.
- SARS-CoV-2 may be able to directly cross that barrier, although recent studies suggest it can.
- Autopsies have also shown that SARS-CoV-2 infections in cells near the brain can cause inflammation in these cells, which can then affect the neurons and glial cells in the brain.
- A study published this week by Koralnik’s team found biomarkers in blood plasma indicative of activated glia and damaged neurons in both long-term COVID patients with mild symptoms and in those hospitalized with severe symptoms.
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Tracking damage: Some MRI studies link brain lesions with the virus, but not all patients have them.
- A study conducted on 785 people aged 51 to 81 published this week in Nature suggests that COVID can shrink the brain, causing some people to appear to be ten years older even months after infection.
- Co-author Anderson M. Winkler, senior associate scientist at the National Institute of Mental Health, says those with even mild cases of the disease showed cognitive decline, degeneration of parts of the brain, and brain shrinkage.
- Comparing MRI scans before and after the pandemic started, infected participants “may have lost 2.9% gray matter in a given brain region, whereas non-infected participants will have lost only 0.9% over the same three-year period,” Winkler shared with Axios.
- “The data available for the study doesn’t allow us to indicate a specific mechanism for the effects observed; these can be because the virus invades the brain, or because of the inflammation it causes,” Winkler added.
Long-term implications: The extent of this damage is unknown, as the brain is remarkably capable of recovering or compensating.
- There are concerns, however, that it might cause or accelerate Alzheimer’s or Parkinson’s disease.
- A JAMA Neurology study examined the long-term health of 1,438 COVID survivors and 438 uninfected peers from Wuhan, China, all 60 or older, for more than a year. They found a “markedly higher” dementia risk in patients who had suffered severe COVID. The risk appears to be higher even for patients with mild symptoms.
- However, Winkler says much remains unknown. “Small previous studies using functional imaging seem to indicate improvement over time” of brain function, he said.
In the future: Researchers at the NIH and elsewhere are exploring whether changes in the brain are reversible and if they affect young and old individuals alike, whether these changes are connected to brain fog, and what the best therapeutic options are.
