Before-and-After MRIs Show How COVID Changes Brain

Brain scans from before and after a COVID-19 infection show that the virus appears to cause modest changes in the structure of the brain.

The findings come from an analysis of volunteers with the UK Biobank, a biomedical database of half a million people in the United Kingdom. Seven hundred and eighty five of the participants were involved in this COVID-19 brain study, 401 of whom tested positive for COVID-19 between their two scans. The majority of the COVID-19 infections were mild.

Researchers identified signs of tissue damage and loss of gray matter in people who had been infected with COVID-19 that were not found in people who never had the virus.

Whether the changes in brain structure are permanent or not remains to be seen.

“Generally, the brain has a great capacity for plasticity and recovery,” Anderson Winkler, MD, PhD, DPhil, senior associate scientist with the National Institute of Mental Health and a coauthor of the study, told Verywell via email.

Which Areas of the Brain Were Impacted?

Before-and-after MRIs showed the brains of those who had been infected with COVID-19 had a greater loss of gray matter, as well as abnormalities in the areas associated with smell, taste, and episodic memory, Winkler said. On average, imaging was completed 4.5 months after a COVID-19 infection.

The people who had been infected demonstrated a greater cognitive decline than the uninfected control group, as well as greater difficulty performing complex tasks. While everyone involved in the study was between the ages of 51 and 81, this decline was larger in individuals in their mid 60s and older.

However, the changes in the brain were not large.

“On average, the infected participants showed an additional 0.2% to 2% loss or tissue damage compared with the non-infected participants,” reads an FAQ about the study.

Changes in the brain and brain shrinkage are a normal part of aging; the control group demonstrated some loss as well. Starting in middle age, people generally lose between 0.2% and 0.3% of their gray matter per year in areas of the brain related to memory.

Are the Changes Reversible?

David Putrino, PT, PhD, director of rehabilitation innovation at Mount Sinai Health System in New York City, said he finds the results of the study troubling.

“We’ve known for quite some time now that people with long COVID experience cognitive impairment,” he told Verywell, explaining the hope was that these were transient changes, and that people would recover over time without lasting damage. “[But this study] links a physiological finding to some of the symptoms that we’re seeing. It’s not to say necessarily that this is a permanent impairment. But it does point us toward the idea that it’s going to be much harder to reverse.”

The study did not determine how many of the participants who were infected developed long COVID, the persistent form of the infection, Putrino noted.

“We can’t say for certain right now that these are permanent changes,” Putrino reiterated. “When these individuals are managed appropriately and treated appropriately, they can show some recovery.”

If You Had COVID, Should You See a Neurologist?

If you had a mild case of COVID-19, the results of this study may seem concerning. But Winkler says the findings don’t warrant a precautionary neurology consult or any sort of testing with a general practitioner.

“The data we had available for the study doesn’t allow us to make specific recommendations that could change the natural history of the disease, or make recommendations about therapeutic options that could be considered by a neurologist,” Winkler said.

But if you’re experiencing any cognitive difficulties, it’s time to schedule an appointment.

“An individual who presents neurological symptoms, including cognitive deficits, regardless of having had COVID-19 or not, should consult with a physician,” he added.

Is COVID-19 Definitely the Culprit?

Many viral infections can affect the brain, not just COVID-19, Winkler said.

“While not typical, the literature shows that neurological manifestations can occur, for example, after infection by the influenza virus, among others,” Winkler said. “However, we are not aware of investigations of specific tissue losses.”

Winkler and his colleagues looked at UK Biobank participants who had pneumonia or influenza between scans to see if they experienced brain changes as well, and did not see a similar tissue loss pattern as the participants with COVID-19.

Winkler adds it is possible that the structural brain changes occurred because of the deprivation of the sense of smell, as opposed to because of the virus itself.

In that case, as people begin to regain their sense of smell, those brain changes could be reversible. But researchers don’t know yet.

It will be important to follow this group of people to learn more about these changes in their brains, Putrino said. In the U.S., the National Institutes of Health’s RECOVER initiative is backing hundreds of long COVID studies involving brain scans which may be helpful.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.