COVID: Scans reveal how areas of the brain shrink because of the virus

A study published in the journal Nature discusses substantial variations in MRI (magnetic resonance imaging) scans before and after COVID-19 infection. It suggests that during COVID, the brain decreases in size.

Dr Max Taquet, NIHR Oxford Health BRC senior research fellow at the University of Oxford, adds:

This is the first large-scale study to investigate the actual changes in the brain that can occur after a Covid-19 infection.

Cognitive decline of the brain

The research looked at people who underwent brain scans before and during the epidemic as part of the UK Biobank study.

Lead author of the study, Prof Gwenaelle Douaud, from the Wellcome Centre for Integrative Neuroimaging, at the University of Oxford, says:

We were looking at essentially mild infection, so to see that we could really see some differences in their brain and how much their brain had changed compared with those who had not been infected, was quite a surprise.

According to the BBC, scientists scanned 401 volunteers for an average of 4.5 months after they were infected. There were 96% of individuals with moderate COVID and 384 individuals with no COVID.

Scientists discovered that the total size of the brain had reduced, with less grey matter in the areas of the brain connected to smell and memory. COVID patients took longer to complete cognitive tests and overall had lower average scores.

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Findings of the study

1. Infected participant's brains shrank by 0.2 to 2%.
2. Grey matter was lost in the olfactory areas, which are associated to smell, and memory centres.
3. Complex mental activities were more difficult to execute for those who had just recovered from COVID.
4. The decrease was particularly apparent among the elderly.

Prof Douaud remarks:

We need to bear in mind that the brain is really plastic - by that we mean it can heal itself - so there is a really good chance that, over time, the harmful effects of infection will ease.

The data also suggests that rather than having a long-term influence, the aforesaid findings may be reversible. Scientists continue to emphasize the brain's ability to recover.