Brain Changes Seen After Mild COVID Infection

Tissue damage and shrinkage in brain areas related to smell were seen months after people had mild SARS-CoV-2 infection, longitudinal data from the U.K. Biobank showed.

Compared with controls, people who had mild COVID demonstrated a greater reduction in grey matter thickness and tissue contrast in the orbitofrontal cortex and parahippocampal gyrus, and greater changes in markers of tissue damage in regions functionally connected to the primary olfactory cortex, reported Gwenaëlle Douaud, PhD, of the University of Oxford in England, and co-authors in Nature.

COVID patients also had a greater reduction in global brain size. On average, infected participants showed larger cognitive decline.

“Using the U.K. Biobank resource, we were in a unique position to look at changes that took place in the brain following mild — as opposed to more moderate or severe — SARS-CoV-2 infection,” Douaud said in a statement.

“Despite the infection being mild for 96% of our participants, we saw a greater loss of grey matter volume, and greater tissue damage in the infected participants, on average 4.5 months after infection,” she noted. “They also showed greater decline in their mental abilities to perform complex tasks, and this mental worsening was partly related to these brain abnormalities. All these negative effects were more marked at older ages.”

“This is an outstanding study,” observed Avindra Nath, MD, of the National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, who wasn’t involved with the research.

“A novel aspect of this study is the access to MRI scans prior to COVID-19 and then on average 140 days after COVID-19,” Nath told MedPage Today. “They show that the olfactory pathways in the brain are atrophic in these patients as a group. This also includes areas involved in cognition although, interestingly, it was an area in the cerebellum.”

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