Long-term cognitive problems after a diagnosis of COVID-19 may be the result of fatigue rather than pathological changes in the brain, according to a study published before print in The Journal of Nuclear Medicine. An analysis of neuropsychological tests and 18F-FDG PET imaging showed that little or no objective impairment was observed in the cognition and brain pathology of long-term COVID patients; however, many of the group suffered from subjective complaints such as severe fatigue.

The term “long COVID syndrome” is used to describe symptoms that occur following infection with COVID-19 (generally defined as being present more than 12 weeks after infection), including cognitive deficits, such as brain fog, memory loss and attention problems, as well as fatigue and exhaustion. The underlying cause of these symptoms is unknown.

Previously published studies have shown that patients requiring hospital treatment due to a new diagnosis of COVID-19 reduced glucose metabolism in the brain, which is associated with impaired cognitive function. To assess whether patients with long COVID have similar deficits, the researchers performed neuropsychological tests and 18F-FDG PET brain imaging.

Thirty-one patients who sought counseling for persistent neurocognitive symptoms were included in the present study. The patients participated in a battery of neuropsychological tests, and the results were analyzed to determine levels of cognitive impairment. The group’s average test results showed no impairment. Slight deficits have been observed in some patients at the single subject level, however, primarily with regard to visual memory.

18F-FDG PET imaging was recommended for all counseling patients, and 14 of 31 patients continued on treatment. Clinical evaluation of each patient’s analysis revealed no distinct pathological signs or alternative diagnosis. When the scans were compared to those of a control group, no significant difference was noted.

The absence of significant results on 18F-FDG CT scans and only mild impairment on neuropsychological tests contrasts with the severe and lasting disability self-reported by patients. Fatigue, however, was particularly prevalent in the group, reported by 61 percent of study participants. Fatigue often follows viral infections and inflammation and has been linked to immune processes and chronic fatigue syndrome throughout COVID.

“This suggests that fatigue, and not regional brain dysfunction, may be responsible for many long-lasting symptoms of COVID,” the researchers concluded.


Dressing A, Bormann T, Blazhenets G, et al. Neuropsychological Profiles and Brain Glucose Metabolism in Long COVID Neurocognitive Syndrome. Journal of Nuclear Medicine. Published online October 1, 2021. doi:10.2967 / jnumed.121.262677

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