Long COVID Smell Loss Associated with Changes in Brain

A recent study found that people with long COVID who lost their smell had reduced brain activity and impaired communication between two regions of the brain which process smell information.

The study, published in eClinicalMedicine, was led by Jed Wingrove, PhD, a postdoctoral research fellow at Kings College in London, England. Using MRI scanning, Wingrove and his colleagues compared the brain activity of those who has lost their sense of smell after a COVID-19 infection, those whose sense of smell had returned after a COVID-19 infection, and those who never tested positive for the virus.

Researchers found that participants who had loss of smell, known as anosmia, had reduced activity and impaired communication between their orbitofrontal cortex and the pre-frontal cortex. These brain changes, the authors said, stopped smells from being properly processed. Changes in the brain were not found in patients who had recovered from their COVID-19 infection nor in those who had never tested positive.

In addition, the MRI scans showed that patients with long COVID and anosmia had increased activity between areas of the brain that process smell and sight. These findings suggest that while their neurons that would normally process smell were functioning differently, they were still present, Wingrove said.

According to the study’s authors, these brain changes have been shown to be clinically reversable, indicating that it may be possible for patients to retrain their brain and recover their sense of smell.

“Persistent loss of smell is just one way long COVID is still impacting people’s quality of life – smell is something we take for granted, but it guides us in lots of ways and is closely tied to our overall wellbeing,” said Wingrove. “Our study gives reassurance that, for the majority of people whose sense of smell comes back, there are no permanent changes to brain activity.”