Title: Structural and metabolic brain abnormalities in COVID-19 patients
with sudden loss of smell PREPRINT Oct. 18, 2020
Overview of the study:
Researchers from Belgium did MRIs and PET scans on the brains of 12 COVID-19patients with a sudden loss of smell. Here is what they found:
- Six (50%) of the patients had a blockage of the olfactory cleft, which is the upper part of the nasal cavity where the olfactory receptors are located.
- “No MRI signal abnormality downstream of the olfactory tract was observed”
- The PET scan showed glucose metabolism abnormalities in core olfactory and high-order neocortical areas.
The conclusion of the study:
“This PET-MR study shows that sudden loss of smell in COVID-19 is not related to central involvement due to SARS-CoV-2 neuroinvasiveness. Loss of smell is associated with heterogeneous cerebral metabolic changes in core olfactory and high-order cortical areas likely related to combined processes of deafferentation and active functional reorganisation secondary to the lack of olfactory stimulation. ”
Why is this important?
Many articles, headlines, and social media postings have proclaimed that the loss of smell that some COVID-19 patients experience is due to the virus invading the central nervous system. While that was one possible explanation, this study shows that the speculation was incorrect. This is why studies need to be done before everyone starts posting on Facebook that loss of smell means that COVID invaded the brain.
Interestingly, about half of the patients in the study continued to have some degree of altered ability to smell even 15-weeks after their diagnosis. The researchers theorized that it was due to the death of the olfactory cells and time needed for regenerating them.