Objective: To assess the physiopathology of olfactory function loss (OFL) in COVID-19 patients, we evaluated the olfactory clefts on MRI during the early stage of the disease and one month later.

Methods: This was a prospective monocentric case-controlled study. Twenty SARS-CoV2-infected patients with OFL were included and compared to 20 age-matched control healthy subjects. All infected patients underwent olfactory function assessment and 3T MRI, performed both at the early stage of the disease and at one-month follow-up.

Results: At the early stage, SARS-CoV2-infected patients had a mean olfactory score of 2.8 +/- 2.7 (range 0-8), and MRI displayed a complete obstruction of the OC in 19 out of 20 patients. Controls had normal olfactory scores and no obstruction of the OC on MRI. At one month follow-up, the olfactory score had improved to 8.3 +/- 1.9 (range 4-10) in patients, and only 7 out of 20 patients still had an obstruction of the OC. There was a correlation between olfactory score and obstruction of the OC (p=0.004).

Conclusion: OFL in SARS-CoV2-infected patients is associated with a reversible obstruction of the OC.