Observational study: prospective longitudinal cohort (Green)
In this prospective single-centre case-controlled study recently published in Neurology, the authors investigated the physiopathology of olfactory function loss (OFL) in COVID-19 patients, by evaluating the olfactory clefts (OC) on MRI during the early stage of the disease and one month later. Twenty SARS-CoV2-infected patients with OFL were included and compared to 20 age-matched healthy controls. All infected patients underwent olfactory function assessment and 3 Tesla MRI, performed both at the early stage of the disease and at one-month follow-up. At the early stage, SARS-CoV2-infected patients had a mean olfactory score of 2.8 +/- 2.7 (range 0–8), and MRI displayed 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 obstruction of the OC. The authors found a correlation between olfactory score and obstruction of the OC (p=0.004). They concluded that OFL in SARS-CoV2-infected patients is associated with reversible obstruction of the OC.