Olfactory and Gustatory Dysfunction
It is not uncommon for anosmia and dysgeusia to be the sole presenting symptoms of COVID-19.[12,65] A systematic review and meta-analysis of 1627 COVID-19 patients from 10 studies yielded a pooled proportion of 41 and 38% for olfactory and gustatory dysfunction, respectively. Overall, this review reported a high prevalence of new-onset olfactory and gustatory dysfunction in confirmed COVID-19 cases. However, there was substantial heterogeneity among the included studies, a lack of a standardized objective assessment method, and the majority were from European populations, which may affect generalizability.
A small prospective study of 20 confirmed SARS-COV-2 infected patients with sudden olfactory function loss underwent olfactory function assessment and 3 T MRI within 15 days of symptom onset and at 1 month follow up. All but one patient had evidence of olfactory cleft obstruction on MRI imaging in comparison to age-matched controls. At 1 month follow up, all olfactory function assessment scores improved and most patients had complete resolution of obstruction on imaging. While pathological data suggests that SARS-CoV-2 infects olfactory mucosal support cells, direct olfactory nerve injury is uncertain, even in studies that implicate SARS-CoV-2 entry into the olfactory bulb and tubercle.[12,14,65,66–67] One study did find pathological evidence of neuronophagia in the olfactory bulb, though there was no evidence of SARS-CoV-2 present and it is possible that other mechanisms contributed to neuronal death.
Curr Opin Infect Dis. 2021;34(3):217-227. © 2021 Lippincott Williams & Wilkins