Olfactory Dysfunction in the COVID-19 Era: an Umbrella Review Focused on Neuroimaging, Management, and Follow-Up

Author(s): Mohammadreza Kalantarhormozi, Houman Sotoudeh, Mohammad Amin Habibi, Mehdi Mahmudpour, Ramin Shahidi, Fattaneh Khalaj, Shaghayegh Karami, Ali Asgarzadeh, Mansoureh Baradaran, Fatemeh Chichagi, Sara Hassanzadeh, Narjes Sadat Farizani Gohari, Mahsa Shirforoush Sattari, Amir Azimi, Ali Dadjou, Mahsan Eskandari

Introduction: The coronavirus disease 2019 (COVID-19) is surrounded the world and is associated with multiorgan damage. Olfactory dysfunction is a common manifestation in COVID-19 patients, and in some cases, presents before the coryza signs. We conducted this umbrella review to provide a practical guide on managing, imaging findings, and follow-up of COVID-19 patients with olfactory dysfunction (OD).

Materials and Methods: A comprehensive search was performed in PubMed, Embase, Scopus, and Web of Science databases from December 2019 until the end of July 2022. Systematic reviews and metaanalyses addressing management and imaging findings of the olfactory manifestations of COVID-19 were included in the study. The quality assessment of included articles was carried out using the Assessment of Multiple Systematic Reviews-2 (AMSTAR-2) tool.

Results: A total of 23 systematic reviews were reviewed in this umbrella review. The number of included studies varied between 2 to 155 articles. Several demographic variables were not adequately reported across all the included systematic reviews, including age, gender, preexisting comorbidities, or whether participants had been hospitalized or admitted to the intensive care unit (ICU) due to COVID-19.

Conclusion: It seems that the coronavirus can infect olfactory system structures that play roles in the transmission and interpretation of smell sense. Based on studies, a large proportion of patients experienced OD following COVID-19 infection, and the majority of OD was resolved spontaneously. The possibility of long-lasting OD was higher in young adults with moderate clinical manifestation. Olfactory training (OT) was the most effective therapy. Intranasal corticosteroids (ICS) are also recommended.