Clinical and Imaging Evaluation of COVID-19-Related Olfactory Dysfunction

Background: Olfactory dysfunction (OD) has been reported in 47.85% of COVID-19 patients and can be conductive or sensorineural. Conductive loss stems from impaired nasal airflow, whereas sensorineural loss indicates dysfunction of the olfactory epithelium or central pathways. Objectives: To analyze clinical and imaging findings in COVID-related OD and investigate potential mechanisms. Methods: Prospective study of 110 patients with post-COVID-19 OD and 50 COVID-negative controls with normal olfaction. All underwent endoscopic nasal examination focusing on the olfactory cleft (OC), smell testing using smell diskettes, and olfactory pathway MRI assessing OC condition and olfactory bulb (OB) dimensions/volume. Results: OD was not associated with nasal symptoms in 51.8% of patients. MRI showed significantly increased OB dimensions and volume versus controls, and OC edema in 57.3% of patients. Radiologic sinusitis was found in 15.5% of patients. Conclusion: OB volumes were significantly higher in patients than controls, indicating OB edema/swelling in COVID-related OD. The frequent absence of sinonasal symptoms and low incidence of sinusitis suggest a predominantly sensorineural mechanism via viral spread and damage to the olfactory epithelium and pathways.