Olfactory Bulb MRI Findings in Patients with Post-COVID Anosmia

Abstract

Background: Olfactory dysfunction has been recognized as a key symptom of COVID-19. The pathogenesis of COVID-19 anosmia has not been fully defined. A dedicated MRI study allows assessment of olfactory bulb volume, morphology and signal intensity which is helpful to differentiate between different etiologies and predict prognosis of olfactory function recovery.Objective: To investigate the MRI radiological changes of the olfactory bulb (OB) in patients with post-covid anosmia in comparison with a normal group of subjects for further identification of the underlying cause of anosmia.Patients and Methods: In this study, we evaluated 50 patients with persistent COVID-19 olfactory dysfunction. All patients were anosmic at the time of imaging based on UPSIT scores. We noted a high percentage of olfactory bulb changes. There was reduction of olfactory bulb volumes, change in bulb shape, and signal abnormalities.Results: Our results showed a marked decrease in OB volumes and hyperintensities in the patient group in comparison to the control group. This indicated that the cause of persistent anosmia in post-COVID-19 patients is highly suggestive due to nerve degeneration. Furthermore, we have correlated the degree of anosmia (by UPSIT score) with the degree of affection of the olfactory bulb indicating that a dedicated MRI study for OB could be used as a non-invasive objective method of assessment of anosmia.Conclusion: In the current study, we revealed that there was a highly significant difference between cases and controls as regards results of MRI with lower mean right, left, and average bulb volume among cases. Similarly, the bulb flair signal and T1 signal on each side were significantly different between cases and controls. Also, we found that there was a highly significant positive correlation between Right, left, and average bulb volume, and UPSIT score among cases indicating that a dedicated MR study of the OB could be used for objective assessment of anosmia. Further studies with larger scales are needed to confirm our results.