Persistent olfactory dysfunction after COVID-19 is associated with reduced perfusion in the frontal lobe

Area of Science:

• Neuroscience
• Infectious Diseases
• Radiology

Background:

• Olfactory dysfunction is a frequent symptom of SARS-CoV-2 infection.
• The underlying mechanisms of persistent smell loss and potential central nervous system (CNS) involvement remain unclear.

Purpose of the Study:

• To investigate the neural correlates of persistent olfactory dysfunction in patients with post-COVID syndrome.
• To explore the relationship between olfactory deficits and neuroimaging findings.

Main Methods:

• Eighty-two patients with post-COVID syndrome underwent olfactory testing (Brief Smell Identification Test) and multimodal MRI.
• MRI techniques included 3D-T1, T2-FLAIR, diffusion-tensor imaging (DTI), and arterial spin labeling (ASL).
• Examinations were conducted approximately 11 months post-infection, with voxel-based analyses correlating olfactory function with brain structure and perfusion.

Main Results:

• Reduced tissue perfusion in orbital and medial frontal regions was associated with olfactory dysfunction, identified via ASL.
• No significant differences in brain volumes or white matter microstructure (DTI) were found.
• Minor sinonasal changes were observed in a small percentage of patients, unrelated to olfactory deficits.

Conclusions:

• Persistent olfactory dysfunction following COVID-19 involves alterations in brain regions critical for olfaction.
• Findings suggest a neurovascular component to long-term smell impairment after SARS-CoV-2 infection.