Brain Metabolic Correlates of Persistent Olfactory Dysfunction after SARS-Cov2 Infection

Area of Science:

• Neuroimaging
• Infectious Diseases
• Neurology

Background:

• Persistent olfactory dysfunction is a common sequela of SARS-CoV-2 infection.
• The underlying neurological mechanisms and long-term brain effects of COVID-19 related smell loss remain incompletely understood.
• Positron Emission Tomography (PET) with fluorodeoxyglucose (FDG) is a valuable tool for assessing brain metabolism.

Purpose of the Study:

• To investigate the brain hypometabolic signature in patients with persistent isolated olfactory dysfunction following SARS-CoV-2 infection.
• To identify specific brain regions affected by hypometabolism using [18F]-FDG PET.
• To explore the structural connectivity of these affected brain regions.

Main Methods:

• Twenty-two patients recovered from SARS-CoV-2 infection underwent whole-body [18F]-FDG PET with dedicated brain acquisition.
• Fourteen patients with isolated persistent hyposmia (smell dysfunction) were analyzed.
• Voxel-wise analysis using Statistical Parametric Mapping (SPM8) and structural connectivity assessment (BCB toolkit) were performed to compare patients with controls.

Main Results:

• Patients with persistent hyposmia exhibited relative hypometabolism in the bilateral parahippocampal and fusiform gyri, and the left insula compared to controls.
• Structural connectivity analysis indicated involvement of the bilateral longitudinal fasciculi.
• These findings demonstrate a distinct pattern of cortical hypometabolism associated with post-COVID-19 olfactory dysfunction.

Conclusions:

• Persistent isolated olfactory dysfunction after SARS-CoV-2 infection is associated with significant cortical hypometabolism.
• [18F]-FDG PET imaging can identify long-term functional brain sequelae of COVID-19.
• The study highlights the potential role of neuroimaging in understanding and managing post-COVID neurological conditions.