[Multi-dimension MRI study of morphological changes of the right orbitofrontal cortex in patients with olfactory...

Objective: To explore the alterations in gray matter morphology and contributing factors in patients with post-infectious olfactory dysfunction (PIOD) using voxel-based morphometry (VBM) and surface-based morphometry (SBM), thereby providing scientific insights into the neuropathological mechanisms underlying PIOD. Methods: A total of 46 PIOD patients (PIOD group) and 46 normosmic volunteers (control group) were recruited from the Smell and Taste Disorders Clinic of Beijing Anzhen Hospital, Capital Medical University, between January 2020 and December 2024. All participants underwent olfactory psychophysical tests (Sniffin' Sticks) and olfactory event-related potential (oERP) examination. High-resolution T1-weighted 3D MRI structural images were obtained for both groups. VBM was employed to analyze inter-group differences in gray matter volume, while SBM was used to assess cortical thickness and folding index. Correlations between gray matter volume in significant difference brain regions and disease duration, Sniffin' Sticks scores, oERP parameters were analyzed. A two-tailed P<0.05 was considered statistically significant. Results: No significant differences were observed in age, sex, education level, or Mini-Mental State Examination (MMSE) scores (t=1.80, χ²=0.41, t=0.17, t=1.77, all P>0.05). Compared with controls, the PIOD group showed significantly lower Sniffin' Sticks scores (t=28.70, P<0.001), prolonged oERP latencies and reduced amplitudes (all P<0.001). VBM revealed significantly reduced gray matter volume in the right orbitofrontal cortex (OFC) in the PIOD group (t=5.38, P<0.001). SBM demonstrated decreased cortical thickness in the right OFC (t=5.27, P<0.001), with no significant differences in folding index. The gray matter volume in the right OFC was negatively correlated with disease duration (r=-0.61, P<0.001), but no significant correlations were found with Sniffin' Sticks scores or oERP parameters. Conclusion: Patients with PIOD show atrophy in the right OFC, which correlates with disease duration, suggesting that persistent olfactory dysfunction may be associated with neurodegenerative changes.