Olfactory-related cortical atrophy is associated with olfactory dysfunction in Parkinson's disease.

BACKGROUND: Olfactory dysfunction is often associated with Parkinson's disease (PD) and can precede characteristic motor symptoms by several years. Olfactory-related cortical atrophy has been reported in PD, although the extent and association between cortical atrophy and olfactory dysfunction have been controversial. The present study examined whether olfactory dysfunction is associated with gray matter (GM) volume in brain regions subserving primary and secondary olfactory processing. METHODS: High-resolution T1-weighted brain MRIs were acquired from 40 PD without dementia and 40 matched controls along with smell identification scores. Brain volumes were compared using voxel-based morphometry. RESULTS: Compared to controls, PD patients sustained greater GM loss localized to bilateral piriform cortex (PC) and orbitofrontal cortex (OFC). Reduced olfactory performance in PD was significantly associated with lower GM volumes in PC and OFC. CONCLUSIONS: Both primary and secondary olfactory cortical atrophy occurred in PD and were associated with olfactory dysfunction.