Microstructural Correlates of Olfactory Dysfunction in Parkinson’S Disease: A Systematic Review of Diffusion Mri Studies Publisher Pubmed



Seyedmirzaei H¹ ; Rasoulian P¹ ; Parsaei M² ; Hamidi M³ ; Ghanbari A⁴ ; Soltani Khaboushan A⁴ ; Fatehi F^{5, 6} ; Kamali A⁷ ; Sotoudeh H⁸ Show Affiliations
Source: Brain Imaging and Behavior Published:2025

Abstract

Olfactory dysfunction (OD) is a non-motor symptom of Parkinson's Disease, affecting 75–95% of the patients. This symptom usually emerges before the clinical diagnosis, and patients with OD present with more severe forms of PD and need higher doses of therapy. It remains unknown whether OD is just a mere non-motor symptom or if it is a part of a series of pathological changes in different brain regions of the affected patients. We performed a systematic review to find the microstructural correlates of OD in people with PD. The systematic search in PubMed, Scopus, Embase, and Web of Science yielded ten eligible studies. Assessments in most included studies were inconclusive. However, we found variable brain regions and tracts associated with OD. The most repeated areas included the primary olfactory cortex, gyrus rectus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, corticospinal tract, uncinate fasciculus, cingulum, and cerebellar peduncle. Despite some limitations, we pointed out the microstructural correlates of OD, which were also present in areas other than the olfactory system. These findings imply that OD might be a manifestation of an unknown, greater pathology in the brain of patients with PD. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.