White matter alterations in right-onset versus left-onset Parkinson's disease in an early stage

This study aimed to investigate the differences in White Matter (WM) microstructure between early-stage patients with left-onset PD (LPD) and right-onset PD (RPD), looking for possible neuroimaging mechanisms.

Diffusion tensor imaging data were acquired from eighteen RPD patients, fourteen LPD patients, and a control group of 18 healthy controls (HC). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated for all participants. Tract-based spatial statistics (TBSS) were applied to each diffusion parameter to compare WM differences among RPD, LPD, and HC. Furthermore, correlation between diffusivity indices values in the regions showing abnormality and clinical indicators were calculated.

Compared to HC and LPD patients, RPD patients exhibited increased MD and RD values in the corpus callosum, multiple association fibers, and the corona radiata, with more significant white matter changes in the left hemisphere than in the right. The regions with elevated RD largely overlapped with those showing increased MD. No statistically significant differences were found between LPD patients, the combined PD group, and HC. An exploratory trend-level correlation was observed between RD values in the left anterior corona radiata and the Unified Parkinson's Disease Rating Scale (UPDRS) and UPDRS-III scores in RPD patients.

Impaired white matter microstructure, mainly in the left hemisphere and potentially characterized by myelin injury, is associated with right-onset, but not left-onset PD patients in an early stage. The microstructure changes of corpus callosum, multiple associated fibers and corona radiata may be involved in the pathogenesis of RPD.