Different iron distribution patterns in Parkinson's disease and its motor subtypes: a quantitative susceptibility mapping study

Background This study utilized quantitative susceptibility mapping (QSM) to evaluate magnetic susceptibility of brain nuclei in Parkinson's disease (PD). Purpose To explore iron deposition patterns in PD and ascertain if these patterns can distinguish between motor subtypes. Material and Methods This study enrolled 30 healthy controls and 34 patients with PD categorized mainly into postural instability and gait disorder (PIGD) (n = 12) and tremor dominance (TD) (n = 16). A total of 18 regions of interest were delineated, and a comprehensive classification of nuclei was conducted, including the differentiation of globus pallidus (GP) into its external (GPe) and internal (GPi) segments. All participants underwent brain magnetic resonance imaging. Results Notable differences in magnetic susceptibility were identified in bilateral substantia nigra pars reticulate (SNr) and substantia nigra pars compacta (SNc) between PD and HC. Significant differences in QSM values of bilateral GPe, SNr, and SNc-R were found between TD and PIGD. The susceptibility values of bilateral putamen (PUT) were positively correlated with MDS-UPDRSIII score and Hoehn-Yahr scale in PD. QSM values of bilateral PUT and SNc-L showed associations with MDS-UPDRSIII score in TD. QSM values showed associations with MDS-UPDRSIII in bilateral PUT and Hoehn-Yahr scale in PUT-L and TH-L in PIGD. Conclusion Pathologic iron deposition exhibits variability across nuclei of PD, with age also influencing this distribution. SN may be meaningful in identifying different subtypes of PD, such as differentiating PD from HC in the future.