One‐Year Substantia Nigra R2* Changes across Parkinson's Disease Stages

Background Magnetic resonance imaging (MRI) relaxometry using measurement is a promising non‐invasive marker of brain iron‐related changes in Parkinson's disease (PD). Although longitudinal susceptibility MRI studies have demonstrated progression over time, the stage‐dependent dynamics of changes across the full spectrum of PD duration remain incompletely characterized. Objectives The goal was to assess 1‐year longitudinal changes across PD stages within a multicenter framework, compared with healthy controls (HC). Methods In this prospective multicenter study, 95 PD patients and 65 age‐ and sex‐matched HC underwent 3 T MRI and clinical evaluation at baseline and 1 year. PD patients were stratified by disease duration (<5, 5–10, 10–15, >15 years). values were extracted from basal ganglia regions, focusing primarily on the substantia nigra (SN). Motor and non‐motor assessments, performed in the on ‐medication state, included the Movement Disorder Society‐Unified Parkinson's Disease Rating Scale, Montreal Cognitive Assessment, and mood/apathy scales. Results SN increased significantly over 1 year across PD patients (+5% within‐group) and HC (+2% within‐group), resulting in a +3% greater longitudinal change in PD versus HC ( P < 0.001). Larger SN changes were observed in patients with longer disease duration ( r = 0.28; P = 0.006). Significant changes were also detected in other basal ganglia regions. No significant change in motor or non‐motor disability in the on ‐medication state was observed over 1 year. Conclusions S N increased over 1 year in PD across disease stages, with larger changes in more advanced patients and no evidence of an early plateau. These findings support the potential of as a sensitive imaging marker of PD progression over short intervals.