Longitudinal changes of iron in the substantia nigra of early-stage Parkinson’s disease

Background: Higher iron occurs in the substantia nigra in Parkinson's disease (PD), but its behavior over time is poorly understood. Objective: To determine if nigral iron measured by quantitative susceptibility MRI can track progression of early stages of PD. Methods: Thirty-four early-stage PD patients (disease duration < 4 yrs) and 35 matched controls were recruited. Iron content in the substantia nigra and related regions was obtained using quantitative susceptibility mapping with zero-referencing at both baseline and one-year follow-up, along with clinical metrics. Results: Of five clinic metrics and five regional iron measures, only MDS-UPDRS II (p = 0.046) and SNc iron (p = 0.004) showed significant changes for PD subjects in the one-year epoch. The changes of SNc iron also were correlated with changes of MDS-UPDRS II (p = 0.005). Conclusion: Nigral iron content measured by zero-referencing is sensitive for tracking disease progression in early-stage PD.