Different iron deposition patterns in Parkinson's disease subtypes: a quantitative susceptibility mapping study

Background: Parkinson's disease (PD) is a heterogeneous neurodegenerative disorder with various subtypes and uncertain pathogenesis. Iron deposition is considered to be involved in the pathological mechanisms of PD. The present study aimed to investigate the iron deposition in deep gray matter in patients with different PD subtypes using quantitative susceptibility mapping (QSM).

Methods: Forty-six PD patients and 22 healthy controls (HCs) were recruited for the study. PD patients were allocated to the tremor-dominant (TD) group (n=22), postural instability and gait disorder-dominant (PIGD) group (n=19), and intermediate group (n=5). Susceptibility values in deep gray matter nuclei measured by QSM among the PD-TD and PD-PIGD groups and the HCs, as well as the relationship between iron accumulation and clinical motor features, were investigated.

Results: Susceptibility values in the dentate nucleus (DN) were greater in the PD-TD (118.73±70.45) group than in the PD-PIGD (72.14±39.85, P=0.02) group and HCs (78.26±41.38, P=0.042). Further, a significant positive correlation was observed between the DN susceptibility values and tremor scores (r=0.324, P=0.028). Compared with the HCs (182.60±85.35), both the PD-TD (282.00±102.49, P=0.006) and PD-PIGD groups (284.91±118.54, P=0.007) exhibited greater susceptibility values in the substantia nigra (SN) pars reticulata. The susceptibility values in the SN pars compacta were also greater in the PD-PIGD group (164.51±89.44) than in the HCs (107.78±63.11, P=0.048).

Conclusions: The present study demonstrated various iron deposition patterns in different PD phenotypes. These findings give insight into the pathophysiology underlying different PD phenotypes, and potentially illustrate the involvement of iron deposition in the PD-TD and PD-PIGD subtypes.