Objective:

To characterize regional brain dysfunction patterns associated with RBD and VH in PD and to explore candidate-region symptom-related effects within regions showing overall between-group differences.

Approach:

• Study Design: Cross-sectional study involving 96 PD patients divided into four groups based on the presence or absence of RBD and VH.
• Imaging Analysis: Resting-state fMRI analyzed using amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo).
• Statistical Methods: Whole-brain four-group analyses followed by exploratory ROI-based 2 × 2 factorial analyses and voxel-wise analyses.

Key Findings:

• Patients with both RBD and VH exhibited the greatest clinical burden and worse cognitive performance.
• Whole-brain analyses revealed abnormalities in frontal, temporal, cerebellar, supplementary motor, and precuneus regions.
• RBD-related patterns were found in precuneus ReHo, cerebellar lobule VIII ReHo, and SMA ALFF.
• VH-related patterns were identified in OFC ReHo, precuneus ReHo, cerebellar Crus I ReHo, SMA ALFF, and temporal pole ALFF.
• Imaging abnormalities correlated with RBD severity, freezing of gait, hallucination burden, and cognition.

Interpretation:

Coexisting RBD and VH may indicate a clinically more severe PD subtype associated with regional abnormalities in various brain regions.

Limitations:

• Findings are exploratory and require confirmation in larger studies.
• Imaging abnormalities were interpreted as post hoc exploratory results rather than independent confirmatory evidence.

Conclusion:

Symptom-related main and interaction patterns should be interpreted as candidate-region exploratory findings.