MRI-based evidence of rectus capitis posterior minor hypertrophy and its correlation with disease progression in Parkinson's disease

Background Recent research on Parkinson’s disease(PD) has increasingly focused on alterations in cerebrospinal fluid(CSF) dynamics and the glymphatic system(GS). The rectus capitis posterior minor (RCPmi), a key component of the myodural bridge complex(MDBC), is reported to modulate CSF dynamics. Using magnetic resonance imaging (MRI), this study investigated changes in the net cross-sectional areas (CSA) of the RCPmi in PD patients to explore its potential impact on CSF dynamics and its role in the pathogenesis and progression of PD. Materials and Methods In this retrospective MRI study, 349 participants were enrolled, including 156 patients with PD and 193 healthy controls. The net CSA of the MDBC constituent muscles and control non-component muscles were quantitatively assessed. Correlation analysis between RCPmi CSA and disease duration was conducted in a subgroup of 51 PD patients with documented disease history ranging from 1 to 14 years. Moreover, three-dimensional volumetric analysis of the occipito-atlantal cistern (OAC) was performed in 277 participants (114 with PD, 163 controls) who exhibited typical morphological features. Results Compared to the healthy control group(HC), the PD group showed significantly larger net CSA of all MDBC constituent muscles ( P < 0.05), with the most pronounced hypertrophy observed in the RCPmi (PD: 1.97 ± 1.35 mm² vs. healthy control: 1.58±1.07 mm²; P = 0.003). A moderate positive correlation was identified between RCPmi CSA and disease duration (r = 0.47, P < 0.001). Additionally, the PD group exhibited significantly increased OAC volume, evidenced by greater dorsal distances at both the atlas and axis levels ( P = 0.020 and P = 0.004, respectively). Conclusion This MRI study demonstrates pathological hypertrophy of the RCPmi in PD, the extent of which correlates with both disease duration and enlargement of the OAC. Such hypertrophy may impair the clearance efficiency of neurotoxic metabolites via dual biomechanical pathways-encompassing both short-and long-term effects-thereby contributing to PD pathogenesis. Consequently, morphological alterations in the RCPmi hold promise as an imaging biomarker for monitoring disease progression in PD.