Regional-specific structural and functional changes of posterior cerebellar vermis across different stages of...

Stage-specific roles of posterior cerebellar vermis (PV) subdivisions, the posterior superior vermis (PSV) and posterior inferior vermis (PIV), in Parkinson's disease postural instability/gait difficulty (PD-PIGD) remain unclear. This retrospective, cross-sectional study investigated their volumetric and functional connectivity (FC) changes and clinical correlates across PD-PIGD stages. We analyzed 94 PD-PIGD patients (Hoehn & Yahr, HY1-4) and 46 healthy controls (HCs). Patient data were from outpatients and baseline assessments in two clinical trials (ClinicalTrials.gov: NCT02969941, reg. 2016-06-01; NCT05192759, reg. 2021-11-22). Compared with HCs, early-stage (HY1) patients showed enhanced PSV-left paracentral lobule (L_PCL) FC, alongside a trend toward increased PSV volume. This PSV-L_PCL FC correlated with better cognition function and gait performance, an association partly cognition-mediated. Our findings reveal a PSV-specific nonlinear pattern of structural and functional changes in PD-PIGD, distinct from PIV or other cerebellar subregions, potentially reflecting early compensatory mechanisms transitioning to later network dysfunction.