Similarities and differences in cerebellar grey matter volume and disrupted functional connectivity in idiopathic Parkinson's disease and multiple system atrophy

Objective: This study investigated the potential differences in changes to cerebellar grey matter volume (GMV) and functional connectivity (FC) and the association between them, which might elucidate cerebellar function in multiple system atrophy (MSA) and idiopathic Parkinson's disease (IPD). Methods: Resting-state functional magnetic resonance imaging and three-dimensional T1 scans were obtained from 38 IPD, 62 MSA, and 59 healthy controls (HC). Seed-based connectivity analysis and voxel-based morphometry analysis were performed to assess the changes of cerebellar FC and GMV between the patient groups. Result Decreased cerebellar GMV was found in the motor cerebellum in both patient groups relative to HC, and broader reduction of GMV was observed in both cognitive and motor cerebellum in MSA compared with IPD and HC. Compared with IPD, the MSA group exhibited decreased FC between bilateral dentate nucleus (DN) and default mode network (DMN). Decreased intracerebellar FC was observed in both patient groups relative to HC. Cerebellar GMV was positively correlated with FC of intracerebellum and DN-DMN in MSA. Motor/cognitive scores were associated with DN-DMN FC, with considerable cerebellar GMV loss in MSA patients. Conclusion: Cerebellar GMV loss and cerebellar FC alterations showed similarities in IPD and MSA, along with more widespread changes to GMV in motor and cognitive cerebellum and altered DN-DMN FC in MSA. Further research is needed to better describe the alterations of cerebellar GMV in the cognitive cerebellum and association between cerebellar GMV and intracerebellar FC during the early stages of MSA and IPD.