Medullo-ponto-cerebellar white matter degeneration altered brain network organization and cortical morphology in multiple system atrophy.

The cerebellum involves diverse functions from motor coordination to higher cognitive functions. Impairment of the cerebellum can cause ataxia and cerebellar cognitive affective syndrome. Multiple system atrophy of the cerebellar type (MSA-C) is a neurodegenerative disorder with atrophy of medullo-ponto-cerebellar (MPC) white matter (WM). To understand the role of the cerebellum from the perspective of the local structure to the global function in the presence of MPC WM degeneration, we acquired T1-weighted and diffusion tensor images for 17 patients with MSA-C and 19 normal controls. We concurrently used the measures of local morphology, including MPC WM volume and inner surface area, and properties of global network organization based on graph theory for the MSA-C and control groups. The results showed that MPC WM degeneration caused the destruction of cerebello-ponto-cerebral loops, resulting in reduced communication efficiency between regions in the whole-brain network. In addition, the sulcal area of the inner cortical surface in the cerebellum decreased linearly with the MPC WM volume, and the inferoposterior lobe exhibited a steeper atrophy rate than that of vermis regions. We concluded that the integrity of MPC WM is critical in sustaining the local morphology and the global functions of the whole-brain fiber network.