“Hot cross bun” Sign Grades Means Different White Matter Changes in MSA-C: A Neurite Orientation Dispersion and Density Imaging Study

White matter (WM) changes play an important role in the progression of multiple system atrophy cerebellar type (MSA-C), and doctors need an imaging marker to grade the WM alterations. We observed different WM alterations between MSA-C patients with unclear “hot cross bun” sign (HCBs) and patients with complete HCBs, using NODDI, analyzed by TBSS. Compared with healthy controls, patients with complete HCBs showed broader different regions of intracellular volume fraction (ICVF) than ones with unclear HCBs, and meanwhile, difference of orientation dispersion index (ODI) and isotropic volume fraction (ISOVF) were only shown in complete HCBs ones. Difference of ICVF between patients with unclear and complete HCBs was also obvious. All of these findings indicated HCBs might be an imaging marker to assess the WM changes in MSA patients.