Fig. 2: Results of the white matter ROI analysis and schematic imaging of significant regions.

Within the white matter, there were significantly lower (P < 0.05, false discovery rate [FDR]-corrected) ICVF and MVF values, and significantly higher FW or RD_T in the middle cerebellar peduncle (MCP; green line in schematic) and inferior cerebellar peduncle (ICP; light blue line) in MSA-P patients compared with HCs and PDs. The MVF values in the pontine crossing tract (yellow line) were significantly lower in MSA-P patients compared with HCs and PD, whereas FW in the corticospinal tract (CST; light red line) was significantly higher in MSA-P patients. In the second cohort of white matter, very similar results of first cohort were observed in the four regions of MCP, ICP, PCT, and CST. The differences from the first cohort were the absence of significant differences in FW in the ICP (although a non-significant trend remained), significantly higher FW in the PCT, and significantly lower ICVF in the CST of MSA-P patients compared with HCs and PD patients. In the boxplot, the center line represents the median, the box represents the third quartile, and the whiskers represent the maximum and minimum values. FW free water, ICVF intracellular volume fraction, MVF myelin volume fraction, pSN posterior part of SNc, RD_T free water-corrected radial diffusivity, aSN anterior part of SNc, SNc substantia nigra pars compacta.