Tract based spatial statistics in multiple system atrophy: a comparison between clinical subtypes.

Objective: Using a novel method of tract-based spatial statistics (TBSS), this study aimed to investigate micro-structural white matter similarities and differences between the two MSA variants.
Methods: Diffusion tensor image data were acquired from 10 MSA-P, 15 MSA-C patients and 15 controls. Using TBSS, we performed pairwise comparison by examining the fractional anisotropy (FA), mean diffusivity, axial diffusivity (AD) and radial diffusivity (RD) maps of the white matter tract. Clusters showing diffusivity abnormalities were used as region of interests for correlation analysis.
Results: Both in MSA-C and MSA-P, we detected significantly decreased FA values in bilateral corticospinal tract (CST) and right anterior thalamic radiation (ATR), increased RD values in bilateral CST, which correlated significantly with clinical severity. Direct comparison of two variants showed higher AD values of superior longitudinal fasciculus (SLF) in MSA-P than in MSA-C.
Conclusions: These findings indicate that patients with MSA-C and MSA-P share similar diffusivity abnormalities in the bilateral CST and right ATR. Higher AD values of SLF in MSA-P than in MSA-C might be a reason for faster functional deterioration in MSA-P than in MSA-C.
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