title: Tract based spatial statistics in multiple system atrophy: a comparison between clinical subtypes.
abstract: 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.
authors.affiliation: Department of Neurology, Nanjing Brain Hospital, Nanjing Medical University, No. 264 Guangzhou Road, Nanjing 210029, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Ji
authors.affiliation: Department of Neurology, Nanjing Brain Hospital, Nanjing Medical University, No. 264 Guangzhou Road, Nanjing 210029, PR China.
authors.forename: Donglin
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Department of Radiology, Nanjing Brain Hospital, Nanjing Medical University, No. 264 Guangzhou Road, Nanjing 210029, PR China.
authors.forename: Chaoyong
authors.initials: C
authors.lastname: Xiao
authors.affiliation: Department of Neurology, Nanjing Brain Hospital, Nanjing Medical University, No. 264 Guangzhou Road, Nanjing 210029, PR China; Department of Neurology, School of Medicine, Nanjing University, No. 22 Hankou Road, Nanjing 210093, PR China. Electronic address: profshijp@163.com.
authors.forename: Jingping
authors.initials: J
authors.lastname: Shi
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D016880:Anisotropy; D001921:Brain / Q000473:pathology; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000145:classification* / Q000175:diagnosis*; D011712:Pyramidal Tracts / Q000473:pathology*; D013223:Statistics as Topic; D066127:White Matter / Q000473:pathology*
keywords: Diffusion tensor image; MSA variants; Superior longitudinal fasciculus; Tract based spatial statistic analysis; White matter