title: Diffusion tensor tractography-based group mapping of the pyramidal tract in relapsing-remitting multiple sclerosis patients.
abstract: OBJECTIVE
  Many studies have reported abnormal changes in relapsing-remitting multiple sclerosis (RRMS) by histogram and region-of-interest-based methods by using diffusion tenor imaging. However, there are few studies on specific white matter fiber tracts of RRMS. Our study sought to use diffusion tensor tractography-based group mapping to investigate the presence of abnormal diffusion in the normal-appearing pyramidal tract (PYT) of RRMS and its possible mechanism.
  
  
  METHODS
  A PYT probability map was first constructed from data on 20 healthy patients based on the deterministic-based tractography method. The PYT probability map was then applied to 29 RRMS patients to calculate diffusion indices of the PYT. In this study, 4 quantitative indices-fractional anisotropy (FA), directionally averaged diffusion coefficient (D(av)), axial diffusion coefficient (lambda(1)), and radial diffusion coefficient (lambda(23))-were used to characterize the abnormal diffusion.
  
  
  RESULTS
  Compared with healthy controls, RRMS patients had a significantly higher D(av) and lambda(23) but a lower FA and a trend toward a lower lambda(1) in the normal-appearing PYT. In RRMS patients, PYT lesions had a significantly higher lambda(23) and a lower FA, but there were no differences for D(av) and lambda(1) when compared with the normal-appearing PYT. Moreover, the diffusion indices derived from the normal-appearing PYT were significantly correlated with PYT lesion volumes by using the Spearman correlation analysis.
  
  
  CONCLUSIONS
  Our findings confirm the presence of abnormal diffusion in the normal-appearing PYT of RRMS patients and suggest that wallerian degeneration might be its mechanism.
authors.affiliation: National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: F
authors.initials: F
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: Yu
authors.forename: T
authors.initials: T
authors.lastname: Jiang
authors.forename: K
authors.initials: K
authors.lastname: Li
authors.forename: P
authors.initials: P
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000473:pathology*; D011712:Pyramidal Tracts / Q000473:pathology*