title: Quantitative evaluation of the axonal degeneration of central motor neurons in chronic cerebral stroke with diffusion tensor imaging.
abstract: BACKGROUND
  Conventional magnetic resonance imaging (MRI) can only show the degeneration-induced morphological changes but fail to quantitatively reveal the degree and extent of the axonal damage of nerve fibers. Diffusion tensor imaging (DTI) has the ability to detect the diffusion of water molecules and thus suitable to the study of axonal degeneration of central motor neurons.
  
  
  OBJECTIVE
  To illustrate and quantitatively evaluate the axonal degeneration of central motor neurons in patients with chronic cerebral stroke.
  
  
  METHODS
  DTI and conventional MRI were carried out with 10 normal control subjects and 25 patients who suffered from chronic cerebral stroke in the region supplied by middle cerebral artery and had varying degrees of limb movement disorders (the mean time of onset was 2.5 months), to measure the fractional anisotropy (FA), volume ratio (VR), apparent diffusion coefficient (ADC), tensor eigenvalues (λ1, λ2, and λ3), and signal intensity (SI) on T2-weighted images, of the central motor fibers (pyramidal tract) in the plane of cerebral peduncle. Results from the ipsilateral side were compared with those from the contralateral side in the same patient and with those from normal control.
  
  
  RESULTS
  The axonal degeneration of central motor neurons manifests in DTI as the decline of FA of the pyramidal tract and the reduction and distortion of the high signal area. While all the FA, VR, ADC, and λ1 in the ipsilateral side reduce on DTI, λ3 increases; the T2-weighted signals exhibit no significant differences among groups.
  
  
  CONCLUSIONS
  The changes and diffusions of water molecule associated with the axonal degeneration of central motor neurons after chronic cerebral stroke can be detected by DTI, which can directly quantitatively reflect the degree and extent of axonal degeneration of central motor neurons and can compensate the shortcomings of conventional MRI and diffusion-weighted imaging (DWI).
authors.affiliation: Department of Radiology, Children's Hospital, Zhejiang University School of Medicine, Hangzhou, PR China.
authors.forename: Can
authors.initials: C
authors.lastname: Lai
authors.forename: Hai-Chun
authors.initials: HC
authors.lastname: Zhou
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Ma
authors.forename: Hong-Xi
authors.initials: HX
authors.lastname: Zhang
mesh_terms: D000368:Aged; D016880:Anisotropy; D001369:Axons / Q000473:pathology*; D016022:Case-Control Studies; D002908:Chronic Disease; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000473:pathology*; D009410:Nerve Degeneration / Q000473:pathology*; D020521:Stroke / Q000473:pathology*
keywords: Chronic cerebral stroke; axonal degeneration; central motor neuron; diffusion tensor imaging; quantitative evaluation