title: Corticospinal tract degeneration and possible pathogenesis in ALS evaluated by MR diffusion tensor imaging.
abstract: BACKGROUND
  MR diffusion tensor imaging (DTI) appears to be a powerful method to investigate the neuronal and axonal fibre distribution in the human brain. Changes in diffusion characteristics of water molecules in the white matter can be estimated as the apparent diffusion coefficient (ADC) and the fractional anisotropy index (FA).
  
  
  OBJECTIVE
  To characterize DTI changes at three different levels in the corticospinal tract (CST) (corona radiata, internal capsule and pons) in order to elucidate if pathogenesis of ALS is due to an anterograde or retrograde axonal degeneration.
  
  
  METHODS
  We studied eight ALS patients with clinical signs of upper motor neuron involvement. The patients were compared with 11 healthy age-matched controls.
  
  
  RESULTS
  ADC was significantly increased in the CST in ALS patients at the level of the internal capsule and also increased in the pons, but without statistical significance. ADC was unchanged at the level of the corona radiata. FA was significantly reduced at the lowest level (pons), only tended to be reduced in the internal capsule, but was also unchanged in the corona radiata.
  
  
  CONCLUSIONS
  Segmentation of the CST into three regions supports the hypothesis of a 'dying back' mechanism in ALS and suggests that ADC is a more sensitive measure than FA to detect pathological changes in ALS.
authors.affiliation: Department of Neurology, Bispebjerg Hospital, Copenhagen, Denmark. merete.karlsborg@inet.uni2.dk
authors.forename: Merete
authors.initials: M
authors.lastname: Karlsborg
authors.forename: Sverre
authors.initials: S
authors.lastname: Rosenbaum
authors.forename: Mette
authors.initials: M
authors.lastname: Wiegell
authors.forename: Helle
authors.initials: H
authors.lastname: Simonsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Larsson
authors.forename: Lene
authors.initials: L
authors.lastname: Werdelin
authors.forename: Ole
authors.initials: O
authors.lastname: Gredal
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology; D000704:Analysis of Variance; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011712:Pyramidal Tracts / Q000473:pathology*; D013132:Spinocerebellar Degenerations / Q000175:diagnosis* / Q000209:etiology