title: Diffusion tensor tractography: corticospinal tract fiber reduction is associated with temporary hemiparesis in benign extracerebral lesions.
abstract: OBJECTIVE
  Benign extracerebral lesions such as meningiomas may cause hemiparesis by compression and deviation without infiltrating the white matter. We used magnetic resonance diffusion tensor imaging and diffusion tensor tractography to investigate the effects of benign extracerebral lesions on the corticospinal tract (CST).
  
  
  METHODS
  Thirteen patients with extracerebral lesions (11 benign meningiomas and 2 benign cysts) underwent magnetic resonance diffusion tensor imaging and diffusion tensor tractography of the CST using fiber assignment by continuous tractography. The CST was reconstructed and assessed by comparing the ipsilateral and unaffected contralateral fibers. The tumor volume, relative fractional anisotropy, fiber deviation, relative fiber number, and relative fiber per voxel were compared between patients without and with temporary presurgical hemiparesis.
  
  
  RESULTS
  Seven patients without hemiparesis and five patients with temporary hemiparesis were analyzed; one patient had permanent weakness and was excluded from analysis. There was no significant difference in the tumor volume, relative fractional anisotropy, presence of cerebral edema, or CST deviation between groups. In patients with temporary hemiparesis, the median relative fiber number (mean, 0.35 +/- 0.32) and relative fiber per voxel (mean, 0.49 +/- 0.14) were significantly reduced compared with patients without hemiparesis (0.92 +/- 0.55, P = 0.04; and 0.96 +/- 0.28, P < 0.01, respectively).
  
  
  CONCLUSIONS
  In patients with benign extracerebral lesions, reduction in fiber number and fiber per voxel, but not fiber deviation, correlated with temporary hemiparesis. Clinical recovery was possible even if the CST fibers detected by diffusion tensor tractography were reduced by benign extracerebral lesions.
authors.affiliation: Department of Neurosurgery, National Neuroscience Institute, Singapore.
authors.forename: Wai Hoe
authors.initials: WH
authors.lastname: Ng
authors.forename: Dennis Lai-Hong
authors.initials: DL
authors.lastname: Cheong
authors.forename: Kathleen Joy
authors.initials: KJ
authors.lastname: Khu
authors.forename: Govidasamy
authors.initials: G
authors.lastname: Venkatesh
authors.forename: Yee Kong
authors.initials: YK
authors.lastname: Ng
authors.forename: C C Tchoyoson
authors.initials: CC
authors.lastname: Lim
mesh_terms: D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000601:surgery*; D008579:Meningioma / Q000175:diagnosis / Q000601:surgery*; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000009:adverse effects* / Q000379:methods; D010291:Paresis / Q000175:diagnosis / Q000209:etiology*; D011712:Pyramidal Tracts / Q000473:pathology / Q000601:surgery*