title: Brain atrophy in mild or moderate traumatic brain injury: a longitudinal quantitative analysis.
abstract: OBJECTIVE
  Although mild or moderate traumatic brain injury (TBI) is known to cause persistent neurologic sequelae, the underlying structural changes remain elusive. Our purpose was to assess decreases in the volume of brain parenchyma (VBP) in patients with TBI and to determine if clinical parameters are predictors of the extent of atrophy.
  
  
  METHODS
  We retrospectively assessed the total VBP in 14 patients with mild or moderate TBI at more than 3 months after injury and in seven patients at two time points more than 3 months apart. VBP was calculated from whole-brain MR images and then normalized by calculating the percent VBP (%VBP) to correct for intraindividual variations in cranial size. Clinical parameters at the time of trauma were evaluated for potential predictors of atrophy. Findings were compared with those of control subjects of similar ages.
  
  
  RESULTS
  In the single time-point analysis, brain volumes, CSF volumes, and %VBP were not significantly different between patients and control subjects. In the longitudinal analysis, the rate of decline in %VBP (0.02 versus 0.0064 U/day, P =.05) and the change in %VBP between the first and second time points (-4.16 +/- 1.68 versus -1.49 +/- 1.7, P =.022 [mean +/-SD]) were significantly greater in patients. Change in %VBP was significantly greater in patients with loss of consciousness (LOC) than in those without LOC (P =.023).
  
  
  CONCLUSIONS
  Whole-brain atrophy occurs after mild or moderate TBI and is evident at an average of 11 months after trauma. Injury that produces LOC leads to more atrophy. These findings may help elucidate an etiology for the persistent or new neurologic deficits that occur months after injury.
authors.affiliation: Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: MacKenzie
authors.forename: Faez
authors.initials: F
authors.lastname: Siddiqi
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Bagley
authors.forename: Lois J
authors.initials: LJ
authors.lastname: Mannon
authors.forename: Grant P
authors.initials: GP
authors.lastname: Sinson
authors.forename: Robert I
authors.initials: RI
authors.lastname: Grossman
mesh_terms: D000328:Adult; D001284:Atrophy; D001921:Brain / Q000473:pathology*; D001924:Brain Concussion / Q000150:complications / Q000473:pathology; D001930:Brain Injuries / Q000150:complications / Q000473:pathology*; D016489:Head Injuries, Closed / Q000150:complications / Q000473:pathology; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D038223:Post-Concussion Syndrome / Q000175:diagnosis