title: Extent of microstructural white matter injury in postconcussive syndrome correlates with impaired cognitive reaction time: a 3T diffusion tensor imaging study of mild traumatic brain injury.
abstract: OBJECTIVE
  Diffusion tensor imaging (DTI) may be a useful index of microstructural changes implicated in diffuse axonal injury (DAI) linked to persistent postconcussive symptoms, especially in mild traumatic brain injury (TBI), for which conventional MR imaging techniques may lack sensitivity. We hypothesized that for mild TBI, DTI measures of DAI would correlate with impairments in reaction time, whereas the number of focal lesions on conventional 3T MR imaging would not.
  
  
  METHODS
  Thirty-four adult patients with mild TBI with persistent symptoms were assessed for DAI by quantifying traumatic microhemorrhages detected on a conventional set of T2*-weighted gradient-echo images and by DTI measures of fractional anisotropy (FA) within a set of a priori regions of interest. FA values 2.5 SDs below the region average, based on a group of 26 healthy control adults, were coded as exhibiting DAI.
  
  
  RESULTS
  DTI measures revealed several predominant regions of damage including the anterior corona radiata (41% of the patients), uncinate fasciculus (29%), genu of the corpus callosum (21%), inferior longitudinal fasciculus (21%), and cingulum bundle (18%). The number of damaged white matter structures as quantified by DTI was significantly correlated with mean reaction time on a simple cognitive task (r = 0.49, P = .012). In contradistinction, the number of traumatic microhemorrhages was uncorrelated with reaction time (r = -0.08, P = .71).
  
  
  CONCLUSIONS
  Microstructural white matter lesions detected by DTI correlate with persistent cognitive deficits in mild TBI, even in populations in which conventional measures do not. DTI measures may thus contribute additional diagnostic information related to DAI.
authors.affiliation: Department of Psychiatry, Sackler Institute, Weill Medical College of Cornell University, New York, NY 10065, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Niogi
authors.forename: P
authors.initials: P
authors.lastname: Mukherjee
authors.forename: J
authors.initials: J
authors.lastname: Ghajar
authors.forename: C
authors.initials: C
authors.lastname: Johnson
authors.forename: R A
authors.initials: RA
authors.lastname: Kolster
authors.forename: R
authors.initials: R
authors.lastname: Sarkar
authors.forename: H
authors.initials: H
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Meeker
authors.forename: R D
authors.initials: RD
authors.lastname: Zimmerman
authors.forename: G T
authors.initials: GT
authors.lastname: Manley
authors.forename: B D
authors.initials: BD
authors.lastname: McCandliss
mesh_terms: D000293:Adolescent; D000328:Adult; D001924:Brain Concussion / Q000473:pathology*; D001930:Brain Injuries / Q000473:pathology*; D003072:Cognition Disorders / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D011930:Reaction Time; D013223:Statistics as Topic; D013577:Syndrome