title: White matter microstructure in subjects with attention-deficit/hyperactivity disorder and their siblings.
abstract: OBJECTIVE
  Previous voxel-based and regions-of-interest (ROI)-based diffusion tensor imaging (DTI) studies have found above-normal mean diffusivity (MD) and below-normal fractional anisotropy (FA) in subjects with attention-deficit/hyperactivity disorder (ADHD). However, findings remain mixed, and few studies have examined the contribution of ADHD familial liability to white matter microstructure.
  
  
  METHODS
  We used refined DTI tractography methods to examine MD, FA, axial diffusivity (AD), and radial diffusivity (RD) of the anterior thalamic radiation, cingulum, corticospinal tract, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, forceps major, forceps minor, superior longitudinal fasciculus, and uncinate fasciculus in children and adolescents with ADHD (n = 56), unaffected siblings of ADHD probands (n = 31), and healthy controls (n = 17).
  
  
  RESULTS
  Subjects with ADHD showed significantly higher MD than controls in the anterior thalamic radiation, forceps minor, and superior longitudinal fasciculus. Unaffected siblings of subjects with ADHD displayed similar differences in MD as subjects with ADHD. Although none of the tested tracts showed a significant effect of FA, the tracts with elevated MD likewise displayed elevated AD both in subjects with ADHD and in unaffected siblings. Differences in RD between subjects with ADHD, unaffected siblings, and controls were not as widespread as differences in MD and AD.
  
  
  CONCLUSIONS
  Our findings suggest that disruptions in white matter microstructure occur in several large white matter pathways in association with ADHD and indicate a familial liability for the disorder. Furthermore, MD may reflect these abnormalities more sensitively than FA.
authors.affiliation: Department of Neurology, David Geffen School of Medicine, University of California-Los Angeles, USA.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Lawrence
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Levitt
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Loo
authors.forename: Ronald
authors.initials: R
authors.lastname: Ly
authors.forename: Victor
authors.initials: V
authors.lastname: Yee
authors.forename: Joseph
authors.initials: J
authors.lastname: O'Neill
authors.forename: Jeffry
authors.initials: J
authors.lastname: Alger
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Narr
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D002648:Child; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D056784:Leukoencephalopathies / Q000473:pathology*; D008297:Male; D035781:Siblings