title: White matter differences in euthymic bipolar I disorder: a combined magnetic resonance imaging and diffusion tensor imaging voxel-based study.
abstract: OBJECTIVE
  A broad range of subtle and markedly heterogenous neuroanatomical abnormalities of grey matter and white matter have been reported in bipolar disorder. Euthymic bipolar disorder patients represent a clinically homogenous group in which to identify trait-based biomarkers of bipolar disorder. In this study, we sought to clarify the nature and extent of neuroanatomical differences in a large, clinically homogeneous group of euthymic bipolar disorder patients.
  
  
  METHODS
  Structural magnetic resonance imaging (sMRI) was obtained for 60 patients with prospectively confirmed euthymic bipolar I disorder and 60 individually age- and gender-matched healthy volunteers. High angular resolution diffusion tensor imaging (DTI) scans were obtained for a subset of this sample comprising 35 patients and 43 controls. Voxel-based analysis of both sMRI and DTI data sets was performed.
  
  
  RESULTS
  Bipolar disorder patients displayed global reductions in white matter volume and fractional anisotropy reductions in the corpus callosum, posterior cingulum, and prefrontal white matter compared with controls. There were corresponding increases in radial diffusivity in the callosal splenium in patients compared with controls. No significant group differences were detected in grey matter. In patients, lithium was associated with a bilateral increase in grey matter volume in the temporal lobes, but not with any DTI parameter.
  
  
  CONCLUSIONS
  Euthymic bipolar I disorder is characterized by both diffuse global white matter deficits and potential regional disorganization in interhemispheric and longitudinal tracts, while grey matter appears to be preserved.
authors.affiliation: Clinical Neuroimaging Laboratory, National University of Ireland Galway, Galway, Ireland; Translational MRI, Department of Imaging and Pathology, KU Leuven and Radiology, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Louise
authors.initials: L
authors.lastname: Emsell
authors.forename: Camilla
authors.initials: C
authors.lastname: Langan
authors.forename: Wim
authors.initials: W
authors.lastname: Van Hecke
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Barker
authors.forename: Alexander
authors.initials: A
authors.lastname: Leemans
authors.forename: Stefan
authors.initials: S
authors.lastname: Sunaert
authors.forename: Peter
authors.initials: P
authors.lastname: McCarthy
authors.forename: Rachel
authors.initials: R
authors.lastname: Nolan
authors.forename: Dara M
authors.initials: DM
authors.lastname: Cannon
authors.forename: Colm
authors.initials: C
authors.lastname: McDonald
mesh_terms: D000328:Adult; D000339:Affect / Q000145:classification / Q000502:physiology; D018692:Antimanic Agents / Q000494:pharmacology; D001714:Bipolar Disorder / Q000188:drug therapy / Q000473:pathology / Q000523:psychology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D056324:Diffusion Tensor Imaging / Q000379:methods; D066128:Gray Matter / Q000187:drug effects / Q000473:pathology; D006801:Humans; D018020:Lithium Compounds / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000187:drug effects; D017063:Outcome Assessment, Health Care; D011569:Psychiatric Status Rating Scales; D066127:White Matter / Q000473:pathology
chemical_list: D018692:Antimanic Agents; D018020:Lithium Compounds
keywords: bipolar disorder; diffusion tensor imaging; euthymic; morphometry; voxel-based analysis; white matter