title: Limbic and callosal white matter changes in euthymic bipolar I disorder: an advanced diffusion magnetic resonance imaging tractography study.
abstract: BACKGROUND
  White matter microstructural changes detected using diffusion tensor imaging have been reported in bipolar disorder. However, findings are heterogeneous, which may be related to the use of analysis techniques that cannot adequately model crossing fibers in the brain. We therefore sought to identify altered diffusion anisotropy and diffusivity changes using an improved high angular resolution fiber-tracking technique.
  
  
  METHODS
  Diffusion magnetic resonance imaging data was obtained from 35 prospectively confirmed euthymic bipolar disorder type 1 patients (age 22-59) and 43 control subjects (age 22-59) drawn from a sample of 120 age- and gender-matched demographically similar case-control pairs. Tractography using a constrained spherical deconvolution approach to account for crossing fibers was implemented. Changes in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity between patient and control groups in subdivisions of the corpus callosum, cingulum, and fornix were measured as indicators of trait differences in white matter microstructural organization in bipolar disorder.
  
  
  RESULTS
  Patients had significantly reduced fractional anisotropy and increased mean diffusivity and radial diffusivity in all divisions of the corpus callosum, left fornix, and subgenual cingulum compared with control subjects. Axial diffusivity was increased in the fornix bilaterally and right dorsal-anterior cingulum.
  
  
  CONCLUSIONS
  By using an improved fiber-tracking method in a clinically homogeneous population, we were able to localize trait diffusivity changes to specific subdivisions of limbic fiber pathways, including the fornix. Our findings extend previous reports of altered limbic system microstructural disorganization as a trait feature of bipolar disorder.
authors.affiliation: Department of Radiology, University Hospital of the KU Leuven, Radiology/MIRC, UZ Herestraat 49, Box 7003, Leuven 3000, Belgium. louise.emsell@med.kuleuven.be
authors.forename: Louise
authors.initials: L
authors.lastname: Emsell
authors.forename: Alexander
authors.initials: A
authors.lastname: Leemans
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: Peter
authors.initials: P
authors.lastname: McCarthy
authors.forename: Ben
authors.initials: B
authors.lastname: Jeurissen
authors.forename: Jan
authors.initials: J
authors.lastname: Sijbers
authors.forename: Stefan
authors.initials: S
authors.lastname: Sunaert
authors.forename: Dara M
authors.initials: DM
authors.lastname: Cannon
authors.forename: Colm
authors.initials: C
authors.lastname: McDonald
mesh_terms: D000328:Adult; D016880:Anisotropy; D001714:Bipolar Disorder / Q000175:diagnosis / Q000473:pathology*; D016022:Case-Control Studies; D003337:Corpus Callosum / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods / Q000523:psychology; D005260:Female; D020712:Fornix, Brain / Q000473:pathology*; D006179:Gyrus Cinguli / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology; D059906:Neuroimaging / Q000379:methods* / Q000523:psychology*