title: Tract-specific white matter structural disruption in patients with bipolar disorder.
abstract: OBJECTIVE
  A growing body of evidence suggests that, independent of localized brain lesions, mood disorders can be associated with dysfunction of brain networks involved in the modulation of emotional and cognitive behavior. We used diffusion tensor (DT) tractography to quantify the presence and extent of structural injury to the connections between the amygdala and other brain regions, which included the subgenual, the supragenual and posterior cingulate, the parahippocampal, the orbitofrontal and dorsolateral prefrontal cortices, as well as the insula.
  
  
  METHODS
  Using a 3.0 Tesla scanner, conventional and DT magnetic resonance imaging sequences of the brain were acquired from 15 adult patients with major depressive disorder (MDD), 15 with bipolar disorder (BD), and 21 age-matched healthy controls. Using FSL software, diffusivity changes of the white matter (WM) fiber bundles belonging to the emotional network were measured.
  
  
  RESULTS
  Compared to controls and MDD patients, BD patients had significantly decreased average fractional anisotropy, increased average mean diffusivity, and increased average axial and radial diffusivity values in the majority of the WM fiber bundles connecting structures of the anterior limbic network (p-values ranging from 0.002 to 0.040). Medication load did not influence the results with the exception of lithium, which was associated with normal diffusivity values in tracts connecting the amygdala with the subgenual cingulate cortex.
  
  
  CONCLUSIONS
  We detected specific WM abnormalities, suggestive of disrupted integrity of fiber bundles in the brains of patients with BD. These abnormalities might contribute to understanding both mood dysregulation and cognitive disturbances in BD, and might provide an objective marker to monitor treatment efficacy in this condition.
authors.affiliation: Department of Clinical Neurosciences, Scientific Institute and University Vita-Salute San Raffaele, Milano, Italy. benedetti.francesco@hsr.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Benedetti
authors.forename: Martina
authors.initials: M
authors.lastname: Absinta
authors.forename: Maria A
authors.initials: MA
authors.lastname: Rocca
authors.forename: Daniele
authors.initials: D
authors.lastname: Radaelli
authors.forename: Sara
authors.initials: S
authors.lastname: Poletti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bernasconi
authors.forename: Sara
authors.initials: S
authors.lastname: Dallaspezia
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Pagani
authors.forename: Andrea
authors.initials: A
authors.lastname: Falini
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Copetti
authors.forename: Cristina
authors.initials: C
authors.lastname: Colombo
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Comi
authors.forename: Enrico
authors.initials: E
authors.lastname: Smeraldi
authors.forename: Massimo
authors.initials: M
authors.lastname: Filippi
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016880:Anisotropy; D001714:Bipolar Disorder / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D003865:Major Depressive Disorder / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology