title: Traumatic brain injury, major depression, and diffusion tensor imaging: making connections.
abstract: It is common for depression to develop after traumatic brain injury (TBI), yet despite poorer recovery, there is a lack in our understanding of whether post-TBI brain changes involved in depression are akin to those in people with depression without TBI. Modern neuroimaging has helped recognize degrees of diffuse axonal injury (DAI) as being related to extent of TBI, but its ability to predict long-term functioning is limited and has not been considered in the context of post-TBI depression. A more recent brain imaging technique (diffusion tensor imaging; DTI) can measure the integrity of white matter by measuring the directionality or anisotropy of water molecule diffusion along the axons of nerve fibers.
  
  
  OBJECTIVE
  To review DTI results in the TBI and depression literatures to determine whether this can elucidate the etiology of the development of depression after TBI.
  
  
  METHODS
  We reviewed the TBI/DTI (40 articles) and depression/DTI literatures (17 articles). No articles were found that used DTI to investigate depression post-TBI, although there were some common brain regions identified between the TBI/DTI and depression/DTI studies, including frontotemporal, corpus callosum, and structures contained within the basal ganglia. Specifically, the internal capsule was commonly reported to have significantly reduced fractional anisotropy, which agrees with deep brain stimulation studies.
  
  
  CONCLUSIONS
  It is suggested that measuring the degree of DAI by utilizing DTI in those with or without depression post-TBI, will greatly enhance prediction of functional outcome.
authors.affiliation: Monash Alfred Psychiatry Research Centre, The Alfred and Monash University School of Psychology and Psychiatry, Melbourne Victoria, Australia. j.maller@alfred.org.au
authors.forename: Jerome J
authors.initials: JJ
authors.lastname: Maller
authors.forename: Richard H S
authors.initials: RH
authors.lastname: Thomson
authors.forename: Philip M
authors.initials: PM
authors.lastname: Lewis
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Rose
authors.forename: Kerstin
authors.initials: K
authors.lastname: Pannek
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fitzgerald
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology; D001921:Brain / Q000473:pathology*; D001930:Brain Injuries / Q000473:pathology*; D003865:Major Depressive Disorder / Q000473:pathology*; D056324:Diffusion Tensor Imaging / Q000379:methods; D006801:Humans; D009434:Neural Pathways / Q000473:pathology