title: Evidence for fractional anisotropy and mean diffusivity white matter abnormalities in the internal capsule and cingulum in patients with obsessive-compulsive disorder.
abstract: BACKGROUND
  There is evidence to suggest that obsessive-compulsive disorder (OCD) is associated with structural abnormalities in cortico-striato-thalamic circuits, yet the extent of white matter abnormalities is not well established. In this study, we used diffusion tensor imaging (DTI) to examine white matter integrity in specific regions of interest (ROIs) in patients with OCD.
  
  
  METHODS
  Patients with OCD and sex-, age- and IQ-matched healthy controls underwent DTI. The primary objective was to explore whether patients with OCD had white matter abnormalities in the anterior limb of the internal capsule (ALIC), the uncinate fasciculus, the genu of the corpus callosum and the cingulum. The secondary objective was to evaluate the relation between fractional anisotropy and mean diffusivity in these ROIs and other clinical variables (including age at onset of OCD, OCD severity and levels of depressive and anxiety symptomatology) in patients with OCD.
  
  
  RESULTS
  There were 15 patients and 17 controls enrolled in our study. Compared with healthy controls, patients with OCD showed increased fractional anisotropy in bilateral regions of the ALIC adjacent to the body of the caudate, as well as decreased fractional anisotropy in the right anterior limb near the head of the caudate. Patients also had decreased mean diffusivity in the body of the right cingulum and the left anterior cingulum compared with controls. Correlational analyses revealed significant associations of fractional anisotropy and mean diffusivity in select circuits with OCD, depression and anxiety severity scores.
  
  
  CONCLUSIONS
  Inclusion of patients with OCD receiving pharmacotherapy may have been a limitation. In addition, the patients were heterogeneous in terms of their obsessive-compulsive symptom profiles; we did not distinguish between different obsessive-compulsive symptom dimensions.
  
  
  CONCLUSIONS
  The study results provide further evidence for OCD-related white matter abnormalities in the ALIC and cingulum, consistent with a cortico striatal model of OCD.
authors.affiliation: MRC Unit on Anxiety and Stress Disorders, Department of Psychiatry, University of Stellenbosch, South Africa. cl2@sun.ac.za
authors.forename: Christine
authors.initials: C
authors.lastname: Lochner
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Fouché
authors.forename: Stefan
authors.initials: S
authors.lastname: du Plessis
authors.forename: Bruce
authors.initials: B
authors.lastname: Spottiswoode
authors.forename: Soraya
authors.initials: S
authors.lastname: Seedat
authors.forename: Naomi
authors.initials: N
authors.lastname: Fineberg
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Chamberlain
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Stein
mesh_terms: D000328:Adult; D017668:Age of Onset; D016880:Anisotropy; D001369:Axons / Q000473:pathology; D018592:Cross-Over Studies; D039721:Diagnostic and Statistical Manual of Mental Disorders; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006179:Gyrus Cinguli / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D020772:Internal Capsule / Q000473:pathology*; D007406:Interview, Psychological; D008279:Magnetic Resonance Imaging; D008297:Male; D009412:Nerve Fibers / Q000473:pathology; D009483:Neuropsychological Tests; D009771:Obsessive-Compulsive Disorder / Q000473:pathology*