title: Obsessive-compulsive disorder is a heterogeneous disorder: evidence from diffusion tensor imaging and magnetization transfer imaging.
abstract: BACKGROUND
  Current models of obsessive compulsive disorder (OCD) propose abnormalities of cortico-striatal circuits that involve the orbitofrontal cortex, anterior cingulate cortex, thalamus and the striatum. Nevertheless, during the last years, results of morphometric studies were contradictory. Since fully automated whole-brain voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) are used to assess structural changes in OCD patients, increased consistent evidence has been reported that brain abnormalities are not limited exclusively to the "affective" orbitofronto-striatal circuit. Moreover, several studies conducted using a symptom dimensional approach demonstrated that different symptoms are mediated by distinct neural systems.
  
  
  METHODS
  We investigated structural brain abnormalities in 14 carefully selected adult (≥18 years), male and unmedicated patients with OCD - separately for obsession and compulsion scores (Y-BOCS) - compared to 20 healthy controls as reflected according to white matter changes by fractional anisotropy and apparent diffusion coefficient. Moreover, this is the first study in OCD patients, using magnetization transfer imaging (MTI). This method is said to be more sensitive to subtle structural brain changes than conventional volumetric imaging.
  
  
  RESULTS
  In our study, we show a positive correlation between MTR and Y-BOCS obsession scores with an increased integrity of tissue structure in the parietal cortex, including myelination and axonal density reflected by the magnetization transfer ratio (MTR) which was used for the first time in our study. Furthermore, Y-BOCS scores for compulsions correlated negatively with ADC-maps in the left nucleus lentiformis and the cingulum.
  
  
  CONCLUSIONS
  The results support the hypothesis that OCD is a heterogeneous disorder with distinct neural correlates across symptom dimensions and call for a substantial revision of such a model that takes into account the heterogeneity of the disorder.
authors.affiliation: Department of Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School, Hannover, Germany. glahn.alexander@mh-hannover.de.
authors.forename: Alexander
authors.initials: A
authors.lastname: Glahn
authors.affiliation: Department of Neurology, University Hospital Jena, Jena, Germany. Tino.Prell@med.uni-jena.de.
authors.forename: Tino
authors.initials: T
authors.lastname: Prell
authors.affiliation: Department of Neurology, University Hospital Jena, Jena, Germany. Julian.Grosskreutz@med.uni-jena.de.
authors.forename: Julian
authors.initials: J
authors.lastname: Grosskreutz
authors.affiliation: Department of Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School, Hannover, Germany. Thomas.peschel@email.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Peschel
authors.affiliation: Department of Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School, Hannover, Germany. Mueller-vahl.kirsten@mh-hannover.de.
authors.forename: Kirsten R
authors.initials: KR
authors.lastname: Müller-Vahl
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006179:Gyrus Cinguli; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009771:Obsessive-Compulsive Disorder / Q000473:pathology*; D010296:Parietal Lobe; D017397:Prefrontal Cortex; D013788:Thalamus; D055815:Young Adult