White matter abnormalities of fronto-striato-thalamic circuitry in obsessive-compulsive disorder: A study using diffusion spectrum imaging tractography.

Previous studies have reported white matter abnormalities in patients with obsessive-compulsive disorder (OCD). This study aimed to further explore white matter abnormalities in OCD patients through diffusion spectrum imaging (DSI) and tractography of the two white matter tracts which most probably play an important role in OCD neuropathology: the anterior segment of cingulum bundles (ACB) and the anterior thalamic radiations (ATR). Twelve right-handed, medicated adult patients with OCD and 12 matched controls underwent DSI on a 3 tesla magnetic resonance imaging (MRI) system. Tractography based on DSI data was reconstructed to define the ACB and ATR. Mean generalized fractional anisotropy (GFA) was calculated for each targeted tract and was used to analyze local changes in microstructural integrity along individual tracts. There was a significantly lower mean GFA in both the right ATR and left ACB in OCD subjects compared to controls. OCD subjects also demonstrated decreased left-lateralized asymmetry of the ACB when compared to controls. Furthermore, the mean GFA of the left ACB positively correlated with OCD subjects' obsessive subscores on the Yale-Brown Obsessive-Compulsive scale. This study supports the white matter abnormalities in the ACB and ATR of OCD subjects, which corroborates neurobiological models that posit a defect in fronto-striato-thalamic circuitry in OCD.