AbstractIntroductionThe aim of this study was to investigate white matter (WM) abnormalities in obsessive-compulsive disorder (OCD) and its relationship to severity of obsessive-compulsive symptoms.MethodsConventional and diffusion tensor imaging were acquired in nine patients with OCD and nine gender- and age-matched healthy volunteers. Changes in fractional anisotropy (FA) and mean diffusivity (MD) were investigated using selected regions of interest (ROIs) analyses and whole brain tract-based spatial statistic analyses. A priori ROIs were placed bilaterally in internal capsule (IC), superior longitudinal fascicule (SLF), cingulate bundle (CB), and corpus calosum (CC).ResultsROIs analyses showed that, as compared to healthy volunteers, patients with OCD exhibited reduced FA values bilaterally in regions of the posterior limb of the IC and in the SLF and increased MD values bilaterally in the posterior limb of the IC, in the left CB, and in the splenium of CC. Voxelwise analysis showed that, as compared to controls, patients with OCD exhibited reduced FA and increased MD in regions of the cortical spinal tract (genu and posterior limb of internal capsule and corona radiata) and the SLF. Severity of OCD correlated with WM alterations in different brain regions, ie, the left (rho=0.70 [MD]) and right (rho=0.70 [MD]) anterior limb of the IC, the left (rho=0.97 [MD]) and right SLF (rho=0.81 [MD]), and the genu of CC (rho=0.66 [MD]; rho=-0.69 [FA]).ConclusionOur findings support the involvement of different WM tracts in OCD and suggest that greater impairment in WM integrity is associated with increased severity of OCD symptoms.