White matter abnormalities in pediatric obsessive-compulsive disorder.

Diffusion tensor imaging (DTI) has been useful in allowing us to examine the nature and extent of neuronal disruption associated with obsessive-compulsive disorder (OCD). However, little is known about the underlying brain structure in OCD. Diffusion-weighted magnetic resonance imaging was performed in 16 children with OCD and 22 typically developing children. Tract-based spatial statistics (TBSS) was used to compare the microstructure of white-matter tracts of OCD children with those of typically developing children. Correlation/regression analyses were also performed on each diffusion measure in order to detect any correlation of white-matter microstructure with scales of symptom severity. Analysis revealed significantly greater axial diffusivity in both the genu and the splenium of the corpus callosum in the control compared to the OCD group; these regions consecutively connect bilateral medial frontal regions and bilateral parietal regions. Secondly, correlation and voxel-based regression analysis revealed that lower axial diffusion correlated with greater severity of symptoms within the OCD group, as measured by the Child Behaviour Checklist-Obsessive Compulsive Scale (CBCL-OCS). The findings demonstrated a correlation of axial diffusivity with severity of symptoms in children with OCD. DTI may provide novel ways to help reveal the relationships between clinical symptoms and altered brain regions.