The subdivisions of the corpus callosum (CC) were attempted to define corresponding areas of the cortex from which the fibers originate. Previous neuroanatomic studies of the CC provide impetus for investigating its role in obsessive-compulsive disorder (OCD).

In this study diffusion tensor imaging (DTI) was employed to microstructural abnormalities of white matter of the CC in OCD patients. Nine patients with OCD and matched control subjects underwent DTI. Fractional anisotropy (FA), an index of the integrity of white matter tracts, was determined in the seven subdivisions of the CC. We placed each reagions of interest (ROI) over the sagittal plane and all subdivisions were measured.

Significant reduction in FA was found in the rostrum of the CC of patients with OCD compared with one of controls. FA of the other subdivisions except the rostrum in OCD patients did not differ significantly compared with control subjects. Higher FA in the rostrum correlated significantly with lower Y-BOCS scores (r = -0.803, p = 0.009).

The rostrum contains fibers from inferior premotor as well as medial and caudate/orbital prefrontal regions. These results supported the theory of dysfunction of prefrontal cortex and striatal circuits in OCD and suggested the implication of the orbitofrontal circuit for symptom severity in the OCD patients.