Orbital frontal and amygdala volume reductions in obsessive-compulsive disorder

Background: Functional neuroimaging studies have implicated the frontal lob es and the hippocampus-amygdala complex in the pathophysiology of obsessive -compulsive disorder (OCD). These brain regions have not been well investig ated in patients with OCD, however, using magnetic resonance imaging. Methods: Volumes of the superior frontal gyrus, anterior cingulate gyrus, o rbital frontal region, hippocampus, and amygdala were computed from contigu ous magnetic resonance images in a sample of 26 patients with OCD and 26 he althy comparison subjects. Results: Patients with OCD had significantly reduced bilateral orbital fron tal and amygdala volumes com-pared with healthy comparison subjects and lac ked the normal hemispheric asymmetry of the hippocampus-amygdala complex. N either brain structure volumes nor asymmetry indices were significantly cor related with total illness duration or length of current OCD episode. Conclusions: Findings of reduced orbital frontal and amygdala volumes in pa tients implicate a structural abnormality of these brain regions in the pat hophysiology of OCD. Absence of the normal hemispheric asymmetry of the hip pocampus-amygdala complex in patients is consistent with an anomalous neuro developmental process.