Comprehensive evaluation of cortical structure abnormalities in drug-naïve, adult patients with obsessive-compulsive disorder: a surface-based morphometry study

The study objective was to comprehensively evaluate drug-naïve, adult patients with Obsessive Compulsive Disorder (OCD) for cortical structure abnormalities in comparison with healthy controls. In this cross-sectional study of case-control design, Magnetic Resonance Imaging (1-mm) was performed in drug-naïve OCD patients (N = 50) & age- sex-, education- and handedness-matched healthy controls (N = 40). We examined cortical volume, thickness, surface area & local Gyrification Index (LGI) through a completely automated surface-based morphometric analysis using FreeSurfer software. OCD symptoms and insight were assessed using Yale-Brown Obsessive Compulsive Symptom (Y-BOCS) check-list and severity scale. Illness severity was assessed using Clinical Global Impression Severity (CGI-S) Scale. OCD patients had significantly deficient volume, thickness and surface area of right anterior cingulate gyrus (ACG). Right lingual gyrus surface area was found to be significantly decreased in patients. Y-BOCS obsession score had significant negative correlation with left frontal pole volume. Y-BOCS compulsion score had significant negative correlations with right ACG volume and surface area and right lateral orbitofrontal cortex LGI. CGI-Severity score had significant negative correlations with right lingual gyrus volume, thickness and surface area as well as right lateral orbitofrontal area. Y-BOCS insight score showed a significant negative correlation with LGI of left medial OFC and left rostral ACG. Identification of novel deficits involving occipital brain regions and first-time observations of relevant correlations between various illness characteristics and cortical measures in OCD patients supports a network involving anterior cingulate, orbitofrontal and occipital brain regions in the pathogenesis of OCD.