REGIONAL CEREBRAL BLOOD-FLOW IN OBSESSIVE-COMPULSIVE DISORDERED PATIENTS AT REST - DIFFERENTIAL CORRELATES WITH OBSESSIVE-COMPULSIVE AND ANXIOUS-AVOIDANT DIMENSIONS

Background. We tested whether cortical and subcortical regional cerebr al blood flow (rCBF) differs between patients with obsessive-compulsiv e disorder (OCD) and healthy controls. We then explored the relationsh ip between rCBF and OCD mental state. Method. Thirty out-patients from the Maudsley Hospital with OCD as defined in DSM-III-R were scanned a t rest using brain-dedicated, high-resolution, single photon emission tomography. RCBF was measured as uptake of 99mTc-HMPAO in 15 regions o f interest and compared with rCBF data in 30 healthy people matched fo r age, sex and handedness. Symptom ratings were obtained using standar d measures on the scanning day. Principal components factor analysis i dentified two distinct clinical dimensions: obsessive-compulsive (OC) and anxious-avoidant (AA). These were correlated with patients' rCBF m easurements, using Spearman's rank correlation coefficient, and multip le regression coefficients calculated. Results. We found significant r eductions in rCBF measurements of OCD patients compared with resting, healthy controls (F=7.92, P=0.04) in seven brain regions: the right an d left superior frontal cortex, right inferior frontal cortex, left te mporal cortex, left parietal cortex, right caudate nucleus and right t halamus. Regional differences were not secondary to generalised reduct ion in patients' brain perfusion. Reduced blood flow to the right infe rior frontal cortex correlated significantly with illness severity (r= 0.37, P=0.02). There was no relationship with age, age-of-onset, sex, handedness, depression or medication status. OC clinical dimension, co ncerning obsessions, compulsions and low mood, was significantly negat ively correlated with left inferior frontal, medial frontal and right parietal rCBF. AA dimension, concerning anxiety and avoidance, was sig nificantly positively associated with left and right superior frontal, right inferior frontal, medial frontal cortical, and right and left c audate and thalamic rCBF. Conclusions. rCBF differs significantly betw een resting OCD patients and healthy controls, and separate clinical d imensions are associated with functionally distinct rCBF patterns.