Interhemispheric asymmetry of regional cerebral blood flow in prepubescentboys with attention deficit hyperactivity disorder

The prefrontal cortex is asymmetric in both structure and function. In norm al subjects, the right prefrontal cortex is activated more than the left du ring response inhibition. Patients with attention deficit hyperactivity dis order (ADHD) have impaired response inhibition and altered structural inter hemispheric asymmetry. This study was conducted to examine the functional i nterhemispheric asymmetry during response inhibition in children with ADHD. Subjects were divided into three groups according to the level of motor hy peractivity. Blood flow tracer Tc-99m-ethyl cysteinate dimer was injected w hile subjects were performing a response inhibition task (RIT), followed by single photon emission computerized tomography (SPECT). After three-dimens ional reconstruction, filtering and smoothing, individual scans were morphe d to a template. Three average group images were created from individual sc ans. Each average group image was subtracted voxel-by-voxel from its mirror image to compare the regional cerebral blood flow (rCBF) in the right and left cerebral hemispheres, yielding images of significant interhemispheric rCBF asymmetry. The severe hyperactivity group exhibited most prefrontal le ft>right rCBF asymmetry and left>right occipitoparietal asymmetry. Reversal of functional prefrontal asymmetry in boys with severe motor hyperactivity supports the hypothesis of right prefrontal cortex dysfunction in ADHD. (( C) 2001 Lippincott Williams & Wilkins).