Grey-matter abnormalities at the cortical surface and regional brain size were mapped by high-resolution MRI and surface-based, computational image analytical techniques in a group of 27 children and adolescents with attention deficit hyperactivity disorder (ADHD) and 46 controls, matched by age and sex, at the University of California at Los Angeles. Fifteen patients were taking stimulant drugs. Significant structural cortical abnormalities were noted in patients with ADHD. These included bilateral reduction in the size of inferior portions of the dorsal prefrontal and the lateral aspects of anterior and midtemporal cortices. Also, the density of grey matter was increased in posterior aspects of the temporal lobes and inferior aspects of the parietal lobes bilaterally. These dorsolateral, prefrontal, lateral temporal, and parietal regions serve as association areas for integration of information from lower order sensory systems into higher order percepts and functions. These cortical regions and connections are important in the maintenance of attentional focus and the inhibitory control of distracting behavioral impulses, functions that are disrupted in children with ADHD. [1]

COMMENT. The identification of region-specific structural abnormalities in the brain cortices of children with ADHD corroborates previous studies and provides a more detailed analysis and further evidence of a neurobiological basis for ADHD. Variations with sex, age, and IQ in brain volumetric MRI studies, and the need for controls were demonstrated in reports from Johns Hopkins Hospital (Reiss AL et al, 1996). A lack of normal asymmetry of regional brain structures, and decreased volume of the prefrontal cortex, caudate nucleus, and globus pallidus on the right side were demonstrated in MRI studies of 57 boys with ADHD at the National Institutes of Health, Bethesda, MD (Castellanos FX et al, 1996). Underdevelopment of the splenium of the corpus callosum was found in an MRI study of 15 children with ADHD at the Massachusetts General Hospital, Boston (Semrud-Clikeman M et al, 1994). Further studies should include attempts to distinguish patients with subtypes of ADHD. (see Progress in Pediatric Neurology III, PNB Publishers, 1997;pp212 and 294).