Reduced volumes in some regions with increased volumes in other areas of the brain appear to be consistent in children and adolescents with attention deficit hyperactivity disorder, according to an article in the November 22nd issue of the Lancet. Further study of the structural correlates of the disorder may provide insight into the mechanisms underlying clinical symptoms.

Attention-deficit hyperactivity disorder is a serious neuropsychiatric problem in U.S. schoolchildren, with an estimate that 3 to 6 percent of students are affected. IN the current study, Elizabeth R Sowell, MD, and her American colleagues undertook the first detailed morphological study using high-resolution magnetic resonance imaging and sophisticated computational systems to more accurately determine the specific areas of the brain underlying the disorder. Brain assessment of 27 children and adolescents (11 girls, 16 boys) with the disorder was compared with that of 46 healthy, control children who were matched for age and sex.

Abnormal brain structure was observed in the frontal cortexes of affected children, with reduced regional brain size localized mainly to small areas of the dorsal prefrontal cortex. Children with attention deficit hyperactivity disorder also had reduced brain size bilaterally in the anterior temporal region. Substantial increases in gray matter were seen in large portions of the posterior temporal and inferior parietal cortexes in affected children.

Sowell commented, "Our morphometric procedures allow more precise localization of group differences than do the methods used in previous studies. Our results therefore suggest that the disturbances in prefrontal cortices are localized to more inferior aspects of prefrontal regions than was previously appreciated. Our findings also indicate that prefrontal abnormalities are represented bilaterally, by contrast to the predominantly right-sided findings that were emphasized in other reports."

Bradley Peterson, MD, a study coauthor, said, "The findings are not only in brain regions controlling attention, but also in regions that subserve impulse control. Disordered impulse control is often the most clinically debilitating symptom in children with attention deficit hyperactivity disorder. These findings may help us understand the sites of action of the medications used to treat [the disorder], particularly stimulant medications. In conjunction with other imaging techniques, the findings may help us to develop new therapeutic agents given our knowledge of the cellular and neurochemical make-up of brain regions where we detected the greatest abnormalities."