MRI Visualizes Anatomical Abnormalities in ADHD
Laurie Barclay, MD
Nov. 20, 2003 — Anatomical abnormalities associated with attention deficit–hyperactivity disorder (ADHD) can be visualized on high-resolution magnetic resonance imaging (MRI), according to the results of a study published in the Nov. 22 issue of The Lancet.
"Our morphometric procedures allow more precise localization of group differences than do the methods used in previous studies," lead author Elizabeth R. Sowell, PhD, from the University of California at Los Angeles, says in a news release. "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."
Of 27 children and adolescents with ADHD evaluated in this study, 11 were girls and 16 were boys. Compared with 46 controls without ADHD who were matched for age and sex, those with ADHD had reduced regional brain size localized predominantly to small areas of the dorsal prefrontal cortices, as well as in bilateral anterior temporal areas.
The ADHD group also had significant increases in the gray matter in large regions of the posterior temporal and inferior parietal cortices.
"The findings are not only in brain regions controlling attention, but also in regions that subserve impulse control," says coauthor Bradley Peterson, MD, from Columbia University and the New York State Psychiatric Institute in New York City. "Disordered impulse control is often the most clinically debilitating symptom in children with ADHD."
Although measures of the severity of ADHD symptom subtypes generally did not correlate significantly with these morphological measures, gray matter in the occipital lobe was inversely correlated with measures of inattention.
Study limitations include small sample size precluding subtyping by anatomical abnormalities and possible confounding by stimulant drugs, which were used by 15 of the 27 patients.
"These findings may help us understand the sites of action of the medications used to treat ADHD, particularly stimulant medications," Dr. Peterson says. "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."
The National Institutes of Mental Health and the Suzanne Crosby Murphy Endowment at Columbia University helped support this study. The authors report no financial conflicts of interest.
Reviewed by Gary D. Vogin, MD