Anatomic brain MRIs for 57 boys with ADHD and 55 healthy matched controls, aged 5 to 18 years, were compared at the National Institute of Mental Health, Bethesda, MD. ADHD subjects had a 4.7% smaller total cerebral volume, a significant loss of normal right>left asymmetry in the caudate nucleus, smaller right globus pallidus, smaller right anterior frontal region, smaller cerebellum, and reversal of normal (L>R) lateral ventricular asymmetry. Whereas ventricular volume increased significantly with age for normal subjects, no age-related changes were found in ADHD subjects. Within the ADHD group, Full-Scale WISC-R IQ score correlated with total cerebral volume. Decreased normal caudate asymmetry was associated with increasing perinatal risk only in the ADHD boys. 
COMMENT. Evidence that a lack of normal asymmetry of regional brain structures is involved in the pathophysiology of ADHD is further supported by this study. Decreased volume of the prefrontal cortex, caudate nucleus, and globus pallidus on the right side point to a dysfunction of right-sided prefrontal-striatal systems in ADHD. A decrease in size of the splenium of the corpus callosum, previously reported in ADHD children (see Ped Neur Briefs July 1994;8:55), was not observed.