The global brain size and a midline area of corpus callosum were measured by MRI in 15 boys with ADHD (mean age 10 years) and compared with 15 healthy male siblings of children with ADHD of the same age. No significant differences occurred in the two groups, nor when compared to unaffected siblings of ADHD children. Development and size of the corpus callosum should not be used as a marker for ADHD. 
COMMENT. No differences are found between the corpus callosum size in ADHD children and their siblings, suggesting that corpus callosum changes reported in groups of ADHD patients are not responsible for the phenotypic expression of the syndrome. Previous studies have shown a smaller splenial area of the corpus callosum in ADHD children compared to normal controls. Also, a smaller total cerebral volume, a loss of the normal right>left asymmetry in the caudate nucleus, smaller right globus pallidus, smaller right anterior frontal region, smaller cerebellum, and reversal of the normal (L>R) lateral ventricular asymmetry, (see Progress in Pediatric Neurology III, PNB Publ, 1997;pp212-3).