ATTENTION-DEFICIT HYPERACTIVITY DISORDER AND ASYMMETRY OF THE CAUDATE-NUCLEUS

The neurologic basis of attention deficit-hyperactivity disorder (ADHD ) is poorly understood. Based on previous studies that have implicated metabolic deficiencies in the caudate-striatal region in ADHD, we emp loyed magnetic resonance imaging to investigate patterns of morphology of the head of the caudate nucleus in normal and ADHD children. In no rmal children, 72.7% evidenced a left-larger-than-right (L > R) patter n of asymmetry, whereas 63.6% of the ADHD children had the reverse (L < R) pattern of asymmetry of the head of the caudate nucleus. This rev ersal of normal asymmetry in ADHD children was due to a significantly smaller left caudate nucleus. The reversal in asymmetry of the head of the caudate was most notable in ADHD males. These results suggest tha t normal (L > R) morphologic asymmetry in the region of the caudate nu cleus may be related to asymmetries observed in neurotransmitter syste ms implicated in ADHD. The behavioral symptoms of ADHD may reflect dis inhibition from normal levels of dominant hemispheric control, possibl y correlated with deviations in asymmetric caudate-striatal morphology and deficiencies in associated neurotransmitter systems.