Attention-deficit hyperactivity disorder (ADHD) and frontal-motor cortex disconnection.

Attention-Deficit Hyperactivity Disorder (ADHD) is a very common pediatric-neuropsychiatric entity of still unknown etiology, and is thus a topic of controversy. A neurological concept is presented in order to attain a better conceptualization of ADHD. This concept focuses on the frontal lobe as the inhibitor of excessive motor activity. This inhibitory function is presumed to be most active during childhood. The concept of a disturbed frontal-motor cortex connection was first developed in view of a completely different and rare disorder of childhood: Rett Syndrome (RS) with smallness of the frontal lobe, excessive motor activity and EEG abnormalities often confined to the Rolandic region. Accordingly, what is due to structural damage in RS, might be caused by simple dysfunction in ADHD under essential ly benign circumstances. Not a damaged but a "lazy" frontal lobe results in disinhibited motor activity and also in disturbed attention ( a predominantly frontal lobe function). In the light of this concept, the calming effect of methylphenidate in ADHD is quite logical (frontal stimulation improving motor inhibition) and not paradoxical. It is the "lazy" frontal lobe that responds to "the whip" whereas a truly sick frontal lobe as in RS would be unable to respond.