Attention deficit hyperactivity disorder: the childhood co-morbidity that most influences the disability burden in Tourette syndrome.

ADHD is a complex co-morbidity, as it is heteregeneous in terms of the clinical subtypes, but also in terms of the circuits involved and the level of involvement within those circuits. Specially focusing on the relationship of ADHD to TS, this author's studies have added some neurobehavioral and some anatomical magnetic resonance imaging evidence suggesting the ADHD occurring with TS, appears like "garden-variety" ADHD, at least in the matched research sample. The similarities of neuroanatomical findings in the TS plus ADHD and ADHD groups and their distinctness from neuroanatomical findings in childdren with "pure TS provide some parallels to the observed similarity of functional deficit in TS plus ADHD and ADHD alone groups and the relative lack of functional deficits in children with TS only. More specifically, the results of a decade of this author's research with the approximately 40% of children with TS who are free of ADHD indicate that they are entirely free of the motor control and executive control deficits of children with ADHD alone or TS plus ADHD, but they do have oculomotor control deficits in the initiation of prosaccades, regardless of their ADHD status. The neuroanatomical data in TS only is also of interest because it reflects increased white matter, particularly in the right frontal lobe and four out of five regions of the corps callosum, including the rostral portion most affiliated with the frontal lobes. It should be emphasized that almost everything summarized abouve is true for boys, whereas samples of girls grouped similarly have not yielded the same results.