No abstract

Although behavioral evidence provides support for the notion that attention deficit-hyperactivity disorder (ADHD) is related to central nervous system dysfunction, there is little direct evidence to reveal which neurometabolic systems or brain structures are involved. Recent magnetic resonance imaging (MRI) studies suggest that, compared to nondisabled controls, ADHD children may have a smaller right frontal region. Morphometric analysis of MRI scans was used in this exploratory study to determine whether correlated regional variation might exist in the corpus callosum of children with ADHD. While all MRI scans were judged to be clinically normal, morphometric analysis revealed that, compared to nondisabled controls, ADHD children had a smaller corpus callosum, particularly in the region of the genu and splenium, and in the area just anterior to the splenium. Interhemispheric fibers in these regions interconnect the left and right frontal, occipital, parietal, and posterior temporal regions. These results suggest that subtle differences may exist in the brains of children with ADHD and that deviations in normal corticogenesis may underlie the behavioral manifestations of this disorder.

This study examined the issue as to whether or not children carefully diagnosed as having either attention deficit disorder with hyperactivity (ADDH) or without hyperactivity (ADDnoH) could be distinguished on selected cognitive, academic, rapid naming, and behavioral measures. Employing a previously validated multimodal, multi-informant diagnostic process that results in reliable clinical diagnoses, 10 ADDH and 10 ADDnoH children were examined. While no significant differences in cognitive ability were noted between groups, significant underachievement was found in the children diagnosed as ADDnoH, particularly in mathematics achievement. The ADDnoH children were also significantly slower on rapid naming tasks than the ADDH children. Further, 60% of the ADDnoH children had a codiagnosis of a developmental reading or arithmetic disorder while none of the ADDH children received such a codiagnosis. Conversely, 40% of the ADDH children had a codiagnosis of conduct disorder and were rated by their parent as significantly more motorically active, impulsive, and deviant in the demonstration of age-appropriate social skills. These findings are discussed as they relate to the notion that children with attention deficit disorder may suffer from a right hemispheric syndrome.

Recent behavioral and neuropharmacological evidence suggests that the differentiation of children with Attention Deficit Disorder with (ADD/H) and without hyperactivity (ADD/WO) may reflect an appropriate nosological distinction. There is also evidence that attention-regulatory mechanisms possibly associated with anterior-posterior processes may be independently implicated in these children. To test this hypothesis, 100 clinic-referred children were reliably diagnosed as ADD/H (n = 48). ADD/WO (n = 26) and as having an internalizing disorder (n = 26) for inclusion as a clinic-control (CC) group. An analysis of covariance using Full-Scale IQ, chronological age, and the number of conduct-disorder symptoms provided little support for such a behavioral distinction using selected WISC-R, Luria-Nebraska-Children's Revision, and reaction-time variables. Alternative conceptualizations, possibly reflecting deficient right-hemispheric processes in ADD/H, may provide more productive avenues for research in distinguishing deficient neurocognitive processes in subtypes of ADD.

The WISC-R factors, Verbal Comprehension, Perceptual Organization and Freedom from Distractibility (FFD) were examined for their discriminant validity in diagnosing children with Attention Deficit Hyperactivity Disorder (ADHD), ADHD with co-occurring Conduct Disorder (ADHD + CD) and those comprising a clinic control population. Contrary to expectations and clinical practice, the FFD factor did not significantly discriminate among children comprising the three diagnostic groups. The verbal comprehension and perceptual organizational factors significantly distinguished between children with and without conduct disorder, but not between the clinic control and ADHD children. Therefore, the ADHD + CD group's performance on the WISC-R factors qualitatively differs from children with internalizing disorders or ADHD, and as such is most likely a separate population. Furthermore, the use of the FFD factor did not provide sufficient sensitivity for a discriminative diagnosis (a miss rate of 50 percent for clinic control, 64.3 percent for ADHD and 38.1 percent for ADHD + CD).