Functional significance of corpus callosum anatomy in chronically treated and treatment naïve ADHD

Neuroimaging has revealed differences between control and ADHD groups in corpus callsoum (CC) size, although the reported findings have been somewhat variable. Since ADHD is commonly treated with stimulants, concerns have been raised about the long-term neurological consequences of chronic stimulant treatment, yet this has not been controlled for in previous studies. Furthermore, since all previous studies have utilized the mid-sagittal area of the CC as the unit of measurement, additional objectives of this investigation were to determine 1) whether CC volume could be reliably measured and 2) whether using mid-sagittal CC area provides a valid estimation of CC volume. Anatomical MRI’s were obtained from children aged 9-15 in three diagnostic groups 1) chronically-treated ADHD (n=12), 2) stimulant-naïve ADHD (n=13), and 3) a control group (n=15) to determine whether differences in CC size existed. These children also completed a battery of neuropsychological tests to determine whether the functions of sustained attention, speed of information processing, planning, and inhibitory control were related to CC size. Parental ratings of hyperactive and impulsive behavior were also collected. The three groups did not differ in overall CC volume. Differences between the groups in the area of the splenium were approaching significance, with the treatment-naïve group exhibiting the smallest splenium area. Therefore, the results of this investigation do not indicate maladaptive structural changes in the CC associated with chronic (at least one year) stimulant use. It was also found that volume of the CC can be reliably obtained when strict definitional criteria are applied. However, mid sagittal area is highly related to CC volume and therefore is likely an accurate estimate, an important finding given the significant time required to obtain volumetric measures. Finally, smaller splenium size was found to be related to higher levels of hyperactivity and restlessness; however, no associations between measures of CC size and neuropsychological measures were found.