Evidence Of Distinctive Structural Alterations That Differentiate Adhd Boys With And Without A Comorbid Reading Disability

Attention deficit hyperactivity disorder (ADHD) and reading disability (RD) are neurodevelopmental disorders that often co-occur. Children with ADHD and co-occurring RD (ADHD/+RD) tend to show greater cognitive deficits than children with ADHD alone (ADHD/-RD). However, the extents to which comorbid RD impact structural alteration in children with ADHD have never been investigated. The overall goal of this study was to assess structural alterations in the subcortical, cortical and white matter that may differentiate ADHD/-RD from ADHD/+RD. The general hypothesis was that ADHD/+RD would show extensive alterations in regions implicated in ADHD than ADHD/-RD as well as show additional abnormalities in regions associated with RD. To this end, structural MRI and DTI scans obtained from 22 ADHD/-RD boys, 15 ADHD/+RD boys and 29 healthy control (HC) boys comparable in age and IQ were analyzed to assess alterations in striatal morphology, cortical thickness and white matter integrity. Analysis of the striatum showed greater and widespread alterations in the caudate in ADHD/+RD relative to ADHD/-RD but not putamen where the alterations were only seen in ADHD/-RD. Similarly, ADHD/+RD showed significantly thinner cortex in the regions associated with attention and cognitive control as well as additional regions associated with reading relative to ADHD/-RD and HC. Finally, analysis of DTI parameters showed greater extent of alteration in white matter architecture of the frontostriatal fiber tracts. Together, these findings provide evidence of excessive disturbances in the frontostriatal and frontoparietal networks that regulate executive functions, attention and cognitive control. Furthermore, there is evidence of additional alterations in the regions associated with reading skills. Overall, the results indicate a distinctive profile of structural alterations that differentiate ADHD/-RD from ADHD/+RD relative to HC and may underpin the greater neuropsychological impairments observed in ADHD/+RD