Dissociating executive function and ADHD influences on reading ability in children with dyslexia.

Developmental dyslexia (DD) and attention-deficit/hyperactivity disorder (ADHD) are two of the most common neurodevelopmental disorders among school-age children. These disorders frequently co-occur, with up to 40-50% of children with one diagnosis meeting criteria for the other, and similar percentages of children with either DD or ADHD exhibiting impaired executive functions (EF). Although both ADHD and EF deficits are common in dyslexia, there is little evidence about how ADHD and EF deficits specifically influence the brain basis of reading difficulty in dyslexia, and whether the influences of ADHD and EF on dyslexia can be disentangled. The goal of the current study was to investigate, at both behavioral and brain levels, whether reading performance in individuals with dyslexia is more strongly associated with EF or with diagnostic status of comorbid ADHD. We examined reading abilities and EF in children (8-13 years old) with typical reading ability, DD only, or both DD + ADHD. Across both groups with dyslexia, impaired EF was associated with greater impairment on measures loading onto a reading fluency, but not a reading accuracy, factor. There were no significant differences between the DD and DD + ADHD groups on measures of reading fluency or reading accuracy. During functional magnetic resonance imaging (fMRI) while performing a rhyme-matching reading task requiring phonological awareness, typically developing readers showed greater left-hemisphere reading network activation than children with DD or DD + ADHD. Children with DD and DD + ADHD did not show differential activation, but DD children with unimpaired EF showed greater activation than those with impaired EF in reading-related areas. Thus, ADHD status alone had no measurable influence on reading performance or brain activation. Impaired EF in dyslexia, independent of ADHD status, was associated with greater deficits in reading fluency and greater reductions of activation in response to print in the typical left-hemisphere reading network.

Developmental Dyspraxia in Children With Learning Disorders: Four-Year Experience in a Referred Sample.

OBJECTIVE: The term apraxia is clearly understood in adult behavioral neurology, with assessment of gesture central to the diagnosis. In contrast, the concept of "developmental dyspraxia" has been more problematic. In an effort to better specify its potential significance, we describe preliminary practice-based evidence for understanding developmental dyspraxia acquired within a theoretical framework informed by both adult behavioral neurology and a neuroconstructivist appreciation of neurodevelopmental disorders. Specifically, we describe the experience of a diagnostic clinic for children with learning disorders that adopted this framework and compare clinical characteristics of children diagnosed with dyspraxia with those of children diagnosed with dyslexia during the same time period. METHOD: The dyspraxia diagnosis was based on the presence of impaired gesture and/or cognitive problems with planning. Over the target period, 71 children were diagnosed with dyspraxia and 114 children were diagnosed with dyslexia. Twenty-nine of the 71 children with dyspraxia were also diagnosed with dyslexia. Domains assessed included early developmental milestones, neurologic findings, cognition, speech and language, academic skills, and psychosocial functioning. RESULTS: Compared to the dyslexia group, children with dyspraxia (with or without dyslexia) had more problems with speech and language planning and planning in everyday life. Children with dyspraxia without dyslexia had more frequent early motor delays and deficits in visuospatial production than the other groups. The dyslexia groups predictably demonstrated poorer single word reading and phonologic processing compared to the dyspraxia only group (all P < .01). CONCLUSIONS: A neurologic finding of impaired gesture in children with learning disorders may signal a broader neurodevelopmental profile of developmental dyspraxia with both theoretical relevance and meaningful implications for evaluation and treatment. Cognitive problems with planning are particularly relevant.