Pediatric traumatic brain injury (TBI) is often associated with difficulties in word decoding, text comprehension, and reading speed. Injury-related brain changes (e.g., loss of cortical gray matter, reduced integrity of white matter, etc.) in the dominant hemisphere may underlie these reading difficulties. FreeSurfer v4.0.5 was used to derive measures of MRI morphology (i.e., cortical volume, surface area, and thickness) associated with three cortical regions implicated in reading in 33 children with TBI and 55 comparison children. Diffusion tensor imaging (DTI) tissue integrity metrics (i.e., fractional anisotropy [FA], mean diffusion [Day], axial diffusivity, and radial diffusivity) from regions of interest in the arcuate fasciculus (AF) were obtained in a similar sample of 58 children with TBI and 72 comparison children. Statistical models revealed that DTI metrics, but not measures of MRI morphology, mediated relations between brain injury and reading skills. Specifically, TBI was associated with higher FA and lower radial diffusivity in the AF region linked to Broca's area, which in turn was associated with slower reading speed. TBI was also associated with higher Day, lower axial diffusivity, and higher radial diffusivity in the AF region linked to Geschwind's territory, which in turn was associated with poorer reading comprehension. Lastly, TBI was associated with higher axial diffusivity in the AF region linked to Wernicke's area, which in turn was associated with poorer word decoding. In sum, DTI metrics were sensitive to pathological white matter changes following TBI and were related to specific reading outcomes. Contrary to expectation, age-at-injury effects were not found with regard to performance on word decoding and reading comprehension tasks. Nevertheless, longitudinal DTI/MRI studies are needed to investigate the interaction between normal developmental processes in reading that may be affected by white and gray matter changes associated with TBI and the age at which TBI occurs.
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