The impact of pediatric traumatic brain injury on written expression: a diffusion tensor imaging study utilizing tract-based spatial statistics

The aim of this study was to determine if cerebral white matter integrity is predictive of Written Expression (WE) performance in children, and if the relation between white matter integrity and WE performance differs between children with traumatic brain injury (TBI) and children with orthopedic injury (OI). White matter integrity was approximated via diffusion tensor imaging (DTI) using tract-based spatial statistics. The current study utilized two DTI metrics, fractional anisotropy (FA) and mean diffusivity (MD), to assess integrity of white matter tracts. White matter tract integrity values were used to predict WE performance in the TBI group and the OI comparison group. General linear modeling (GLM) and multiple mediation analyses were used to predict performance on measures of WE at twelve months post-injury from white matter integrity at three months post-injury. Measures of WE included Thematic Maturity, Writing Fluency, and Spelling. Children with OI demonstrated significantly stronger performance on Writing Fluency and Spelling than children with TBI but there was no significant difference between groups on TMI performance. Children with TBI showed significantly decreased white matter integrity three months post-injury as compared to children with OI. Writing Fluency and TMI performance were fully mediated by FA values of the anterior thalamic radiation and corticospinal tract and Writing Fluency performance was also predicted by group differences in cingulum bundle microstructure. Taken together, these findings suggest that TBI negatively impacts the microstructural integrity of specific pathways that support WE performance and that these microstructural alterations account for post-traumatic changes in the content and fluency of production of written narratives. These findings are relevant for further understanding the role of white matter in academic performance and the impact of TBI on the developing brain.