The effect of injury timing on white matter changes in the corpus callosum following unilateral brain injury☆

Motor impairments following unilateral brain injuries may be related to changes in the corpus callosum. The purpose of this study was to determine if the corpus callosum is impacted differently in pediatric versus adult hemiplegia. Diffusion tensor imaging was completed on 41 participants (11 pediatric hemiplegia, 10 adult hemiplegia, 10 pediatric control and 10 adult control). Fractional anisotropy values and cross-sectional areas for five regions of the corpus callosum were compared between subject groups. Additionally, the amount of involuntary activity in the paretic elbow was quantified during non-paretic elbow flexion tasks for a subset of pediatric hemiplegia participants. Fractional anisotropy values were reduced in pediatric hemiplegia compared to pediatric control subjects in callosal regions corresponding to premotor and supplementary motor areas, primary sensory cortex, and parietal, temporal, and occipital cortices. Differences in fractional anisotropy between adult stroke and adult controls were only found in the region corresponding to parietal, temporal, and occipital cortices. Cross-sectional area was affected in all regions of the corpus callosum in pediatric hemiplegia, but only in the primary sensory region in adult hemiplegia. Additionally, changes in the cross-sectional areas were correlated with involuntary mirror movements in the pediatric hemiplegia group. In conclusion, the corpus callosum is affected to a greater extent in pediatric compared to adult hemiplegia, which may explain why unsuppressed mirror movements and difficulty with bimanual coordination are greater problems in this population.