Structural connectivity of the corpus callosum is more important for upper limb motor function in children with unilateral cerebral palsy in case both hemispheres are damaged

Introduction Up to 50% of children with unilateral cerebral palsy (uCP) have bilateral lesions despite clinically lateralized impairments. However, the underlying neuropathophysiology of impaired upper limb (UL) function in these children is poorly understood. Hence, we hypothesized that structural connectivity of the corpus callosum (CC) would be more decreased in children with bilateral compared to unilateral lesions, and that secondly, correlations between CC structural connectivity and UL function would be higher in the bilateral lesions group. Patients and methods Thirty-four children with congenital uCP (mean age 10y7m±2y3m; 21 unilateral lesions; 13 bilateral lesions) underwent an UL motor evaluation (grip strength, unimanual capacity and bimanual performance) and diffusion weighted imaging. Streamline count, fractional anisotropy and mean diffusivity of the CC were extracted. Results Although no differences in UL motor function were found (p>0.12), streamline count (p=0.007) and fractional anisotropy (p=0.03) of the CC were significantly higher in the unilateral compared to the bilateral lesions group. In the unilateral group, only low correlations were found between fractional anisotropy and mean diffusivity of the CC and UL function (r=-0.30-0.50). In contrast, mean diffusivity was highly correlated with grip strength, unimanual capacity and bimanual performance in the bilateral group (r=-0.70-(-0.83)). Conclusion These results suggest a stronger adverse impact of reduced structural connectivity of the CC on UL motor function in children with uCP in case both hemispheres are damaged. Such findings aid in improving our understanding of the structure-function relationship in these children and might contribute to developing more individualized prognoses in the future.status: accepte