White matter microstructure of motor and sensory tracts and the corpus callosum underlying impaired upper limb function in children with unilateral cerebral palsy

Introduction This study examined whether white matter microstructure of the corticospinal tract (CST), medial lemniscus (ML), superior thalamic radiations (STR) and corpus callosum (CC) differed depending on lesion timing or type of CST (re)organization (ipsilateral, bilateral or contralateral) in children with unilateral cerebral palsy (uCP). Secondly, we investigated the relation between diffusion parameters of these tracts and upper limb function. Patients and methods Thirty-four children with congenital uCP (mean age 10y3m ± 2y7m) underwent a comprehensive upper limb evaluation (assessment of sensorimotor impairments, bimanual performance and unimanual capacity) and diffusion weighted imaging. Type of CST (re)organization was determined using transcranial magnetic stimulation (N=29). Results CST structural connectivity was decreased in children with cortical and deep grey matter (or later) lesions (N=10) and children with an ipsilateral reorganization (N=11) compared to children with periventricular white matter (or earlier) lesions (N=24; p<0.01) and children with a contralateral organization (N=9; p<0.005), respectively. Upper limb function was significantly correlated with structural connectivity of the CST, ML, STR and CC (r=0.38-0.74). Moreover, structural connectivity of the CST and ML explained 71% of the variance in bimanual performance (p<0.04). Conclusion This study demonstrated that white matter microstructure of the CST differs depending on lesion timing or type of CST (re)organization. We further highlighted the importance of both motor and sensory tracts along with the interhemispheric pathways for upper limb function. The high amount of explained variance emphasizes the potential of white matter microstructure to predict upper limb function.

Publication year:2018