The relation between bimanual coordination, lesion timing, and corticospinal tract wiring pattern in children with unilateral cerebral palsy

Abstract

In children with unilateral cerebral palsy (uCP), it is well-described that the corticospinal tract (CST) wiring pattern and lesion timing are strongly related to unimanual upper limb function.1 Remarkably, the relation between those neurological factors and bimanual coordination is not yet thoroughly examined, while most daily life activities require the integrated use of both hands. Does bimanual coordination differ depending on the CST-wiring pattern and lesion timing in children with uCP? Bimanual coordination was assessed in 29 children with uCP (12.1 y±2.7 y) using the ball-on-bar task on the Kinarm robotic exoskeleton.2 This task consists of two levels of increasing difficulty, during which participants move a ball to a target while balancing it on a bar through two-dimensional virtual reality visual guidance. Eight parameters of each level were included. Using transcranial magnetic stimulation, the participants were classified into two groups according to their CST-wring pattern: the contralateral (N=10) versus the reorganized ipsilateral or bilateral (N=3/7) CST-wiring. In 9 children, this assessment was not feasible. Based on magnetic resonance imaging, the participants were classified according to their lesion timing in predominant white matter (PWM) lesions (N=16) versus predominant grey matter (PGM) lesions (N=5). In 8 children, brain imaging was missing. Between-group comparisons were calculated with ANCOVA or the non-parametric Quade’s Rank (p<0.05), with age as covariate. Effect sizes were calculated using partial eta squared (np2) and interpreted as: ηp2=0.01 small effect, ηp2=0.06 medium effect, ηp2=0.14 large effect Between the CST-wiring groups, a significant difference was found for hand speed difference in level 2 (F=4.876, p=0.04, ηp2=0.22), indicating a better hand synchrony in children with a contralateral CST-wiring compared to children with a reorganized CST-wiring. Between the lesion timing groups, a significant difference was found for bar tilt standard deviation (SD) in level 1 (F=7.679, p=0.01, ηp2=0.29), reflecting a more stable maintenance of the bar by the PGM-group compared to the PWM-group. Interestingly, a significant group*age interaction was found for level 2 of this parameter (p=0.03), revealing more variability of the bar tilt in the PGM-group with increasing age, in contrast to the PWM-group, which had less variability (Fig. 1).Download : Download high-res image (49KB)Download : Download full-size image Our findings are partially in line with current literature suggesting that children with a contralateral wiring have a better motor function. However, in contrast to previous studies, our results suggest worse bimanual coordination in children with PWM-lesions, which could be explained by the higher incidence of bilateral lesions in PWM-lesions compared to PGM-lesions.3 Nevertheless, future research with larger samples accounting for age interactions is warranted.