Mirror movements in children with unilateral cerebral palsy have a negative impact on upper limb function

Introduction Mirror movements (MMs) are involuntary movements of one hand that accompany voluntary movements of the other hand. In children with unilateral cerebral palsy (uCP), MMs have been suggested to negatively impact on upper limb (UL) function, although they were assessed by means of an ordinalobservation-based scale. Here, we used a novel quantitative assessment tool to investigate the impact of MM on UL function in children with uCP. Patients and methods Sixty-seven children with uCP (mean age 10y7m (SD 2y4m), 34 girls, Manual Ability Classification System (MACS): 16 level 1, 26 level 2 and 11 level 3) performed a repetitive unimanual squeezing task, making a windmill turn by squeezing a force transducer with one hand while recording force profiles in both hands. MM intensity was calculated as the cross-correlation coefficient between the two force profiles. UL function was assessed using theAssisting Hand Assessment (AHA) and ABILHAND-Kids questionnaire. Results Children with MACS 2 showed higher MM intensity in the dominant hand compared to MACS 1 or 3 (p<0.01). Children with higher MM intensity presented with poorer manual ability, measured by the ABILHAND-Kids (MM in dominant-hand, rho= -0.34, p<0.05; MMs in non-dominant hand, rho= -0.36, p<0.01) and bimanual performance measured using the AHA (MMs in dominant-hand, rho= -0.43, p<0.01; MMs in non-dominant hand, rho= -0.36, p