Development of postural adjustments during reaching in infants at risk for cerebral palsy from 4 to 18 months

Aim. To investigate postural adjustments during reaching in infants at high risk for cerebral palsy (CP). Method. Observational cohort study in which 25 infants at high risk (11 males, 14 females) and 11 infants with typical development (six males, five females) were assessed at 4, 6, and 18 months corrected age. Reaching movements were elicited during supported and unsupported sitting, while surface electromyography was recorded of arm, neck, and trunk muscles. Percentages of direction-specific adjustments (first level of control), and recruitment patterns and anticipatory activation (second level of control) were calculated. Statistical analyses were performed with a binomial generalized estimating equations model for dichotomous variables and a linear mixed model for continuous variables. Results. Postural activity of infants at high risk for CP at 4 months was virtually similar to that of infants with typical development. At 18 months, infants at high risk differed from infants with typical development with less direction-specificity (median values 20% vs 58% at trunk and neck level, OR 0.38, 95% CI 0.18–0.82); longer latencies to trunk muscle activation; and less anticipatory activation (41% vs 55%, in any direction-specific muscle, OR 0.53, 95% CI 0.32–0.89). In unsupported sitting, results were largely similar to those in supported sitting. Interpretation. Infants at high risk for CP grew into a postural deficit: at 18 months they showed delayed development of direction-specificity, and postural dysfunction as evidenced by slower recruitment of postural muscles and less frequent anticipatory activation.