Ultrasound-derived diaphragmatic kinematic and morphometry parameters in children with cerebral palsy: a comparative cross-sectional study

The purpose was. to evaluate diaphragmatic mechanics and morphometry using ultrasound in children with cerebral palsy (CP) compared to typically developing controls. By quantifying parameters such as excursion, contraction/relaxation velocity, and thickness, we aimed to distinguish primary respiratory muscle impairment from anthropometric and clinical confounders to inform targeted management. This comparative cross-sectional study included 102 participants: 51 children with spastic CP (GMFCS levels I-V) and 51 age- and sex-matched healthy controls. Diaphragmatic ultrasound was used to assess excursion, thickness and contraction/relaxation velocity. Multivariate linear regression models, adjusted for age, sex, and weight, as well as clinical confounders (medication use, prior surgeries, and history of pulmonary disease), were applied to determine independent associations with CP. In the unadjusted analysis, children with CP showed significantly reduced expiratory excursion (p = 0.00) and shorter respiratory times (p = 0.00) than controls, together with greater inspiratory thickness (p = 0.03) and contraction velocity (p = 0.01). After adjustment for demographic, anthropometric, and clinical confounders, the inspiratory differences were no longer significant, indicating that they reflected body size-related effects. In contrast, reduced expiratory excursion (p = 0.03) and shorter expiratory time (p = 0.01) remained independently associated with CP, particularly in nonambulatory participants (GMFCS IV-V). CONCLUSION: Most observed differences in diaphragmatic mechanics and morphometry in children with CP are attributable to lower weight and related confounders. However, the persistent reduction in expiratory excursion and expiratory time, independent of anthropometric and clinical confounders, identifies the expiratory phase as a critical and distinct marker of respiratory impairment in children with CP. Clinical interpretation of diaphragmatic ultrasound in this population requires rigorous adjustment to avoid diagnostic misinterpretation. WHAT IS KNOWN: • Respiratory dysfunction is a major contributor to morbidity in children with cerebral palsy (CP), driven by neuromuscular impairment and altered chest wall mechanics. • Diaphragm ultrasound is a reliable, noninvasive tool for assessing respiratory muscle function, although its application in children with CP remains limited. WHAT IS NEW: • After adjustment for demographic, anthropometric, and clinical confounders, most diaphragmatic parameters were not independently associated with CP. • Expiratory dysfunction (characterized by reduced expiratory excursion and shortened expiratory time) emerged as a distinct feature, suggesting that impaired abdominal muscle function may represent a previously underrecognized mechanism of respiratory dysfunction in children with CP.