Diaphragmatic Thickness as a Marker of Systemic Muscle Depletion in Non-Ambulatory Children with Cerebral Palsy: Implications for Integrated Neurorehabilitation Assessment

Purpose: To examine the association between diaphragmatic thickness and upper arm muscle area (AMA), as a surrogate of nutritional status, in children and adolescents with cerebral palsy (CP) stratified by gross motor function severity. Methods: In this cross-sectional study, participants were stratified into ambulatory (Gross Motor Function Classification System [GMFCS] I–III) and non-ambulatory (GMFCS IV–V) groups. AMA was estimated from anthropometric measurements, and diaphragmatic thickness was assessed by B- and M-mode ultrasonography; between-group comparisons used the Mann–Whitney U test and associations were examined using Spearman’s rank correlation coefficient (ρ). Results: Fifty children aged 2–12 years with a confirmed CP diagnosis were evaluated (14 ambulatory, 36 non-ambulatory). In the non-ambulatory group, diaphragmatic thickness showed significant positive correlations with AMA during inspiration (ρ = 0.50; p = 0.002) and expiration (ρ = 0.67; p < 0.001). These subgroup-specific associations should be interpreted as exploratory, as the AMA × GMFCS interaction did not reach statistical significance. No significant correlations were observed in ambulatory participants. Moderate muscle mass deficits were prevalent among non-ambulatory children, and approximately 63% of the total sample presented adipose tissue deficit or risk thereof. Conclusions: In children with severe CP, a significant association between peripheral muscle reserve and diaphragmatic thickness suggests a possible functional link between nutritional status and respiratory muscle morphology. These preliminary findings support further investigation of diaphragmatic ultrasonography as a non-invasive tool for combined nutritional and respiratory monitoring in pediatric neurorehabilitation.