LAUSR

BACKGROUND Cerebral palsy (CP) is a neurological disorder characterized by a profound skeletal muscle deficit. However, whether there is a regional-specific skeletal muscle deficit in children with CP is unknown. The purpose of this study was to determine whether fat-free soft tissue mass (FFST), a commonly used surrogate for skeletal muscle mass, is more compromised in the limbs than in the trunk in children with CP. A second purpose was to determine whether physical characteristics can be used to accurately estimate appendicular FFST (AFFST) in children with CP. METHODS Forty-two children with CP (4-13 y) and 42 typically developing children matched to children with CP for sex, age and race were studied. Whole body FFST (FFSTwhole), FFST in the upper limbs (FFSTupper), FFST in the lower limbs (FFSTlower), the ratio of AFFST to height (AFFST/ht), the ratio of AFFST to height2 (AFFST/ht2) and non-appendicular FFST were estimated from dual-energy X-ray absorptiometry. Statistical models were developed to estimate AFFST, AFFST/ht and AFFST/ht2 in both groups of children, and the leave-one-out method was used to validate the models. RESULTS Children with CP had 21% lower FFSTwhole, 30% lower AFFST, 34% lower FFSTlower, 14% lower non-appendicular FFST, 23% lower AFFST/ht, 19% lower AFFST/ht2 and 9% lower AFFST/FFSTwhole (all p < 0.05). Statistical models developed using data from typically developing children overestimated AFFST, AFFST/ht and AFFST/ht2 by 35%, 30% and 21% (all p < 0.05), respectively, in children with CP. Separate models developed using data from children with CP yielded better accuracy, with the estimated results highly correlated (r2 = 0.78, 0.66 and 0.50, respectively; all p < 0.001) and not different from calculated AFFST, AFFST/ht and AFFST/ht2 (all p > 0.99). However, when the difference in estimated values and measured values of AFFST, AFFST/ht and AFFST/ht2 were plotted against measured values, there was an inverse relationship (r = -0.38, -0.47 and -0.61, respectively, all p < 0.05). CONCLUSION Children with CP have a remarkable deficit in FFST that is more pronounced in the appendicular than in the non-appendicular region and more pronounced in the lower than in the upper limbs. Preliminary models developed using data from children with CP can provide reasonable estimates of AFFST and indexes of AFFST relative to height, but further development of the models may be needed.