Heterogeneity of muscle sizes in the lower limbs of children with cerebral palsy.

INTRODUCTION Cerebral palsy (CP) is associated with reduced muscle volumes, but previous studies have reported deficits in only a small number of muscles. The extent of volume deficits across lower limb muscles is not known. This study presents an imaging-based assessment of muscle volume and length deficits in 35 lower limb muscles. METHODS We imaged and segmented 35 muscles in 10 subjects with CP and 8 typically developing (TD) controls using MRI. Muscle volumes were normalized, and Z-scores were computed using TD data. Volume Z-scores and percent deficits in volume, length, and cross-sectional area are reported. RESULTS Muscle volumes are 20% lower, on average, for subjects with CP. Volume deficits differ significantly between muscles (12%-43%) and display significant heterogeneity across subjects. Distal muscles, especially the soleus, are commonly and severely small. CONCLUSIONS Heterogeneity across muscles and across subjects reinforces the subject specificity of CP and the need for individualized treatment planning. Muscle Nerve 53: 933-945, 2016.