Gastrocnemius muscle properties in children with cerebral palsy: An exploratory cross-sectional study of variability in gastrocnemius properties.

Muscle strength is a key predictor of physical functioning, yet the influence of patient and treatment factors on muscle properties in young people with cerebral palsy is not fully known. We explored whether medial gastrocnemius properties vary by age, ambulatory status and spasticity treatment (botulinum toxin or selective dorsal rhizotomy). In this exploratory cross-sectional study, microbiopsies of the medial gastrocnemius were obtained from 16 children (6-17 years of age) with cerebral palsy. Outcomes included muscle thickness, collagen content, myofibre cross-sectional area, capillaries, myofibres with centrally located nuclei, lipid area, satellite cell density and myosin heavy chain myofibre type. Myofibre cross-sectional area (P = 0.02) and myofibres with centrally located nuclei (P = 0.02) were positively correlated with age. Non-ambulatory individuals had smaller myofibre cross-sectional area (P = 0.02). The number of botulinum toxin injections was associated with more capillary contacts per myofibre (P = 0.04). Selective dorsal rhizotomy was not associated with any statistically significant findings. Preliminary data suggest that gastrocnemius muscle properties might vary across patient factors and spasticity treatment history. Confirmatory prospective studies with matched control groups are needed to evaluate properly the effects of age, ambulatory status, botulinum toxin and selective dorsal rhizotomy.