Muscle pathology and clinical measures of disability in children with cerebral palsy.

We performed a histologic and morphometric study of spastic muscle from 10 children with diplegic cerebral palsy, comparing muscle structure with the gait parameters of energy expenditure index and dynamic electromyography. Variations in fiber area within and between fiber types were increased significantly in children with cerebral palsy. In each of the control subjects, the combined coefficient of variation for type-1 and type-2 fiber area was less than 25% and the average was 17%; in the subjects with cerebral palsy, the combined coefficient of variation was more than 25% and the average was 36% (p < or = 0.004). The average difference between the mean area of type-1 and type-2 fibers was 26.7 +/- 18.9% for subjects with cerebral palsy and 4.2 +/- 2.4% for control subjects (p < or = 0.004). There was a 67% predominance of one fiber type in the subjects with cerebral palsy compared with a 55% predominance in the control subjects (p < or = 0.03). The difference between the total area of type-1 and type-2 fibers was 57% in the subjects with cerebral palsy and 17% in the control subjects (p < or = 0.002). There was a significant correlation between the combined coefficient of variation of fiber area and the energy expenditure index (r = 0.77, p < or = 0.03). The difference between the mean area of type-1 and type-2 fibers correlated with prolongation of electromyographic activity (r = 0.69, p < or = 0.05). No abnormalities in fiber ultrastructure were found in the subjects with cerebral palsy. Children with cerebral palsy had abnormal variation in the size of muscle fibers and altered distribution of fiber types. The values for variation in fiber area correlated with the energy expenditure index and with prolongation of electromyographic activity during walking.