MUSCLE STRENGTH, GROSS MOTOR FUNCTION AND GAIT PATTERN IN CHILDREN WITH CEREBRAL PALSY

Aim The main purpose was to explore the relationship between muscle strength and walking ability in children with bilateral spastic cerebral palsy (CP), and to analyse whether muscle strength training can improve walking ability. Another aim was to establish normative values for muscle strength in terms of torque in typically developing children and adolescents, and in relation to sex, age and body weight. Methods A total of 174 typically developing children and 63 children with CP between the ages of five and 15 years participated in the studies. Muscle strength was measured with a handheld myometer. Motor function in children with CP was classified with the Gross Motor Function Classification System (GMFCS), graded with the Gross Motor Function Measure (GMFM) and gait pattern was measured with computerised three dimensional gait analysis. Muscle strength training in 16 children was conducted during eight weeks, three times a week. Results Normative data for muscle strength showed an increase in torque with age and weight, and strong correlations with both. There were few differences between boys and girls. Equations for predicted torque based on age, weight and sex were developed. Muscle strength in the legs was below predicted values in children with CP. It was lowest in the ankle, followed by muscles around the hip. Weakness increased with severity of motor involvement, strength over 50% of the norm was needed for independent walking. Muscle strength was correlated to walking ability and gait pattern, most obvious at the ankle. The gait moments (torque) in the children with CP were closer to their maximal muscle strength than in typically developing children. With eight weeks of strength training there was an increase in muscle strength, walking ability and push off in gait. Conclusions Muscle weakness was found in children with CP, increasing with severity of gross motor impairment and most pronounced at the ankle. There were correlations between muscle strength and walking ability and between muscle strength and gait pattern, most obvious at the ankle. After training, there was an increase in muscle strength and in walking ability and gait pattern

NO DECREASE IN MUSCLE STRENGTH AFTER BOTULINUM NEUROTOXIN-A INJECTION IN CHILDREN WITH CEREBRAL PALSY

Spasticity and muscle weakness is common in children with cerebral palsy (CP). Spasticity can be treated with Botulinum Neurotoxin-A (BoNT-A), but this drug has also been reported to induce muscle weakness. Our purpose was to describe the effect on muscle strength in the lower extremities after BoNT-A injections in children with cerebral palsy. A secondary aim was to relate the effect of BoNT-A to gait pattern and range of motion.Twenty children with spastic cerebral palsy were included in the study, eight girls and 12 boys (mean age 7.7 years). All were able to walk without support, but with increased muscle tone interfering with motor function and gait pattern. Sixteen children had unilateral spastic CP and four bilateral spastic CP. Twenty-four legs received injections with BoNT-A in the plantar flexor muscles. The children were tested before treatment, around six weeks after at the peak effect of BoNT-A, and at six months after treatment, with measurement of muscle strength, gait analysis and range of motion.There were no differences in muscle strength in plantar flexors of treated legs at peak effect compared to baseline. Six months after treatment, there was still no change in untreated plantar flexor muscles, but an increasing trend in plantar flexor strength in legs treated with BoNT-A. Parents reported positive effects in all children, graded as: small in three children, moderate in eight, and large in nine children. The gait analysis showed a small improvement in knee extension at initial contact, and there was a small increase in passive range of motion for ankle dorsiflexion. Two children had a period with transient weakness and pain.We found that voluntary force production in plantar flexor muscles did not decrease after BoNT-A, instead there was a trend to increased muscle strength at follow-up. The increase may be explained as an effect of the blocking of involuntary nerve impulses, leading to an opportunity to using and training the muscles with voluntary control.Adequate muscle strength is important for maintaining the ability to walk and knowledge of how a treatment affects muscle strength is useful when selecting interventions