Standing in children with bilateral spastic cerebral palsy : aspects of muscle strength, vision and motor function

Sammanfattning: The movement and posture disorder of cerebral palsy (CP) is presumed to mainly be a consequence of the motor disorder, but accompanying disturbances with sensations and perception have also been suggested to influence motor function. The aim was to investigate factors influencing standing posture in children with bilateral spastic CP (BSCP) with varying standing abilities. Three-dimensional motion analysis with surface electromyography was recorded to describe posture during three standing tasks: in a habitual standing position, while blindfolded, and during an attention-demanding task. Muscle strength in the lower limbs was measured with a hand-held dynamometer. Motor function was measured with the Gross Motor Function Measure. The children also underwent a neuro-ophthalmological examination. Almost half of the participants required hand-held support to stand. Investigation of standing posture verified a crouched body position during standing which was more obvious in the children who required hand-held support. Muscle strength measurements indicated that the children in both groups were equally strong in the lower limb muscles despite their variation in standing abilities. The children who stood with support were as capable to perform motor activities in lying, sitting and kneeling positions as the children who stood unsupported. Vision influenced posture differently depending on the children's standing ability. During the attention demanding task, the children who stood unsupported stood more still and with less lower limb muscle activity. While blindfolded, they adapted their posture to the environmental change by activating muscles around the ankle with no changes in overall body position. In contrast, the children who required hand-held support to stand used another strategy; the already flexed body position became even more flexed, and muscle activity increased in the knee extensors while blindfolded, despite the use of external support. Motor disorders could not explain the support for standing or the crouched body position during standing. The children were equally strong in the lower limb muscles and had reasonably similar abilities to perform motor activities in positions with no requirement of standing on the feet opposing gravity. The crouched body position and the reduced ability to maintain posture while blindfolded indicate proprioception deficits in the children who required support. The increased quadriceps muscle activity could be an indication of compensatory co-contraction caused by perceptual impairments. That motor function difficulty arises in a standing position opposing gravity indicates that standing difficulties may be attributable to sensory and/or perceptual disturbances.