Assessment of spasticity in hemiplegic cerebral palsy. I. Proximal lower-limb reflex excitability.

The quadriceps and hamstring muscles of 13 children with hemiplegic cerebral palsy were studied using ramp and sinusoidal stretches at three different muscle lengths. Overall, the hamstring muscles showed greater velocity sensitivity than the quadriceps, with the hamstrings having the lowest reflex velocity and frequency thresholds close to maximum knee extension. At this position, the hemiparetic hamstrings alone showed a weakly significant reduced reflex frequency threshold compared with non-paretic muscles. For all other muscle lengths, non-paretic and hemiparetic muscles displayed similar reflex thresholds when subjected to sudden, discontinuous or repetitive rhythmical, sinusoidal stretches. The number of muscles for which a reflex threshold could be established declined progressively as the angle at the knee joint approached 90 degrees of flexion. Muscles for which no reflex threshold could be demonstrated had similar velocities and frequencies of stretch as those in which a reflex was obtained.