SPASTICITY AND RIGIDITY: AN EXPERIMENTAL STUDY AND REVIEW

Abstract

By means of recording instruments and using 1% procaine as a nerve blocking agent, spasticity, rigidity and dystonia were studied in 50 patients. The exaggerated stretch reflexes characteristic of spasticity and parkinsonian rigidity are dependent upon gamma motor fibers of the muscle spindle. The procaine blocks these fibers, desensitizes the stretch receptors in the muscle and abolishes these hyperactive reflexes while voluntary activity is preserved. When compared with the state of rigidity, a spastic limb displays a progressive increase of resistance to the stretch of muscle groups; the intensity of the stretch reflex is often proportional to the rate of stretch; and a sudden cessation in the reflex occurs when stretch is relaxed. The phenomenon of occlusion in regard to voluntary action or tendon jerks is explained by the convergence of many reflexes on a common motor neuron pool. In addition to analyzing the data obtained from the patients, the author briefly reviews literature pertaining to the stretch reflex.