Assessment of Muscle Overactivity and Spasticity with Dynamic Polyelectromyography and Motion Analysis

Damage of the central nervous system often produces an upper motoneuron (UMN) syndrome. Characteristics of the UMS include the presence of positive and negative signs. Positive signs are increased phasic and tonic stretch reflexes, clonus, co-contraction, released flexor reflexes, spastic dystonia, and associated reactions, whereas negative signs signify the loss or impairment of voluntary movement assembly and production. Muscle overactivity seems to be a more suitable term than spasticity, because it evokes more an image of dynamic muscle contraction, which is the general hallmark of all positive signs of UMS. Some of the main patterns of UMN dysfunction include: equinovarus foot, hyperextended great toe, stiff knee, adducted (scissoring) thighs, and flexed hip. The dynamic poly-EMG recordings of trunk and lower limb muscles in combination with the clinical examination provide a more detailed understanding of the genesis of these abnormal patterns in the UMN.