Assessment of muscle overactivity and spasticity with dynamic polyelectromyography and motion analysis

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