Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyper excitability of the stretch reflex. The hyper-excitability of the stretch reflex is due to loss of inhibitory influences from descending supraspinal structures.
The word spasm comes from the Greek word (spasmos) which means to ‘pull or drag’. It is also referred to as an unusual “tightness”, stiffness, and/or “pull” of muscles. Spasticity is isokinetic (abnormal but not increased movements), while dystonia and other movement disorders are hyperkinetic (abnormal and increased movements).
Spasticity is frequent and often disabling feature of many neurological diseases, the treatment of which involves a combination of medical and surgical management.