What Causes Spasticity?
Spasticity arises when there is loss of inhibitory controls from the central nervous system. Normally, our muscles have a certain degree of resting tension. This is most prominent in the muscles that keep us upright (antigravity muscles). This normal reflex occurs at the spinal level and is evident, in an exaggerated form, when the doctor taps your knee or ankle with a reflex hammer. Your responses do not require voluntary control, but are controlled by central nervous system pathways. For the most part these pathways, which extend from the brain to the spinal cord, inhibit (to various degrees) the tension in muscle groups. When these central pathways are disrupted, a loss of inhibition occurs. As a result, muscle tension increases. This may affect muscle in a variety of patterns, but most often causes the lower extremities to stretch out or straighten and the upper extremities to bend or contract. This can produce a stiff and “spastic” gait and/or limit the functional use of your limb
