Hypertonia refers to an elevated muscle tone. Hypertonia may be the result of a disease affecting a motor nerve or affecting the muscle itself. There are two very different types of hypertonia. It's called plastic hypertonia when a limb of the body is frozen in the same position or, when it is mobilized, the limb resists and yields by fits and starts. This plastic hypertension is encountered in certain diseases, such as Parkinson's disease, for example. The other type of hypertension is called elastic or spastic, when the limb is mobilized and returns to its original position when the action is finished. This occurs especially in cases of pathology responsible for paralysis, as after a stroke.