Ballism or ballismus is a hyperkinetic involuntary movement disorder characterized by wild, flinging, throwing movements of a limb. These movements most usually involve one half of the body (hemiballismus), although they may sometimes involve a single extremity (monoballismus) or both halves of the body (paraballismus). The movements are often continuous during wakefulness but cease during sleep. Hemiballismus may be associated with limb hypotonia. Clinical and pathophysiological studies suggest that ballism is a severe form of chorea. It is most commonly associated with lesions of the contralateral subthalamic nucleus.