[Myoclonus, Chorea, and Ballism].

Myoclonus is a sudden, shock-like involuntary movement in the extremities, face, or trunk without loss of awareness (LOA). However, if it becomes generalized and lasts more than 3 s, LOA occurs. Chorea is characterized by gross generalized movements without LOA. Ballism is a rapid, violent, and lateralized movement in the upper or lower extremities, usually in the proximal part of the body, such as throwing or flinging without LOA. These three abnormal movements commonly show hypermotor and hypotonic (or orthotonic) states. Although their underlying pathophysiology is varied, it is often attributed to hereditary diseases, and thus investigating the family history is important.