Myoclonus: a pragmatic approach.

Myoclonus is a brief (less than half a second)contraction involving agonist and antagonist muscles, leading to a sudden jerk. It may be a normal phenomenon,as in the so-called 'sleep starts'. When pathological, myoclonus is a symptom of a broad range of neurological and systemic diseases. Alternatively, it may signal non-organic illness (8% of myoclonus is psychogenic). This review provides pragmatic and systematic guidance to the assessment and differential diagnosis of adult patients presenting with myoclonus.