Myoclonus.

Myoclonus is defined as sudden, brief, shocklike, involuntary movements caused by muscular contractions or inhibitors. Myoclonic movements have now been recognized to have many possible variants and pathophysiologic features. Myoclonus may arise from several sites within the neuraxis, of which the cortex and brain stem reticular formation are the most common. An etiologic classification scheme and electrodiagnostic tests are useful for clinical purposes. Therapy is limited and usually involves symptomatic treatment with valproic acid or clonazepam. Careful attention to the basic characteristics of the movement appearance, the clinical circumstances in which the myoclonus occurs, and the results of the electrodiagnostic assessment techniques provide a basis for identifying the syndrome in which the myoclonus occurs.