NEGATIVE MYOCLONUS

Negative myoclonus (NM) is a motor phenomenon characterized by involun tary jerky movements due to a brief, sudden interruption of muscular a ctivity. This motor disturbance can be observed in a variety of clinic al conditions, that can range from physiological NM, occurring when fa lling asleep or after prolonged exercise, to asterixis, a form of NM o bserved in patients with toxic-metabolic encephalopathies or with foca l brain lesions, or, as a paroxysmal phenomenon, labelled as epileptic negative myoclonus, in epileptic patients. Neurophysiological investi gations are essential to diagnose NM and to distinguish it from other motor disorders, such as tremor or positive myoclonus. Furthermore, ne urophysiological findings can provide useful information supporting a subcortical or cortical origin of NM. In cortical NM, recent data sugg est a role of cortical active inhibitory areas in the generation of th is motor phenomenon. (C) 1996 Wiley-Liss, Inc.