Asterixis, or negative myoclonus, is a symptom
encountered in neurology, characterized by a sudden and violent loss of tone in the extensor muscles of the hand
. The hand makes brief movements inward, resembling the beating of wings, when it is supposed to be motionless. Asterixis is a clinical sign that is observable in cases of respiratory deficiency
, when the blood contains too much carbon dioxide, and also in cases of hepatic encephalopathies.