Asterixis is often called a “flapping tremor,” but it is not a true tremor. It occurs when the brain briefly fails to maintain the motor command required for sustained posture, producing short lapses in muscle activity that allow the hand to drop before corrective motor activity restores position. Learn the neurophysiology of negative myoclonus, the role of hepatic encephalopathy, hypercapnia, uremia, and drug toxicity, and why asterixis remains one of the most valuable bedside signs of reversible brain dysfunction.