asterixis

Asterixis is a flapping tremor, also known as a negative myoclonus or liver flap, produced by brief interruptions of muscle tone. It is most easily observed when the patient extends the arms with the wrists dorsiflexed and the fingers spread; the hands then exhibit irregular, nonrhythmic flexion and extension that creates a short, fluttering motion.

The sign is typically a marker of metabolic or toxic encephalopathy rather than a focal motor disorder. It is most classically associated with hepatic encephalopathy in patients with liver failure or cirrhosis, but it can occur with other conditions that disturb brain function, including uremia, severe hypercapnia or hypoxemia, hypoglycemia, sepsis, electrolyte disturbances, and certain drug intoxications or withdrawal states.

To elicit asterixis, the examiner asks the patient to hold the arms straight with the wrists dorsiflexed and the fingers extended; the observer notes for a lapse in tone followed by a brief rebound, producing the characteristic flapping motion. The sign may be more prominent when the patient is agitated or fatigued and can lessen or disappear during sleep.

Diagnosis is clinical and supported by the underlying condition. It is not a disease itself but a sign indicating possible encephalopathy. Management involves treating the underlying cause and supportive care; in hepatic encephalopathy this may include measures such as lactulose or rifaximin to reduce ammonia, along with careful correction of fluids, electrolytes, and other metabolic abnormalities. Prognosis depends on the reversibility of the encephalopathy.