|Classification and external resources|
Asterixis (also called the flapping tremor, or liver flap) is a tremor of the hand when the wrist is extended, sometimes said to resemble a bird flapping its wings. This motor disorder is characterized by an inability to actively maintain a position, which is demonstrated by jerking movements of the outstretched hands when bent upward at the wrist. The tremor is caused by abnormal function of the diencephalic motor centers in the brain, which regulate the muscles involved in maintaining position. Asterixis is associated with various encephalopathies due especially to faulty metabolism.The term derives from the Greek a, "not" and stērixis, "fixed position".
Associated conditions and presentation
Usually there are brief, arrhythmic interruptions of sustained voluntary muscle contraction causing brief lapses of posture, with a frequency of 3–5 Hz. It is bilateral, but may be asymmetric.
- It can be a sign of hepatic encephalopathy, damage to brain cells presumably due to the inability of the liver to metabolize ammonia to urea. The cause is thought to be predominantly related to abnormal ammonia metabolism.
- Asterixis is seen most often in drowsy or stuporous patients with metabolic encephalopathies, especially in decompensated cirrhosis or acute hepatic failure.
- It is also seen in some patients with renal failure and azotemia, and in carbon dioxide toxicity.
- It can also be a feature of Wilson's disease.
- it is also seen in respiratory failure.
- can be prominent after receiving IV phenytoin, also if on narcotics.
R.D. Adams and J.M. Foley first described asterixis in 1949 in patients with severe liver failure and encephalopathy.
- "Asterixis - Definition". Retrieved 6.1.2011.
- Anne M. Larson, Diagnosis and management of acute liver failure, Curr Opin Gastroenterol., 2010, 26(3):212:221, 2010
- Adams RD, Foley JM. The neurological changes in the more common types of severe liver disease. Trans American Neurology Association 1949; 74: 217-219.