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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.〔(【引用サイトリンク】url=http://www.merriam-webster.com/medical/asterixis )〕 The term derives from the Greek ''a'', "not" and ''stērixis'', "fixed position". Asterixis is the inability to maintain posture due to a metabolic encephalopathy. This can be elicited on physical exam by having the patient extend their arms and bend their hands back. With a metabolic encephalopathy, the patient is unable to hold their hands back resulting in a “flapping” motion consistent with asterixis. It can be seen in any metabolic encephalopathy e.g. chronic renal failure, severe congestive heart failure, acute respiratory failure and of course commonly decompensated liver failure. ==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.〔Anne M. Larson, Diagnosis and management of acute liver failure, Curr Opin Gastroenterol., 2010, 26(3):212:221, 2010〕 * Asterixis is seen most often in drowsy or stuporous patients with metabolic encephalopathies, especially in decompensated cirrhosis or acute liver failure. * It is also seen in some patients with kidney failure and azotemia, and in carbon dioxide toxicity. * It can also be a feature of Wilson's disease. * Asterixis is also seen in respiratory failure. * Asterixis can be prominent after receiving IV phenytoin, and also if the patient is on narcotics. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「asterixis」の詳細全文を読む スポンサード リンク
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