Asterixis


Article Author:
Rasiq Zackria


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Savio John


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Phillip Hynes


Updated:
12/17/2018 9:43:52 AM

Definition/Introduction

Asterixis is a clinical sign that describes the inability to maintain sustained posture with subsequent brief, shock-like, involuntary movements. This motor disorder is myoclonus characterized by muscular inhibition (whereas muscle contractions produce positive myoclonus).[1] Initially described in 1949 by James Foley and Raymond Adams to describe the flapping tremor they observed in liver disease,[2] this clinical sign is not pathognomonic for any condition. However, it may indicate a serious underlying disease process. 

Asterixis can be elicited on physical examination by having the patient extend their arms, dorsiflex the wrists, and spreading the fingers (similar to pushing against a wall) with their eyes closed. This is used to test for the “flap” at the wrist and is the most common method of assessment. One can also elicit asterixis at the hip joint by keeping the patient in the dorsal recumbent position (supine with their knees bent up in an outward position while the feet are flat) and allowing the knees to fall to the sides.[1] The presence of "flapping" shows the presence of asterixis. 

Issues of Concern

The exact pathophysiology of asterixis is still unknown. Several theories suggest a role for the ascending activating systems associated with arousal, which is disturbed in encephalopathy and lesions of the thalamus and midbrain.[3] Two types of surface electromyographic (EMG) patterns have been demonstrated in patients with encephalopathy: pure silent period (type 1) and the silent period following a brief EMG discharge (type 2).[4] These patterns are like the EMG patterns of asterixis caused by a thalamic lesion. However, the pathophysiology of thalamic asterixis has not been definitively established.

Clinical Significance

Asterixis can either be unilateral or bilateral and is typically asynchronous, irregular and variable in frequency and amplitude. Although the clinical sign may suggest an underlying process, the clinical history of the presenting illness is fundamental in triggering further workup.

Bilateral asterixis is most commonly associated with metabolic encephalopathies, especially hepatic. The presumption in hepatic encephalopathy was that damage to brain cells due to the impaired metabolism of ammonia was predominantly related to the development of asterixis in hepatic encephalopathy,[5] however, new research shows that ammonia level does not directly correlate with the development of this phenomenon.[6][7] Bilateral asterixis may also present in patients with cardiac and respiratory failure, uremia, electrolyte abnormalities (primarily hypoglycemia, hypokalemia, and hypomagnesemia), and drug intoxication. Phenytoin intoxication is the most commonly reported drug-induced asterixis, while other drugs implicated include benzodiazepines, barbiturates, valproate, gabapentin, carbamazepine, lithium, ceftazidime, and metoclopramide.[8]

Unilateral asterixis is usually because of focal brain lesions in the thalamus, although there have been reports of lesions in the midbrain, parietal cortex, and frontal cortex causing unilateral asterixis[4].

Asterixis is a significant yet poorly understood clinical sign and is part of the West Haven Criteria used to grade the severity of hepatic encephalopathy as it seems to be a relatively sensitive sign of the disease but is non-specific.[9] Asterixis is the most widely known motor abnormality in hepatic encephalopathy. It is not present at rest, and best elicited on sustained posture. It can also be elicited by asking the patient to grip the examiner's hands tightly. It is usually bilateral but may not be bilaterally synchronous as one side may be affected more than the other. Previously thought to have been exclusively associated with hepatic encephalopathy, this phenomenon may present in different contexts. The evaluation and management depend on the underlying disease process, and one should consider a broad differential diagnosis based on clinical history. The treatment of asterixis is the treatment of the underlying pathology.


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Asterixis - Questions

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When trying to elicit asterixis, the patient should not do which of the following?



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Which of the following is associated with asterixis?



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Asterixis is a sign of which of the following?



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Asterixis has been associated with all of the following except:



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A 63-year-old man presents to the emergency department for evaluation of new onset altered mental status. He has history of alcoholic cirrhosis. He reported that the confusion started a few hours ago while he was watching TV. He also reports recently undergoing evaluation for a liver transplant. His last alcohol use was three months ago. Current medications include spironolactone, furosemide, propranolol, and lactulose. He reports compliance with his medications. On examination, vitals show blood pressure of 100/65 mmHg, heart rate of 78 beats per minute, respiratory rate of 18 breaths per minute, and temperature 37 C. Physical exam reveals scleral icterus, soft but distended abdomen with a positive fluid wave, spider angioma on the anterior chest wall. He is alert and oriented to person, place but not time. Asterixis is noted at bilateral wrists. Lab studies are unremarkable. What is the most likely etiology for the patient's acute presentation?



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Asterixis - References

References

Kojovic M,Cordivari C,Bhatia K, Myoclonic disorders: a practical approach for diagnosis and treatment. Therapeutic advances in neurological disorders. 2011 Jan     [PubMed]
ADAMS RD,FOLEY JM, The neurological disorder associated with liver disease. Research publications - Association for Research in Nervous and Mental Disease. 1953     [PubMed]
Butz M,Timmermann L,Gross J,Pollok B,Südmeyer M,Kircheis G,Häussinger D,Schnitzler A, Cortical activation associated with asterixis in manifest hepatic encephalopathy. Acta neurologica Scandinavica. 2014 Oct     [PubMed]
Inoue M,Kojima Y,Mima T,Sawamoto N,Matsuhashi M,Fumuro T,Kinboshi M,Koganemaru S,Kanda M,Shibasaki H, Pathophysiology of unilateral asterixis due to thalamic lesion. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 2012 Sep     [PubMed]
Ge PS,Runyon BA, Serum ammonia level for the evaluation of hepatic encephalopathy. JAMA. 2014 Aug 13     [PubMed]
Larson AM, Diagnosis and management of acute liver failure. Current opinion in gastroenterology. 2010 May     [PubMed]
Ninan J,Feldman L, Ammonia Levels and Hepatic Encephalopathy in Patients with Known Chronic Liver Disease. Journal of hospital medicine. 2017 Aug     [PubMed]
Nayak R,Pandurangi A,Bhogale G,Patil N,Chate S, Asterixis (flapping tremors) as an outcome of complex psychotropic drug interaction. The Journal of neuropsychiatry and clinical neurosciences. 2012 Winter     [PubMed]
Ellul MA,Gholkar SA,Cross TJ, Hepatic encephalopathy due to liver cirrhosis. BMJ (Clinical research ed.). 2015 Aug 11     [PubMed]

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