Asterixis in Hepatic Encephalopathy Staging
Asterixis typically occurs in the early to middle stages of hepatic encephalopathy (West Haven Grades 1-2), preceding stupor or coma, and its presence marks the onset of overt hepatic encephalopathy. 1
Clinical Staging Context
The International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) consensus specifically defines the onset of disorientation or asterixis as the threshold for overt hepatic encephalopathy (OHE). 1 This means:
Asterixis is absent in minimal hepatic encephalopathy (MHE), where only psychometric testing abnormalities exist without clinical signs 1
Asterixis emerges at West Haven Grade 1-2, when patients begin showing personality changes, sleep disturbances, and early cognitive dysfunction but before progressing to stupor 1
Asterixis disappears in advanced stages (Grade 3-4) as patients progress to stupor and coma, where deep tendon reflexes diminish and eventually disappear 1
Practical Clinical Detection
Asterixis manifests as a "flapping tremor" but is actually a negative myoclonus—a brief loss of postural tone rather than a true tremor. 1 To elicit it:
- Have the patient hyperextend their wrists with fingers separated (classic maneuver) 1
- Alternatively, ask them to rhythmically squeeze your fingers 1
- Check other areas including feet, legs, arms, tongue, and eyelids 1
Important Clinical Caveats
Asterixis is not pathognomonic for hepatic encephalopathy—it occurs in other metabolic encephalopathies including uremia, hypercapnia, and medication toxicity. 1, 2 In prospective observational studies, asterixis was documented in only 45% of overt hepatic encephalopathy episodes, making it a specific but not sensitive marker. 3
The detection of asterixis combined with disorientation has good inter-rater reliability and serves as a practical marker for distinguishing covert from overt hepatic encephalopathy in clinical practice. 1 However, mental and motor signs may not progress in parallel in individual patients, creating staging difficulties. 1
Key takeaway: Asterixis appears when hepatic encephalopathy transitions from covert (minimal/Grade 0) to overt (Grade 1-2), persists through middle stages, then vanishes as consciousness deteriorates toward coma (Grade 3-4). 1