From the Guidelines
Asterixis, or flapping tremor, is assessed by having the patient hyperextend their wrists with separated fingers or by having them rhythmically squeeze the examiner's fingers, as it is easily elicited by actions that require postural tone.
Assessment of Asterixis
To assess for asterixis, the following steps can be taken:
- Have the patient hyperextend their wrists with separated fingers, as this action requires postural tone and can elicit asterixis 1.
- Alternatively, have the patient rhythmically squeeze the examiner's fingers, as this action also requires postural tone and can help identify asterixis 1.
- Asterixis can be observed in other areas, such as the feet, legs, arms, tongue, and eyelids, although the wrists are the most common site for assessment 1.
- It is essential to note that asterixis is not pathognomonic of hepatic encephalopathy (HE) and can be observed in other diseases, such as uremia 1.
Clinical Context
In the context of HE, asterixis is often present in the early to middle stages of the disease, preceding stupor or coma 1. The presence of asterixis, along with other signs such as disorientation, can indicate the onset of overt HE (OHE) 1.
Diagnosis and Classification
The diagnosis and classification of HE can be challenging, and the assessment of asterixis is just one part of the overall evaluation. The West-Haven criteria are commonly used to classify the severity of HE, although they have limitations due to subjective factors and interobserver deviation 1. The International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) defines the onset of disorientation or flapping tremor as the start of OHE 1.
From the Research
Assessment of Asterixis (Flapping Tremor)
To assess for asterixis, the following steps can be taken:
- Observe the patient for brief, arrhythmic lapses of sustained posture due to involuntary pauses in muscle contraction 2
- Check for asterixis in the upper and lower extremities, as it can be easier to elicit in one or the other, or can be unilateral or bilateral 3
- Look for negative myoclonus, which is characterized by irregular myoclonic lapses of posture affecting various parts of the body independently 4
- Be aware that asterixis can be asymptomatic and not spontaneously reported by patients, highlighting the importance of actively searching for this sign in the physical exam of encephalopathic patients 2
Clinical Presentation
Asterixis can present in various patterns, including:
- Bilateral or unilateral involvement 3
- Involvement of the upper or lower extremities, or both 3
- Association with other neurological signs, such as encephalopathy or cerebrovascular disease 3, 2
Diagnostic Considerations
Asterixis is not specific to any pathophysiological process, but it is more commonly reported in: