Hepatic Flap (Asterixis)
November 26th, 2019
Overview
Asterixis, also known as hepatic flap or uraemic flap, is an important sign of metabolic encephalopathy that occurs due to dysregulation of the diencephalic motor centers in the brain that regulate innervation of muscles responsible for maintaining position.
How to Elicit
- Ask the patient to place their arms up and out in front of them with the wrists extended.
- Look for an intermittent loss of tone in the wrists, with the appearance of a flap.
It is important to note that asterixis is a loss of motor control, rather than a tremor.
Causes of Asterixis
Bilateral Asterixis
- Hepatic encephalopathy
- Uraemia (renal failure)
- Hypercarbia
- Medications - clozapine, carbemazepine, valproate, levodopa
Unilateral Asterixis
- CNS lesions - thalamus, midbrain, basal ganglia, frontal lobe
- Subdural haematoma
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