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August 13th, 2017


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. CO₂ retention causes toxicity at these centres.
  • 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.
  • Causes of Asterixis

  • Bilateral Asterixis

  • Hepatic encephalopathy
  • Uraemia (renal failure)
  • Hypercarbia
  • Medications - clozapine, carbamazepine, valproate, levodopa
  • Unilateral Asterixis

  • CNS lesions - thalamus, midbrain, basal ganglia, frontal lobe
  • Subdural haematoma
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