| The Asterixis
or 'flapping tremor' is a motor
sign characterized by a gross tremor, like a
flap, produced by saccadic movements of the extremities.
It is especially visible in the upper extremities,
particularly the hands.
The best method of producing it is to ask the
patient (when they are conscious and cooperative)
to hyperextend the hands, with arms extended
and fingers separated. The saccadic movements
are observed when the patient closes their eyes.
This produces a drop in maintenance of extensor
muscle tone followed by abrupt recovery. That
is to say the flexion movement in the hands is
produced by the loss of muscular tone and its
tremor in extension by its abrupt recovery.
If the patient is not cooperative, one can investigate
using passive hyperextension of the patient's
hands, without releasing them, noting the clonic
tremor.
It was first described in hepatic encephalopathy,
but is a sign of diffuse affectation of the cerebral
cortex and is therefore seen in hypercapnic encephalopathy,
uremic encephalopathy, acute intoxication, delirium
and confusional state etc.
It is bilateral. When it presents unilaterally,
one should suspect the existence of an underlying
structural lesion.
Author:
Juan Ignacio Pérez Calvo
Servicio de Medicina
Interna
Hospital Clínico Universitario "Lozano
Blesa"
Zaragoza
Translation: Kelly
Watt |
