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Updated: Sep 26, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Twitch response in a myopathy with impaired relaxation but no myotonia
J G Quinlan1, P A Iaizzo, G A Gronert
1Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota.
Abstract:
A patient with slow muscle relaxation but without accompanying motor unit or myotonic electrical activity had a unique staircase twitch response to repeated nerve stimulation. During 1-Hz stimulation, twitches recorded by measurement of the ankle dorsiflexor group displayed progressively increasing relaxation times with successive stimuli (37% increase) unlike the progressively decreasing relaxation time of the normal response (12-37% decrease). The response may be diagnostic of this unusual myopathy; the test methods are noninvasive and easily tolerated.
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