Twitch response in a myopathy with impaired relaxation but no myotonia

John G. Quinlan, Paul A. Iaizzo, Gerald A. Gronert, Edward H. Lambert

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)326-329
Number of pages4
JournalMuscle & Nerve
Issue number4
StatePublished - Apr 1990


  • calcium uptke
  • calcium‐magnesium‐ATPase
  • muscle relaxation
  • muscle twitch
  • sarcoplasmic reticulum
  • staircase


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