Paramyotonia congenita: Abnormal short exercise test, and improvement after mexiletine therapy

Carlayne E. Jackson, Richard J. Barohn, Louis J. Ptacek

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The diagnosis of paramyotonia congenita (PC) can be aided by demonstrating a decrease in compound motor action potential amplitude after exercise and a decrement on repetitive stimulation, following cold exposure. We report a patient with PC who presented with complaints of cold‐induced hand and jaw stiffening, in the absence of any episodes of weakness. Treatment with mexiletine led to resolution of the abnormalities exhibited during a short exercise test and repetitive stimulation following ice bath immersion. Molecular genetic analysis revealed a missense mutation (cytosine to thymidine) on chromosome 17 in the alpha‐subunit of the skeletal muscle sodium channel gene that results in the replacement of threonine with methionine. This case demonstrates that, despite the absence of weakness, the short exercise test following cold exposure can be used to confirm the diagnosis of PC in patients without episodic weakness. Furthermore, improvement of the electrophysiologic abnormalities with mexiletine was documented, corresponding with clinical improvement. © 1994 John Wiley & Sons, Inc.

Original languageEnglish (US)
Pages (from-to)763-768
Number of pages6
JournalMuscle & Nerve
Volume17
Issue number7
DOIs
StatePublished - Jul 1994

Keywords

  • exercise test
  • mexiletine
  • myotonia
  • paramyotonia congenita
  • repetitive stimulation

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)

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