Guidelines on clinical presentation and management of nondystrophic myotonias

Bas C. Stunnenberg, Samantha LoRusso, W. David Arnold, Richard J. Barohn, Stephen C. Cannon, Bertrand Fontaine, Robert C. Griggs, Michael G. Hanna, Emma Matthews, Giovanni Meola, Valeria A. Sansone, Jaya R. Trivedi, Baziel G.M. van Engelen, Savine Vicart, Jeffrey M. Statland

Research output: Contribution to journalReview articlepeer-review

41 Scopus citations


The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.

Original languageEnglish (US)
Pages (from-to)430-444
Number of pages15
JournalMuscle and Nerve
Issue number4
StatePublished - Oct 1 2020


  • management
  • myotonia congenita
  • nondystrophic myotonias
  • paramyotonia congenita
  • skeletal muscle channelopathies

ASJC Scopus subject areas

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


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