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Guidelines on clinical presentation and management of nondystrophic myotonias
Author(s) -
Stunnenberg Bas C.,
LoRusso Samantha,
Arnold W. David,
Barohn Richard J.,
Can Stephen C.,
Fontaine Bertrand,
Griggs Robert C.,
Hanna Michael G.,
Matthews Emma,
Meola Giovanni,
Sansone Valeria A.,
Trivedi Jaya R.,
van Engelen Baziel G.M.,
Vicart Savine,
Statland Jeffrey M.
Publication year - 2020
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.26887
Subject(s) - mexiletine , myotonia , myotonia congenita , medicine , channelopathy , weakness , muscle relaxation , muscle weakness , anesthesia , surgery , myotonic dystrophy
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.