Document Detail

Comparative efficacy of repetitive nerve stimulation, exercise, and cold in differentiating myotonic disorders.
MedLine Citation:
PMID:  17654559     Owner:  NLM     Status:  MEDLINE    
The decremental response of the compound muscle action potential (CMAP) to provocative tests is not characterized in genetically verified myotonic disorders. We therefore studied the relationship between decremental responses and mutation type in 10 patients with recessive myotonia congenita (rMC), two with paramyotonia congenita (PMC), nine with myotonic dystrophy type 1 (DM1), four with DM2, and 14 healthy people. CMAPs were measured at rest, just after a short exercise test (SET), and during short, 5- and 10-HZ, repetitive nerve stimulation (RNS) trains at 32 degrees C and at 20 degrees C. The degree of decrement was not related to the severity of clinical myotonia. Controls and PMC patients had similar responses when warm, but with cooling PMC patients had a persistent decrement of CMAPs. In the rMC patients the decremental responses were related to the type of mutation of the CLCN1 gene, as a decrement was encountered in the T268M, R894X, IVS17+1 G>T, K248X, and 2149 del G, but not with the IVS1+3 A>T, F167L, or dominant A313T mutations. In DM1 patients there was no relationship between decrement and CTG repeats. The degree of partial inexcitability in myotonic muscle membrane therefore depends on the mutation type rather than degree of clinical myotonia. RNS at 10 HZ is more sensitive than SET for demonstrating abnormalities in rMC patients when warm; differences are less marked when cold, which is useful to diagnose PMC. Provocative tests are therefore useful in myotonias to demonstrate muscle inexcitability, which depends on the chloride or sodium channelopathy.
Patrik Michel; Damien Sternberg; Pierre-Yves Jeannet; Murielle Dunand; Francine Thonney; Wolfram Kress; Bertrand Fontaine; Emmanuel Fournier; Thierry Kuntzer
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Muscle & nerve     Volume:  36     ISSN:  0148-639X     ISO Abbreviation:  Muscle Nerve     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-08     Completed Date:  2008-01-04     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7803146     Medline TA:  Muscle Nerve     Country:  United States    
Other Details:
Languages:  eng     Pagination:  643-50     Citation Subset:  IM    
Nerve-Muscle Unit, Neurology Service, CHU Vaudois and University of Lausanne, Room BH7/469, 1011 Lausanne, Switzerland.
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MeSH Terms
Action Potentials / genetics,  physiology*,  radiation effects
Chloride Channels / genetics
Cold Temperature*
DNA Mutational Analysis
Dose-Response Relationship, Radiation
Electric Stimulation / methods
Electromyography / methods
Middle Aged
Muscle, Skeletal / physiopathology*,  radiation effects
Mutation / physiology
Myotonic Disorders / classification,  diagnosis*,  genetics,  physiopathology*
Reaction Time / genetics,  radiation effects
Statistics, Nonparametric
Reg. No./Substance:
0/CLC-1 channel; 0/Chloride Channels

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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