Distinguishing paramyotonia congenita and myotonia congenita by electromyography

Subramony, S. H.; Malhotra, C. P.; Mishra, Shrikant

doi:10.1002/mus.880060506

Cited by 32 publications

(7 citation statements)

References 12 publications

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“…In the two PMC patients, cooling induced a significant and persistent reduction of CMAP amplitude and area, in agreement with earlier electrophysiological results 19, 24. These patients had the R1448H and T1700_E1703del mutations, respectively, in the muscle sodium channel gene.…”

Section: Discussionsupporting

confidence: 90%

Comparative efficacy of repetitive nerve stimulation, exercise, and cold in differentiating myotonic disorders

et al. 2007

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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.

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Section: Discussionsupporting

confidence: 90%

Comparative efficacy of repetitive nerve stimulation, exercise, and cold in differentiating myotonic disorders

et al. 2007

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“…23 Cold temperature-induced changes in CMAP amplitude have also been described as specifically separating HPP and PC. 24,26 In two members of a family with PC, cold temperature provoked decreases in both CMAP area and amplitude.24 By contrast, in a family with HPP there was only a mild temperature-related decrease in CMAP amplitude which was offset by a concomitant increase in CMAP area, similar to results reported for normal individuals.26 Because of the distinctly different responses which ran true within each family, it was suggested that HPP and PC were two distinct disorders.…”

Section: Discussionsupporting

confidence: 56%

Paramyotonia congenita or hyperkalemic periodic paralysis? Clinical and electrophysiological features of each entity in one family

et al. 1990

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The nosological distinction between paramyotonia congenita (PC) and hyperkalemic periodic paralysis (HPP) continues to generate debate. Recently, electrophysiological signs thought to be specific for each entity have been described and have been used to bolster the argument that the two disorders are distinct. We report a particularly instructive family wherein individual members had clinical features of either PC or HPP and electrophysiological features of both. We suggest that PC and HPP represent part of the spectrum of a single genetic disorder. Evoked response testing, with exercise and cold provocation, may be useful in determining the physiologic pattern that predominates in any one individual.

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“…Assessment of myotonic syndromes relies on the detection of myotonic discharges with needle electromyography (EMG). Several provocative tests using surface‐recorded muscle responses have been proposed to distinguish the main clinical phenotypes before the advent of molecular diagnosis: repetitive nerve stimulation,5, 6 short exercise,7, 8 long exercise,9, 10 or cold exposure 8, 11, 12. In a recent study, we showed that changes of the compound muscle action potential (CMAP) after a repeated short exercise and after a long exercise allowed to separate muscle channelopathies into five patterns (I‐V), linked to the main clinical phenotypes and to subgroups of ion channel mutations 13.…”

mentioning

confidence: 99%

Cold extends electromyography distinction between ion channel mutations causing myotonia

Fournier

Viala

Gervais

et al. 2006

Annals of Neurology

136

174

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Distinguishing paramyotonia congenita and myotonia congenita by electromyography

Cited by 32 publications

References 12 publications

Comparative efficacy of repetitive nerve stimulation, exercise, and cold in differentiating myotonic disorders

Comparative efficacy of repetitive nerve stimulation, exercise, and cold in differentiating myotonic disorders

Paramyotonia congenita or hyperkalemic periodic paralysis? Clinical and electrophysiological features of each entity in one family

Cold extends electromyography distinction between ion channel mutations causing myotonia

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