Transient paresis in myotonic syndromes: A simplified electrophysiologic approach

Streib, Erich W.; Sun, Sallie F.; Yarkowsky, Tony

doi:10.1002/mus.880050909

Cited by 48 publications

(40 citation statements)

References 11 publications

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“…This provides the most striking example of disparate electrophysiological manifestations of mutations in the same channel (e.g., T1313M vs T704M), albeit with different phenotypes. In six patients with myotonia congenita (four recessive, one dominant, one unknown inheritance), they also noted similar findings to those reported by Streib et al 2 : the initial decline in CMAP amplitude following exercise gradually improves with repeated exercise, in a manner similar to the warm-up effect.…”

Section: Short Exercise Testsupporting

confidence: 85%

“…The remarkably dynamic alteration in membrane excitability in response to even brief exercise may result in CMAP changes even in the absence of clinically detectable weakness, thus forming the basis for the short exercise CMAP test initially reported by Streib et al, 2 and the long exercise CMAP test later reported by McManis et al 3 The relative ease of short and long exercise testing using commercially available standard electrodiagnostic equipment has made these the most widely used tests for the assessment of patients with suspected muscle channelopathy.…”

Section: Exercise Testingmentioning

confidence: 99%

“…Streib et al 2 originally reported the short exercise test as an alternative to repetitive stimulation in the diagnosis of myotonic disorders, based on the transient paresis and CMAP decrement initially noted 30 years earlier. 8 Often regarded as simply a shortened and more convenient version of the long exercise test, the short exercise test has been most widely used in the diagnosis of generalized myotonia.…”

Section: Short Exercise Testmentioning

confidence: 99%

“…Fournier et al 1 extended the study of Streib et al 2 by performing three sequential short exercise tests separated by 60 s (in contrast to the 10-min rest period between repeat tests used in the Streib study). They found a dramatic decline of CMAP amplitude in all 11 patients with T1313M sodium channel mutations (paramyotonia congenita phenotype) and, by contrast, a progressive increment in six patients with T704M sodium channel mutations (HyperPP phenotype) (FIG.…”

Section: Short Exercise Testmentioning

confidence: 99%

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Clinical Evaluation of Membrane Excitability in Muscle Channel Disorders: Potential Applications in Clinical Trials

Cleland

Logigian

2007

Neurotherapeutics

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Summary:Muscle channelopathies are inherited disorders that cause paralysis and myotonia. Molecular technology has contributed immeasurably to diagnostic testing, to correlation of genotype with phenotype, and to insight into the pathophysiology of these disorders. In most cases, the diagnosis of muscle channelopathy is still made on clinical grounds, but is supported by ancillary laboratory and electrodiagnostic testing such as serum potassium measurement, exercise testing, repetitive nerve stimulation, needle electromyography, calculation of muscle fiber conduction velocity, or electromyography power spectra. Although provocative glucose or potassium challenges are now infrequently performed, they have contributed greatly to our understanding of the pathophysiology of these disorders, and to our ability to differentiate between periodic paralysis types. Despite considerable progress, ample opportunity remains for future clinical research, particularly in expanding genotype-phenotype correlations and in optimizing electrodiagnostic methods. With respect to diagnostic testing, there is a need for accurate, efficient, and cost-effective bedside testing, given the substantial proportion (as high as 20%) of genetically undefined cases. Even in genetically defined cases, minimal clinical expressivity due to incomplete penetrance poses a significant challenge to currently available nonmolecular testing.

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Section: Short Exercise Testsupporting

confidence: 85%

Section: Exercise Testingmentioning

confidence: 99%

Section: Short Exercise Testmentioning

confidence: 99%

Section: Short Exercise Testmentioning

confidence: 99%

See 2 more Smart Citations

Clinical Evaluation of Membrane Excitability in Muscle Channel Disorders: Potential Applications in Clinical Trials

Cleland

Logigian

2007

Neurotherapeutics

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“…Sarcolemmal excitability can be measured indirectly as the variability of the compound muscle action potential (CMAP) following different stimuli. The CMAP size varies in skeletal muscle channelopathies in response to short (10-20 s) or long (3-5 min) exercise tests (Streib, 1982;McManis et al, 1986). Using these exercise protocols in combination with muscle cooling, distinct electrophysiological patterns-termed patterns I, II and III-are now recognized for each of the non-dystrophic myotonia groups (Fournier et al, , 2006.…”

Section: Clinical Electrophysiologymentioning

confidence: 99%

The non-dystrophic myotonias: molecular pathogenesis, diagnosis and treatment

Matthews

Fialho

Tan

et al. 2009

Brain

196

226

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The non-dystrophic myotonias are an important group of skeletal muscle channelopathies electrophysiologically characterized by altered membrane excitability. Many distinct clinical phenotypes are now recognized and range in severity from severe neonatal myotonia with respiratory compromise through to milder late-onset myotonic muscle stiffness. Specific genetic mutations in the major skeletal muscle voltage gated chloride channel gene and in the voltage gated sodium channel gene are causative in most patients. Recent work has allowed more precise correlations between the genotype and the electrophysiological and clinical phenotype. The majority of patients with myotonia have either a primary or secondary loss of membrane chloride conductance predicted to result in reduction of the resting membrane potential. Causative mutations in the sodium channel gene result in an abnormal gain of sodium channel function that may show marked temperature dependence. Despite significant advances in the clinical, genetic and molecular pathophysiological understanding of these disorders, which we review here, there are important unresolved issues we address: (i) recent work suggests that specialized clinical neurophysiology can identify channel specific patterns and aid genetic diagnosis in many cases however, it is not yet clear if such techniques can be refined to predict the causative gene in all cases or even predict the precise genotype; (ii) although clinical experience indicates these patients can have significant progressive morbidity, the detailed natural history and determinants of morbidity have not been specifically studied in a prospective fashion; (iii) some patients develop myopathy, but its frequency, severity and possible response to treatment remains undetermined, furthermore, the pathophysiogical link between ion channel dysfunction and muscle degeneration is unknown; (iv) there is currently insufficient clinical trial evidence to recommend a standard treatment. Limited data suggest that sodium channel blocking agents have some efficacy. However, establishing the effectiveness of a therapy requires completion of multi-centre randomized controlled trials employing accurate outcome measures including reliable quantitation of myotonia. More specific pharmacological approaches are required and could include those which might preferentially reduce persistent muscle sodium currents or enhance the conductance of mutant chloride channels. Alternative strategies may be directed at preventing premature mutant channel degradation or correcting the mis-targeting of the mutant channels.

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The exercise test distinguishes proximal myotonic myopathy from myotonic dystrophy

et al. 1997

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Transient paresis in myotonic syndromes: A simplified electrophysiologic approach

Cited by 48 publications

References 11 publications

Clinical Evaluation of Membrane Excitability in Muscle Channel Disorders: Potential Applications in Clinical Trials

Clinical Evaluation of Membrane Excitability in Muscle Channel Disorders: Potential Applications in Clinical Trials

The non-dystrophic myotonias: molecular pathogenesis, diagnosis and treatment

The exercise test distinguishes proximal myotonic myopathy from myotonic dystrophy

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