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Raja Rayan DL, Hanna MG. Managing pregnancy and anaesthetics in patients with skeletal muscle channelopathies. Neuromuscul Disord 2020; 30:539-545. [PMID: 32622512 DOI: 10.1016/j.nmd.2020.05.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/14/2020] [Accepted: 05/22/2020] [Indexed: 11/15/2022]
Abstract
The skeletal muscle channelopathies are a group of rare diseases and include non-dystrophic myotonia and periodic paralysis. Given their rarity, little has been published on the management of anaesthesia and pregnancy in this cohort despite being important aspects of care. We have conducted a large study of over 70 patients who underwent anaesthesia and 87 pregnancies to investigate the problems encountered following anaesthesia or during pregnancy. This was performed via patient surveys sent out to genetically confirmed channelopathy patients seen at the National Hospital for Neurology and Neurosurgery. Most significantly in our cohort, patients frequently experienced a worsening or precipitation of symptoms during pregnancy (75%) or following anaesthetic (31%). None of our patients developed malignant hyperthermia, although there are confirmed reports of this in patients with periodic paralysis and mutations in RYR1. There was a significantly higher number of miscarriages compared to the normal population. There was no significant difference in antenatal or delivery complications compared to the general population. However, three neonates did have complications, all of whom were found to carry mutations in SCN4A. This study highlights the importance of counselling patients and clinicians for the possibility of worsening symptoms during pregnancy or anaesthesia and the careful management of neonates following delivery.
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Affiliation(s)
- Dipa L Raja Rayan
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK.
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK
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Nam TS, Zhang J, Chandrasekaran G, Jeong IY, Li W, Lee SH, Kang KW, Maeng JS, Kang H, Shin HY, Park HC, Kim S, Choi SY, Kim MK. A zebrafish model of nondystrophic myotonia with sodium channelopathy. Neurosci Lett 2020; 714:134579. [PMID: 31669315 DOI: 10.1016/j.neulet.2019.134579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 10/07/2019] [Accepted: 10/21/2019] [Indexed: 11/17/2022]
Abstract
Nondystrophic myotonias are disorders of Na+ (Nav1.4 or SCN4A) and Cl- (CLCN1) channels in skeletal muscles, and frequently show phenotype heterogeneity. The molecular mechanism underlying their pathophysiology and phenotype heterogeneity remains unclear. As zebrafish models have been recently exploited for studies of the pathophysiology and phenotype heterogeneity of various human genetic diseases, a zebrafish model may be useful for delineating nondystrophic myotonias. Here, we generated transgenic zebrafish expressing a human mutant allele of SCN4A, referred to as Tg(mylpfa:N440K), and needle electromyography revealed increased number of myotonic discharges and positive sharp waves in the muscles of Tg(mylpfa:N440K) than in controls. In addition, forced exercise test at a water temperature of 24 °C showed a decrease in the distance moved, time spent in and number of visits to the zone with stronger swimming resistance. Finally, a forced exercise test at a water temperature of 18 °C exhibited a higher number of dive-bombing periods and drifting-down behavior than in controls. These findings indicate that Tg(mylpfa:N440K) is a good vertebrate model of exercise- and cold-induced human nondystrophic myotonias. This zebrafish model may contribute to provide insight into the pathophysiology of myotonia in sodium channelopathy and could be used to explore a new therapeutic avenue.
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Affiliation(s)
- Tai-Seung Nam
- Department of Neurology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Jun Zhang
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | | | - In Young Jeong
- Department of Biomedical Sciences, Korea University, Ansan, 15355, Republic of Korea
| | - Wenting Li
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - So-Hyun Lee
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Kyung-Wook Kang
- Department of Neurology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Jin-Soo Maeng
- Research Group of Bioprocess Engineering, Korea Food Research Institute, Wanju-gun, 55365, Republic of Korea; Center for Convergent Research of Emerging Virus Infection, Korea Institute of Chemical Technology, Daejeon, 34114, Republic of Korea
| | - Hyuno Kang
- Korea Basic Science Institute, Gwangju Center, Gwangju, 61186, Republic of Korea
| | - Hee-Young Shin
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea
| | - Hae-Chul Park
- Department of Biomedical Sciences, Korea University, Ansan, 15355, Republic of Korea
| | - Sohee Kim
- Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea.
| | - Seok-Yong Choi
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
| | - Myeong-Kyu Kim
- Department of Neurology, Chonnam National University Medical School, Gwangju, 61469, Republic of Korea.
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Hunter M, Ekstrom AB, Campbell C, Hung M, Bounsaga J, Bates K, Adams HR, Luebbe E, Moxley RT, Heatwole C, Johnson NE. Patient-reported study of the impact of pediatric-onset myotonic dystrophy. Muscle Nerve 2019; 60:392-399. [PMID: 31298737 PMCID: PMC10970714 DOI: 10.1002/mus.26632] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 07/07/2019] [Accepted: 07/09/2019] [Indexed: 12/12/2022]
Abstract
INTRODUCTION The prevalence and impact of symptoms affecting individuals with pediatric forms of myotonic dystrophy type-1 (DM1) are not well understood. METHODS Patients from the United States, Canada, and Sweden completed a survey that investigated 20 themes associated with pediatric-onset DM1. Participants reported the prevalence and importance of each theme affecting their lives. Surveys from participants were matched with surveys from their caregivers for additional analysis. RESULTS The most prevalent symptomatic themes included problems with hands or fingers (79%) and gastrointestinal issues (75%). Problems with urinary/bowel control and gastrointestinal issues were reported to have the greatest impact on patients' lives. Responses from participants and their caregivers had varying levels of agreement among symptomatic themes. DISCUSSION Many symptoms have meaningful impact on disease burden. The highest levels of agreement between caregivers and individuals with pediatric forms of myotonic dystrophy were found for physical activity themes.
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Affiliation(s)
- Michael Hunter
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Anne-Berit Ekstrom
- Regional Pediatric Rehabilitation Center, Queen Silvia Children’s Hospital, Gothenburg, Sweden
| | - Craig Campbell
- Department of Neurology, London Health Science Centre, London, ON, Canada
| | - Man Hung
- Roseman University of Health Sciences College of Dental Medicine, The University of Utah, Salt Lake City, UT, USA
| | - Jerry Bounsaga
- Department of Orthopedics, University of Utah School of Medicine, Salt Lake City, UT USA
| | - Kameron Bates
- Department of Neurology, University of Rochester, Rochester, NY, USA
| | - Heather R. Adams
- Department of Neurology, Virginia Commonwealth University, Richmond, VA, USA
| | - Elizabeth Luebbe
- Department of Neurology, Virginia Commonwealth University, Richmond, VA, USA
| | - Richard T Moxley
- Department of Neurology, Virginia Commonwealth University, Richmond, VA, USA
| | - Chad Heatwole
- Department of Neurology, Virginia Commonwealth University, Richmond, VA, USA
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Elia N, Palmio J, Castañeda MS, Shieh PB, Quinonez M, Suominen T, Hanna MG, Männikkö R, Udd B, Cannon SC. Myasthenic congenital myopathy from recessive mutations at a single residue in Na V1.4. Neurology 2019; 92:e1405-e1415. [PMID: 30824560 PMCID: PMC6453767 DOI: 10.1212/wnl.0000000000007185] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 11/04/2018] [Indexed: 01/12/2023] Open
Abstract
OBJECTIVE To identify the genetic and physiologic basis for recessive myasthenic congenital myopathy in 2 families, suggestive of a channelopathy involving the sodium channel gene, SCN4A. METHODS A combination of whole exome sequencing and targeted mutation analysis, followed by voltage-clamp studies of mutant sodium channels expressed in fibroblasts (HEK cells) and Xenopus oocytes. RESULTS Missense mutations of the same residue in the skeletal muscle sodium channel, R1460 of NaV1.4, were identified in a family and a single patient of Finnish origin (p.R1460Q) and a proband in the United States (p.R1460W). Congenital hypotonia, breathing difficulties, bulbar weakness, and fatigability had recessive inheritance (homozygous p.R1460W or compound heterozygous p.R1460Q and p.R1059X), whereas carriers were either asymptomatic (p.R1460W) or had myotonia (p.R1460Q). Sodium currents conducted by mutant channels showed unusual mixed defects with both loss-of-function (reduced amplitude, hyperpolarized shift of inactivation) and gain-of-function (slower entry and faster recovery from inactivation) changes. CONCLUSIONS Novel mutations in families with myasthenic congenital myopathy have been identified at p.R1460 of the sodium channel. Recessive inheritance, with experimentally established loss-of-function, is a consistent feature of sodium channel based myasthenia, whereas the mixed gain of function for p.R1460 may also cause susceptibility to myotonia.
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Affiliation(s)
- Nathaniel Elia
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Johanna Palmio
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Marisol Sampedro Castañeda
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Perry B Shieh
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Marbella Quinonez
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Tiina Suominen
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Michael G Hanna
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Roope Männikkö
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Bjarne Udd
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland
| | - Stephen C Cannon
- From the Departments of Physiology (N.E., M.Q., S.C.C.) and Neurology (P.B.S.), David Geffen School of Medicine at UCLA; Molecular and Cellular Integrative Physiology Program at UCLA (N.E., S.C.C.), Los Angeles, CA; Tampere Neuromuscular Center (J.P., T.S., B.U.), Tampere University and University Hospital, Finland; MRC Centre for Neuromuscular Diseases (M.S.C., M.G.H., R.M.), Department of Neuromuscular Disease, UCL Institute of Neurology, London, UK; Folkhälsan Genetic Institute (B.U.), Helsinki; and Neurology Department (B.U.), Vasa Central Hospital, Finland.
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Ghovanloo MR, Abdelsayed M, Peters CH, Ruben PC. A Mixed Periodic Paralysis & Myotonia Mutant, P1158S, Imparts pH-Sensitivity in Skeletal Muscle Voltage-gated Sodium Channels. Sci Rep 2018; 8:6304. [PMID: 29674667 PMCID: PMC5908869 DOI: 10.1038/s41598-018-24719-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 03/27/2018] [Indexed: 02/07/2023] Open
Abstract
Skeletal muscle channelopathies, many of which are inherited as autosomal dominant mutations, include myotonia and periodic paralysis. Myotonia is defined by a delayed relaxation after muscular contraction, whereas periodic paralysis is defined by episodic attacks of weakness. One sub-type of periodic paralysis, known as hypokalemic periodic paralysis (hypoPP), is associated with low potassium levels. Interestingly, the P1158S missense mutant, located in the third domain S4-S5 linker of the "skeletal muscle", Nav1.4, has been implicated in causing both myotonia and hypoPP. A common trigger for these conditions is physical activity. We previously reported that Nav1.4 is relatively insensitive to changes in extracellular pH compared to Nav1.2 and Nav1.5. Given that intense exercise is often accompanied by blood acidosis, we decided to test whether changes in pH would push gating in P1158S towards either phenotype. Our results suggest that, unlike in WT-Nav1.4, low pH depolarizes the voltage-dependence of activation and steady-state fast inactivation, decreases current density, and increases late currents in P1185S. Thus, P1185S turns the normally pH-insensitive Nav1.4 into a proton-sensitive channel. Using action potential modeling we predict a pH-to-phenotype correlation in patients with P1158S. We conclude that activities which alter blood pH may trigger the noted phenotypes in P1158S patients.
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Affiliation(s)
- Mohammad-Reza Ghovanloo
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Mena Abdelsayed
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Colin H Peters
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Peter C Ruben
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada.
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Kato H, Kokunai Y, Dalle C, Kubota T, Madokoro Y, Yuasa H, Uchida Y, Ikeda T, Mochizuki H, Nicole S, Fontaine B, Takahashi MP, Mitake S. A case of non-dystrophic myotonia with concomitant mutations in the SCN4A and CLCN1 genes. J Neurol Sci 2016; 369:254-258. [PMID: 27653901 DOI: 10.1016/j.jns.2016.08.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 08/11/2016] [Accepted: 08/12/2016] [Indexed: 11/17/2022]
Abstract
Non-dystrophic myotonias are caused by mutations of either the skeletal muscle chloride (CLCN1) or sodium channel (SCN4A) gene. They exhibit several distinct phenotypes, including myotonia congenita, paramyotonia congenita and sodium channel myotonia, and a genotype-phenotype correlation has been established. However, there are atypical cases that do not fit with the standard classification. We report a case of 27-year-old male who had non-dystrophic myotonia with periodic paralysis and two heterozygous mutations, E950K in CLCN1 and F1290L in SCN4A. His mother, who exhibited myotonia without paralytic attack, only harbored E950K, and no mutations were identified in his asymptomatic father. Therefore, the E950K mutation was presumed to be pathogenic, although it was reported as an extremely rare genetic variant. The proband experienced paralytic attacks that lasted for weeks and were less likely to be caused by CLCN1 mutation alone. Functional analysis of the F1290L mutant channel heterologously expressed in cultured cells revealed enhanced activation inducing membrane hyperexcitability. We therefore propose that the two mutations had additive effects on membrane excitability that resulted in more prominent myotonia in the proband. Our case stresses the value of performing genetic analysis of both CLCN1 and SCN4A genes for myotonic patients with an atypical phenotype.
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Affiliation(s)
- Hideki Kato
- Department of Neurology, Tosei General Hospital, Japan
| | - Yosuke Kokunai
- Department of Neurology, Osaka University Graduate School of Medicine, Japan; INSERM U1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle Épinière - ICM and National Reference Center for Muscular Channelopathies, University Hospital Pitié-Salpêtrière, France
| | - Carine Dalle
- INSERM U1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle Épinière - ICM and National Reference Center for Muscular Channelopathies, University Hospital Pitié-Salpêtrière, France
| | - Tomoya Kubota
- Department of Neurology, Osaka University Graduate School of Medicine, Japan; Department of Biochemistry and Molecular Biology, The University of Chicago, United States; Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Japan
| | - Yuta Madokoro
- Department of Neurology, Tosei General Hospital, Japan
| | | | - Yuto Uchida
- Department of Neurology, Tosei General Hospital, Japan
| | | | - Hideki Mochizuki
- Department of Neurology, Osaka University Graduate School of Medicine, Japan
| | - Sophie Nicole
- INSERM U1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle Épinière - ICM and National Reference Center for Muscular Channelopathies, University Hospital Pitié-Salpêtrière, France
| | - Bertrand Fontaine
- INSERM U1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle Épinière - ICM and National Reference Center for Muscular Channelopathies, University Hospital Pitié-Salpêtrière, France
| | - Masanori P Takahashi
- Department of Neurology, Osaka University Graduate School of Medicine, Japan; Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Japan.
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Kazamel M, Sorenson EJ, Milone M. Clinical and Electrophysiological Findings in Hereditary Inclusion Body Myopathy Compared With Sporadic Inclusion Body Myositis. J Clin Neuromuscul Dis 2016; 17:190-196. [PMID: 27224433 DOI: 10.1097/cnd.0000000000000113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
OBJECTIVE To compare the clinical and electrophysiological findings in hereditary inclusion body myopathy (hIBM) and sporadic inclusion body myositis (sIBM) patients. METHODS We retrospectively identified 8 genetically proven hIBM patients and 1 DNAJB6 myopathy with pathological features of hIBM, and compared their clinical, electromyographic, and serological data with a group of 51 pathologically proven sIBM patients. RESULTS hIBM patients had a younger mean age of onset (36 vs. 60 years, P = 0.0001). Diagnostic delay was shorter in sIBM (6 vs. 15 years, P = 0.0003). Wrist flexors (P = 0.02), digit flexors (P = 0.01), digit extensors (P = 0.02), and quadriceps (P = 0.008) muscles were more frequently affected in sIBM. Fibrillation potentials were more common in sIBM patients (P = 0.03). Electrical myotonia was found in 4 hIBM patients, not significantly different from sIBM patients (P = 0.45). Creatinine kinase was higher in sIBM patients (799 vs 232, P = 0.03). CONCLUSIONS sIBM and hIBM seem to have similar electromyographic changes. The combination of clinical, serological, and histopathological findings can guide genetic testing to the final diagnosis.
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Barulin AE, Kurushina OV, Riazantsev AI. [Diagnostic of neurological manifestation in dorsopathies]. Zh Nevrol Psikhiatr Im S S Korsakova 2012; 112:56-57. [PMID: 23250601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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Dabby R, Sadeh M, Herman O, Leibou L, Kremer E, Mordechai S, Watemberg N, Frand J. Clinical, electrophysiologic and pathologic findings in 10 patients with myotonic dystrophy 2. Isr Med Assoc J 2011; 13:745-747. [PMID: 22332444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
BACKGROUND Myotonic dystrophy type 2 (DM2) is an autosomal dominant, multisystem disorder caused by a CCTG tetranucleotide repeat expansion located in intron 1 of the zinc finger protein 9 gene (ZNF9 gene) on chromosome 3q 21.3. OBJECTIVES To describe the clinical, electrophysiologic and pathologic findings in patients with myotonic dystrophy 2. METHODS We evaluated 10 patients genetically, clinically and electrophysiologically during the years 2007 to 2008. RESULTS All patients were of Jewish European ancestry. Among affected individuals, eight patients had symptoms of proximal muscle weakness, two had muscle pain, and two exhibited myotonia. On physical examination six patients had severe weakness of hip flexor muscles. Seven individuals underwent cataract surgery, and cardiac involvement was seen in one case. On the initial electromyographic (EMG) examination five patients demonstrated myotonic discharges; repeated studies showed these discharges in nine cases. Six muscle biopsies showed non-specific pathological changes. Seven patients had an affected first-degree relative with either a diagnosed or an undiagnosed muscular disorder consistent with an autosomal dominant trait. CONCLUSIONS DM2 may often present with proximal muscle weakness without myotonia. EMG may initially fail to show myotonic discharges, but these discharges may eventually show in most cases on repeated EMG. Thus, DM2 may be underdiagnosed and should be included in the differential diagnosis of adult patients of Jewish European ancestry presenting with proximal lower limb weakness.
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Affiliation(s)
- Ron Dabby
- Department of Neurology, Wolfson Medical Center, Holon, Israel.
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Lehmann-Horn F, Jurkat-Rott K, Rüdel R. Diagnostics and therapy of muscle channelopathies--Guidelines of the Ulm Muscle Centre. Acta Myol 2008; 27:98-113. [PMID: 19472919 PMCID: PMC2858942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This article is dedicated to our teacher, Prof. Erich Kuhn, Heidelberg, on the occasion of his 88th birthday on 23rd November 2008. In contrast to muscular dystrophies, the muscle channelopathies, a group of diseases characterised by impaired muscle excitation or excitation-contraction coupling, can fairly well be treated with a whole series of pharmacological drugs. However, for a proper treatment proper diagnostics are essential. This article lists state-of-the-art diagnostics and therapies for the two types of myotonic dystrophies, for recessive and dominant myotonia congenita, for the sodium channel myotonias, for the primary dyskalemic periodic paralyses, for central core disease and for malignant hyperthermia susceptibility in detail. In addition, for each disorder a short summary of aetiology, symptomatology, and pathogenesis is provided.
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Affiliation(s)
- F Lehmann-Horn
- Institute of Applied Physiology, Ulm University, Ulm, Germany.
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Abstract
PURPOSE OF REVIEW To provide a current review of clinical phenotypes, genetics, molecular pathophysiology, and electro-diagnostic testing strategies of periodic paralysis and nondystrophic myotonias. RECENT FINDINGS The number of pathogenic mutations causing periodic paralysis and nondystrophic myotonias continues to increase. Important insight into the molecular pathogenesis of muscle sodium channelopathies has been revealed by the finding of 'leaky' closed sodium channels. Previously, alterations in sodium-channel activation or inactivation have been identified as important disease mechanisms. The recent discovery that substitutions of key arginine residues in the voltage-sensing segment of the channel may lead to a 'pore leak' when the channel is closed suggests a new mechanism. Since similar mutations exist in corresponding positions of other channels, this mechanism may apply to other channel diseases. The recognition of different electrophysiological patterns that are specific to muscle ion-channel genotypes will be useful in diagnosis and in guiding genetic testing. Recent studies demonstrate that magnetic resonance imaging may be used to detect intramuscular accumulation of sodium during episodes of weakness. SUMMARY Recent advances have refined our ability to make a precise molecular diagnosis in muscle channelopathies. The description of a pore leak with voltage-sensor mutations may represent a new disease mechanism.
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Affiliation(s)
- Aisling M Ryan
- MRC Centre for Neuromuscular Disease, Department of Molecular Neuroscience, Institute of Neurology, University College London, London, UK
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12
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Abstract
INTRODUCTION Hypothyroidism is frequently associated with different neuromuscular disorders. However myotonia is rarely a revealing feature. CLINICAL CASES Two patients aged 28 and 31 years consulted for a progressive myotonia. Blood and thyroid analysis revealed peripheral hypothyroidism with low FT4 and high TSH levels. Outcome was favorable with thyroid hormone substitution. Myotonia regressed and thyroid hormone levels returned to normal. CONCLUSION Myotonia may reveal hypothyroidism. The pathogenic mechanism of this myotonia is an unknown. Good outcome with thyroid hormone substitution requires a systematic thyroid hormone screening in patients presenting neuromuscular manifestations.
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Affiliation(s)
- H Mrabet
- Service de Neurologie, EPS Charles Nicolle, Boulevard 9 Avril, 1006 Tunis, Tunisia
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13
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Trip J, Faber C, Ginjaar H, van Engelen B, Drost G. Warm-up phenomenon in myotonia associated with the V445M sodium channel mutation. J Neurol 2007; 254:257-8. [PMID: 17334961 PMCID: PMC1915614 DOI: 10.1007/s00415-006-0353-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Accepted: 07/11/2006] [Indexed: 11/22/2022]
Affiliation(s)
- J. Trip
- Dept. of Neurology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands
| | - C.G. Faber
- Dept. of Neurology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands
| | - H.B. Ginjaar
- Dept. of Human and Clinical Genetics, University Medical Centre Leiden, Leiden, The Netherlands
| | - B.G.M. van Engelen
- Neuromuscular Centre Nijmegen, Institute of Neurology, Radboud University Nijmegen Medical Centre, The Netherlands
| | - G. Drost
- Neuromuscular Centre Nijmegen, Institute of Neurology, Radboud University Nijmegen Medical Centre, The Netherlands
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14
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Fournier E, Viala K, Gervais H, Sternberg D, Arzel-Hézode M, Laforêt P, Eymard B, Tabti N, Willer JC, Vial C, Fontaine B. Cold extends electromyography distinction between ion channel mutations causing myotonia. Ann Neurol 2006; 60:356-65. [PMID: 16786525 DOI: 10.1002/ana.20905] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE Myotonias are inherited disorders of the skeletal muscle excitability. Nondystrophic forms are caused by mutations in genes coding for the muscle chloride or sodium channel. Myotonia is either relieved or worsened by repeated exercise and can merge into flaccid weakness during exposure to cold, according to causal mutations. We designed an easy electromyography (EMG) protocol combining repeated short exercise and cold as provocative tests to discriminate groups of mutations. METHODS Surface-recorded compound muscle action potential was used to monitor muscle electrical activity. The protocol was applied on 31 unaffected control subjects and on a large population of 54 patients with chloride or sodium channel mutations known to cause the different forms of myotonia. RESULTS In patients, repeated short exercise test at room temperature disclosed three distinct abnormal patterns of compound muscle action potential changes (I-III), which matched the clinical symptoms. Combining repeated exercise with cold exposure clarified the EMG patterns in a way that enabled a clear correlation between the electrophysiological and genetic defects. INTERPRETATION We hypothesize that segregation of mutations into the different EMG patterns depended on the underlying pathophysiological mechanisms. Results allow us to suggest EMG guidelines for the molecular diagnosis, which can be used in clinical practice.
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Affiliation(s)
- Emmanuel Fournier
- Fédération de Neurophysiologie Clinique, Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Université Pierre et Marie Curie, Paris.
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15
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Abstract
Myotonia permanens is associated with a G1306E mutation in the SCN4A gene. Two sporadic patients have been reported, but the clinical phenotype has not been fully characterized. The authors report a family in which the disease is autosomal dominantly inherited. The patients have severe myotonia, but the clinical picture is not qualitatively different from that seen in other nondystrophic myotonias.
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Affiliation(s)
- Eskild Colding-Jørgensen
- Department of Clinical Neurophysiology, Glostrup Hospital, University of Copenhagen, Glostrup, Denmark.
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16
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Mahadevan MS, Yadava RS, Yu Q, Balijepalli S, Frenzel-McCardell CD, Bourne TD, Phillips LH. Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy. Nat Genet 2006; 38:1066-70. [PMID: 16878132 PMCID: PMC2909745 DOI: 10.1038/ng1857] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Accepted: 06/30/2006] [Indexed: 12/24/2022]
Abstract
Myotonic dystrophy (DM1), the most common muscular dystrophy in adults, is caused by an expanded (CTG)n tract in the 3' UTR of the gene encoding myotonic dystrophy protein kinase (DMPK), which results in nuclear entrapment of the 'toxic' mutant RNA and interacting RNA-binding proteins (such as MBNL1) in ribonuclear inclusions. It is unclear if therapy aimed at eliminating the toxin would be beneficial. To address this, we generated transgenic mice expressing the DMPK 3' UTR as part of an inducible RNA transcript encoding green fluorescent protein (GFP). We were surprised to find that mice overexpressing a normal DMPK 3' UTR mRNA reproduced cardinal features of myotonic dystrophy, including myotonia, cardiac conduction abnormalities, histopathology and RNA splicing defects in the absence of detectable nuclear inclusions. However, we observed increased levels of CUG-binding protein (CUG-BP1) in skeletal muscle, as seen in individuals with DM1. Notably, these effects were reversible in both mature skeletal and cardiac muscles by silencing transgene expression. These results represent the first in vivo proof of principle for a therapeutic strategy for treatment of myotonic dystrophy by ablating or silencing expression of the toxic RNA molecules.
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Affiliation(s)
- Mani S Mahadevan
- Department of Pathology, University of Virginia, PO Box 800904, Charlottesville, Virginia 22908-0904, USA.
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17
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Aoike F, Takahashi MP, Sakoda S. Class Ic antiarrhythmics block human skeletal muscle Na channel during myotonia-like stimulation. Eur J Pharmacol 2006; 532:24-31. [PMID: 16473348 DOI: 10.1016/j.ejphar.2005.12.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 11/30/2005] [Accepted: 12/12/2005] [Indexed: 10/25/2022]
Abstract
Flecainide, a class Ic antiarrhythmic drug, has been anecdotally reported to improve myotonia, but little is known about its kinetics on human skeletal muscle sodium channels applicable in vivo. Here we explored the anti-myotonic action of flecainide for human skeletal muscle sodium channels heterologously expressed in cultured cells. Flecainide blocked sodium channels in a highly state-dependent manner with 20-fold difference in IC(50) between use-dependent and tonic blocks. When pulses of brief depolarization simulating myotonia were applied from a holding potential of -90 mV, flecainide at therapeutic concentrations significantly blocked sodium currents. Flecainide slowed the time course of recovery but most channels recovered from block within 10-20 s. In contrast to mexiletine, flecainide did not markedly block sodium current during prolonged depolarization, suggesting an open-channel blocking action. Considering the slow recovery from block and the specific action against repetitive depolarization, flecainide may represent a potent therapeutic agent for myotonia.
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Affiliation(s)
- Futoshi Aoike
- Department of Neurology, Osaka University Graduate School of Medicine D-4, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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18
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19
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Aarrestad DD, Williams MD, Fehrer SC, Mikhailenok E, Leonard CT. Intra- and interrater reliabilities of the Myotonometer when assessing the spastic condition of children with cerebral palsy. J Child Neurol 2004; 19:894-901. [PMID: 15658795 DOI: 10.1177/08830738040190110801] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The purposes of this study were to assess intra- and interrater reliabilities by novice users of the Myotonometer (Neurogenic Technologies, Inc., Missoula, MT), a portable electronic device that quantifies muscle tone (stiffness) and paresis, in assessing children with cerebral palsy. Two raters used the Myotonometer to assess the biceps brachii and medial gastrocnemius muscles of 10 children with spastic-type cerebral palsy. Muscles were measured in a relaxed state and during a voluntary isometric contraction. Intraclass correlation coefficients and repeatability coefficients were calculated for each muscle and for each condition (relaxed and contracted). Intrarater reliabilities ranged from 0.82 to 0.99 (biceps brachii muscles) and 0.88 to 0.99 (medial gastrocnemius muscles). Interrater reliabilities ranged from 0.74 to 0.99 (biceps brachii muscles) and 0.84 to 0.99 (medial gastrocnemius muscles). Repeatability coefficients indicated a 98% level of agreement between raters across all conditions. Novice users of the Myotonometer, with few exceptions, had high to very high intra- and interrater reliabilities for measurements of the biceps brachii and medial gastrocnemius muscles of children with spastic-type cerebral palsy.
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20
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Abstract
Electrodiagnostic testing should always be tailored to the clinical setting; in the muscle channelopathies, provocative tests are essential to demonstrate the modifications of the muscle excitability. When a permanent muscle weakness is present, a post-exercise (or post-tetanic) potentiation should be search to demonstrate a presynaptic neuromuscular channelopathy; when the weakness is fluctuating it is useful to perform repetitive nerve stimulation to see if a decrement is present or if the jitter is prolonged, indicative of a postsynaptic neuromuscular channelopathy; when the weakness is episodic, the prolonged exercise test is the only test to demonstrate the appearance of a late post-exercise decrement (sodium and calcium channelopathies), and when a myotonic reaction is seen to search the myotonic discharges by needle emg. The concomitant presence of myotonic discharges and abnormal decrement of the motor responses during repetitive nerve stimulation train depend on the type of mutations in the chloride gene and the amount of CTG repeats in myotonic dystrophy type 1. In paramyotonia congenita there a prolonged decrement when the tests are carried out with cooling the recorded muscle. Electrophysiological testings appear therefore useful to diagnose muscle channelopathies but also give information about the prognosis of the disorder; they could also be viewed as useful tests to predict response to treatments.
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Affiliation(s)
- T Kuntzer
- Service de Neurologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Suisse.
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21
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Abstract
As voltage-gated ion channels are essential for membrane excitation, it is not surprising that mutations in the respective channel genes cause diseases characterised by altered cell excitability. Skeletal muscle was the first tIssue in which such diseases, namely the myotonias and periodic paralyses, were recognised as ion channelopathies. The detection of the functional defect that is brought about by the disease-causing mutation is essential for the understanding of the pathology. Much progress on the road to this aim was achieved by the combination of molecular biology and electrophysiological patch clamp techniques. The functional expression of the mutations in expression systems allows to study the functional alterations of mutant channels and to develop new strategies for the therapy of ion channelopathies, e.g. by designing drugs that specifically suppress the effects of malfunctioning channels.
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Affiliation(s)
- K Jurkat-Rott
- Department of Physiology, Ulm University, Ulm, Germany
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22
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Abstract
The myotonic disorders, including the myotonic dystrophies (myotonic dystrophy type 1, DM1; myotonic dystrophy type 2, DM2/PROMM/PDM), the muscle channelopathies or non-dystrophic myotonias (chloride, sodium, calcium and potassium channelopathies) are all characterized by myotonia and muscle weakness despite different pathophysiology involved in these disorders. Myotonia may affect the eye, facial and jaw muscles as well as the hands and legs. It may be painful and disabling. Muscle weakness may be episodical as in the paralytic attacks of the sodium and calcium channelopathies or culminate in permanent muscle weakness as in the calcium channelopathies and some sodium channelopathies associated to specific point mutations. The severity of myotonia may fluctuate in the myotonic dystrophies, but weakness is usually fixed, affecting neck flexors, facial and jaw muscles as well as proximal and distal muscles of the limbs. Despite the recent progress in molecular genetics the precise mechanisms responsible for myotonia and weakness are not fully understood and there is no standardized treatment strategy. We present a review of selected treatment trials in the myotonic disorders and the muscle channelopathies, and discuss our experience in the treatment of myotonia and muscle weakness, with reference to the limits and advantages of treatment trials in this field.
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Affiliation(s)
- G Meola
- Department of Neurology, University of Milan, Istituto Policlinico San Donato, Italy
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23
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Abstract
There is increasing evidence that autoimmunity is implicated in the pathogenesis of peripheral nerve hyperexcitability (neuromyotonia, NMT and Cramp-fasciculation syndrome C-FS ) and in Maladie de Morvan in which CNS features are also present. All three conditions can associate with thymoma, myasthenia gravis and other autoimmune disorders, and can often respond to plasma exchange. In NMT, patient's plasma or IgG can transfer the electrophysiological features to mice, and can reduce voltage-gated potassium channel currents in vitro. Antibodies to voltage-gated potassium channels can be detected in the serum of many patients who have peripheral nerve hyperexcitability, and also in those with Maladie de Morvan. These latter patients have clinical features similar to limbic encephalitis in which VGKC antibodies can also occur. Thus neuromyotonia, cramp-fasciculation syndrome and Maladie de Morvan can occur as antibody-mediated autoimmune ion channelopathies like myasthenia gravis and the Lambert-Eaton myasthenic syndrome. These discoveries should aid diagnosis and offer new approaches to treatment.
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Affiliation(s)
- J Newsom-Davis
- Department of Clinical Neurology, University of Oxford, Radcliffe Infirmary, Oxford OX2 6HE, UK.
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24
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Abstract
PURPOSE To describe the characteristics and significance of acquired oculomotor nerve paresis with cyclic spasm. METHOD Retrospective case series of two patients with a history of previous skull base irradiation for intracranial tumor who developed double vision and were found to have oculomotor nerve paresis with cyclic spasm. Both patients underwent a complete neuroophthalmologic assessment, including testing of eyelid position, pupillary size and reactivity, and ocular motility and alignment during both the paretic and spastic phases of the condition. RESULTS Both patients developed unilateral lid retraction and ipsilateral esotropia with limitation of abduction during the spastic phase of the cycle, with ipsilateral ptosis, exotropia, and variable limitation of adduction during the paretic phase. The cycles were continuous and were not induced or altered by eccentric gaze. CONCLUSIONS Cyclic oculomotor nerve paresis with spasms may occur years after irradiation of the skull base. This condition is different from the more common ocular motor disturbance that occurs in this setting-ocular neuromyotonia. However, in view of the similarity between these two disorders, it seems likely that they are caused by a similar peripheral mechanism.
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Affiliation(s)
- Neil R Miller
- Neuro-Ophthalmology Unit of the Wilmer Eye Institute, Department of Ophthalmology, the Johns Hopkins Hospital, Baltimore, Maryland 21287, USA.
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25
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Howse MLP, Wardell TM, Fisher CJ, Tilley PJB, Chinnery PF, Bindoff L. Late-onset mitochondrial disorder with electromyographic evidence of myotonia. Muscle Nerve 2003; 28:757-9. [PMID: 14639592 DOI: 10.1002/mus.10492] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We describe a patient with chronic progressive external ophthalmoplegia (CPEO) due to a deletion of mitochondrial DNA (mtDNA) who had electromyographic evidence of myotonic discharges. Myotonia has not previously been described in association with mitochondrial disease and this report extends the known phenotypic expression of these disorders.
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Affiliation(s)
- Mathew L P Howse
- Department of Neurology, Middlesbrough General Hospital, Middlesbrough, Teeside, United Kingdom
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26
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Abstract
OBJECTIVE In this paper we report a painful nondystrophic myotonia which has not been previously described. Pain is a rare symptom in myotonia. We report a myotonic disorder in a 34-year-old woman and her 14-year-old daughter. Painful cramps occur during and after exercise in the mother, and both patients can demonstrate unusual contractions in the tongue. In the present study we try to evaluate the mechanisms behind the unique finding of trains of high amplitude of positive waves, not seen in the earlier known myotonic conditions. METHODS Clinical investigations and electromyography with single and dual channel recordings and muscle morphometry were performed. RESULTS The electromyographic recordings reveal positive waves, fibrillation potentials and myotonic discharges. In addition, extraordinary findings were made of trains of high frequency positive potentials with very high amplitudes and with conduction block along the muscle fibres. CONCLUSIONS In this new form of myotonia with likely dominant heredity, the specific finding of trains of high amplitude positive waves indicates ephaptic transmission within bundles of neighbouring muscle fibres.
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Affiliation(s)
- T Torbergsen
- Department of Neurology, Tromsø University Hospital, Tromsø, Norway.
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27
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Grunnet M, Jespersen T, Colding-Jørgensen E, Schwartz M, Klaerke DA, Vissing J, Olesen SP, Dunø M. Characterization of two new dominant ClC-1 channel mutations associated with myotonia. Muscle Nerve 2003; 28:722-32. [PMID: 14639587 DOI: 10.1002/mus.10501] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Voltage-gated ClC-1 chloride channels encoded by the CLCN1 gene have a major role in setting the membrane potential in skeletal muscle. More than 60 CLCN1 mutations have been associated with myotonia congenita. These mutations are traditionally classified as recessive (Becker's disease) or dominant (Thomsen's disease). In this study, we have electrophysiologically characterized two new dominant ClC-1 mutations, thereby elucidating the observed phenotype in patients. The two ClC-1 mutants M128V and E193K were identified, and the DNA was isolated from patients and subsequently expressed in Xenopus laevis oocytes for electrophysiological characterization. Both ClC-1 mutants, M128V and E193K, showed a large rightward shift in the current-voltage relationship. In addition, the activation kinetics were slowed in the ClC-1 M128V mutant, as compared to the wild-type ClC-1. Interestingly, ClC-1 E193K revealed a change in reversal potential compared to wild-type channels. This finding supports the notion that the E193 amino acid is an important determinant in the selectivity filter of the human ClC-1 channel. The electrophysiological behavior of both mutants demonstrates a severe reduction in ClC-1 channel conductance under physiologically relevant membrane potentials. These studies thereby explain the molecular background for the observed myotonia in patients.
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Affiliation(s)
- Morten Grunnet
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
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28
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Abstract
Mutations in the voltage-dependent skeletal muscle chloride channel, ClC-1, result in dominant or recessive myotonia congenita. The Q552R mutation causes a variant of dominant myotonia with a milder phenotype, myotonia levior. To characterise the functional properties of this mutation, homodimeric mutant and heterodimeric wild-type (WT) mutant channels were expressed in tsA201 cells and studied using the whole-cell recording technique. Q552R ClC-1 mutants formed functional channels with normal ion conduction but altered gating properties. Mutant channels were activated by membrane depolarisation, with a voltage dependence of activation that was shifted by more than +90 mV compared to WT channels. Q552R channels were also activated by hyperpolarisation, and this process was dependent upon the intracellular chloride concentration ([Cl(-)](i)). Together, these alterations resulted in a substantial reduction in the open probability at -85 mV at a physiological [Cl(-)](i). Heterodimeric WT-Q552R channels did not exhibit hyperpolarisation-activated gating transitions. As was the case for WT channels, activation occurred upon depolarisation, but the activation curve was shifted by 28 mV to more positive potentials. The functional properties of heterodimeric channels suggest a weakly dominant effect, a finding that correlates with the inheritance pattern and symptom profile of myotonia levior.
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Affiliation(s)
- Aisling Ryan
- Department of General Physiology, University of Ulm, 89069 Ulm, Germany
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29
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Abstract
Ion channelopathies have common clinical features, recurrent patterns of mutations, and almost predictable mechanisms of pathogenesis. In skeletal muscle, disorders are associated with mutations in voltage-gated Na(+), K(+), Ca(2+), and Cl(-) channels leading to hypoexcitability, causing periodic paralysis and to hyperexcitabilty, resulting in myotonia or susceptibility to malignant hyperthermia.
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Affiliation(s)
- Karin Jurkat-Rott
- Department of Applied Physiology, University of Ulm, 89069 Ulm, Germany
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30
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Abstract
Advances in physiology and molecular genetics have promoted greater understanding of the various clinical manifestations of muscle disorders. For example, myotonia or profound weakness may be observed in sodium channel disease (e.g., paramyotonia congenita or hyperkalemic periodic paralysis), depending on the specific channel defect or with slight changes in membrane potential. Observed effects of anesthetic techniques have been essential to elucidating the primary muscular nature of myotonia. Commonly used anesthetic medications have potentially lethal (e.g., MH) or serious (e.g., myotonic dystrophy) adverse effects. Conversely, lidocaine or propofol may have therapeutic benefit for patients with skeletal muscle sodium channel disorders. Additional investigation is required to improve our understanding of how age, gender, or other factors determine the phenotypic expression of malignant hyperthermia. Future research holds the promise for more accurate pre-anesthetic identification of persons with heritable myopathies, especially those who are asymptomatic. Enhanced awareness of multiple organ system involvement in myotonic dystrophy is essential for planning perioperative care. Patients with periodic paralysis require that we know factors that incite or inhibit the development of their attacks. Advances in bench research and detailed clinical studies will further improve our ability to provide optimal care for patients with muscle disorders.
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Affiliation(s)
- Harvey K Rosenbaum
- UCLA Department of Anesthesiology, UCLA Malignant Hyperthermia Program, Box 951778, Los Angeles, CA 90095-1778, USA
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31
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Atlas EE. [Rehabilitation of children with diffuse muscular hypotonia and neurophysiologic criteria of its effectiveness]. Vopr Kurortol Fizioter Lech Fiz Kult 2002:26-9. [PMID: 12132220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Neuromapping, neuromyography, cerebrovascular mapping, cardiointervalography were conducted in children with the diagnosis "natal trauma of the cervical spine and vertebral arteries with ischemia of the reticular formation of the cerebral trunk in the form of myatonic syndrome". Adaptation reserves in the children were also studied. In addition to conventional methods, the treatment included kinesitherapy. The efficacy of the kinesitherapy was assessed.
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32
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Sunohara N. [Lambert-Brody syndrome]. Ryoikibetsu Shokogun Shirizu 2002:375-8. [PMID: 11596415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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33
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Nemoto H, Kurihara T. [Na channel myotonia]. Ryoikibetsu Shokogun Shirizu 2002:140-3. [PMID: 11555893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Affiliation(s)
- H Nemoto
- Fourth Department of Internal Medicine, Toho University School of Medicine
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34
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Renner DR, Ptácek LJ. Periodic paralyses and nondystrophic myotonias. Adv Neurol 2002; 88:235-52. [PMID: 11908229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Affiliation(s)
- David R Renner
- Department of Neurology, University of Utah, Salt Lake City, Utah 84132, USA
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35
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Talon S, De Luca A, De Bellis M, Desaphy JF, Lentini G, Scilimati A, Corbo F, Franchini C, Tortorella P, Jockusch H, Conte Camerino D. Increased rigidity of the chiral centre of tocainide favours stereoselectivity and use-dependent block of skeletal muscle Na(+) channels enhancing the antimyotonic activity in vivo. Br J Pharmacol 2001; 134:1523-31. [PMID: 11724759 PMCID: PMC1573071 DOI: 10.1038/sj.bjp.0704366] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Searching for the structural requirements improving the potency and the stereoselectivity of Na(+) channel blockers as antimyotonic agents, new derivatives of tocainide, in which the chiral carbon atom is constrained in a rigid alpha-proline or pyrrolo-imidazolic cycle, were synthesized as pure enantiomers. 2. Their ability to block Na(+) currents, elicited from -100 to -20 mV at 0.3 Hz (tonic block) and 2-10 Hz (use-dependent block) frequencies, was investigated in vitro on single fibres of frog semitendinosus muscle using the vaseline-gap voltage-clamp method. 3. The alpha-proline derivative, To5, was 5 and 21 fold more potent than tocainide in producing tonic and 10 Hz-use-dependent block, respectively. Compared to To5, the presence of one methyl group on the aminic (To6) or amidic (To7) nitrogen atom decreased use-dependence by 2- and 6-times, respectively. When methylene moieties were present on both nitrogen atoms (To8), both tonic and use-dependent block were reduced. 4. Contrarily to tocainide, all proline derivatives were stereoselective in relation to an increased rigidity. A further increase in the molecular rigidity as in pyrrolo-imidazolic derivatives markedly decreased the drug potency with respect to tocainide. 5. Antimyotonic activity, evaluated as the shortening of the time of righting reflexes of myotonic adr/adr mice upon acute drug in vivo administration was 3 fold more effective for R-To5 than for R-Tocainide. 6. Thus, constraining the chiral centre of tocainide in alpha-proline cycle leads to more potent and stereoselective use-dependent Na(+) channel blockers with improved therapeutic potential.
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Affiliation(s)
- Sophie Talon
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Michela De Bellis
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Jean-François Desaphy
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Giovanni Lentini
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Antonio Scilimati
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Filomena Corbo
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Carlo Franchini
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Paolo Tortorella
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Harald Jockusch
- Developmental Biology Unit, W7, University of Bielefeld, D-33501, Germany
| | - Diana Conte Camerino
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
- Author for correspondence:
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Seznec H, Agbulut O, Sergeant N, Savouret C, Ghestem A, Tabti N, Willer JC, Ourth L, Duros C, Brisson E, Fouquet C, Butler-Browne G, Delacourte A, Junien C, Gourdon G. Mice transgenic for the human myotonic dystrophy region with expanded CTG repeats display muscular and brain abnormalities. Hum Mol Genet 2001; 10:2717-26. [PMID: 11726559 DOI: 10.1093/hmg/10.23.2717] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The autosomal dominant mutation causing myotonic dystrophy (DM1) is a CTG repeat expansion in the 3'-UTR of the DM protein kinase (DMPK) gene. This multisystemic disorder includes myotonia, progressive weakness and wasting of skeletal muscle and extramuscular symptoms such as cataracts, testicular atrophy, endocrine and cognitive dysfunction. The mechanisms underlying its pathogenesis are complex. Recent reports have revealed that DMPK gene haploinsufficiency may account for cardiac conduction defects whereas cataracts may be due to haploinsufficiency of the neighboring gene, the DM-associated homeobox protein (DMAHP or SIX5) gene. Furthermore, mice expressing the CUG expansion in an unrelated mRNA develop myotonia and myopathy, consistent with an RNA gain of function. We demonstrated that transgenic mice carrying the CTG expansion in its human DM1 context (>45 kb) and producing abnormal DMPK mRNA with at least 300 CUG repeats, displayed clinical, histological, molecular and electrophysiological abnormalities in skeletal muscle consistent with those observed in DM1 patients. Like DM1 patients, these transgenic mice show abnormal tau expression in the brain. These results provide further evidence for the RNA trans-dominant effect of the CUG expansion, not only in muscle, but also in brain.
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Affiliation(s)
- H Seznec
- INSERM UR383, Hôpital Necker-Enfants Malades, Université René Descartes Paris V, 149-161 rue de Sèvres, 75743 Paris Cedex 15, France
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Abstract
Severe clinical myotonia can be physically disabling and socially impairing but as yet there is no standardized treatment regimen. The aim of our study is to present a protocol to measure myotonia using quantitative muscle assessment measures. The proposed protocol addresses two main issues. Muscle strength is assessed in 8 muscles on the right and on the left using a myometer (QMA, quantitative muscle assessment) and by testing strength manually using the 5-point MRC scale (5 = normal) in 15 muscles on the right and on the left. Grip myotonia is assessed by: (a) measuring 1/2 and 3/4 relaxation times (RT) after maximum voluntary contraction (MVC) using QMA apparatus; (b) functional tests (time to open a fist 10 times, time to open and squeeze the eyes 10 times, time to climb 10 steps starting from a seated position, time to protrude the tongue 10 times, time to step onto a chair 10 times; (c) subjective measures of the severity of myotonia using an arbitrary 4-point scale (0 = absent, 4 = severe); and (d) electromyography (EMG) relaxation times after MVC. Although QMA seems to be a reliable tool to measure myotonia, there are still a number of unsolved issues. Further studies are needed to ensure the ability of QMA to quantify myotonia and to guarantee the reliability of the results for clinical research purposes.
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Affiliation(s)
- V Sansone
- Department of Neurology, University of Milan, Istituto Policlinico San Donato, Via Morandi 30, I-20097 San Donato Milanese (MI), Italy
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Ugalde V, Walsh S, Abresch RT, Bonekat HW, Breslin E. Respiratory abdominal muscle recruitment and chest wall motion in myotonic muscular dystrophy. J Appl Physiol (1985) 2001; 91:395-407. [PMID: 11408457 DOI: 10.1152/jappl.2001.91.1.395] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Abdominal muscles are selectively active in normal subjects during stress and may increase the potential energy for inspiration by reducing the end-expiratory lung volume (EELV). We hypothesized that a similar process would occur in subjects with myotonic muscular dystrophy (MMD), but would be less effective, because of to their weakness and altered chest wall mechanics. Fine-wire electromyography (EMG) of the transversus abdominis (TA), internal oblique (IO), external oblique, and rectus abdominis was recorded in 10 MMD and 10 control subjects. EMG activity, respiratory inductive plethysmography, and gastric pressure were recorded during static pressure measurement and at increasing levels of inspiratory resistance breathing. EELV was reduced and chest wall motion was synchronous only in controls. Although the TA and IO were selectively recruited in both groups, EMG activity of the MMD group was twice that of controls at the same inspiratory pressure. In MMD subjects with mildly reduced forced vital capacity, significant differences can be seen in abdominal muscle recruitment, wall motion, work of breathing, and ventilatory parameters.
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Affiliation(s)
- V Ugalde
- Department of Physical Medicine and Rehabilitation, University of California Davis Medical Center, Sacramento, California 95817, USA.
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Wu FF, Takahashi MP, Pegoraro E, Angelini C, Colleselli P, Cannon SC, Hoffman EP. A new mutation in a family with cold-aggravated myotonia disrupts Na(+) channel inactivation. Neurology 2001; 56:878-84. [PMID: 11294924 DOI: 10.1212/wnl.56.7.878] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To identify the molecular and physiologic abnormality in familial myotonia with cold sensitivity, hypertrophy, and no weakness. BACKGROUND Sodium channel mutations were previously identified as the cause of several allelic disorders with varying combinations of myotonia and periodic paralysis. A three-generation family with dominant myotonia aggravated by cooling, but no weakness, was screened for mutations in the skeletal muscle sodium channel alpha-subunit gene (SCN4A). METHODS Single-strand conformation polymorphism was used to screen all 24 exons of SCN4A and abnormal conformers were sequenced to confirm the presence of mutations. The functional consequence of a SCN4A mutation was explored by recording sodium currents from human embryonic kidney cells transiently transfected with an expression construct that was mutated to reproduce the genetic defect. RESULTS A three-generation Italian family with myotonia is presented, in which a novel SCN4A mutation (leucine 266 substituted by valine, L266V) is identified. This change removes only a single methylene group from the 1,836-amino-acid protein, and is present in a region of the protein previously not known to be critical for channel function (domain I transmembrane segment 5). Electrophysiologic studies of the L266V mutation showed defects in fast inactivation, consistent with other disease-causing SCN4A mutations studied to date. Slow inactivation was not impaired. CONCLUSIONS This novel mutation of the sodium channel indicates that a single carbon change in a transmembrane alpha-helix of domain I can alter channel inactivation and cause cold-sensitive myotonia.
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Affiliation(s)
- F F Wu
- Department of Human Genetics, University of Pittsburgh, PA, USA
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40
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Shmidt AN. [On myotonia doctrine. Myotonia in myxedema patients. 1903]. Zh Nevrol Psikhiatr Im S S Korsakova 2001; 100:4-9. [PMID: 10983359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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Abstract
OBJECTIVES To describe a case of equine muscular dystrophy with myotonia. METHODS A 5-year-old horse presented with hypertrophy and delayed relaxation of the muscles of the hindlimbs from age 2 months. Testicular atrophy developed from 2 years of age. Action and percussion myotonia was associated with weakness in these muscles, and EMG showed diffuse myotonic discharges and myopathic features. Biopsy of the gluteal muscle showed adipose and connective tissue infiltration, marked variation in muscle fibre size, and moth-eaten, ring and whorled fibres. RESULTS Injection of apamin, a peptide blocker of calcium-activated potassium channels, which inhibits myotonia in human myotonic dystrophy, was ineffective in blocking myotonic discharges. Discharges promptly abated with 2% lidocaine injection. CONCLUSIONS Myotonia in this horse is associated with dystrophic changes similar to human myotonic dystrophy, though there are some pharmacological differences.
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Affiliation(s)
- P Montagna
- Institute of Clinical Neurology, University of Bologna Medical School, Via U. Foscolo 7, 40123, Bologna, Italy.
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Ricker K. The expanding clinical and genetic spectrum of the myotonic dystrophies. Acta Neurol Belg 2000; 100:151-5. [PMID: 11098287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Core features of the dominantly inherited myotonic dystrophies are myotonia, muscle weakness and cataract. Classic myotonic dystrophy (Steinert's disease) has been defined as a genetic entity by the underlying CTG repeat expansion on chromosome 19q13.3 (= DM1 locus). Later on, another disorder similar to but different from myotonic dystrophy was described as proximal myotonic myopathy (PROMM). The majority of PROMM families have been linked to a recently discovered locus on chromosome 3q21 (= DM2 locus).--This article analyses the clinical features of 70 patients from 14 German PROMM families linked to the 3q locus. In contrast to Steinert's disease, these patients did not reveal mental deficiency; no congenital type was found; weakness was mainly located in the proximal leg muscles; clinical myotonia was very mild and sometimes absent; episodes of pain occurred. In the majority of patients, the disorder seems to be more benign compared to Steinert's disease. However, life threatening cardiac involvement is possible; rarely, muscle weakness may progress until the patient is bedridden.--Some families with a PROMM-like phenotype do not link to the locus on 3q. The group of the myotonic dystrophies will get new members in the future.
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Affiliation(s)
- K Ricker
- Department of Neurology, University of Würzburg, Germany.
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Abstract
Channelopathy is a term used to describe clinical problems caused by disorders of membrane ion channels. Included in this disease category are certain types of periodic paralyses, ataxia, myotonia, migraine headache, epilepsy, nephrolithiasis, and long QT syndrome. This article briefly summarizes membrane ion channel structure and function and details several relatively common channelopathies. In hyperkalemic periodic paralysis, mutant skeletal muscle sodium channels fail to close completely after an action potential. This evokes two apparently opposite symptoms: myotonia (caused by a small depolarization and repetitive excitation) or paralysis (caused by larger depolarization and inexcitability). In hypokalemic periodic paralysis, mutation affects the closing of skeletal muscle calcium channels, causing transient paresis or paralysis. The task of the advanced practice nurse is to recognize these disorders, institute appropriate prophylactic measures and treatments, monitor symptom progression, and avoid complications. Understanding of channelopathies is advancing rapidly. On the horizon are therapies tailored to counter specific membrane ion channel defects.
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Affiliation(s)
- E F Bond
- Department of Biobehavioral Nursing and Health Systems, Box 357266, School of Nursing, University of Washington, Seattle, WA 98195, USA.
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44
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Arimura K, Higuchi I. [Recent topics. 1. Channel diseases and involuntary movements]. Nihon Naika Gakkai Zasshi 2000; 89:704-10. [PMID: 10876930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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Abstract
Several heritable forms of myotonia and periodic paralysis are caused by missense mutations in the voltage-gated sodium channel of skeletal muscle. Mutations produce gain-of-function defects, either disrupted inactivation or enhanced activation. Both defects result in too much inward Na current which may either initiate pathologic bursts of action potentials (myotonia) or cause flaccid paralysis by depolarizing fibers to a refractory inexcitable state. Myotonic stiffness and periodic paralysis occur as paroxysmal attacks often triggered by environmental factors such as serum K+, cold, or exercise. Many gaps remain in our understanding of the interactions between genetic predisposition and these environmental influences. Targeted gene manipulation in animals may provide the tools to fill in these gaps.
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Affiliation(s)
- S C Cannon
- Department of Neurobiology, Harvard Medical School, Massachusetts General Hospital, Boston, USA.
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46
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Duranti A, Franchini C, Lentini G, Loiodice F, Tortorella V, De Luca A, Pierno S, Conte Camerino D. Homologation of mexiletine alkyl chain and stereoselective blockade of skeletal muscle sodium channels. Eur J Med Chem 2000; 35:147-56. [PMID: 10733611 DOI: 10.1016/s0223-5234(00)00115-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The optical isomers (-)-(S)- and (+)-(R)-3-(2, 6-dimethylphenoxy)-2-methyl-1-propanamine (Me2), homologues of the antiarrhythmic and antimyotonic drug mexiletine (Mex), were synthesized and assayed as new potential antimyotonic agents. As observed with Mex, Me2 exhibits an enantioselective behaviour. Tests carried out on sodium currents of single muscle fibres of Rana esculenta demonstrated that (-)-(S)- and (+)-(R)-Me2 were less potent than Mex in producing tonic block, but showed a higher use-dependent block. (-)-(S)-Me2 and (-)-(R)-Mex were also used to study the excitability of muscle fibres of myotonic ADR mice, a phenotype of a recessive form of low G(Cl) myotonia. (-)-(S)-Me2 reduced spontaneous discharges and after discharges better than (-)-(R)-Mex in agreement with the use-dependent block of sodium currents.
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Affiliation(s)
- A Duranti
- Istituto di Chimica Farmaceutica e Tossicologica, Facoltà di Farmacia, Piazza del Rinascimento 6, Università degli Studi di Urbino, 61029, Urbino, Italy
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Desaphy JF, Camerino DC, Franchini C, Lentini G, Tortorella V, De Luca A. Increased hindrance on the chiral carbon atom of mexiletine enhances the block of rat skeletal muscle Na+ channels in a model of myotonia induced by ATX. Br J Pharmacol 1999; 128:1165-74. [PMID: 10578128 PMCID: PMC1571747 DOI: 10.1038/sj.bjp.0702901] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1 The antiarrhythmic drug mexiletine (Mex) is also used against myotonia. Searching for a more efficient drug, a new compound (Me5) was synthesized substituting the methyl group on the chiral carbon atom of Mex by an isopropyl group. Effects of Me5 on Na+ channels were compared to those of Mex in rat skeletal muscle fibres using the cell-attached patch clamp method. 2 Me5 (10 microM) reduced the maximal sodium current (INa) by 29.7+/-4.4 % (n=6) at a frequency of stimulation of 0.3 Hz and 65.7+/-4.4 % (n=6) at 1 Hz. At same concentration (10 microM), Mex was incapable of producing any effect (n=3). Me5 also shifted the steady-state inactivation curves by -7. 9+/-0.9 mV (n=6) at 0.3 Hz and -12.2+/-1.0 mV (n=6) at 1 Hz. 3 In the presence of sea anemone toxin II (ATX; 5 microM), INa decayed more slowly and no longer to zero, providing a model of sodium channel myotonia. The effects of Me5 on peak INa were similar whatever ATX was present or not. Interestingly, Me5 did not modify the INa decay time constant nor the steady-state INa to peak INa ratio. 4 Analysis of ATX-induced late Na+ channel activity shows that Me5 did not affect mean open times and single-channel conductance, thus excluding open channel block property. 5 These results indicate that increasing hindrance on the chiral atom of Mex increases drug potency on wild-type and ATX-induced noninactivating INa and that Me5 might improve the prophylaxis of myotonia.
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Affiliation(s)
- Jean-François Desaphy
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Diana Conte Camerino
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
- Author for correspondence:
| | - Carlo Franchini
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Giovanni Lentini
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Vincenzo Tortorella
- Department of Medicinal Chemistry, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacobiology, Unit of Pharmacology, Faculty of Pharmacy, University of Bari, I-70125 Bari, Italy
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Nagado T, Arimura K, Sonoda Y, Kurono A, Horikiri Y, Kameyama A, Kameyama M, Pongs O, Osame M. Potassium current suppression in patients with peripheral nerve hyperexcitability. Brain 1999; 122 ( Pt 11):2057-66. [PMID: 10545391 DOI: 10.1093/brain/122.11.2057] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Acquired neuromyotonia (Isaac's syndrome) is considered to be an autoimmune disease, and the pathomechanism of nerve hyperexcitability in this syndrome is correlated with anti-voltage-gated K(+) channel (VGKC) antibodies. The patch-clamp technique was used to investigate the effects of immunoglobulins from acquired neuromyotonia patients on VGKCs and voltage-gated Na(+) channels in a human neuroblastoma cell line (NB-1). K(+) currents were suppressed in cells that had been co-cultured with acquired neuromyotonia patients' immunoglobulin for 3 days but not for 1 day. The activation and inactivation kinetics of the outward K(+) currents were not altered by these immunoglobulins, nor did the immunoglobulins significantly affect the Na(+) currents. Myokymia or myokymic discharges, with peripheral nerve hyperexcitability, also occur in various neurological disorders such as Guillain-Barré syndrome and idiopathic generalized myokymia without pseudomyotonia. Immuno-globulins from patients with these diseases suppressed K(+) but not Na(+) currents. In addition, in hKv 1.1- and 1.6-transfected CHO (Chinese hamster ovary)-K1 cells, the expressed VGKCs were suppressed by sera from acquired neuromyotonia patients without a change in gating kinetics. Our findings indicate that nerve hyperexcitability is mainly associated with the suppression of voltage-gated K(+) currents with no change in gating kinetics, and that this suppression occurs not only in acquired neuromyotonia but also in Guillain-Barré syndrome and idiopathic generalized myokymia without pseudomyotonia.
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Affiliation(s)
- T Nagado
- Third Department of Internal Medicine, Kagoshima University School of Medicine, Kagoshima, Japan
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Abstract
The strength-duration time constant (SDTC) of a myelinated axon is a property of the nodal membrane and is sensitive to changes in membrane potential. Strength-duration time constants for motor axons and cutaneous afferents of the median nerve were measured in 9 patients with acquired neuromyotonia (NMT), a condition of peripheral nerve hyperexcitability, and 15 control patients. Mean motor axon time constants were significantly prolonged (344 +/- 100 micros) in patients compared to healthy controls (264 +/- 34 micros; P = 0.038), but sensory axon time constants were not significantly different. Motor axon time constants were longer than sensory axon time constants in 4 of the patients with neuromyotonia, suggesting that the nodal membrane was depolarized by an ectopic focus at the site of nerve stimulation at the wrist, ionic conductances were altered at the node, or that the size of the node was increased, possibly as a result of immune-mediated damage. The anti-voltage-gated potassium channel antibodies thought to generate peripheral nerve hyperexcitability in acquired neuromyotonia may be indirectly responsible for changes in motor axon nodal membrane properties.
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Affiliation(s)
- P Maddison
- University Department of Clinical Neurology, Radcliffe Infirmary, Oxford OX2 6HE, UK
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