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Tikhonova TB, Sharkov AA, Zhorov BS, Vassilevski AA. Diverse biophysical mechanisms in voltage-gated sodium channel Na v1.4 variants associated with myotonia. FASEB J 2024; 38:e23883. [PMID: 39150825 DOI: 10.1096/fj.202400867r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 07/14/2024] [Accepted: 07/31/2024] [Indexed: 08/18/2024]
Abstract
Mutations in SCN4A gene encoding Nav1.4 channel α-subunit, are known to cause neuromuscular disorders such as myotonia or paralysis. Here, we study the effect of two amino acid replacements, K1302Q and G1306E, in the DIII-IV loop of the channel, corresponding to mutations found in patients with myotonia. We combine clinical, electrophysiological, and molecular modeling data to provide a holistic picture of the molecular mechanisms operating in mutant channels and eventually leading to pathology. We analyze the existing clinical data for patients with the K1302Q substitution, which was reported for adults with or without myotonia phenotypes, and report two new unrelated patients with the G1306E substitution, who presented with severe neonatal episodic laryngospasm and childhood-onset myotonia. We provide a functional analysis of the mutant channels by expressing Nav1.4 α-subunit in Xenopus oocytes in combination with β1 subunit and recording sodium currents using two-electrode voltage clamp. The K1302Q variant exhibits abnormal voltage dependence of steady-state fast inactivation, being the likely cause of pathology. K1302Q does not lead to decelerated fast inactivation, unlike several other myotonic mutations such as G1306E. For both mutants, we observe increased window currents corresponding to a larger population of channels available for activation. To elaborate the structural rationale for our experimental data, we explore the contacts involving K/Q1302 and E1306 in the AlphaFold2 model of wild-type Nav1.4 and Monte Carlo-minimized models of mutant channels. Our data provide the missing evidence to support the classification of K1302Q variant as likely pathogenic and may be used by clinicians.
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Affiliation(s)
- Tatiana B Tikhonova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Artem A Sharkov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Veltischev Research and Clinical Institute for Pediatrics and Pediatric Surgery of the Pirogov Russian National Research Medical University, Moscow, Russia
- Genomed Ltd., Moscow, Russia
| | - Boris S Zhorov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
| | - Alexander A Vassilevski
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Moscow Institute of Physics and Technology, State University, Dolgoprudny, Russia
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2
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Zou X, Zhang Z, Lu H, Zhao W, Pan L, Chen Y. Functional effects of drugs and toxins interacting with Na V1.4. Front Pharmacol 2024; 15:1378315. [PMID: 38725668 PMCID: PMC11079311 DOI: 10.3389/fphar.2024.1378315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 04/08/2024] [Indexed: 05/12/2024] Open
Abstract
NaV1.4 is a voltage-gated sodium channel subtype that is predominantly expressed in skeletal muscle cells. It is essential for producing action potentials and stimulating muscle contraction, and mutations in NaV1.4 can cause various muscle disorders. The discovery of the cryo-EM structure of NaV1.4 in complex with β1 has opened new possibilities for designing drugs and toxins that target NaV1.4. In this review, we summarize the current understanding of channelopathies, the binding sites and functions of chemicals including medicine and toxins that interact with NaV1.4. These substances could be considered novel candidate compounds or tools to develop more potent and selective drugs targeting NaV1.4. Therefore, studying NaV1.4 pharmacology is both theoretically and practically meaningful.
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Affiliation(s)
- Xinyi Zou
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Zixuan Zhang
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Hui Lu
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Wei Zhao
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
| | - Lanying Pan
- Key Laboratory of Artificial Organs and Computational Medicine in Zhejiang Province, Shulan International Medical College, Zhejiang Shuren University, Hangzhou, China
| | - Yuan Chen
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou, China
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Mohammed SR, Gafoor S, Panday A. Acute myotonic reaction during succinylcholine anaesthesia. Pract Neurol 2023; 23:74-77. [PMID: 36192135 DOI: 10.1136/pn-2022-003352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2022] [Indexed: 02/02/2023]
Abstract
A 21-year-old woman developed an acute myotonic reaction while undergoing anaesthesia using succinylcholine. Examination later showed she had shoulder, neck and calf hypertrophy, bilateral symmetrical ptosis and eyelid, handgrip and percussion myotonia. Peripheral neurophysiology studies identified significant, continuous myotonic discharges in both upper and lower limbs. Genetic analysis identified a c.3917G>A (p.Gly1306Glu) mutation in the SCN4A gene, confirming a diagnosis of sodium channel myotonia. Succinylcholine and other depolarising agents can precipitate life-threatening acute myotonic reactions when given to patients with myotonia. Patients with neuromuscular disorders are at an increased risk of perioperative anaesthetic complications. We report a woman who developed an acute myotonic reaction whilst undergoing anaesthesia, in the context of an unrecognised myotonic disorder. We then discuss an approach to the diagnosis of myotonic disorders.
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Affiliation(s)
- Saeed Rashaad Mohammed
- Department of Clinical Medical Sciences, The University of the West Indies at St Augustine Faculty of Medical Sciences, St Augustine, Trinidad and Tobago
| | - Stefan Gafoor
- Department of Medicine, Eric Williams Medical Sciences Complex Compound, Champ Fleurs, Trinidad and Tobago
| | - Avidesh Panday
- Department of Clinical Medical Sciences, The University of the West Indies at St Augustine Faculty of Medical Sciences, St Augustine, Trinidad and Tobago
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Desaphy JF, Altamura C, Vicart S, Fontaine B. Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine. J Neuromuscul Dis 2021; 8:357-381. [PMID: 33325393 PMCID: PMC8203248 DOI: 10.3233/jnd-200582] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. OBJECTIVE This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. METHODS We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. RESULTS For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from CAI compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. CONCLUSIONS These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.
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Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Savine Vicart
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
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5
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Brooks EK, Schweitzer D, Robinson HL. A case of paramyotonia congenita in pregnancy. Obstet Med 2020; 13:192-194. [PMID: 33343696 PMCID: PMC7726174 DOI: 10.1177/1753495x18816171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 11/05/2018] [Indexed: 11/17/2022] Open
Abstract
Paramyotonia congenita is a rare autosomal dominant non-dystrophic myopathy caused by mutations in the SNC4A gene, which encodes for the voltage-gated sodium channel in skeletal muscle. Symptom onset is typically during early childhood and is characterised by myotonia followed by flaccid paralysis or weakness, usually exacerbated by repeated muscle contractions or cold temperatures. Pregnancy has been reported to increase symptoms of myotonia; however, there is limited information in the literature regarding the possible effects of paramyotonia congenita on pregnancy and labour. We present a successful case of a 20-year-old primigravida with confirmed paramyotonia congenita and review the literature regarding paramyotonia congenita during pregnancy.
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Affiliation(s)
- EK Brooks
- Department of Medicine, Ipswich Hospital, Ipswich, Queensland, Australia
| | - D Schweitzer
- Department of Neurology, Mater Hospital, Brisbane, Queensland, Australia
| | - HL Robinson
- Department of Medicine, Ipswich Hospital, Ipswich, Queensland, Australia
- Department of Obstetric Medicine, Royal Brisbane and Women’s Hospital, Brisbane, Queensland, Australia
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Stunnenberg BC, LoRusso S, Arnold WD, Barohn RJ, Cannon SC, Fontaine B, Griggs RC, Hanna MG, Matthews E, Meola G, Sansone VA, Trivedi JR, van Engelen BG, Vicart S, Statland JM. Guidelines on clinical presentation and management of nondystrophic myotonias. Muscle Nerve 2020; 62:430-444. [PMID: 32270509 PMCID: PMC8117169 DOI: 10.1002/mus.26887] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 04/01/2020] [Accepted: 04/04/2020] [Indexed: 12/26/2022]
Abstract
The nondystrophic myotonias are rare muscle hyperexcitability disorders caused by gain-of-function mutations in the SCN4A gene or loss-of-function mutations in the CLCN1 gene. Clinically, they are characterized by myotonia, defined as delayed muscle relaxation after voluntary contraction, which leads to symptoms of muscle stiffness, pain, fatigue, and weakness. Diagnosis is based on history and examination findings, the presence of electrical myotonia on electromyography, and genetic confirmation. In the absence of genetic confirmation, the diagnosis is supported by detailed electrophysiological testing, exclusion of other related disorders, and analysis of a variant of uncertain significance if present. Symptomatic treatment with a sodium channel blocker, such as mexiletine, is usually the first step in management, as well as educating patients about potential anesthetic complications.
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Affiliation(s)
- Bas C. Stunnenberg
- Department of Neurology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Samantha LoRusso
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - W. David Arnold
- Department of Neurology, Ohio State University Wexner Medical Center, Columbus, Ohio
| | - Richard J. Barohn
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Bertrand Fontaine
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Robert C. Griggs
- Department of Neurology, University of Rochester, Rochester, New York
| | - Michael G. Hanna
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Emma Matthews
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular diseases, UCL Queen Square Institute of Neurology, United Kingdom
| | - Giovanni Meola
- Department of Neurorehabilitation Sciences, Casa Cura Policlinico, Milan, Italy
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
| | - Valeria A. Sansone
- Department of Biomedical Sciences for Health, University of Milan, Milan, Italy
- Neurorehabilitation Unit, University of Milan, NEuroMuscular Omnicentre (NEMO), Fondazione Serena Onlus, Milan, Italy
| | - Jaya R. Trivedi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, Texas
| | | | - Savine Vicart
- Assistance Publique-Hôpitaix de Paris, Sorbonne Université, INSERM, Service of Neuro-Myology and UMR 974, Institute of Myology, University Hospital Pitié-Salpêtrière, Paris, France
| | - Jeffrey M. Statland
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas
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Maggi L, Brugnoni R, Canioni E, Tonin P, Saletti V, Sola P, Piccinelli SC, Colleoni L, Ferrigno P, Pini A, Masson R, Manganelli F, Lietti D, Vercelli L, Ricci G, Bruno C, Tasca G, Pizzuti A, Padovani A, Fusco C, Pegoraro E, Ruggiero L, Ravaglia S, Siciliano G, Morandi L, Dubbioso R, Mongini T, Filosto M, Tramacere I, Mantegazza R, Bernasconi P. Clinical and Molecular Spectrum of Myotonia and Periodic Paralyses Associated With Mutations in SCN4A in a Large Cohort of Italian Patients. Front Neurol 2020; 11:646. [PMID: 32849172 PMCID: PMC7403394 DOI: 10.3389/fneur.2020.00646] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 05/29/2020] [Indexed: 11/25/2022] Open
Abstract
Background: Four main clinical phenotypes have been traditionally described in patients mutated in SCN4A, including sodium-channel myotonia (SCM), paramyotonia congenita (PMC), Hypokaliemic type II (HypoPP2), and Hyperkaliemic/Normokaliemic periodic paralysis (HyperPP/NormoPP); in addition, rare phenotypes associated with mutations in SCN4A are congenital myasthenic syndrome and congenital myopathy. However, only scarce data have been reported in literature on large patient cohorts including phenotypes characterized by myotonia and episodes of paralysis. Methods: We retrospectively investigated clinical and molecular features of 80 patients fulfilling the following criteria: (1) clinical and neurophysiological diagnosis of myotonia, or clinical diagnosis of PP, and (2) presence of a pathogenic SCN4A gene variant. Patients presenting at birth with episodic laryngospasm or congenital myopathy-like phenotype with later onset of myotonia were considered as neonatal SCN4A. Results: PMC was observed in 36 (45%) patients, SCM in 30 (37.5%), Hyper/NormoPP in 7 (8.7%), HypoPP2 in 3 (3.7%), and neonatal SCN4A in 4 (5%). The median age at onset was significantly earlier in PMC than in SCM (p < 0.01) and in Hyper/NormoPP than in HypoPP2 (p = 0.02). Cold-induced myotonia was more frequently observed in PMC (n = 34) than in SCM (n = 23) (p = 0.04). No significant difference was found in age at onset of episodes of paralysis among PMC and PP or in frequency of permanent weakness between PP (n = 4), SCM (n = 5), and PMC (n = 10). PP was more frequently associated with mutations in the S4 region of the NaV1.4 channel protein compared to SCM and PMC (p < 0.01); mutations causing PMC were concentrated in the C-terminal region of the protein, while SCM-associated mutations were detected in all the protein domains. Conclusions: Our data suggest that skeletal muscle channelopathies associated with mutations in SCN4A represent a continuum in the clinical spectrum.
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Affiliation(s)
- Lorenzo Maggi
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Raffaella Brugnoni
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Eleonora Canioni
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Paola Tonin
- Section of Clinical Neurology, Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Veronica Saletti
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Patrizia Sola
- Clinica Neurologica, Azienda Ospedaliero Universitaria di Modena, Modena, Italy
| | - Stefano Cotti Piccinelli
- Unit of Neurology, Center for Neuromuscular Diseases, ASST Spedali Civili and University of Brescia, Brescia, Italy
| | - Lara Colleoni
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Paola Ferrigno
- SC Neurologia e Stroke Unit, Azienda Ospedaliera Brotzu, Cagliari, Italy
| | - Antonella Pini
- Child Neurology and Psychiatry Unit, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - Riccardo Masson
- Developmental Neurology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Fiore Manganelli
- Department of Neurosciences, Reproductive Sciences and Odontostomatology, University of Naples "Federico II", Naples, Italy
| | | | - Liliana Vercelli
- Department of Neurosciences Rita Levi Montalcini, University of Turin, Turin, Italy
| | - Giulia Ricci
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Claudio Bruno
- Center of Translational and Experimental Myology, Istituto Giannina Gaslini, Genova, Italy
| | - Giorgio Tasca
- Unità Operativa Complessa di Neurologia, Dipartimento di Scienze Dell'Invecchiamento, Neurologiche, Ortopediche e della Testa-Collo, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Antonio Pizzuti
- Fondazione IRCCS Casa Sollievo della Sofferenza, Laboratory of Medical Genetics, San Giovanni Rotondo, Italy.,Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Alessandro Padovani
- Unit of Neurology, Center for Neuromuscular Diseases, ASST Spedali Civili and University of Brescia, Brescia, Italy
| | - Carlo Fusco
- Dipartimento Materno-Infantile, S.C. Neuropsichiatria Infantile, Presidio Ospedaliero Provinciale Santa Maria Nuova, IRCCS di Reggio Emilia, Reggio Emilia, Italy
| | - Elena Pegoraro
- Department of Neurosciences, University of Padova, Padova, Italy
| | - Lucia Ruggiero
- Department of Neurosciences, Reproductive Sciences and Odontostomatology, University of Naples "Federico II", Naples, Italy
| | | | - Gabriele Siciliano
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Lucia Morandi
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Raffaele Dubbioso
- Department of Neurosciences, Reproductive Sciences and Odontostomatology, University of Naples "Federico II", Naples, Italy
| | - Tiziana Mongini
- Department of Neurosciences Rita Levi Montalcini, University of Turin, Turin, Italy
| | - Massimiliano Filosto
- Unit of Neurology, Center for Neuromuscular Diseases, ASST Spedali Civili and University of Brescia, Brescia, Italy
| | - Irene Tramacere
- Research and Clinical Development Department, Scientific Directorate, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Renato Mantegazza
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Pia Bernasconi
- Neuroimmunology and Neuromuscular Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
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Paroxysmal Laryngospasm: A Rare Condition That Respiratory Physicians Must Distinguish from Other Diseases with a Chief Complaint of Dyspnea. Can Respir J 2020; 2020:2451703. [PMID: 32695244 PMCID: PMC7361892 DOI: 10.1155/2020/2451703] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/19/2020] [Accepted: 06/10/2020] [Indexed: 12/21/2022] Open
Abstract
Background In recent years, we have observed respiratory difficulty manifested as paroxysmal laryngospasm in a few outpatients, most of whom were first encountered in a respiratory clinic. We therefore explored how to identify and address paroxysmal laryngospasm from the perspective of respiratory physicians. Methods The symptoms, characteristics, auxiliary examination results, treatment, and prognosis of 12 patients with paroxysmal laryngospasm treated in our hospital from June 2017 to October 2019 were analyzed. Results Five males (42%) and 7 females (58%) were among the 12 Han patients sampled. The average age of the patients was 49.25 ± 13.02 years. The disease course ranged from 14 days to 8 years and was characterized by sudden dyspnea, an inability to inhale and exhale, a sense of asphyxia, and voice loss during an attack. Eight patients with gastroesophageal reflux were cured after antacid treatment. One case of upper respiratory tract infection (URI) was completely relieved after symptomatic treatment. One patient with left vocal cord paralysis experienced complete relief after specialist treatment by an otorhinolaryngologist. Episodes in 1 patient were significantly reduced after lifestyle improvement. One patient experienced spontaneous relief after rejecting treatment. Conclusions Paroxysmal laryngospasm is a rare laryngeal disease that generally occurs secondary to gastroesophageal reflux disease (GERD), and antireflux therapy is frequently effective for its treatment. A respiratory physician should master and identify the symptoms and differentiate this condition from hysterical stridor, reflux-related laryngospasm, and asthma. Timely referral to otolaryngologists, gastroenterologists, and other specialists for standardized examination and regular treatment should be provided when necessary.
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Vivekanandam V, Männikkö R, Matthews E, Hanna MG. Improving genetic diagnostics of skeletal muscle channelopathies. Expert Rev Mol Diagn 2020; 20:725-736. [PMID: 32657178 DOI: 10.1080/14737159.2020.1782195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Skeletal muscle channelopathies are rare inherited conditions that cause significant morbidity and impact on quality of life. Some subsets have a mortality risk. Improved genetic methodology and understanding of phenotypes have improved diagnostic accuracy and yield. AREAS COVERED We discuss diagnostic advances since the advent of next-generation sequencing and the role of whole exome and genome sequencing. Advances in genotype-phenotype-functional correlations have improved understanding of inheritance and phenotypes. We outline new phenotypes, particularly in the pediatric setting and consider co-existing mutations that may act as genetic modifiers. We also discuss four newly identified genes associated with skeletal muscle channelopathies. EXPERT OPINION Next-generation sequencing using gene panels has improved diagnostic rates, identified new mutations, and discovered patients with co-existing pathogenic mutations ('double trouble'). This field has previously focussed on single genes, but we are now beginning to understand interactions between co-existing mutations, genetic modifiers, and their role in pathomechanisms. New genetic observations in pediatric presentations of channelopathies broadens our understanding of the conditions. Genetic and mechanistic advances have increased the potential to develop treatments.
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Affiliation(s)
- Vinojini Vivekanandam
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Roope Männikkö
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Emma Matthews
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
| | - Michael G Hanna
- Queen Square Centre for Neuromuscular Diseases and Department of Neuromuscular Diseases, Queen Square Institute of Neurology, UCL and National Hospital for Neurology and Neurosurgery , London, UK
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10
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Avila-Smirnow D, Vargas Leal CP, Beytía Reyes MDLA, Cortés Zepeda R, Escobar RG, Kleinsteuber Saa K, Lagos Lucero M, Avaria Benapres MDLA, Padilla Pérez O, Casar Leturia JC, Mellado Sagredo C, Sternberg D. Non-dystrophic myotonia Chilean cohort with predominance of the SCN4A Gly1306Glu variant. Neuromuscul Disord 2020; 30:554-561. [DOI: 10.1016/j.nmd.2020.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 04/03/2020] [Accepted: 04/23/2020] [Indexed: 01/31/2023]
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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] [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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Matthews E, Balestrini S, Sisodiya SM, Hanna MG. Muscle and brain sodium channelopathies: genetic causes, clinical phenotypes, and management approaches. THE LANCET CHILD & ADOLESCENT HEALTH 2020; 4:536-547. [PMID: 32142633 DOI: 10.1016/s2352-4642(19)30425-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/29/2019] [Accepted: 12/12/2019] [Indexed: 01/26/2023]
Abstract
Voltage-gated sodium channels are essential for excitability of skeletal muscle fibres and neurons. An increasing number of disabling or fatal paediatric neurological disorders linked to mutations of voltage-gated sodium channel genes are recognised. Muscle phenotypes include episodic paralysis, myotonia, neonatal hypotonia, respiratory compromise, laryngospasm or stridor, congenital myasthenia, and myopathy. Evidence suggests a possible link between sodium channel dysfunction and sudden infant death. Increasingly recognised phenotypes of brain sodium channelopathies include several epilepsy disorders and complex encephalopathies. Together, these early-onset muscle and brain phenotypes have a substantial morbidity and a considerable mortality. Important advances in understanding the pathophysiological mechanisms underlying these channelopathies have helped to identify effective targeted therapies. The availability of effective treatments underlines the importance of increasing clinical awareness and the need to achieve a precise genetic diagnosis. In this Review, we describe the expanded range of phenotypes of muscle and brain sodium channelopathies and the underlying knowledge regarding mechanisms of sodium channel dysfunction. We also outline a diagnostic approach and review the available treatment options.
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Affiliation(s)
- Emma Matthews
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK.
| | - Simona Balestrini
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Sanjay M Sisodiya
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London, UK; Chalfont Centre for Epilepsy, Buckinghamshire, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, Medical Research Council Centre for Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK; National Hospital for Neurology and Neurosurgery, University College London Hospitals National Health Service Foundation Trust, London, UK
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Elia N, Nault T, McMillan HJ, Graham GE, Huang L, Cannon SC. Myotonic Myopathy With Secondary Joint and Skeletal Anomalies From the c.2386C>G, p.L769V Mutation in SCN4A. Front Neurol 2020; 11:77. [PMID: 32117035 PMCID: PMC7031655 DOI: 10.3389/fneur.2020.00077] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 01/22/2020] [Indexed: 11/22/2022] Open
Abstract
The phenotypic spectrum associated with the skeletal muscle voltage-gated sodium channel gene (SCN4A) has expanded with advancements in genetic testing. Autosomal dominant SCN4A mutations were first linked to hyperkalemic periodic paralysis, then subsequently included paramyotonia congenita, several variants of myotonia, and finally hypokalemic periodic paralysis. Biallelic recessive mutations were later identified in myasthenic myopathy and in infants showing a severe congenital myopathy with hypotonia. We report a patient with a pathogenic de novo SCN4A variant, c.2386C>G p.L769V at a highly conserved leucine. The phenotype was manifest at birth with arthrogryposis multiplex congenita, severe episodes of bronchospasm that responded immediately to carbamazepine therapy, and electromyographic evidence of widespread myotonia. Another de novo case of p.L769V has been reported with hip dysplasia, scoliosis, myopathy, and later paramyotonia. Expression studies of L796V mutant channels showed predominantly gain-of-function changes, that included defects of slow inactivation. Computer simulations of muscle excitability reveal a strong predisposition to myotonia with exceptionally prolonged bursts of discharges, when the L796V defects are included. We propose L769V is a pathogenic variant, that along with other cases in the literature, defines a new dominant SCN4A disorder of myotonic myopathy with secondary congenital joint and skeletal involvement.
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Affiliation(s)
- Nathaniel Elia
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
- Molecular, Cellular, and Integrative Physiology Program, UCLA, Los Angeles, CA, United States
| | - Trystan Nault
- Division of Neurology, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Hugh J. McMillan
- Division of Neurology, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Gail E. Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Lijia Huang
- Department of Genetics, Children's Hospital of Eastern Ontario, University of Ottawa, Ottawa, ON, Canada
| | - Stephen C. Cannon
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
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Morales F, Pusch M. An Up-to-Date Overview of the Complexity of Genotype-Phenotype Relationships in Myotonic Channelopathies. Front Neurol 2020; 10:1404. [PMID: 32010054 PMCID: PMC6978732 DOI: 10.3389/fneur.2019.01404] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/23/2019] [Indexed: 12/11/2022] Open
Abstract
Myotonic disorders are inherited neuromuscular diseases divided into dystrophic myotonias and non-dystrophic myotonias (NDM). The latter is a group of dominant or recessive diseases caused by mutations in genes encoding ion channels that participate in the generation and control of the skeletal muscle action potential. Their altered function causes hyperexcitability of the muscle membrane, thereby triggering myotonia, the main sign in NDM. Mutations in the genes encoding voltage-gated Cl− and Na+ channels (respectively, CLCN1 and SCN4A) produce a wide spectrum of phenotypes, which differ in age of onset, affected muscles, severity of myotonia, degree of hypertrophy, and muscle weakness, disease progression, among others. More than 200 CLCN1 and 65 SCN4A mutations have been identified and described, but just about half of them have been functionally characterized, an approach that is likely extremely helpful to contribute to improving the so-far rather poor clinical correlations present in NDM. The observed poor correlations may be due to: (1) the wide spectrum of symptoms and overlapping phenotypes present in both groups (Cl− and Na+ myotonic channelopathies) and (2) both genes present high genotypic variability. On the one hand, several mutations cause a unique and reproducible phenotype in most patients. On the other hand, some mutations can have different inheritance pattern and clinical phenotypes in different families. Conversely, different mutations can be translated into very similar phenotypes. For these reasons, the genotype-phenotype relationships in myotonic channelopathies are considered complex. Although the molecular bases for the clinical variability present in myotonic channelopathies remain obscure, several hypotheses have been put forward to explain the variability, which include: (a) differential allelic expression; (b) trans-acting genetic modifiers; (c) epigenetic, hormonal, or environmental factors; and (d) dominance with low penetrance. Improvements in clinical tests, the recognition of the different phenotypes that result from particular mutations and the understanding of how a mutation affects the structure and function of the ion channel, together with genetic screening, is expected to improve clinical correlation in NDMs.
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Affiliation(s)
- Fernando Morales
- Instituto de Investigaciones en Salud, Universidad de Costa, San José, Costa Rica
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Cea G, Andreu D, Fletcher E, Ramdas S, Sud R, Hanna MG, Matthews E. Sodium channel myotonia may be associated with high-risk brief resolved unexplained events. Wellcome Open Res 2020; 5:57. [PMID: 32509969 PMCID: PMC7241273 DOI: 10.12688/wellcomeopenres.15798.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/23/2020] [Indexed: 11/20/2022] Open
Abstract
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management. A subset of infants with the neuromuscular disorder sodium channel myotonia, due to mutations in the SCN4A gene, experience apnoeic events due to laryngospasm (myotonia) of the upper airway muscles that may present as a BRUE. We sought to ascertain the frequency, severity and outcome of infants carrying the G1306E SCN4A mutation commonly associated with this presentation. We report 12 new cases of individuals with the G1306E mutation from three unrelated families and perform a literature review of all published cases. Infants with the G1306E mutation almost universally experience laryngospasm and apnoeic events. The severity varies significantly, spans both low and high-risk BRUE categories or can be more severe than criteria for a BRUE would allow. At least a third of cases require intensive care unit (ICU) care. Seizure disorder is a common erroneous diagnosis. Apnoeas are effectively reduced or abolished by appropriate treatment with anti-myotonic agents. Probands with the G1306E mutation who are family planning need to be counselled for the likelihood of post-natal complications. There is readily available and extremely effective treatment for the episodic laryngospasm and apnoea caused by this mutation. Proactively seeking clinical evidence of myotonia or muscle hypertrophy with consideration of CK and EMG in high risk BRUEs or more complex apnoeic events may reduce avoidable and prolonged ICU admissions, patient morbidity and potentially mortality.
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Affiliation(s)
- Gabriel Cea
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
- Servicio de Neurología, Hospital Salvador, Santiago, Chile
| | - Daniel Andreu
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
| | - Elaine Fletcher
- Department of Clinical Genetics, Centre for Genomic and Experimental Medicine, Western General Hospital, Edinburgh, EH5 2GL, UK
| | - Sithara Ramdas
- Department of Paediatric Neurology, John Radcliffe Hospital NHS Foundation Trust, Oxford, UK
| | - Richa Sud
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G. Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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Cea G, Andreu D, Fletcher E, Ramdas S, Sud R, Hanna MG, Matthews E. Sodium channel myotonia may be associated with high-risk brief resolved unexplained events. Wellcome Open Res 2020; 5:57. [PMID: 32509969 PMCID: PMC7241273 DOI: 10.12688/wellcomeopenres.15798.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2020] [Indexed: 12/02/2022] Open
Abstract
Brief resolved unexplained events (BRUEs) have numerous and varied causes posing a challenge to investigation and management. A subset of infants with the neuromuscular disorder sodium channel myotonia, due to mutations in the SCN4A gene, experience apnoeic events due to laryngospasm (myotonia) of the upper airway muscles that may present as a BRUE. We sought to ascertain the frequency, severity and outcome of infants carrying the G1306E SCN4A mutation commonly associated with this presentation. We report 14 new cases of individuals with the G1306E mutation from three unrelated families and perform a literature review of all published cases. Infants with the G1306E mutation almost universally experience laryngospasm and apnoeic events. The severity varies significantly, spans both low and high-risk BRUE categories or can be more severe than criteria for a BRUE would allow. At least a third of cases require intensive care unit (ICU) care. Seizure disorder is a common erroneous diagnosis. Apnoeas are effectively reduced or abolished by appropriate treatment with anti-myotonic agents. Probands with the G1306E mutation who are family planning need to be counselled for the likelihood of post-natal complications. There is readily available and extremely effective treatment for the episodic laryngospasm and apnoea caused by this mutation. Proactively seeking clinical evidence of myotonia or muscle hypertrophy with consideration of CK,EMG and genetic testing in high risk BRUEs or more complex apnoeic events may reduce avoidable and prolonged ICU admissions, patient morbidity and potentially mortality.
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Affiliation(s)
- Gabriel Cea
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
- Servicio de Neurología, Hospital Salvador, Santiago, Chile
| | - Daniel Andreu
- Departamento de Ciencias Neurológicas, Universidad de Chile, Santiago, Chile
| | - Elaine Fletcher
- Department of Clinical Genetics, Centre for Genomic and Experimental Medicine, Western General Hospital, Edinburgh, EH5 2GL, UK
| | - Sithara Ramdas
- Department of Paediatric Neurology, John Radcliffe Hospital NHS Foundation Trust, Oxford, UK
| | - Richa Sud
- Neurogenetics Unit, UCL Queen Square Institute of Neurology, London, UK
| | - Michael G. Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Emma Matthews
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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Pechmann A, Eckenweiler M, Schorling D, Stavropoulou D, Lochmüller H, Kirschner J. De novo variant in SCN4A causes neonatal sodium channel myotonia with general muscle stiffness and respiratory failure. Neuromuscul Disord 2019; 29:907-909. [PMID: 31732390 DOI: 10.1016/j.nmd.2019.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 06/16/2019] [Accepted: 09/02/2019] [Indexed: 11/24/2022]
Abstract
Variants of the skeletal muscle sodium channel gene SCN4A are associated with different neuromuscular disorders including sodium channel myotonia. Here, we report an infant with a de novo variant in SCN4A presenting with neonatal onset of severe muscle stiffness with involvement of facial and eyelid muscles, and life-threatening events with respiratory failure due to severe apnoea and thorax rigidity. The boy dramatically improved in both respiratory and motor function under carbamazepine therapy.
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Affiliation(s)
- Astrid Pechmann
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Matthias Eckenweiler
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - David Schorling
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Dimitra Stavropoulou
- Department of General Pediatrics, Divisions of Neonatology/Intensive Care Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Hanns Lochmüller
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; Children's Hospital of Eastern Ontario Research Institute; Division of Neurology, Department of Medicine, The Ottawa Hospital; and Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada
| | - Janbernd Kirschner
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; Department of Neuropediatrics, University Hospital Bonn, University of Bonn, Bonn, Germany.
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18
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Purkey MR, Valika T. A unique presentation and etiology of neonatal paradoxical vocal fold motion. Int J Pediatr Otorhinolaryngol 2019; 125:199-200. [PMID: 31382107 DOI: 10.1016/j.ijporl.2019.07.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 07/11/2019] [Accepted: 07/11/2019] [Indexed: 10/26/2022]
Abstract
We present a unique case of intermittent paradoxical vocal fold motion (PVFM) as the presenting symptom of a rare underlying neuromuscular disorder in a neonate. Paramyotonia congenita (PC) is an autosomal dominant condition that typically presents in infancy with myotonic episodes affecting the skeletal muscles. Our patient developed intermittent episodes of stridor quickly progressing to apnea shortly after birth that were marked by PVFM on laryngoscopy, ultimately leading to the diagnosis of a previously unrecognized mutation in SCN4A, the gene responsible for PC.
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Affiliation(s)
- Matthew R Purkey
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology - Head and Neck Surgery, 675 N St Clair Ct Suite 15-200, Chicago, IL, 60611, USA
| | - Taher Valika
- Northwestern University Feinberg School of Medicine, Department of Otolaryngology - Head and Neck Surgery, 675 N St Clair Ct Suite 15-200, Chicago, IL, 60611, USA; Ann & Robert H. Lurie Children's Hospital of Chicago, Division of Otolaryngology - Head and Neck Surgery, 225 E. Chicago Ave., Chicago, IL, 60611, USA.
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19
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Matthews E, Silwal A, Sud R, Hanna MG, Manzur AY, Muntoni F, Munot P. Skeletal Muscle Channelopathies: Rare Disorders with Common Pediatric Symptoms. J Pediatr 2017; 188:181-185.e6. [PMID: 28662944 DOI: 10.1016/j.jpeds.2017.05.081] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 03/31/2017] [Accepted: 05/31/2017] [Indexed: 10/19/2022]
Abstract
OBJECTIVE To ascertain the presenting symptoms of children with skeletal muscle channelopathies to promote early diagnosis and treatment. STUDY DESIGN Retrospective case review of 38 children with a skeletal muscle channelopathy attending the specialist pediatric neuromuscular service at Great Ormond Street Hospital over a 15-year period. RESULTS Gait disorder and leg cramps are a frequent presentation of myotonic disorders (19 of 29). Strabismus or extraocular myotonia (9 of 19) and respiratory and/or bulbar symptoms (11 of 19) are common among those with sodium channelopathy. Neonatal hypotonia was observed in periodic paralysis. Scoliosis and/or contractures were demonstrated in 6 of 38 children. School attendance or ability to engage fully in all activities was often limited (25 of 38). CONCLUSIONS Children with skeletal muscle channelopathies frequently display symptoms that are uncommon in adult disease. Any child presenting with abnormal gait, leg cramps, or strabismus, especially if intermittent, should prompt examination for myotonia. Those with sodium channel disease should be monitored for respiratory or bulbar complications. Neonatal hypotonia can herald periodic paralysis. Early diagnosis is essential for children to reach their full educational potential.
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Affiliation(s)
- Emma Matthews
- Medical Research Council Center for Neuromuscular Diseases, University College London and National Hospital for Neurology and Neurosurgery, London, UK.
| | - Arpana Silwal
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Richa Sud
- Neurogenetics Unit, Institute of Neurology, London, UK
| | - Michael G Hanna
- Medical Research Council Center for Neuromuscular Diseases, University College London and National Hospital for Neurology and Neurosurgery, London, UK
| | - Adnan Y Manzur
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Francesco Muntoni
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Pinki Munot
- Dubowitz Neuromuscular Center and MRC Center for Neuromuscular Diseases, UCL Great Ormond Street Institute of Child Health, London, UK
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Al-Ghamdi F, Darras BT, Ghosh PS. Spectrum of Nondystrophic Skeletal Muscle Channelopathies in Children. Pediatr Neurol 2017; 70:26-33. [PMID: 28325641 DOI: 10.1016/j.pediatrneurol.2017.02.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 02/10/2017] [Indexed: 01/21/2023]
Abstract
BACKGROUND The nondystrophic skeletal muscle channelopathies are a group of disorders caused by mutations of various voltage-gated ion channel genes, including nondystrophic myotonia and periodic paralysis. METHODS We identified patients with a diagnosis of muscle channelopathy from our neuromuscular database in a tertiary care pediatric center from 2005 to 2015. We then performed a retrospective review of their medical records for demographic characteristics, clinical features, investigations, treatment, and follow-up. RESULTS Thirty-three patients were identified. Seventeen had nondystrophic myotonia. Seven of them had chloride channelopathy (four Becker disease and three Thomsen disease). Warm-up phenomenon and muscle hypertrophy were common clinical manifestations in this subgroup. Ten patients had sodium channelopathy (four paramyotonia congenita and six other sodium channel myotonia). Stiffness of the facial muscles was an important presenting symptom, and eyelid myotonia was a common clinical finding in this subgroup. The majority of these patients had electrical myotonia. Mexiletine was effective in controlling the symptoms in patients who had received treatment. Sixteen children had periodic paralysis (four hyperkalemic periodic paralysis, eight hypokalemic periodic paralysis, and four Andersen-Tawil syndrome). Acetazolamide was commonly used to prevent paralytic attacks and was found to be effective. CONCLUSIONS Nondystrophic muscle channelopathies present with diverse clinical manifestations (myotonia, muscle hypertrophy, proximal weakness, swallowing difficulties, and periodic paralysis). Cardiac arrhythmias are potentially life threatening in Andersen-Tawil syndrome. Timely identification of these disorders is helpful for effective symptomatic management and genetic counseling.
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Affiliation(s)
- Fouad Al-Ghamdi
- Department of Neurology, Boston Children's Hospital, Boston, MA
| | - Basil T Darras
- Department of Neurology, Boston Children's Hospital, Boston, MA
| | - Partha S Ghosh
- Department of Neurology, Boston Children's Hospital, Boston, MA.
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Abstract
PURPOSE OF REVIEW This is an update on skeletal muscle sodium channelopathies since knowledge in the field have dramatically increased in the past years. RECENT FINDING The relationship between two phenotypes and SCN4A has been confirmed with additional cases that remain extremely rare: severe neonatal episodic laryngospasm mimicking encephalopathy, which should be actively searched for since patients respond well to sodium channel blockers; congenital myasthenic syndromes, which have the particularity to be the first recessive Nav1.4 channelopathy. Deep DNA sequencing suggests the contribution of other ion channels in the clinical expressivity of sodium channelopathies, which may be one of the factors modulating the latter. The increased knowledge of channel molecular structure, the quantity of sodium channel blockers, and the availability of preclinical models would permit a most personalized choice of medication for patients suffering from these debilitating neuromuscular diseases. SUMMARY Advances in the understanding of the molecular structure of voltage-gated sodium channels, as well as availability of preclinical models, would lead to improved medical care of patients suffering from skeletal muscle, as well as other sodium channelopathies.
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Desaphy JF, Carbonara R, D'Amico A, Modoni A, Roussel J, Imbrici P, Pagliarani S, Lucchiari S, Lo Monaco M, Conte Camerino D. Translational approach to address therapy in myotonia permanens due to a new SCN4A mutation. Neurology 2016; 86:2100-8. [PMID: 27164696 PMCID: PMC4891212 DOI: 10.1212/wnl.0000000000002721] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 02/19/2016] [Indexed: 01/26/2023] Open
Abstract
Objective: We performed a clinical, functional, and pharmacologic characterization of the novel p.P1158L Nav1.4 mutation identified in a young girl presenting a severe myotonic phenotype. Methods: Wild-type hNav1.4 channel and P1158L mutant were expressed in tsA201 cells for functional and pharmacologic studies using patch-clamp. Results: The patient shows pronounced myotonia, slowness of movements, and generalized muscle hypertrophy. Because of general discomfort with mexiletine, she was given flecainide with satisfactory response. In vitro, mutant channels show a slower current decay and a rightward shift of the voltage dependence of fast inactivation. The voltage dependence of activation and slow inactivation were not altered. Mutant channels were less sensitive to mexiletine, whereas sensitivity to flecainide was not altered. The reduced inhibition of mutant channels by mexiletine was also observed using clinically relevant drug concentrations in a myotonic-like condition. Conclusions: Clinical phenotype and functional alterations of P1158L support the diagnosis of myotonia permanens. Impairment of fast inactivation is consistent with the possible role of the channel domain III S4-S5 loop in the inactivation gate docking site. The reduced sensitivity of P1158L to mexiletine may have contributed to the unsatisfactory response of the patient. The success of flecainide therapy underscores the usefulness of in vitro functional studies to help in the choice of the best drug for each individual.
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Affiliation(s)
- Jean-François Desaphy
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy.
| | - Roberta Carbonara
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Adele D'Amico
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Anna Modoni
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Julien Roussel
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Paola Imbrici
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Serena Pagliarani
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Sabrina Lucchiari
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Mauro Lo Monaco
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
| | - Diana Conte Camerino
- From the Departments of Biomedical Sciences and Human Oncology (J.-F.D.) and Pharmacy & Drug Sciences (R.C., J.R., P.I., D.C.C.), University of Bari Aldo Moro, Bari; Unit of Neuromuscular and Neurodegenerative Disorders (A.D.), Bambino Gesù Children's Hospital, Rome; Departments of Geriatrics, Neurosciences, and Orthopedics (A.M., M.L.M.), Institute of Neurology, Catholic University of the Sacred Heart, Rome; Dino Ferrari Centre (S.P., S.L.), Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan; and Neurology Unit (S.P., S.L.), IRCCS Foundation Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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Portaro S, Rodolico C, Sinicropi S, Musumeci O, Valenzise M, Toscano A. Flecainide-Responsive Myotonia Permanens With SNEL Onset: A New Case and Literature Review. Pediatrics 2016; 137:peds.2015-3289. [PMID: 26944947 DOI: 10.1542/peds.2015-3289] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/18/2015] [Indexed: 11/24/2022] Open
Abstract
Sodium channel myotonias are inherited muscle diseases linked to mutations in the voltage-gated sodium channel. These diseases may also affect newborns with variable symptoms. More recently, severe neonatal episodic laryngospasm (SNEL) has been described in a small number of patients. A timely diagnosis of SNEL is crucial because a specific treatment is now available that will likely reduced laryngospasm and improve vital and cerebral outcomes. We report here on an 8-year-old girl who had presented, at birth, with SNEL who subsequently developed myotonia permanens starting at age 3 years. Results of molecular analysis revealed a de novo SCN4A G1306E mutation. The girl was treated with carbamazepine, acetazolamide, and mexiletine, with little improvement; after switching her treatment to flecainide, she experienced a dramatic reduction in muscle stiffness and myotonic symptoms as well as an improvement in behavior.
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Affiliation(s)
- Simona Portaro
- IRCCS Centro Neurolesi "Bonino Pulejo", SS113, via Palermo, c.da Casazza, Messina, Italy;
| | - Carmelo Rodolico
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stefano Sinicropi
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Olimpia Musumeci
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Mariella Valenzise
- Pediatric, Gynecological, Microbiological and Biomedical Sciences, University of Messina, Messina, Italy
| | - Antonio Toscano
- IRCCS Centro Neurolesi "Bonino Pulejo", SS113, via Palermo, c.da Casazza, Messina, Italy; Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
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Torbergsen T, Jurkat-Rott K, Stålberg EV, Løseth S, Hødneø A, Lehmann-Horn F. Painful cramps and giant myotonic discharges in a family with the Nav1.4-G1306A mutation. Muscle Nerve 2015; 52:680-3. [PMID: 26080010 DOI: 10.1002/mus.24672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2015] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Two previously reported Norwegian patients with painful muscle cramps and giant myotonic discharges were genotyped and compared with those of members of 21 families harboring the same mutation. METHODS Using primers specific for SCN4A and CLCN1, the DNA of the Norwegian family members was amplified and bidirectionally sequenced. Clinical and neurophysiological features of other families harboring the same mutation were studied. RESULTS A G1306A mutation in the Nav1.4 voltage-gated sodium channel of skeletal muscle was identified. This mutation is known to cause myotonia fluctuans. No giant myotonic discharges or painful muscle cramps were found in the other G1306A families. CONCLUSIONS Ephaptic transmission between neighboring muscle fibers may not only cause the unusual size of the myotonic discharges in this family, but also a more severe type of potassium-aggravated myotonia than myotonia fluctuans.
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Affiliation(s)
- Torberg Torbergsen
- Department of Clinical Neurophysiology, University Hospital of North Norway, Tromsö, Norway
| | - Karin Jurkat-Rott
- Division of Neurophysiology and Neuromuscular Center, University of Ulm, Ulm, Germany
| | - Erik V Stålberg
- Department of Clinical Neurophysiology, Institute of Neurosciences, Uppsala University, Uppsala, Sweden
| | - Sissel Løseth
- Department of Clinical Neurophysiology, University Hospital of North Norway, Tromsö, Norway
| | - Anne Hødneø
- Department of Neurology, Vestfold County Hospital, Tønsberg, Norway
| | - Frank Lehmann-Horn
- Division of Neurophysiology and Neuromuscular Center, University of Ulm, Ulm, Germany
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25
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Snyder Y, Donlin-Smith C, Snyder E, Pressman E, Ciafaloni E. The course and outcome of pregnancy in women with nondystrophic myotonias. Muscle Nerve 2015; 52:1013-5. [DOI: 10.1002/mus.24684] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Yuliya Snyder
- Department of Neurology, University of Rochester Medical Center; 607 Elmwood Avenue, Rochester, P.O. Box 673 Rochester New York 14642 USA
| | - Colleen Donlin-Smith
- Department of Neurology, University of Rochester Medical Center; 607 Elmwood Avenue, Rochester, P.O. Box 673 Rochester New York 14642 USA
| | - Eric Snyder
- Department of Neurology, University of Rochester Medical Center; 607 Elmwood Avenue, Rochester, P.O. Box 673 Rochester New York 14642 USA
| | - Eva Pressman
- Department of Obstetrics and Gynecology, University of Rochester Medical Center; 607 Elmwood Avenue, Rochester, P.O. Box 673 Rochester New York 14642 USA
| | - Emma Ciafaloni
- Department of Neurology, University of Rochester Medical Center; 607 Elmwood Avenue, Rochester, P.O. Box 673 Rochester New York 14642 USA
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26
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Singh RR, Tan SV, Hanna MG, Robb SA, Clarke A, Jungbluth H. Mutations in SCN4A: a rare but treatable cause of recurrent life-threatening laryngospasm. Pediatrics 2014; 134:e1447-50. [PMID: 25311598 DOI: 10.1542/peds.2013-3727] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Laryngospasm is a rare but potentially life-threatening occurrence in infants and usually has infective, allergic, metabolic, or anatomic causes. Underlying genetic conditions are rarely considered. Mutations in SCN4A encoding the voltage-gated sodium channel NaV1.4 have been implicated in a wide spectrum of neuromuscular disorders with variable onset, ranging from a rare form of congenital myasthenic syndrome to both hypokalemic and hyperkalemic forms of periodic paralysis and paramyotonia congenita. Here we report on 3 unrelated patients without family history presenting with recurrent, life-threatening episodes of laryngospasm from the first months of life. Clinical features more typically associated with SCN4A-related disorders such as generalized muscle hypertrophy with clinical or electrical myotonia evolved later in life. All patients were found to be heterozygous for the same SCN4A mutation, c.3917G>A; p.Gly1306Glu. Treatment with carbamazepine resulted in complete abolition of recurrent laryngospasm and alleviated symptoms associated with myotonia and muscle stiffness. We conclude that SCN4A mutations ought to be considered in the differential diagnosis of recurrent infantile laryngospasm because timely institution of treatment can be life-saving.
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Affiliation(s)
- Rahul R Singh
- Departments of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, and
| | - S Veronica Tan
- Neurology & Neurophysiology, Guy's & St Thomas' Hospital NHS Foundation Trust, London, United Kingdom
| | - Michael G Hanna
- MRC Centre for Neuromuscular Disease and National Hospital for Neurology and Neurosurgery, Queen's Square, London, United Kingdom
| | - Stephanie A Robb
- Dubowitz Neuromuscular Centre, Institute of Child Health and Great Ormond Street Hospital for Children, London, United Kingdom
| | - Antonia Clarke
- Department of Paediatric Neurology, St George's Hospital, London, United Kingdom; and
| | - Heinz Jungbluth
- Departments of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, and Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, and Clinical Neuroscience Division, IOP, King's College, London, United Kingdom
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27
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28
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Matthews E, Hanna MG. Repurposing of sodium channel antagonists as potential new anti-myotonic drugs. Exp Neurol 2014; 261:812-5. [PMID: 25218042 DOI: 10.1016/j.expneurol.2014.09.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 08/22/2014] [Accepted: 09/02/2014] [Indexed: 01/08/2023]
Abstract
Myotonia is often a painful and disabling symptom which can interfere with daily motor function resulting in significant morbidity. Since myotonic disorders are rare it has generally proved difficult to obtain class I level evidence for anti-myotonic drug efficacy by performing randomized placebo controlled trials. Current treatment guidance is therefore largely based on anecdotal reports and physician experience. Despite the genetic channel heterogeneity of the myotonic disorders the sodium channel antagonists have become the main focus of pharmacological interest. Mexiletine is currently regarded as the first choice sodium channel blocker based on a recent placebo controlled randomized trial. However, some patients do not respond to mexiletine or have significant side effects limiting its use. There is a clinical need to develop additional antimyotonic agents. The study of Desaphy et al. is therefore important and provides in vitro evidence that a number of existing drugs with sodium channel blocking capability could potentially be repurposed as anti-myotonic drugs. Translation of these potentially important in vitro findings into clinical practice requires carefully designed randomized controlled trials. Here we discuss Desaphy's findings in the wider context of attempts to develop additional therapies for patients with clinically significant myotonia.
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Affiliation(s)
- E Matthews
- MRC Centre for Neuromuscular Diseases, Department of Molecular Neuroscience, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
| | - M G Hanna
- MRC Centre for Neuromuscular Diseases, Department of Molecular Neuroscience, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
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Desaphy JF, Carbonara R, Costanza T, Conte Camerino D. Preclinical evaluation of marketed sodium channel blockers in a rat model of myotonia discloses promising antimyotonic drugs. Exp Neurol 2014; 255:96-102. [PMID: 24613829 PMCID: PMC4004800 DOI: 10.1016/j.expneurol.2014.02.023] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Revised: 02/17/2014] [Accepted: 02/26/2014] [Indexed: 12/25/2022]
Abstract
Although the sodium channel blocker mexiletine is considered the first-line drug in myotonia, some patients experiment adverse effects, while others do not gain any benefit. Other antimyotonic drugs are thus needed to offer mexiletine alternatives. In the present study, we used a previously-validated rat model of myotonia congenita to compare six marketed sodium channel blockers to mexiletine. Myotonia was induced in the rat by injection of anthracen-9-carboxylic acid, a muscle chloride channel blocker. The drugs were given orally and myotonia was evaluated by measuring the time of righting reflex. The drugs were also tested on sodium currents recorded in a cell line transfected with the human skeletal muscle sodium channel hNav1.4 using patch-clamp technique. In vivo, carbamazepine and propafenone showed antimyotonic activity at doses similar to mexiletine (ED50 close to 5mg/kg); flecainide and orphenadrine showed greater potency (ED50 near 1mg/kg); lubeluzole and riluzole were the more potent (ED50 near 0.1mg/kg). The antimyotonic activity of drugs in vivo was linearly correlated with their potency in blocking hNav1.4 channels in vitro. Deviation was observed for propafenone and carbamazepine, likely due to pharmacokinetics and multiple targets. The comparison of the antimyotonic dose calculated in rats with the current clinical dose in humans strongly suggests that all the tested drugs may be used safely for the treatment of human myotonia. Considering the limits of mexiletine tolerability and the occurrence of non-responders, this study proposes an arsenal of alternative drugs, which may prove useful to increase the quality of life of individuals suffering from non-dystrophic myotonia. Further clinical trials are warranted to confirm these results.
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Affiliation(s)
- Jean-François Desaphy
- Section of Pharmacology, Department of Pharmacy & Drug Sciences, University of Bari-Aldo Moro, Bari I-70125, Italy.
| | - Roberta Carbonara
- Section of Pharmacology, Department of Pharmacy & Drug Sciences, University of Bari-Aldo Moro, Bari I-70125, Italy
| | - Teresa Costanza
- Section of Pharmacology, Department of Pharmacy & Drug Sciences, University of Bari-Aldo Moro, Bari I-70125, Italy
| | - Diana Conte Camerino
- Section of Pharmacology, Department of Pharmacy & Drug Sciences, University of Bari-Aldo Moro, Bari I-70125, Italy
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