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Ricciardi R, Latini E, Guida M, Koneczny I, Lucchi M, Maestri M, De Rosa A, Vincent A. Acetylcholinesterase inhibitors are ineffective in MuSK-antibody positive myasthenia gravis: Results of a study on 202 patients. J Neurol Sci 2024; 461:123047. [PMID: 38759248 DOI: 10.1016/j.jns.2024.123047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 05/04/2024] [Accepted: 05/10/2024] [Indexed: 05/19/2024]
Abstract
BACKGROUND Myasthenia gravis (MG) with MuSK antibodies (MuSK-MG) represents a distinct subtype with different responses to treatments compared to patients with AChR antibodies, especially in terms of tolerance to acetylcholinesterase inhibitors (AChEI). However, AChEI are often used as first line symptomatic treatment in MuSK-MG, despite reports that they are poorly tolerated, seldom effective or even deleterious. METHODS We analyzed demographic, clinical and therapeutic responses and side-effects in the large cohort of 202 MuSK-MG patients cared for at the MG Clinic of Azienda Ospedaliero-Universitaria Pisana. RESULTS 165 patients had received AChEI at first evaluation. Only 7/165 patients (4.2%) reported an initial clinical benefit. Conversely, 76.9% of patients reported at least one side effect, most commonly neuromuscular hyperexcitability (68.4%), gastrointestinal (53.9%) and neurovegetative (35.8%) disturbances. 56 (33.9%) patients reported a concomitant worsening of muscle weakness and twelve patients (7.3%) suffered a cholinergic crisis. According to these patients, the severity of cholinergic side effects was greater at higher doses of AChEI, but side effects occurred regardless of the dose administered and ceased once the drug was discontinued. CONCLUSIONS This is the largest population of MuSK-MG patients reported for perceived responsiveness and tolerance to AChEI treatment. Our obervations strongly suggest avoiding this treatment in MuSK-MG.
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Affiliation(s)
- R Ricciardi
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Italy; CardioThoracic and Vascular Surgery Department, University of Pisa, Italy
| | - E Latini
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Italy.
| | - M Guida
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Italy
| | - I Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, 1090 Vienna, Austria
| | - M Lucchi
- CardioThoracic and Vascular Surgery Department, University of Pisa, Italy
| | - M Maestri
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Italy
| | - A De Rosa
- Department of Clinical and Experimental Medicine, Neurology Unit, University of Pisa, Italy
| | - A Vincent
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
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Vakrakou AG, Karachaliou E, Chroni E, Zouvelou V, Tzanetakos D, Salakou S, Papadopoulou M, Tzartos S, Voumvourakis K, Kilidireas C, Giannopoulos S, Tsivgoulis G, Tzartos J. Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease. Front Immunol 2023; 14:1212757. [PMID: 37564637 PMCID: PMC10410455 DOI: 10.3389/fimmu.2023.1212757] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 07/05/2023] [Indexed: 08/12/2023] Open
Abstract
Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.
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Affiliation(s)
- Aigli G. Vakrakou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Eleni Karachaliou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Elisabeth Chroni
- Department of Neurology, School of Medicine, University of Patras, Patras, Greece
| | - Vasiliki Zouvelou
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Dimitrios Tzanetakos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Stavroula Salakou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Marianna Papadopoulou
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Physiotherapy, University of West Attica, Athens, Greece
| | - Socrates Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
- Department of Pharmacy, University of Patras, Patras, Greece
| | - Konstantinos Voumvourakis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Constantinos Kilidireas
- First Department of Neurology, Medical School, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, Henry Dunant Hospital Center, Athens, Greece
| | - Sotirios Giannopoulos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Georgios Tsivgoulis
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
- Department of Neurology, The University of Tennessee Health Science Center, Memphis, TN, United States
| | - John Tzartos
- Second Department of Neurology, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece
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Waheed W, Newman E, Aboukhatwa M, Moin M, Tandan R. Practical Management for Use of Eculizumab in the Treatment of Severe, Refractory, Non-Thymomatous, AChR + Generalized Myasthenia Gravis: A Systematic Review. Ther Clin Risk Manag 2022; 18:699-719. [PMID: 35855752 PMCID: PMC9288180 DOI: 10.2147/tcrm.s266031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 07/04/2022] [Indexed: 11/28/2022] Open
Abstract
Myasthenia gravis (MG) is a rare autoimmune disorder caused by specific autoantibodies at the neuromuscular junction. MG is classified by the antigen specificity of these antibodies. Acetylcholine receptor (AChR) antibodies are the most common type (74–88%), followed by anti-muscle specific kinase (MuSK) and other antibodies. While all these antibodies lead to neuromuscular transmission failure, the immuno-pathogenic mechanisms are distinct. Complement activation is a primary driver of AChR antibody-positive MG (AChR+ MG) pathogenesis. This leads to the formation of the membrane attack complex and destruction of AChR receptors and the postsynaptic membrane resulting in impaired neurotransmission and muscle weakness characteristic of MG. Broad-based immune-suppressants like corticosteroids are effective in controlling MG; however, their long-term use can be associated with significant adverse effects. Advances in translational research have led to the development of more directed therapeutic agents that are likely to alter the future of MG treatment. Eculizumab is a humanized monoclonal antibody that inhibits the cleavage of complement protein C5 and is approved for use in generalized MG. In this review, we discuss the pathophysiology of MG; the therapeutic efficacy and tolerability of eculizumab, as well as the practical guidelines for its use in MG; future studies exploring the role of eculizumab in different stages and subtypes of MG subtypes; the optimal duration of therapy and its discontinuation; the characterization of non-responder patients; and the use of biomarkers for monitoring therapy are highlighted. Based on the pathophysiologic mechanisms, emerging therapies and new therapeutic targets are also reviewed.
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Affiliation(s)
- Waqar Waheed
- Department of Neurological Sciences, The University of Vermont and the University of Vermont Medical Center, Burlington, VT, USA
| | - Eric Newman
- Department of Neurological Sciences, The University of Vermont and the University of Vermont Medical Center, Burlington, VT, USA
| | - Marwa Aboukhatwa
- Pharmacotherapy Department, University of Vermont Medical Center, Burlington, VT, USA
| | - Maryam Moin
- Department of Neurology, University of Illinois College of Medicine, Peoria, IL, USA
| | - Rup Tandan
- Department of Neurological Sciences, The University of Vermont and the University of Vermont Medical Center, Burlington, VT, USA
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Modoni A, Mastrorosa A, Spagni G, Evoli A. Cholinergic hyperactivity in patients with myasthenia gravis with MuSK antibodies: A neurophysiological study. Clin Neurophysiol 2021; 132:1845-1849. [PMID: 34147009 DOI: 10.1016/j.clinph.2021.04.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/18/2021] [Accepted: 04/21/2021] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Patients with myasthenia gravis associated with muscle-specific tyrosine kinase antibodies (MuSK-MG) often manifest signs of cholinergic hyperactivity with standard doses of acetylcholinesterase inhibitors (AChE-Is). Aim of the study was to investigate whether repetitive compound muscle action potential (R-CMAP), the neurophysiological correlate of cholinergic hyperactivity, was present in MuSK-MG irrespective of AChE-I treatment. METHODS Patients with confirmed diagnosis of MuSK-MG were consecutively enrolled during follow-up visits, from January 2019 to April 2020. All these subjects underwent the same neurophysiological protocol, including motor nerve conduction studies and repetitive nerve stimulation. In patients taking pyridostigmine, neurophysiological testing was performed at least 12 hours after the last dose. For comparison, the presence of R-CMAP was investigated in 20 consecutive acetylcholine receptor antibody positive myasthenia gravis (AChR-MG) patients. RESULTS We enrolled 25 MuSK-MG patients (20 females), aged 16-79 years at the study time, with disease duration ranging 0.6-48.8 years (median: 17.7 years). R-CMAP was detected in 12/25 (48%) MuSK-MG cases and in none of the AChR-MG controls (p = 0.0003). In the MuSK-MG population, a history of muscle cramps and fasciculations, during low-dose pyridostigmine therapy, was significantly more frequent in R-CMAP positive than in R-CMAP negative patients (100% vs 31%, p = 0.001). At the time of the study, the proportion of patients still symptomatic for MG was higher among R-CMAP positive cases (92% vs 23%, p = 0.0005). CONCLUSIONS Cholinergic hyperactivity is a relatively common finding in MuSK-MG patients, independent of AChE-I treatment, and may constitute an intrinsic feature of the disease. SIGNIFICANCE R-CMAP detection can represent a useful diagnostic clue for MuSK-MG and predicts poor tolerance to AChE-Is.
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Affiliation(s)
- Anna Modoni
- Unità Operativa Complessa di Neurologia, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli, 8 - 00168 Rome, Italy
| | - Alessia Mastrorosa
- IRCCS Fondazione Don Gnocchi ONLUS, via di Scandicci 269, 50143, Florence, Italy
| | - Gregorio Spagni
- Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Largo F. Vito, 1 - 00168 Rome, Italy.
| | - Amelia Evoli
- Unità Operativa Complessa di Neurologia, Fondazione Policlinico Universitario "A. Gemelli" IRCCS, Largo A. Gemelli, 8 - 00168 Rome, Italy; Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Largo F. Vito, 1 - 00168 Rome, Italy
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Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
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6
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Okhovat AA, Fatehi F. Cholinergic neuromuscular hyperactivity in a patient with anti-muscle-specific tyrosine kinase myasthenia gravis. CURRENT JOURNAL OF NEUROLOGY 2020; 19:85-86. [PMID: 38011418 PMCID: PMC7874893 DOI: 10.18502/cjn.v19i2.4945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 02/01/2020] [Indexed: 11/24/2022]
Abstract
The article's abstract is not available.
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Affiliation(s)
- Ali Asghar Okhovat
- Department of Neurology, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Farzad Fatehi
- Department of Neurology, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran
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7
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Rivner MH, Pasnoor M, Dimachkie MM, Barohn RJ, Mei L. Muscle-Specific Tyrosine Kinase and Myasthenia Gravis Owing to Other Antibodies. Neurol Clin 2019; 36:293-310. [PMID: 29655451 DOI: 10.1016/j.ncl.2018.01.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Around 20% of patients with myasthenia gravis are acetylcholine receptor antibody negative; muscle-specific tyrosine kinase antibodies (MuSK) were identified as the cause of myasthenia gravis in 30% to 40% of these cases. Anti MuSK myasthenia gravis is associated with specific clinical phenotypes. One is a bulbar form with fewer ocular symptoms. Others show an isolated head drop or symptoms indistinguishable from acetylcholine receptor-positive myasthenia gravis. These patients usually respond well to immunosuppressive therapy, but not as well to cholinesterase inhibitors. Other antibodies associated with myasthenia gravis, including low-density lipoprotein receptor-related protein 4, are discussed.
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Affiliation(s)
- Michael H Rivner
- EMG Lab, Augusta University, 1120 15th Street, BP-4390, Augusta, GA 30912, USA.
| | - Mamatha Pasnoor
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Mazen M Dimachkie
- Department of Neurology, University of Kansas Medical Center, 3599 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66103, USA
| | - Richard J Barohn
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 4017, Kansas City, KS 66160, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Augusta University, 1120 15th Street, CA-2014, Augusta, GA 30912, USA
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Abstract
This article discusses antibodies associated with immune-mediated myasthenia gravis and the pathologic action of these antibodies at the neuromuscular junctions of skeletal muscle. To explain how these antibodies act, we consider the physiology of neuromuscular transmission with emphasis on 4 features: the structure of the neuromuscular junction; the roles of postsynaptic acetylcholine receptors and voltage-gated Na+ channels and in converting the chemical signal from the nerve terminal into a propagated action potential on the muscle fiber that triggers muscle contraction; the safety factor for neuromuscular transmission; and how the safety factor is reduced in different forms of autoimmune myasthenia gravis.
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Affiliation(s)
- Robert L Ruff
- Department of Neurology, Case Western University School of Medicine, The Metro Health System, 2500 Metro Health Drive, Cleveland, OH 44109, USA; Department of Neurosciences, Case Western Reserve University, Cleveland, OH, USA
| | - Robert P Lisak
- Department of Neurology, Wayne State University School of Medicine, 8D University Health Center, 4201 St Antoine, Detroit, MI 48201, USA; Department of Biochemistry, Microbiology and Immunology, Wayne State University, Detroit, MI, USA.
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9
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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Morren J, Li Y. Myasthenia gravis with muscle-specific tyrosine kinase antibodies: A narrative review. Muscle Nerve 2018; 58:344-358. [DOI: 10.1002/mus.26107] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 02/09/2018] [Accepted: 02/18/2018] [Indexed: 12/14/2022]
Affiliation(s)
- John Morren
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| | - Yuebing Li
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
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11
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Clinical and CN-SFEMG evaluation of neostigmine test in myasthenia gravis. Neurol Sci 2018; 39:341-345. [PMID: 29330628 DOI: 10.1007/s10072-017-3194-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Accepted: 11/08/2017] [Indexed: 10/18/2022]
Abstract
Neostigmine test (NT) is a pharmacological test, demonstrating a clinical improvement in patients affected by myasthenia gravis (MG). We aim to compare clinical evaluation and neurophysiological recordings by concentric-needle single-fiber electromyography (CN-SFEMG) in response to acute administration of neostigmine in ocular and generalized MG patients. Twenty-three MG patients (10 with ocular MG and 13 with generalized MG) were evaluated before and after 90 min neostigmine 0.5-mg administration. Clinical responsiveness was assessed by MG composite (MGC) scale. Neurophysiological evaluation by CN-SFEMG considered analysis of mean value of consecutive differences (MCD), single-pair jitter, and blocks. MGC scores significantly improved after NT in generalized MG patients (MGC 11.1 ± 7.6 vs 9.1 ± 6.7, p = 0.02), whereas the improvement was not significant in the ocular group. CN-SFEMG recordings significantly improved after NT in generalized MG patients (MCD 58.9 ± 18.8 vs 45.9 ± 23.2 μs, p = 0.003; single-pair jitter 49.8 ± 26.9 vs 24.1 ± 26.7%, p = 0.0001; blocks 6.2 ± 9.5 vs 2.6 ± 7.4%, p = 0.03) as well as in ocular MG patients (MCD 50.8 ± 22.7 vs 40.1 ± 22.9 μs, p = 0.01; single-pair jitter 35.9 ± 23.7 vs 20.0 ± 25.1%, p = 0.001). CN-SFEMG is a reliable tool to evaluate responsiveness to acute administration of neostigmine in MG. Moreover, neurophysiological modifications to NT could show subclinical improvement in ocular MG better than that of the clinical scale.
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12
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Nazari F, Abdi S. Pyridostigmine-Induced Bradycardia in Patient With MuSK-Ab-Positive Myasthenia Gravis and Alopecia Universalis. J Clin Neuromuscul Dis 2017; 19:49-50. [PMID: 28827491 DOI: 10.1097/cnd.0000000000000162] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Affiliation(s)
- Ferdos Nazari
- *Department of Neurology, Golestan Hospital, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran †Iranian Center of Neurological Research, Shariati Hospital, Tehran University of Medical Sciences, Tehran, IR Iran
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13
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Lee HE, Kim YH, Kim SM, Shin HY. Clinical Significance of Repetitive Compound Muscle Action Potentials in Patients with Myasthenia Gravis: A Predictor for Cholinergic Side Effects of Acetylcholinesterase Inhibitors. J Clin Neurol 2016; 12:482-488. [PMID: 27819419 PMCID: PMC5063876 DOI: 10.3988/jcn.2016.12.4.482] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 01/27/2023] Open
Abstract
Background and Purpose Acetylcholinesterase inhibitors (AChEIs) are widely used to treat myasthenia gravis (MG). Although AChEIs are usually tolerated well, some MG patients suffer from side effects. Furthermore, a small proportion of MG patients show cholinergic hypersensitivity and cannot tolerate AChEIs. Because repetitive compound muscle action potentials (R-CMAPs) are an electrophysiologic feature of cholinergic neuromuscular hyperactivity, we investigated the clinical characteristics of MG patients with R-CMAPs to identify their clinical usefulness in therapeutic decision-making. Methods We retrospectively reviewed the clinical records and electrodiagnostic findings of MG patients who underwent electrodiagnostic studies and diagnostic neostigmine testing (NT). Results Among 71 MG patients, 9 could not tolerate oral pyridostigmine bromide (PB) and 17 experienced side effects of PB. R-CMAPs developed in 24 patients after NT. The highest daily dose of PB was lower in the patients with R-CMAPs (240 mg/day vs. 480 mg/day, p<0.001). The frequencies of PB intolerance and side effects were higher in the patients with R-CMAPs than in those without R-CMAPs [37.5% vs. 0% (p<0.001) and 45.8% vs. 12.8% (p=0.002), respectively]. The MG Foundation of America postintervention status did not differ significantly between MG patients with and without R-CMAPs, and the response to immunotherapy was also good in both groups. Conclusions Side effects of and intolerance to AChEIs are more common in MG patients with R-CMAPs than in those without R-CMAPs. AChEIs should be used carefully in MG patients with R-CMAPs. The presence of R-CMAPs after NT may be a good indicator of the risks of PB side effects and intolerance.
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Affiliation(s)
- Hyo Eun Lee
- Department of Neurology, Keimyung University Kyungju Dongsan Hospital, Gyeongju, Korea
| | - Yool-hee Kim
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
| | - Seung Min Kim
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
| | - Ha Young Shin
- Department of Neurology, Yonsei University College of Medicine, Seoul, Korea
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14
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Plomp JJ, Morsch M, Phillips WD, Verschuuren JJGM. Electrophysiological analysis of neuromuscular synaptic function in myasthenia gravis patients and animal models. Exp Neurol 2015; 270:41-54. [PMID: 25620417 DOI: 10.1016/j.expneurol.2015.01.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 01/07/2015] [Accepted: 01/16/2015] [Indexed: 12/21/2022]
Abstract
Study of the electrophysiological function of the neuromuscular junction (NMJ) is instrumental in the understanding of the symptoms and pathophysiology of myasthenia gravis (MG), an autoimmune disorder characterized by fluctuating and fatigable muscle weakness. Most patients have autoantibodies to the acetylcholine receptor at the NMJ. However, in recent years autoantibodies to other crucial postsynaptic membrane proteins have been found in previously 'seronegative' MG patients. Electromyographical recording of compound and single-fibre muscle action potentials provides a crucial in vivo method to determine neuromuscular transmission failure while ex vivo (miniature) endplate potential recordings can reveal the precise synaptic impairment. Here we will review these electrophysiological methods used to assess NMJ function and discuss their application and typical results found in the diagnostic and experimental study of patients and animal models of the several forms of MG.
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Affiliation(s)
- Jaap J Plomp
- Department of Neurology, Leiden University Medical Centre, Leiden, The Netherlands.
| | - Marco Morsch
- Motor Neuron Disease Research Group, Macquarie University, Sydney, Australia
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