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Jacob S. Treating myasthenia gravis beyond the eye clinic. Eye (Lond) 2024:10.1038/s41433-024-03133-x. [PMID: 38789789 DOI: 10.1038/s41433-024-03133-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 02/17/2024] [Accepted: 05/07/2024] [Indexed: 05/26/2024] Open
Abstract
Myasthenia gravis (MG) is one of the most well characterised autoimmune disorders affecting the neuromuscular junction with autoantibodies targeting the acetylcholine receptor (AChR) complex. The vast majority of patients present with ocular symptoms including double vision and ptosis, but may progress on to develop generalised fatiguable muscle weakness. Severe involvement of the bulbar muscles can lead to dysphagia, dysarthria and breathing difficulties which can progress to myasthenic crisis needing ventilatory support. Given the predominant ocular onset of the disease, it is important that ophthalmologists are aware of the differential diagnosis, investigations and management including evolving therapies. When the disease remains localised to the extraocular muscles (ocular MG) IgG1 and IgG3 antibodies against the AChR (including clustered AChR) are present in nearly 50% of patients. In generalised MG this is seen in nearly 90% patients. Other antibodies include those against muscle specific tyrosine kinase (MuSK) and lipoprotein receptor related protein 4 (LRP4). Even though decremental response on repetitive nerve stimulation is the most well recognised neurophysiological abnormality, single fibre electromyogram (SFEMG) in experienced hands is the most sensitive test which helps in the diagnosis. Initial treatment should be using cholinesterase inhibitors and then proceeding to immunosuppression using corticosteroids and steroid sparing drugs. Patients requiring bulbar muscle support may need rescue therapies including plasma exchange and intravenous immunoglobulin (IVIg). Newer therapeutic targets include those against the B lymphocytes, complement system, neonatal Fc receptors (FcRn) and various other elements of the immune system.
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Affiliation(s)
- Saiju Jacob
- University Hospitals Birmingham, Birmingham, UK.
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK.
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Muscle satellite cells are functionally impaired in myasthenia gravis: consequences on muscle regeneration. Acta Neuropathol 2017; 134:869-888. [PMID: 28756524 DOI: 10.1007/s00401-017-1754-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 06/30/2017] [Accepted: 07/21/2017] [Indexed: 12/14/2022]
Abstract
Myasthenia gravis (MG) is a neuromuscular disease caused in most cases by anti-acetyl-choline receptor (AChR) autoantibodies that impair neuromuscular signal transmission and affect skeletal muscle homeostasis. Myogenesis is carried out by muscle stem cells called satellite cells (SCs). However, myogenesis in MG had never been explored. The aim of this study was to characterise the functional properties of myasthenic SCs as well as their abilities in muscle regeneration. SCs were isolated from muscle biopsies of MG patients and age-matched controls. We first showed that the number of Pax7+ SCs was increased in muscle sections from MG and its experimental autoimmune myasthenia gravis (EAMG) mouse model. Myoblasts isolated from MG muscles proliferate and differentiate more actively than myoblasts from control muscles. MyoD and MyoG were expressed at a higher level in MG myoblasts as well as in MG muscle biopsies compared to controls. We found that treatment of control myoblasts with MG sera or monoclonal anti-AChR antibodies increased the differentiation and MyoG mRNA expression compared to control sera. To investigate the functional ability of SCs from MG muscle to regenerate, we induced muscle regeneration using acute cardiotoxin injury in the EAMG mouse model. We observed a delay in maturation evidenced by a decrease in fibre size and MyoG mRNA expression as well as an increase in fibre number and embryonic myosin heavy-chain mRNA expression. These findings demonstrate for the first time the altered function of SCs from MG compared to control muscles. These alterations could be due to the anti-AChR antibodies via the modulation of myogenic markers resulting in muscle regeneration impairment. In conclusion, the autoimmune attack in MG appears to have unsuspected pathogenic effects on SCs and muscle regeneration, with potential consequences on myogenic signalling pathways, and subsequently on clinical outcome, especially in the case of muscle stress.
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MacDonald R, Barbat-Artigas S, Cho C, Peng H, Shang J, Moustaine A, Carbonetto S, Robitaille R, Chalifour LE, Paudel H. A Novel Egr-1-Agrin Pathway and Potential Implications for Regulation of Synaptic Physiology and Homeostasis at the Neuromuscular Junction. Front Aging Neurosci 2017; 9:258. [PMID: 28824419 PMCID: PMC5541023 DOI: 10.3389/fnagi.2017.00258] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/19/2017] [Indexed: 12/11/2022] Open
Abstract
Synaptic transmission requires intricate coordination of the components involved in processing of incoming signals, formation and stabilization of synaptic machinery, neurotransmission and in all related signaling pathways. Changes to any of these components cause synaptic imbalance and disruption of neuronal circuitry. Extensive studies at the neuromuscular junction (NMJ) have greatly aided in the current understanding of synapses and served to elucidate the underlying physiology as well as associated adaptive and homeostatic processes. The heparan sulfate proteoglycan agrin is a vital component of the NMJ, mediating synaptic formation and maintenance in both brain and muscle, but very little is known about direct control of its expression. Here, we investigated the relationship between agrin and transcription factor early growth response-1 (Egr-1), as Egr-1 regulates the expression of many genes involved in synaptic homeostasis and plasticity. Using chromatin immunoprecipitation (ChIP), cell culture with cell lines derived from brain and muscle, and animal models, we show that Egr-1 binds to the AGRN gene locus and suppresses its expression. When compared with wild type (WT), mice deficient in Egr-1 (Egr-1−/−) display a marked increase in AGRN mRNA and agrin full-length and cleavage fragment protein levels, including the 22 kDa, C-terminal fragment in brain and muscle tissue homogenate. Because agrin is a crucial component of the NMJ, we explored possible physiological implications of the Egr-1-agrin relationship. In the diaphragm, Egr-1−/− mice display increased NMJ motor endplate density, individual area and area of innervation. In addition to increased density, soleus NMJs also display an increase in fragmented and faint endplates in Egr-1−/− vs. WT mice. Moreover, the soleus NMJ electrophysiology of Egr-1−/− mice revealed increased quantal content and motor testing showed decreased movement and limb muscle strength compared with WT. This study provides evidence for the potential involvement of a novel Egr-1-agrin pathway in synaptic homeostatic and compensatory mechanisms at the NMJ. Synaptic homeostasis is greatly affected by the process of aging. These and other data suggest that changes in Egr-1 expression may directly or indirectly promote age-related pathologies.
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Affiliation(s)
- Ryen MacDonald
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | | | - Chulmin Cho
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | - Huashan Peng
- Center for Research in NeuroscienceMontreal, QC, Canada
| | - Jijun Shang
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada
| | - Ayman Moustaine
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Salvatore Carbonetto
- Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Center for Research in NeuroscienceMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Richard Robitaille
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Lorraine E Chalifour
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Hemant Paudel
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
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Laryngeal electromyography: a proposal for guidelines of the European Laryngological Society. Eur Arch Otorhinolaryngol 2012; 269:2227-45. [DOI: 10.1007/s00405-012-2036-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 04/24/2012] [Indexed: 10/28/2022]
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Blitzer A, Crumley RL, Dailey SH, Ford CN, Floeter MK, Hillel AD, Hoffman HT, Ludlow CL, Merati A, Munin MC, Robinson LR, Rosen C, Saxon KG, Sulica L, Thibeault SL, Titze I, Woo P, Woodson GE. Recommendations of the Neurolaryngology Study Group on laryngeal electromyography. Otolaryngol Head Neck Surg 2009; 140:782-793. [PMID: 19467391 PMCID: PMC2758662 DOI: 10.1016/j.otohns.2009.01.026] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 12/08/2008] [Accepted: 01/15/2009] [Indexed: 11/17/2022]
Abstract
The Neurolaryngology Study Group convened a multidisciplinary panel of experts in neuromuscular physiology, electromyography, physical medicine and rehabilitation, neurology, and laryngology to meet with interested members from the American Academy of Otolaryngology Head and Neck Surgery, the Neurolaryngology Subcommittee and the Neurolaryngology Study Group to address the use of laryngeal electromyography (LEMG) for electrodiagnosis of laryngeal disorders. The panel addressed the use of LEMG for: 1) diagnosis of vocal fold paresis, 2) best practice application of equipment and techniques for LEMG, 3) estimation of time of injury and prediction of recovery of neural injuries, 4) diagnosis of neuromuscular diseases of the laryngeal muscles, and, 5) differentiation between central nervous system and behaviorally based laryngeal disorders. The panel also addressed establishing standardized techniques and methods for future assessment of LEMG sensitivity, specificity and reliability for identification, assessment and prognosis of neurolaryngeal disorders. Previously an evidence-based review of the clinical utility of LEMG published in 2004 only found evidence supported that LEMG was possibly useful for guiding injections of botulinum toxin into the laryngeal muscles. An updated traditional/narrative literature review and expert opinions were used to direct discussion and format conclusions. In current clinical practice, LEMG is a qualitative and not a quantitative examination. Specific recommendations were made to standardize electrode types, muscles to be sampled, sampling techniques, and reporting requirements. Prospective studies are needed to determine the clinical utility of LEMG. Use of the standardized methods and reporting will support future studies correlating electro-diagnostic findings with voice and upper airway function.
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Affiliation(s)
| | - Roger L. Crumley
- Department of Otolaryngology-Head and neck Surgery, University of California-Irvine, CA
| | - Seth H. Dailey
- Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Charles N. Ford
- Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Mary Kay Floeter
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Allen D. Hillel
- Department of Otolaryngology – Head and Neck Surgery, University of Washington School of Medicine, Seattle, WA
| | - Henry T. Hoffman
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA
| | - Christy L. Ludlow
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Albert Merati
- Department of Otolaryngology – Head and Neck Surgery, University of Washington School of Medicine, Seattle, WA
| | - Michael C. Munin
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Lawrence R. Robinson
- Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, WA
| | - Clark Rosen
- Department of Otolaryngology, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Keith G. Saxon
- Department of Surgery, Division of Otolaryngology, Harvard Medical School, Boston MA
| | - Lucian Sulica
- Department of Otorhinolaryngology, Weill Medical College of Cornell University, NYC, NY
| | - Susan L. Thibeault
- Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | | | - Peak Woo
- Department of Otolaryngology, Mt Sinai School of Medicine, New York, NY
| | - Gayle E. Woodson
- Department of Otolaryngology-Head and Neck Surgery, Southern Illinois University, Springfield, IL
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Lateva ZC, McGill KC, Johanson ME. Increased jitter and blocking in normal muscles due to doubly innervated muscle fibers. Muscle Nerve 2003; 28:423-31. [PMID: 14506713 DOI: 10.1002/mus.10459] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Increased jitter and intermittent impulse blocking in electromyographic (EMG) signals are considered evidence of transmission abnormality and are not usually associated with normal muscle. However, motor unit action potentials (MUAPs) that exhibit increased jitter and blocking have recently been shown to occur in the brachioradialis muscles of neurologically healthy subjects. The jitter and blocking result from collisions, refractoriness, and conduction-velocity variability in long muscle fibers that are innervated by two different motoneurons at widely separated endplates. We analyzed MUAPs obtained by decomposing EMG signals from the brachioradialis muscles of four normal subjects. The rate of blocking of some MUAP components was as high as 28%, the jitter between some components exceeded 300 micros (mean consecutive difference), and the mean incidence of irregular MUAPs was 14%. These values would be considered abnormal in many other muscles. Jitter from doubly innervated fibers can be distinguished from other types of pathological jitter because one component exhibits amplitude variability. Clinical neurophysiologists should be aware that increased jitter and blocking do not necessarily indicate pathology in brachioradialis and perhaps other long, parallel-fibered muscles.
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Affiliation(s)
- Zoia C Lateva
- Rehabilitation Research and Development Center, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, California 94304-1200, USA.
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Chapter 9 Electromyographic methods. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-4231(09)70119-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Abstract
A review of quantitative methods for electromyography is given. Background information about motor unit anatomy, physiology, and pathology is provided to explain some of the presented electrophysiological phenomena. Different aspects of quantitation, such as motor unit action potential parameters, automatic analysis methods, reference values, and findings in abnormal conditions, are discussed.
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Affiliation(s)
- E Stålberg
- Department of Clinical Neurophysiology, University Hospital, Uppsala, Sweden
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