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Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update. Brain Sci 2021; 11:brainsci11081035. [PMID: 34439654 PMCID: PMC8392118 DOI: 10.3390/brainsci11081035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 07/26/2021] [Accepted: 08/02/2021] [Indexed: 01/17/2023] Open
Abstract
The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.
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Demystifying the spontaneous phenomena of motor hyperexcitability. Clin Neurophysiol 2021; 132:1830-1844. [PMID: 34130251 DOI: 10.1016/j.clinph.2021.03.053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/18/2021] [Accepted: 03/29/2021] [Indexed: 10/21/2022]
Abstract
Possessing a discrete functional repertoire, the anterior horn cell can be in one of two electrophysiological states: on or off. Usually under tight regulatory control by the central nervous system, a hierarchical network of these specialist neurons ensures muscular strength is coordinated, gradated and adaptable. However, spontaneous activation of these cells and their axons can result in abnormal muscular twitching. The muscular twitch is the common building block of several distinct clinical patterns, namely fasciculation, myokymia and neuromyotonia. When attempting to distinguish these entities electromyographically, their unique temporal and morphological profiles must be appreciated. Detection and quantification of burst duration, firing frequency, multiplet patterns and amplitude are informative. A common feature is their persistence during sleep. In this review, we explain the accepted terminology used to describe the spontaneous phenomena of motor hyperexcitability, highlighting potential pitfalls amidst a bemusing and complex collection of overlapping terms. We outline the relevance of these findings within the context of disease, principally amyotrophic lateral sclerosis, Isaacs syndrome and Morvan syndrome. In addition, we highlight the use of high-density surface electromyography, suggesting that more widespread use of this non-invasive technique is likely to provide an enhanced understanding of these motor hyperexcitability syndromes.
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Zhao J, Bhatnagar V, Ding L, Atay SM, David EA, McFadden PM, Stamnes S, Lechtholz-Zey E, Wightman SC, Detterbeck FC, Kim AW. A systematic review of paraneoplastic syndromes associated with thymoma: Treatment modalities, recurrence, and outcomes in resected cases. J Thorac Cardiovasc Surg 2019; 160:306-314.e14. [PMID: 31982129 DOI: 10.1016/j.jtcvs.2019.11.052] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 11/05/2019] [Accepted: 11/06/2019] [Indexed: 12/13/2022]
Abstract
OBJECTIVE Paraneoplastic syndromes associated with thymomas remain incompletely understood. The objective was to examine the association between surgically resected thymomas and paraneoplastic syndromes over the past half century. METHODS A primary PubMed/MEDLINE search was used to identify published articles describing paraneoplastic syndromes associated with thymomas from 1960 to 2019. A secondary search identified additional articles referenced in the articles found in the primary search. Kaplan-Meier and log-rank test were used for time-to-event data analyses. RESULTS From 407 articles describing 507 patients, 123 different paraneoplastic syndromes were associated with thymoma. The 5 most common paraneoplastic syndromes were myasthenia gravis, pure red cell aplasia, lichen planus, Good syndrome, and limbic encephalitis. Complete or partial resolution of paraneoplastic syndrome symptoms after surgery was noted in 76% of patients, of whom 21% had a relapse or new paraneoplastic syndrome onset after surgery. The most common adjunctive therapy associated with resolution of paraneoplastic syndrome was corticosteroids (30%). For all patients after surgery, thymoma recurrence was observed in 17% of cases, whereas recurrence of paraneoplastic syndrome was observed in 34% of cases, and both were observed in approximately 11% of cases. The 5- and 10-year overall survivals were 78% and 66%, respectively. Improved overall survival was associated with patients who had total resolution from paraneoplastic syndrome. CONCLUSIONS A comprehensive assessment of publications over the past half century suggests that a multimodal treatment approach that includes surgical resection of thymomas is able to achieve paraneoplastic syndrome resolution in a majority of patients. Onset of new paraneoplastic syndromes after surgery is associated with the recurrence of the first paraneoplastic syndrome, and resolution of paraneoplastic syndrome is associated with improved overall survival.
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Affiliation(s)
- Jasmine Zhao
- Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | - Vikrant Bhatnagar
- Ohio University Heritage College of Osteopathic Medicine, Athens, Ohio
| | - Li Ding
- Division of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | - Scott M Atay
- Division of Thoracic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | - Elizabeth A David
- Division of Thoracic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | - P Michael McFadden
- Division of Thoracic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | - Stephanie Stamnes
- Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | | | - Sean C Wightman
- Division of Thoracic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, Calif
| | | | - Anthony W Kim
- Division of Thoracic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, Calif.
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Wightman SC, Shrager JB. Non-Myasthenia Gravis Immune Syndromes and the Thymus: Is There a Role for Thymectomy? Thorac Surg Clin 2019; 29:215-225. [PMID: 30928003 DOI: 10.1016/j.thorsurg.2018.12.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Thymectomy has long been considered, performed, and discussed for many different nonmyasthenic immune syndromes. Thymectomy is now an established treatment for MG, and has been performed for other immune syndromes with varying degrees of improvement. Although numerous reports document immune syndromes' association with thymoma, few address the role of thymectomy in symptom resolution. This review assesses thymectomy in the various nonmyasthenic immune syndromes for which it has been tried. Based on this review, it seems appropriate to revisit a more active role for thymectomy in pure red cell aplasia, pemphigus, rheumatoid arthritis, autoimmune hemolytic anemia, and ulcerative colitis.
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Affiliation(s)
- Sean C Wightman
- Division of Thoracic Surgery, Department of Cardiothoracic Surgery, Stanford University Hospitals and Clinics, 300 Pasteur Drive, Stanford, CA 94305, USA
| | - Joseph B Shrager
- Division of Thoracic Surgery, Department of Cardiothoracic Surgery, Stanford University Hospitals and Clinics, 300 Pasteur Drive, Stanford, CA 94305, USA.
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Abstract
PURPOSE OF REVIEW Peripheral nerve hyperexcitability (PNH) syndromes are divided into primary and secondary groups based on the presence or absence of demonstrable peripheral nerve disease. In this review, we systematically evaluate the evidence for current therapies and supportive managements based on autoimmune, paraneoplastic, and genetic components in pathophysiology reported in the literature. RECENT FINDINGS Current therapy options are based on symptomatic management as well as focusing the underlying immune/genetic/paraneoplastic pathology by immunosuppressants, chemotherapy, and surgery. Further research is desired to provide treatment options geared specifically towards addressing PNH. Supportive care can also be an area for future research.
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Venom-derived peptide inhibitors of voltage-gated potassium channels. Neuropharmacology 2017; 127:124-138. [PMID: 28689025 DOI: 10.1016/j.neuropharm.2017.07.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/02/2017] [Accepted: 07/04/2017] [Indexed: 12/11/2022]
Abstract
Voltage-gated potassium channels play a key role in human physiology and pathology. Reflecting their importance, numerous channelopathies have been characterised that arise from mutations in these channels or from autoimmune attack on the channels. Voltage-gated potassium channels are also the target of a broad range of peptide toxins from venomous organisms, including sea anemones, scorpions, spiders, snakes and cone snails; many of these peptides bind to the channels with high potency and selectivity. In this review we describe the various classes of peptide toxins that block these channels and illustrate the broad range of three-dimensional structures that support channel blockade. The therapeutic opportunities afforded by these peptides are also highlighted. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Antozzi C. Immunoadsorption in patients with autoimmune ion channel disorders of the peripheral nervous system. ATHEROSCLEROSIS SUPP 2013; 14:219-22. [PMID: 23357168 DOI: 10.1016/j.atherosclerosissup.2012.10.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Autoimmune ion channel disorders of the peripheral nervous system include myasthenia gravis, the Lambert-Eaton myasthenic syndrome, acquired neuromyotonia and autoimmune autonomic ganglionopathies. These disorders are characterized by the common feature of being mediated by IgG autoantibodies against identified target antigens, i.e. the acetylcholine receptor, the voltage-gated calcium and potassium channels, and the neuronal acetylcholine receptor. Moreover, experimental animal models have been identified for these diseases that respond to immunotherapy and are improved by plasmapheresis. On this basis, autoimmune ion channel disorders represent the ideal candidate for therapeutic apheresis. Immunoadsorption can be the treatment of choice when intensive apheretic protocols or long-term treatments must be performed, in patients needing frequent apheresis to keep a stable clinical condition, in case of unresponsiveness to corticosteroids and immunosuppressive treatments, or failure with TPE or intravenous immunoglobulins, and in patients with severe contraindications to long-term corticosteroids.
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Affiliation(s)
- Carlo Antozzi
- Neuroimmunology and Muscle Pathology Unit, National Neurological Institute Foundation Carlo Besta, Via Celoria 11, 20133 Milan, Italy.
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Pedotti R, Musio S, Scabeni S, Farina C, Poliani PL, Colombo E, Costanza M, Berzi A, Castellucci F, Ciusani E, Confalonieri P, Hemmer B, Mantegazza R, Antozzi C. Exacerbation of experimental autoimmune encephalomyelitis by passive transfer of IgG antibodies from a multiple sclerosis patient responsive to immunoadsorption. J Neuroimmunol 2013; 262:19-26. [PMID: 23768729 DOI: 10.1016/j.jneuroim.2013.05.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 05/10/2013] [Accepted: 05/17/2013] [Indexed: 10/26/2022]
Abstract
The pathogenic role of antibodies in multiple sclerosis (MS) is still controversial. We transferred to mice with experimental autoimmune encephalomyelitis (EAE), animal model of MS, IgG antibodies purified from a MS patient presenting a dramatic clinical improvement during relapse after selective IgG removal with immunoadsorption. Passive transfer of patient's IgG exacerbated motor paralysis and increased mouse central nervous system (CNS) inflammation and demyelination. Binding of patient's IgG was demonstrated in mouse CNS, with a diffuse staining of white matter oligodendrocytes. These data support a growing body of evidence that antibodies can play an important role in the pathobiology of MS.
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Affiliation(s)
- Rosetta Pedotti
- Neuroimmunology and Neuromuscular Disorders Unit, Foundation IRCCS Neurological Institute C. Besta, Via Celoria 11, 20133 Milan, Italy.
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Abstract
Morvan syndrome is characterized by central, autonomic, and peripheral hyperactivity. Examples of central hyperactivity include confusion, memory problems, hallucinations, insomnia, and myoclonus; examples of autonomic hyperactivity include hyperhidrosis and fluctuations in blood pressure; examples of peripheral hyperreactivity include clinical or electrophysiological evidence of painful cramps, myokymia, and neuromyotonia. We present a typical case of Morvan syndrome and the first detailed review of the clinical and therapeutic literature of all 27 cases from the English language literature. Morvan syndrome is considered to be an autoimmune disorder and antibodies against voltage-gated potassium channels are found in most cases. Oral immunomodulatory therapy, intravenous immunoglobulin, and plasmapharesis may be entertained. Thymoma is found in approximately 50% of cases and thymectomy may be curative as in our particular case.
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Kleopa KA. Autoimmune channelopathies of the nervous system. Curr Neuropharmacol 2012; 9:458-67. [PMID: 22379460 PMCID: PMC3151600 DOI: 10.2174/157015911796557966] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 03/16/2010] [Accepted: 03/16/2010] [Indexed: 12/20/2022] Open
Abstract
Ion channels are complex transmembrane proteins that orchestrate the electrical signals necessary for normal function of excitable tissues, including the central nervous system, peripheral nerve, and both skeletal and cardiac muscle. Progress in molecular biology has allowed cloning and expression of genes that encode channel proteins, while comparable advances in biophysics, including patch-clamp electrophysiology and related techniques, have made the functional assessment of expressed proteins at the level of single channel molecules possible. The role of ion channel defects in the pathogenesis of numerous disorders has become increasingly apparent over the last two decades. Neurological channelopathies are frequently genetically determined but may also be acquired through autoimmune mechanisms. All of these autoimmune conditions can arise as paraneoplastic syndromes or independent from malignancies. The pathogenicity of autoantibodies to ion channels has been demonstrated in most of these conditions, and patients may respond well to immunotherapies that reduce the levels of the pathogenic autoantibodies. Autoimmune channelopathies may have a good prognosis, especially if diagnosed and treated early, and if they are non-paraneoplastic. This review focuses on clinical, pathophysiologic and therapeutic aspects of autoimmune ion channel disorders of the nervous system.
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Affiliation(s)
- Kleopas A Kleopa
- Neurology Clinics and Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Cyprus
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Stiff person syndrome: advances in pathogenesis and therapeutic interventions. Curr Treat Options Neurol 2011; 11:102-10. [PMID: 19210912 DOI: 10.1007/s11940-009-0013-9] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Stiff person syndrome (SPS) varies from mild to severe, but if untreated it can be progressive and disabling. Although progress has been made in understanding and treating SPS, the disease remains underdiagnosed, delaying treatment. Antibodies against glutamic acid decarboxylase provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is an antigenic target. Circulating anti-GABARAP antibodies that inhibit GABA(A) receptor expression on GABAergic neurons have been found in up to 65% of SPS patients. The impairment of GABAergic pathways and reduction of brain GABA results in clinical manifestations of stiffness, spasms, and phobias. Increased awareness of SPS among practicing physicians is necessary to recognize the disease early and prevent permanent disability. Most patients with SPS respond to GABA-enhancing drugs, but the high doses required cause unacceptable adverse effects. The disease clearly responds to intravenous immunoglobulin, but repeated infusions are needed to maintain response. New immunomodulating agents are being explored to treat difficult cases and to induce long-lasting remissions.
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Irani SR, Alexander S, Waters P, Kleopa KA, Pettingill P, Zuliani L, Peles E, Buckley C, Lang B, Vincent A. Antibodies to Kv1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan's syndrome and acquired neuromyotonia. ACTA ACUST UNITED AC 2010; 133:2734-48. [PMID: 20663977 PMCID: PMC2929337 DOI: 10.1093/brain/awq213] [Citation(s) in RCA: 877] [Impact Index Per Article: 62.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Antibodies that immunoprecipitate 125I-α-dendrotoxin-labelled voltage-gated potassium channels extracted from mammalian brain tissue have been identified in patients with neuromyotonia, Morvan’s syndrome, limbic encephalitis and a few cases of adult-onset epilepsy. These conditions often improve following immunomodulatory therapies. However, the proportions of the different syndromes, the numbers with associated tumours and the relationships with potassium channel subunit antibody specificities have been unclear. We documented the clinical phenotype and tumour associations in 96 potassium channel antibody positive patients (titres >400 pM). Five had thymomas and one had an endometrial adenocarcinoma. To define the antibody specificities, we looked for binding of serum antibodies and their effects on potassium channel currents using human embryonic kidney cells expressing the potassium channel subunits. Surprisingly, only three of the patients had antibodies directed against the potassium channel subunits. By contrast, we found antibodies to three proteins that are complexed with 125I-α-dendrotoxin-labelled potassium channels in brain extracts: (i) contactin-associated protein-2 that is localized at the juxtaparanodes in myelinated axons; (ii) leucine-rich, glioma inactivated 1 protein that is most strongly expressed in the hippocampus; and (iii) Tag-1/contactin-2 that associates with contactin-associated protein-2. Antibodies to Kv1 subunits were found in three sera, to contactin-associated protein-2 in 19 sera, to leucine-rich, glioma inactivated 1 protein in 55 sera and to contactin-2 in five sera, four of which were also positive for the other antibodies. The remaining 18 sera were negative for potassium channel subunits and associated proteins by the methods employed. Of the 19 patients with contactin-associated protein-antibody-2, 10 had neuromyotonia or Morvan’s syndrome, compared with only 3 of the 55 leucine-rich, glioma inactivated 1 protein-antibody positive patients (P < 0.0001), who predominantly had limbic encephalitis. The responses to immunomodulatory therapies, defined by changes in modified Rankin scores, were good except in the patients with tumours, who all had contactin-associated-2 protein antibodies. This study confirms that the majority of patients with high potassium channel antibodies have limbic encephalitis without tumours. The identification of leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 as the major targets of potassium channel antibodies, and their associations with different clinical features, begins to explain the diversity of these syndromes; furthermore, detection of contactin-associated protein-2 antibodies should help identify the risk of an underlying tumour and a poor prognosis in future patients.
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Affiliation(s)
- Sarosh R Irani
- Neurosciences Group, Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, Oxford, UK
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Antozzi C, Binelli S, Frassoni C, Ciano C, Vincent A, Andreetta F, Panzica F, Franceschetti S, Confalonieri P, Mantegazza R. Immunotherapy responsive startle with antibodies to voltage gated potassium channels. BMJ Case Rep 2009; 2009:bcr9.2008.0988. [PMID: 21686522 DOI: 10.1136/bcr.09.2008.0988] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Antibodies to potassium channels (VGKC-Ab) were first associated with acquired neuromyotonia and its variant with CNS involvement, Morvan's syndrome. Recently, VGKC-Ab were found in patients with non-paraneoplastic limbic encephalitis (LE), characterised by personality changes, seizures and memory impairment. These patients may respond to immunotherapies. Thus the association of VGKC-Ab and non-paraneoplastic LE established the concept of a potentially reversible autoimmune encephalopathy. We describe a patient with startle syndrome and VGKC-Ab, without neuromyotonia or LE, who responded dramatically to plasma exchange (PE) and immunosuppression, adding to the spectrum of disorders associated with VGKC-Ab.
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Affiliation(s)
- Carlo Antozzi
- Myopathology and Immunology Unit, Neurological Institute Foundation "C Besta", Milan, Italy
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14
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Immunoadsorption for the treatment of narcolepsy with cataplexy. Neurol Sci 2008; 29:499-500. [DOI: 10.1007/s10072-008-1036-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 10/10/2008] [Indexed: 10/21/2022]
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Advances in the pathogenesis and treatment of patients with stiff person syndrome. Curr Neurol Neurosci Rep 2008; 8:48-55. [PMID: 18367039 DOI: 10.1007/s11910-008-0009-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Advances in the clinical diagnosis, prognosis, pathogenesis, and therapies for stiff person syndrome (SPS), based on observations in more than 50 consecutive patients, are presented. The syndrome varies from mild to severe, but if untreated it can be progressive and disabling. SPS remains a largely underdiagnosed condition. Anti-glutamic acid decarboxylase (GAD) antibodies provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is a new antigenic target. In up to 65% of SPS patients, there are circulating anti-GABARAP antibodies that inhibit the GABA(A) receptor expression on GABAergic neurons. This review examines the diagnostic criteria for SPS, SPS variants, common errors in diagnosis, and a step-by-step therapeutic approach, including new advances in therapy.
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Kleine BU, Stegeman DF, Drost G, Zwarts MJ. Interspike interval analysis in a patient with peripheral nerve hyperexcitability and potassium channel antibodies. Muscle Nerve 2008; 37:269-74. [PMID: 17636480 DOI: 10.1002/mus.20849] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Neuromyotonia or Isaacs' syndrome is a rare peripheral nerve hyperexcitability disorder caused by antibodies against potassium channels of myelinated axons. We present the high-density surface electromyographic (EMG) recordings of a patient with fasciculations and cramps due to neuromyotonia. To characterize the time course of hyperexcitability, we analyzed the interspike intervals (ISIs) between fasciculation potentials, doublet, and multiplet discharges. ISI duration increased within each burst. The ISI histograms found can be explained by the recovery cycle of the myelinated axon and its dependency on the slow potassium conductance. We conclude that ISI analysis is a useful tool to understand the membrane dynamics underlying abnormal motor unit activity.
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Affiliation(s)
- Bert U Kleine
- Department of Clinical Neurophysiology, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500HB Nijmegen, The Netherlands.
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Antozzi C, Binelli S, Frassoni C, Ciano C, Vincent A, Andreetta F, Panzica F, Franceschetti S, Confalonieri P, Mantegazza R. Immunotherapy responsive startle with antibodies to voltage gated potassium channels. J Neurol Neurosurg Psychiatry 2007; 78:1281-90. [PMID: 17940176 PMCID: PMC2117596 DOI: 10.1136/jnnp.2006.098301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Espay AJ, Chen R. Rigidity and spasms from autoimmune encephalomyelopathies: stiff-person syndrome. Muscle Nerve 2007; 34:677-90. [PMID: 16969837 DOI: 10.1002/mus.20653] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Stiff-person syndrome (SPS) is a disorder characterized by progressive muscle rigidity with superimposed painful muscle spasms and gait impairment due to continuous motor activity. Evidence has accumulated in favor of SPS representing an autoimmune, predominantly encephalomyelopathic disorder resulting from B-cell-mediated clonal production of autoantibodies against presynaptic inhibitory epitopes on the enzyme glutamic acid decarboxylase (GAD) and the synaptic membrane protein amphiphysin. Recognition of the clinical spectrum of SPS is important, particularly the upper-limb, cervical, and cranial nerve involvement that occurs in paraneoplastic variants. The correlation between antibody levels and severity of disease offers evidence for a pathogenic role for the anti-GAD and anti-amphiphysin autoantibodies. The scarcity of neuropathological correlates stand in sharp contrast with the severity of the disability in affected individuals and suggests that functional impairment of inhibitory circuits without structural damage is sufficient to develop the full clinical spectrum of SPS. The rarity of this condition limits the feasibility of controlled clinical trials in the treatment of SPS, but the available evidence suggest that drugs that increase cortical and spinal inhibition such as benzodiazepines and drugs that provide immune modulation such as intravenous immunoglobulin, plasmapheresis, and prednisone are effective treatments.
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Affiliation(s)
- Alberto J Espay
- Department of Neurology, Neuroscience Institute, Movement Disorders Center, University of Cincinnati, Cincinnati, Ohio, USA
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Abstract
Ion channels are crucial elements in neuronal signaling and synaptic transmission, and defects in their function are known to underlie rare genetic disorders, including some forms of epilepsy. A second class of channelopathies, characterized by autoantibodies against ligand- and voltage-gated ion channels, cause a variety of defects in peripheral neuromuscular and ganglionic transmission. There is also emerging evidence for autoantibody-mediated mechanisms in subgroups of patients with central nervous system disorders, particularly those involving defects in cognition or sleep and often associated with epilepsy. In all autoimmune channelopathies, the relationship between autoantibody specificity and clinical phenotype is complex. But with this new information, autoimmune channelopathies are detected and treated with increasing success, and future research promises new insights into the mechanisms of dysfunction at neuronal synapses and the determinants of clinical phenotype.
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Affiliation(s)
- Angela Vincent
- Neurosciences Group, Department of Clinical Neurology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
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Kleopa KA, Elman LB, Lang B, Vincent A, Scherer SS. Neuromyotonia and limbic encephalitis sera target mature Shaker-type K+ channels: subunit specificity correlates with clinical manifestations. ACTA ACUST UNITED AC 2006; 129:1570-84. [PMID: 16613892 DOI: 10.1093/brain/awl084] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Autoantibodies to Shaker-type (Kv1) K+ channels are now known to be associated with three syndromes. Peripheral nerve hyperexcitability is the chief manifestation of acquired neuromyotonia; the combination of neuromyotonia with autonomic and CNS involvement is called Morvan's syndrome (MoS); and CNS manifestations without peripheral involvement is called limbic encephalitis (LE). To determine the cellular basis of these clinical manifestations, we immunostained mouse neural tissues with sera from patients with neuromyotonia (n = 10), MoS (n = 2) or LE (n = 5), comparing with specific antibodies to relevant K+ channel subunits. Fourteen of 17 patients' sera were positive for Kv1.1, Kv1.2 or Kv1.6 antibodies by immunoprecipitation of 125I-alpha-dendrotoxin-labelled rabbit brain K+ channels. Most sera (11 out of 17) labelled juxtaparanodes of peripheral myelinated axons, co-localizing with Kv1.1 and Kv1.2. In the CNS, all sera tested (n = 12) co-localized with one or more areas of high Kv1.1, Kv1.2 or Kv1.6 channel expression: 10 out of 12 sera co-localized with Kv1.1 and Kv1.2 at spinal cord juxtaparanodes or cerebellar layers, while 3 out of 12 sera co-localized additionally (n = 2) or exclusively (n = 1) with Kv1.6 subunits in Purkinje cells, motor and hippocampal neurons. However, only sera from LE patients labelled the hippocampal areas that are enriched in excitatory, Kv1.1-positive axon terminals. All sera (17 out of 17) labelled one or more of these Kv1 subunits when expressed at the cell membrane of transfected HeLa cells, but not when they were retained in the endoplasmic reticulum. Again, LE sera labelled Kv1.1 subunits more prominently than did MoS or neuromyotonia sera, suggesting an association between higher Kv1.1 specificity and limbic manifestations. In contrast, neuromyotonia sera bound more strongly to Kv1.2 subunits than to Kv1.1 or Kv1.6. These studies support the hypothesis that antibodies to mature surface membrane-expressed Shaker-type K+ channels cause acquired neuromyotonia, MoS and LE, and suggest that future assays based on immunofluorescence of cells expressing individual Kv1 subunits will prove more sensitive than the immunoprecipitation assay. Although more than one type of antibody is often detectable in individual sera, higher affinity for certain subunits or subunit combinations may determine the range of clinical manifestations.
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Affiliation(s)
- Kleopas A Kleopa
- Department of Clinical Neurosciences, Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus, PA, USA.
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Maddison P, Mills KR, Newsom-Davis J. Clinical electrophysiological characterization of the acquired neuromyotonia phenotype of autoimmune peripheral nerve hyperexcitability. Muscle Nerve 2006; 33:801-8. [PMID: 16570308 DOI: 10.1002/mus.20536] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Acquired autoimmune neuromyotonia is regarded as part of the spectrum of peripheral nerve hyperexcitability disorders. We aimed to use clinical neurophysiological measurements to study the extent, distribution, and characteristics of spontaneous motor unit potentials in 11 patients with acquired neuromyotonia. Investigations revealed that most spontaneous discharges recorded were motor unit, or partial motor unit potentials of normal size. Bursts of motor unit potentials arose more commonly from distal portions of the peripheral nerve and had abnormal absolute and relative refractory periods. Spontaneous discharges in some patients occurred in semirhythmic bursts in certain muscles. No patient had neurophysiological abnormalities detectable in first-order neurons of the central nervous system when using transcranial magnetic stimulation to estimate the threshold for corticomotor excitation and determine central motor conduction time. Only patients with coexistent myasthenia gravis had neurophysiologically detectable defects in neuromuscular transmission. The pathogenic region of abnormality in peripheral nerve hyperexcitability disorders therefore seems to lie within the terminal branches of peripheral motor nerves.
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Affiliation(s)
- Paul Maddison
- University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK.
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