Myasthenic myopathy and thymoma

Rowland, Lewis P.; Lisak, Robert P.; Schotland, Donald L.; DeJesus, Pacifico V.; Berg, Perry

doi:10.1212/wnl.23.3.282

Cited by 19 publications

(6 citation statements)

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“…In view of this discrepancy it is most likely that the traditional electrophysiological criteria of myopathy cannot be applied in myasthenia gravis and that fiber loss is caused by failure of neuromuscular transmission in certain fibers of the motor unit (Buchlhal & Karnieniecka 1982, Fuglsang-Frederiksen & Krarup 1982). However, there are patients with thymoma and clinical signs of myopathy in addition to some but not all the features of myasthenia gravis ( Rowland et al 1973). This may suggest that particular groups of patients are apt to develop myopathic features in addition to myasthenia gravis.…”

Section: Myopathy Side By Side With Myasthenia Gravis?mentioning

confidence: 99%

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Krarup

1983

Acta Neurologica Scandinavica

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The compound muscle action potential and isometric twitch tension evoked by single and repetitive electrical stimuli are indicators of the number of motor units activated and of the contractile properties of the muscle. The action potentials and mechanical responses were recorded in proximal and distal muscles in patients with myasthenia gravis and myopathy and compared with findings in normal subjects. In normal muscle, at low rates of stimulation (2-3 s-1) the decrement was at most 5% in the action potential and 15-24% in the twitch tension. Tetanic stimuli (50 s-1) were unsuitable for diagnostic purposes because of movement artefact. In patients with myasthenia gravis, the incidence and size of the decrement of evoked responses were greater in the platysma than in the elbow flexors and the adductor pollicis (ADP) muscles. The 2-3 times greater post-tetanic facilitation (PTF) of the action potential in the platysma than in extremity muscles also indicates a more severe functional block in facial muscle. The PTF is an indicator of recruitment of blocked fibres. The maximal decrement was grossly related to the titre of antibodies against the acetylcholine receptor. To reveal failure of neuromuscular transmission in patients with myasthenia gravis without a decrement, a small dose of d-tubocurarine (0.2 mg in 30 ml of saline) was injected i.v. in the upper arm in a regional curare test. The sensitivity was greater in patients with myasthenia gravis than in controls and in patients with myopathy. Potentiation of twitch tension reflects contractile properties. In normal muscle twitch potentiation in the staircase (1-3 s-1, 100 s in duration) and after tetanus (50 s-1, 1.5 s in duration) was 2-3 times greater in the platysma than in the elbow flexors and ADP, presumably related to the greater proportion of fast-twitch fibers in facial muscle. The amplitude of the action potential and the twitch tension varied proportionally with the number of fibers activated and the difference in the decrements of the action potential and the twitch during the staircase in some patients with myasthenia gravis showed that the staircase phenomenon was diminished suggesting abnormalities in the excitation-contraction coupling. The diminution of the staircase and post-tetanic potentiation (PTP) in myopathy also indicates impairment of the excitation-contraction coupling. In rats with severe chronic myasthenia gravis, the staircase and PTP were decreased even when the failing neuromuscular transmission was circumvented by applying direct stimuli to the extensor digitorum longus muscle (EDL).

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Section: Myopathy Side By Side With Myasthenia Gravis?mentioning

confidence: 99%

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Krarup

1983

Acta Neurologica Scandinavica

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“…Hypereosinophilia has been associated with a wide variety of systemic disorders, including myositis 9, 10, 16. In a minority of patients with myasthenia gravis (MG) associated with thymoma, myositis has been reported 2, 3, 6, 7, 15, 17, 18. The case presented is only the second report of the rare concurrence of hypereosinophilia, myositis, and MG associated with a thymoma.…”

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confidence: 87%

Eosinophilia, myositis, and myasthenia gravis associated with a thymoma

et al. 2006

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Hypereosinophilia has been associated with a wide variety of systemic disorders, including myositis. Myositis develops in a minority of patients with myasthenia gravis associated with a thymoma. We present a patient who developed a life-threatening myopathy in which testing demonstrated the concurrence of hypereosinophilia, myositis, and myasthenia gravis associated with thymoma. Thymoma-associated T-cell abnormalities may well have contributed to this rare association. This case underscores the need to reevaluate constantly the presumed cause of clinical complaints, as more than one cause may be present.

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“…The muscle weakness of myositis is not improved by anticholinesterase agents and response to immunotherapy is delayed. This condition may be the same myasthenic myopathy 33. The possible involvement of myositis in patients with MG should be evaluated by serum creatine kinase and electromyography before the start of treatment.…”

Section: Myocarditismentioning

confidence: 99%

Overlooked non-motor symptoms in myasthenia gravis

Suzuki

Utsugisawa

Suzuki

2012

Journal of Neurology, Neurosurgery & Psychiatry

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Patients with myasthenia gravis (MG) may have various non-motor symptoms in addition to fatigability and weakness of skeletal muscles. Thymomas contain abundant immature thymocytes and developing CD4 and CD8 T cells. Thymomas are found in 15-25% of patients with MG and are associated with severe symptoms. We suggest that non-motor symptoms are based on the autoimmune disorders probably owing to an abnormal T cell repertoire from thymomas. Using previously reported cases and cases from our multicentre cooperative study, we review the clinical characteristics of patients with thymoma-associated MG who have non-motor symptoms. CD8 T cell cytotoxicity against haematopoietic precursor cells in bone marrow and unidentified autoantigens in hair follicles lead to the development of pure red cell aplasia, immunodeficiency and alopecia areata. In contrast, neuromyotonia, limbic encephalitis, myocarditis and taste disorders are autoantibody-mediated disorders, as is MG. Autoantibodies to several types of voltage-gated potassium channels and the related molecules can evoke various neurological and cardiac disorders. About 25% of patients with thymoma-associated MG have at least one non-motor symptom. Non-motor symptoms affect many target organs and result in a broad spectrum of disease, ranging from the impairment of quality of life to lethal conditions. Since relatively little attention is paid to non-motor symptoms in patients with thymoma-associated MG, the symptoms may be overlooked by many physicians. Early diagnosis is important, since non-motor symptoms can be treatable. A complete understanding of non-motor symptoms is necessary for the management of patients with thymoma-associated MG.

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Myasthenic myopathy and thymoma

Cited by 19 publications

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Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation

Eosinophilia, myositis, and myasthenia gravis associated with a thymoma

Overlooked non-motor symptoms in myasthenia gravis

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