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PubMed1985

Do true remissions in myasthenia really exist? An electrophysiological study.

To answer the question whether true remissions in myasthenia gravis occurred, 20 patients were studied with a history of evident, typical myasthenia but in full clinical remission. Two control groups served as a comparison: one of 10 healthy volunteers and the other of 10 patients with generalized, presently active myasthenia. In 17 of the 20 patients in remission single-fibre EMG (SFEMG) abnormalities were found, indicating some subclinical disturbances of neuromuscular transmission (in 3 cases the results were overtly pathological, in 11 cases moderately pathological, and in 3 cases slightly pathological). The abnormalities found in the remission group were much less distinct than those in the group with clinically symptomatic myasthenia. A case illustrates these findings: a man in full remission following thymoma extirpation in whom the SFEMG revealed subclinical disturbances of the neuromuscular transmission. Three weeks later a full clinical relapse occurred. The results obtained suggest that in the majority of patients the remissions are only apparently complete. A pathological jitter in a patient in remission calls for special attention: the patient must be spared any immunological stimuli such as vaccination, injections of sera, infections etc.; no drugs can be given which may increase the neuromuscular block; an immunosuppressive course of treatment should be considered; prognosis should be reconsidered.

Adolescent↗

PubMed1987

Basement membrane proteins and reticulin in a normal thymus and the thymus in myasthenia gravis.

The distribution of basement membrane (BM) proteins, laminin and type IV collagen were studied immunohistochemically in a series of 12 normal thymuses representing different age groups (0-52 years) and in 10 cases of myasthenia gravis (age 7-53 years). The staining pattern was compared with that of conventional reticulin staining. BM proteins were present at the capsule-parenchyma interface and scantily distributed in the medullary stroma, where they were closely associated with reticulin fibres. The extrathymic perivascular space was effectively visualized by the staining of the BM's marginal to it. The fiber network present in this space stained with reticulin stain and, less continuously, in BM stainings. Lymph node like tissue with germinal centers was occasionally present in the perivascular spaces in normal thymuses and commonly in the myasthenia gravis cases, where the perivascular spaces were often dilated. The BM's of the perivascular space were mostly continuous in normal cases, but discontinuities were observed in cases of myasthenia gravis, especially in the spaces which were widely dilated. Immunohistochemical detection of BM proteins seems to be useful in the study of thymic structure, particularly in the demonstration of the characteristic changes of the perivascular space in myasthenia gravis. It is suggested that the reticulin fibres present in the medulla and in the perivascular space contain laminin and type IV collagen.

Adolescent↗

PubMed2005

Investigation on the mechanism of exacerbation of myasthenia gravis by aminoglycoside antibiotics in mouse model.

To investigate the underlying mechanism of the exacerbation of myasthenia gravis by aminoglycoside antibiotics. C57/BL6 mice were immunized with acetylcholine receptor (AChR), extracted from electric organ of Narcine timilei according to Xu Haopeng's methods, in complete Fruends adjuvant (CFA) to establish experimental autoimmune myasthenia gravis (EAMG). EAMG mice were divided randomly into 5 groups: MG group, NS group and three antibiotics groups. The clinical symptom scores of mice were evaluated on d7 after the last immunization and d14 of antibiotics treatment. Repetitive nerve stimulation (RNS) was performed and the levels of anti-AChR antibody (AChR-Ab) were tested at the same time. The mean clinical symptom grades of gentamycin group (1.312, 2.067), amikacin group (1.111, 1.889) and etimicin group (1.263, 1.632) were significantly higher than those of MG group (1.000, 1.200) (P<0.05). The positive rates of RNS of three antibiotics groups were 69.23%, 58.82% and 63.16% respectively, which were significantly higher than those of MG group and NS group (40.00%, 40.00%, P<0.05). The AChR-Ab level in serum and the expression of AChR on neuromuscular junction (NMJ) of mice in three antibiotics groups were also higher than those of MG group. Our results indicated that aminoglycoside antibiotics could aggravate the symptom of myasthenia gravis. The exacerbation of myasthenia gravis by these antibiotics probably involves competitively restraining the release of acetylcholine from presynaptic membrane, impairing the depolarization of postsynaptic membrane, depressing the irritability of myocyte membrane around the end-plate membrane and consequently leading to the blockade of neuromuscular junction.

Amikacin↗

PubMed1982

Prediction of the need for postoperative mechanical ventilation in myasthenia gravis: thymectomy compared to other surgical procedures.

In a recent report Leventhal, Orkin, and Hirsh described a scoring system felt to be of value in predicting the need for postoperative mechanical ventilation in patients with myasthenia gravis undergoing thymectomy. Leventhal, et al. identified four risk factors felt to have predictive value, namely: (1) duration of myasthenia gravis greater than or equal to 6 years, (2) chronic respiratory disease, (3) dose of pyridostigmine greater than or equal to 750 mg per day, and (4) vital capacity less than or equal to 2.9 litres. Forty-six patients with myasthenia gravis who received 68 general anaesthetics were studied retrospectively. They represented the past 10 years' anaesthetic experience with myasthenia gravis at the Vancouver General Hospital. The patients were divided into two groups: (1) those who underwent thymectomy, and (2) those who underwent procedures other than thymectomy. Using the risk factors of Leventhal, et al., a predictive score was assessed for each patient; the time of postoperative tracheal extubation was also noted for each patient. From this study it was concluded that the scoring system proposed by Leventhal, et al. may have been of some value in predicting whether or not a particular patient undergoing thymectomy was likely to need ventilation postoperatively. In 41 myasthenics who had procedures other than thymectomy, however, this scoring system was found to be of no value.

Adolescent↗

PubMed1996

Anaesthetic management of a patient with myasthenia gravis and tracheal stenosis.

PURPOSE: The combination of myasthenia gravis and tracheal obstruction presents a number of difficulties for anaesthetic management. This case illustrates the advantages of careful planning. CLINICAL FEATURES: A 66-yr-old man with myasthenia gravis required resection of a stenosis at the site of an old tracheostomy. The primary goal was to accomplish safe management of the airway, a task made more difficult because the airway was shared with the surgeon. Awake fibreoptic examination of the tracheal stenosis performed in the operating room provided useful information in planning the subsequent anaesthetic. From this examination, it was found that the trachea could be intubated by a normal endotracheal tube passed through the stenosis over the fibreoptic bronchoscope. Intraoperatively, the orotracheal tube was withdrawn temporarily and replaced with an endotracheal tube placed by the surgeon into the distal trachea. Extubation was carried out judiciously and a plan for reintubation prepared in advance. The anaesthetic plan was modified because of the myasthenia gravis. Following careful investigation of the extent of the patient's disease and its treatment, an assessment was made of the patient's need for postoperative ventilation. The anaesthetic plan included maintenance of anticholinergic medications until the time of surgery and their early resumption postoperatively, avoidance of neuromuscular blocking agents, and careful monitoring of neuromuscular function during the anaesthetic. CONCLUSION: Careful examination of the area of tracheal stenosis and a carefully considered plan for reintubation are prerequisites for this type of surgery. Clinically well controlled myasthenia gravis was managed successfully using familiar principles.

Aged↗

PubMed1997

Isolated corticotroph insufficiency associated to myasthenia gravis.

Myasthenia gravis, a neuromuscular junction autoimmune disease, may be associated to glandular autoimmune diseases such as adrenalitis. We report here the association of myasthenia gravis with a rare cause of adrenocortical deficiency, i.e. isolated corticotroph deficiency. The patient suffered from myasthenia gravis for 5 yr when she reported increased asthenia. Basal cortisol and ACTH levels were low. Metyrapone failed to increase ACTH and 11-desoxycortisol. Corticotropin-releasing hormone or tetracosactide failed to increase normally the cortisol levels. No other endocrine dysfunction or autoimmune disease could be detected. This observation enlarges the spectrum of endocrine diseases associated to myasthenia gravis and strengthens the need for careful endocrine examination.

Adrenocorticotropic Hormone↗

PubMed1999

Acetylcholinesterase activity of skeletal muscle in a non-immunogenic model for myasthenia gravis in rats.

Myasthenia gravis is caused by an autoimmune attack to acetylcholine receptors of skeletal muscle. Acetylcholine release from motor nerve terminals is upregulated in patients with myasthenia gravis and also in rat "myasthenic" models, dependent on the reduction of the number of acetylcholine receptors. This study addresses the question as to whether at "myasthenic" endplates there are changes in the activity of acetylcholinesterase. To this end we studied acetylcholinesterase activity in junctional and extrajunctional regions of dilator naris, extensor digitorum longus, and hemidiaphragm muscles from rats with alpha-bungarotoxin-induced myasthenia gravis. In all studied muscles from "myasthenic" rats there was no significant change of junctional acetylcholinesterase activity. In contrast, in dilator naris and extensor digitorum longus muscles, there was a 60% and 30% increase of extrajunctional acetylcholinesterase activity. There was no significant change in the extrajunctional activity in hemidiaphragm muscles. Velocity sedimentation analysis revealed that the increase in extrajunctional activity in extensor digitorum longus muscles could be attributed to an increase of the activity of the G4 form of acetylcholinesterase. Treatment of rats with 6.4 microgh(-1) neostigmine bromide for 29 days had no influence on junctional and extrajunctional acetylcholinesterase activity of extensor digitorum longus muscles from rats with alpha-bungarotoxin-induced myasthenia gravis.

Acetylcholinesterase↗

PubMed2005

Differential diagnosis of various forms of myasthenia and endocrine ophthalmopathy by immunoblotting.

Immunoblotting can be used for screening a population of antibodies to acetylcholine receptor subunits circulating in the blot of patients with myasthenia. Torpedo Californica acetylcholine receptor served as the antigen. We found that in generalized myasthenia autoantibodies bind to alpha1- or alpha1- and gamma-subunits, while in ophthalmic form they bind only gamma-subunit of acetylcholine receptor. No antibodies to any of the acetylcholine receptor subunits were detected in patients with endocrine ophthalmopathy and in healthy volunteers. This method can be used for differential diagnosis of ophthalmic myasthenia and endocrine ophthalmopathy and for predicting generalization of the pathological process in patients with myasthenia.

Adolescent↗

PubMed1990

Myasthenia gravis.

Myasthenia Gravis is a disorder of neuromuscular function resulting from an immunologically based premature destruction of acetylcholine receptors. The disease is characterized clinically by variable weakness accentuated by repetitive muscular activity and usually responding to the administration of acetylcholinesterase inhibitors. Myasthenia Gravis is a complex disease and requires understanding of the many facets of its natural history and immunological basis to ensure optimal individual patient management. The long-term goal is control of the immunological imbalance; treatment regimens include thymectomy, corticosteroids, azathioprine, and plasmapheresis. The common use of acetylcholinesterase inhibitors provides symptomatic relief during variable daily muscular activity. Disability due to myasthenia gravis is to a large extent reversible and death is preventable. Early recognition of myasthenia gravis and appropriate treatment are often rewarded by remission that may be permanent.

Diagnosis, Differential↗

PubMed1991

A non-immunogenic myasthenia gravis model and its application in a study of transsynaptic regulation at the neuromuscular junction.

A non-immunological model for myasthenia gravis was developed in rats: 'toxin-induced myasthenia gravis'. Rats were injected once every 48 h with 3-5 micrograms alpha-bungarotoxin for periods of up to 5 weeks. This treatment caused weakness, especially of facial muscles. Respiration, however, was unaffected. Miniature endplate potentials and 125I-alpha-bungarotoxin binding in the extensor digitorum longus muscles were severely reduced. Acetylcholine release evoked by electrical and chemical (50 mM KCl) stimulation was higher in diaphragms from alpha-bungarotoxin-treated rats than in those from control animals. Histological investigation of the tibialis anterior muscle provided no evidence that the endplates were enlarged. It is concluded that the activity of acetylcholine receptors influences the rate of transmitter release in the neuromuscular junction and it is suggested that a transsynaptic regulation process may be active in myasthenia gravis. The present animal model for myasthenia gravis seems very suitable for studying such a regulation of transmitter release.

Acetylcholine↗

PubMedDate not supplied

Occurrence of myasthenia gravis in a patient with congenital myotonia.

Myasthenia gravis developed acutely in a 32-year-old woman, who incidentally was found to have myotonia congenita of the autosomal dominant mode of inheritance. The simultaneous occurrence of myasthenia gravis and myotonia congenita was established clinically, pharmacologically and electromyographically. There was no immunologic abnormality, whereas the thymus was detected by pneumomediastinographic tomograms. About 2 months after the onset of myasthenia gravis, thymectomy was performed resulting in progressive improvement of myasthenia without apparent change in the myotonia.

Adult↗

PubMed1994

Response to thymectomy in Chinese patients with myasthenia gravis.

Myasthenia gravis was diagnosed in 48 patients between 1985 and 1991 in this Chinese community. Thymectomy was performed on 36 patients and the mean postoperative follow-up period was 49 months. Significant improvement was seen in 72% of the thymectomised patients, with 33% achieving complete remission. Patients with mild generalised myasthenia at presentation or those found to have thymic hyperplasia had the best prognosis. Patients with more severe symptoms or those with an underlying thymoma also responded favourably. Only patients with ocular myasthenia or those with a normal or atrophic thymus gland had no more than an even chance of gaining significant improvement. Although previous reports suggested a high prevalence of ocular myasthenia and of thymoma among Chinese myasthenic patients, the present study has found no evidence that they respond differently to thymectomy than their Western counterparts.

Adolescent↗

PubMedDate not supplied

Ocular myasthenia: a protean disorder.

Ocular myasthenia is a localized form of myasthenia clinically involving only the extraocular, levator palpebrae superioris, and/or orbicularis oculi muscles. Ocular manifestations can masquerade as a variety of ocular motility disorders, including cranial nerve and gaze palsies. A history of variable and fatiguable muscle weakness suggests this diagnosis, which may be confirmed by the edrophonium (Tensilon) test and acetylcholine receptor antibody titer. Anticholinesterases, corticosteroids and other immunosuppressive agents, and other therapeutic modalities, including thymectomy and plasmapheresis, are used in treatment. As the pathophysiology of myasthenia has been elucidated in recent years, newer treatment strategies have evolved, resulting in a much more favorable prognosis than several decades ago. This review provides historical background, pathophysiology, immuno-genetics, diagnostic testing, and treatment options for ocular myasthenia, as well as a discussion of drug-induced myasthenic syndromes.

Circadian Rhythm↗

PubMed1993

Myasthenia gravis: recognition of a human autoantigen at the molecular level.

The symptoms of myasthenia gravis are primarily or exclusively due to an autoimmune response against the muscle nicotinic acetylcholine receptor (AChR) and this has been the object of intensive investigations for almost 20 years. A detailed picture at the molecular level of the interaction of this autoantigen with the key elements involved in the autoimmune response, such as anti-AChR antibodies, the T-cell receptor and restricting major histocompatibility complex molecules, is now emerging for both human myasthenia gravis and its experimental model, experimental autoimmune myasthenia gravis. Here, Maria Pia Protti and colleagues focus on the molecular interactions occurring in human myasthenia gravis and summarize recent information on pathogenic mechanisms of the autoimmune response, and the structure of epitopes recognized by B cells and CD4+ T cells of myasthenic patients on the AChR molecule.

Animals↗

PubMed1994

The role of intrapartum vibroacoustic stimulation in the prediction of neonatal myasthenia gravis.

BACKGROUND: The exact mechanism for the development of neonatal myasthenia gravis is unclear, and the occurrence of neonatal myasthenia gravis cannot be predicted. CASE: A case of normal duration of fetal forearm extention with return to flexion in response to vibroacoustic stimulation, and the pertinent details concerning neonatal myasthenia gravis and vibroacoustic stimulation test are described. CONCLUSIONS: Inasmuch as fetal acoustic stimulation test results in a fetal reaction resembling the startle response of the newborn, we think that it will worthwhile to perform this test antenatally in the next encountered fetuses of myasthenic mothers in order to assess its role in the prediction of neonatal myasthenia gravis.

Acoustic Stimulation↗

PubMedDate not supplied

The start of an autoimmune disease: idiotypic network during early progression of myasthenia gravis.

Anti-acetylcholine-receptor antibodies of IgG and IgM classes and antiidiotypic antibodies were determined in patients with myasthenia gravis at various times after the start of the disease. Patients with a disease duration of less than one year had a higher prevalence of antiidiotypic antibodies (31/32) than patients who had had the disease for more than 5 years (49/79), and the concentration of antiidiotypic antibodies was also higher in patients with early disease (p less than 0.005). The concentrations of antiidiotypic antibodies decreased during progression of the disease concomittant with an increase in IgG anti-receptor antibodies. A change from IgM to IgG anti-receptor antibody production was also found. In two patients, who developed myasthenia after bone-marrow grafting and who were followed before start of disease, antiidiotypic antibodies appeared before anti-receptor antibodies and before symptoms of myasthenia were present. The high prevalence and concentration of antiidiotypic antibodies in early disease indicate that development and expression of antiidiotypic antibodies are important in early myasthenia gravis.

Age Factors↗

PubMedDate not supplied

Neonatal myasthenia gravis: specific advantages of repetitive stimulation over edrophonium testing.

A premature infant with neonatal myasthenia gravis is presented to illustrate the utility of electrodiagnosis. The patient, born to a mother with myasthenia gravis, suffered additional problems, including hypoxia and subependymal hemorrhage which potentially contributed to hypotonia and poor respiratory effort, thus complicating the diagnosis. Standard testing with edrophonium originally was negative which cast doubt on the diagnosis; however, a repetitive motor nerve stimulation test demonstrated a significant decremental response which was consistent with neonatal myasthenia gravis. This decremental response was corrected following intravenous infusion of edrophonium. In the newborn with suspected myasthenia gravis, repetitive motor nerve stimulation may be a more reliable diagnostic procedure than the more frequently recommended pharmacologic tests. Use of this electrodiagnostic procedure in combination with pharmacologic testing may improve diagnostic accuracy in the premature infant and lead to earlier treatment.

Edrophonium↗

PubMed2007

A comparison of outcomes after robotic open extended thymectomy for myasthenia gravis.

OBJECTIVE: The aim of this study was to analyze the effect of the surgical approach on surgical and neurologic outcomes after extended thymectomy for myasthenia gravis. METHODS: A retrospective analysis of the institutional extended thymectomies for myasthenia gravis within the last decade was performed. Patients of group A (open access by total median sternotomy; n=10; 1996-2002) and of group B (video assisted thoracoscopic surgery approach with the da Vinci robotic system; n=9; 2003-2006) did not differ with regard to gender distribution, age, body mass index, American Association of Anaesthetists score and Osserman classification of myasthenia gravis. Primary endpoints were surgical complications and the symptomatic/neurologic outcome of the extended thymectomy. Secondary endpoints were operating times and hospital stay. RESULTS: Median follow-up was 74+/-23 months in group A and 13+/-10 months in group B. Surgical complications occurred in 4 patients in group A (requiring 2 re-interventions) and in 1 patient in group B (p<0.05). The median dose of Pyridostigminbromid was reduced 3 and 6 months postoperatively in group A to 80% and 60% of the preoperative level and in group B to 66% and 60% of the preoperative level, respectively. Within the first postoperative year all patients of group B had an improvement of their disease whereas 2 patients of group A did not benefit from thymectomy or had a worsening of symptoms. Operating times were significantly shorter in group A (110 (42-152) min vs 154 (94-312) min, p<0.05), hospital stay was significantly shorter in group B (5 (4-15) vs 10 (10-23) days, p<0.05). CONCLUSIONS: The results of this small series favour the robotic approach for extended thymectomy for myasthenia gravis in respect of both surgical and early neurologic outcome. However, prospective randomized trials are required to prove a general validity.

Female↗