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PubMed1996

Myasthenia gravis and elderly people.

Myasthenia gravis is probably commoner than previously suspected, the annual incidence being nearer 9-10/million than earlier figures of 2-4/million. The current study found an annual incidence in Croyden of 9.1 per million (95% confidence limits 5.7-13.8 per million). Of the 22 patients (59%) seen in Croyden with newly diagnosed myasthenia gravis during the past 7 years, 13 were aged over 60. In a separate study of the age distribution of positive acetylcholine receptor antibody assays, 51% were 60 years or above in 1991, and 64% in 1994. The peak age in both sexes was 70-80, and numbers were greatest in men aged 60-80.

Adolescent↗
PubMedDate not supplied

Myasthenia gravis: dental treatment considerations.

Myasthenia gravis is an autoimmune neuromuscular disorder that presents challenges for the dental practitioner. Facial and masticatory muscles may be involved and complicate dental treatment. Exacerbations of the skeletal muscle weakness and fatigability that characterize this disorder can be precipitated by certain medications used in dentistry. A review of 47 dental treatment episodes in 16 patients with myasthenia gravis was undertaken to identify neuromuscular responses to dental treatment and post-dental treatment medical therapy required for control of resultant exacerbations of muscular weakness. Neuromuscular sequelae occurred in 5 treatment episodes for four different patients. Management considerations and drug precautions are discussed.

Adult↗
PubMed1989

[What does radiologic diagnosis of the thymus gland accomplish in myasthenia gravis?].

Radiologic imaging in myasthenia gravis is used for the evaluation of pathologic changes of the thymus gland. Computed tomography can demonstrate tumors of the anterior mediastinum in nearly 90% and is therefore superior to conventional radiography. Because of the variety of size and shape of the normal thymus gland, differentiation between normal thymus, follicular hyperplasia and thymoma is rarely possible especially in younger patients. In elderly patients with myasthenia gravis and involution of the thymus gland tumors of the thymus are reliably detected by computed tomography, whereas the ability of computed tomography to predict the histological diagnosis is poor even with intravenous administration of contrast media.

Humans↗
PubMed1980

Detection of thymoma in myasthenia gravis.

Twenty patients with myasthenia gravis had chest radiography, conventional tomography, and computed tomography (CT) of the thorax within 1 month of thymectomy. Four of the six macroscopic tumors were detected on routine chest radiography; conventional tomography provided no additional information. CT detected all six macroscopic tumors and provided additional information that was not available by other procedures. However, 18 patients (90%) had anterior mediastinum densities on CT, which could not be distinguished preoperatively from thymic tumors. All six patients with macroscopic tumors had serum antistriational muscle antibody titers; this test was negative in 10 of 11 patients (91%) without thymoma. Chest radiography, CT of the thorax, and antistriational antibodies are the tests recommended for detection of a thymoma in patients with myasthenia gravis.

Acetylcholine↗
PubMed2001

[Myasthenia gravis and sleep].

In myasthenia gravis respiratory function is often disturbed in the night, especially during REM sleep, despite of normal daytime respiratory function. Nevertheless, nocturnal respiratory problems are rarely diagnosed. Sleepiness, concentration and memory problems can be symptoms of a sleep related breathing disorder. Reports of reduction of REM sleep, memory dysfunction, and detection of acetylcholine receptor (AchR)-antibodies in the cerebrospinal fluid have lead to the hypothesis of a central nervous system involvement in myasthenia gravis. Possible mechanisms are centrally acting AchR-antibodies, unspecifically acting cytokines and hypoxia, possibly the most important influence upon REM sleep reduction and impaired cognitive function. In a patient presenting possible CNS-involvement (cephalea, fatigue, concentration and memory problems), a polysomnographic investigation should therefore be performed to detect a sleep related breathing disorder.

Autoantibodies↗
PubMed2001

Mesangial proliferative glomerulonephritis with deposits of anti-nicotinic acetylcholine receptor antibody in a patient with myasthenia gravis.

A patient with myasthenia gravis developed nephrotic syndrome 3 years after thymectomy. The kidney biopsy specimen revealed mesangial proliferative glomerulonephritis with immune deposits. The glomerular mesangial cells and tubular epithelial cells were sensitive to alpha-bungarotoxin (alpha-BT), a ligand for nicotinic acetylcholine receptor (nAChR), and the binding was inhibited by native alpha-BT, as well as other nAChR ligands, nicotine and d-tubocurarine. In addition, FITC-alpha-BT-neuromuscular junction complexes could also bind to the mesangial cells, and preincubation with unlabeled nAChR inhibited the binding. These findings are consistent with the notion that both nAChR-like protein and anti-nAChR antibody are present in t he mesangial cells of the patient. Although the pathogenetic role of anti-nAChR antibody on the development of glomerulonephritis is unclear, the present observations provide an important insight into the autoimmune-mediated pathophysiological relationship between myasthenia gravis and mesangial proliferative glomerulonephritis.

Adult↗
PubMed1992

Role of acetylcholine receptor antibody complexes in muscle in experimental autoimmune myasthenia gravis.

In experimental autoimmune myasthenia gravis anti-rat nicotinic acetylcholine receptor (AChR) antibody titers correlated significantly with the AChR-antibody complexes found in muscle. It was shown that at least a large part of the AChR-antibody complexes are formed in vitro, which can be prevented by washing of the muscle homogenate. Using a modified assay, no differences in AChR-antibody complexes could be detected between rats with and without symptoms of experimental autoimmune myasthenia gravis. Also no difference in AChR loss nor in inhibition of alpha-bungarotoxin binding to AChR was found between these groups of rats. However, a significant difference in the reduction of AChR function was found, using an assay measuring agonist-induced 22Na+ flux into the TE671 cell line.

Animals↗
PubMed1982

Functional activities of autoantibodies to acetylcholine receptors and the clinical severity of myasthenia gravis.

The pathogenesis of myasthenia gravis involves a humorally mediated autoimmune attack directed against acetylcholine receptors of skeletal muscles. Antibodies against acetylcholine receptors are detected in the serum of more than 80 per cent of patients, but the antibody titers correspond poorly with the severity of disease. To distinguish between antibody titers and antibody activity, we measured the ability of serum immunoglobulin from 49 patients to induce accelerated degradation or blockade of the binding sites of acetylcholine receptors, using a mammalian skeletal-muscle tissue-culture system. Immunoglobulin from 41 of 45 patients tested (91 per cent) increased the rate of degradation of acetylcholine receptors, and the relative increase in the degradation rate corresponded closely (P less than 0.001) with clinical status. Immunoglobulin from 42 of 48 patients tested (88 per cent) produced blockade of receptors, and the extent of the blockade also corresponded with clinical status (P less than 0.001). An index of the combined activities of the immunoglobulin in accelerating degradation and producing blockade of acetylcholine receptors was elevated in 43 of 44 patients (98 per cent) whose immunoglobulins were tested for both activities; this index predicted the patients' clinical status significantly better (P less than 0.001) than either measure alone. This finding suggests that the functional ability of antibodies to decrease the number of available acetylcholine receptors by these two mechanisms is clinically relevant in the pathogenesis of myasthenia gravis.

Autoantibodies↗
PubMedDate not supplied

Altered polyamine levels in skeletal muscle of patients with myasthenia gravis.

Forty patients with myasthenia gravis were tested for polyamine content of the musculus sternothyreoideus removed during thymectomy. Cases with slight muscle alteration were found to show elevated values for all the three polyamines (putrescine, spermidine and spermine) examined with an increased spermidine/spermine ratio. In severe muscular atrophy, however, the high spermidine and spermine levels were accompanied by unchanged putrescine content and spermidine/spermine ratio. Denervational changes in polyamine levels parallel to the degree of muscular damage are useful indicators of the actual grade of muscle atrophy associated with myasthenia gravis. In histologically intact samples, without apparent signs of muscular atrophy the spermidine level and spermidine/spermine ratio were increased in comparison to the control. In addition to being very early signs of denervation, these higher values are possibly the biochemical expression of some adaptive, compensatory hyperfunction of the muscle fibers.

Adolescent↗
PubMed2004

Experience with programmed steroid treatment with thymectomy in nonthymomatous myasthenia gravis.

BACKGROUND: The benefit of thymectomy in myasthenia gravis management is recognized but the perioperative course can fluctuate. The goal of this study was to assess the feasibility and clinical benefit of dose-escalated steroid therapy with thymectomy for nonthymomatous myasthenia gravis. METHODS: We reviewed the records of 69 myasthenia gravis patients who were followed up after undergoing transsternal thymectomy with extended anterior mediastinal dissection in our hospital between 1976-2000. Forty-eight patients in the programmed treatment group who had dose-escalated and de-escalated steroid therapy during the perioperative period comprised 17 patients with ocular myasthenia gravis and 31 patients with generalized myasthenia gravis. Clinical benefits and clinical remission, which was diagnosed when the patients were symptom-free without medications for at least 1 year, were compared with those of 21 patients in the occasional treatment group who received medications occasionally over the perioperative period. RESULTS: Postoperative respiratory failure and myasthenic crisis did not occur in the programmed treatment group but did occur in 6 patients in the occasional treatment group. Remission rates in the programmed treatment group (mean follow-up, 6.4 years) were 30% at 3 years, 38% at 5 years, and 46% at 10 years; rates in the occasional treatment group (mean follow-up, 9.6 years) were 25% at 3 years, 25% at 5 years, and 45% at 10 years. CONCLUSIONS: Programmed steroid therapy in patients with nonthymomatous myasthenia gravis is feasible and it provides clinical benefit when fluctuating symptoms occur during the perioperative period.

Adult↗
PubMed1985

Acetylcholine receptor antibody-producing cells in thymus and lymph nodes in myasthenia gravis.

Eleven patients with myasthenia gravis (5 with thymoma) were studied and spontaneous production of antibody to acetylcholine receptor (AChR) in vitro was found by thymus cells in 10 (and in all 5 with thymoma) and by lymph node cells in 8 (and in 3 with thymoma). The rate of AChR antibody production by thymus cells was greater than that by lymph node cells (10.7 +/- 11.6 and 1.4 +/- 1.5 fmol/10(6) cells/week, respectively, mean +/- SD, P less than 0.05 by paired t test), although the B-cell population was always smaller in the thymus than in the lymph nodes (9.5 +/- 9.4 and 31 +/- 12.7%, P less than 0.001), suggesting the principal role of the thymus in AChR antibody production. It is suggested that lymph nodes can be one of the main sites of AChR antibody production in myasthenia gravis but the antibody-producing cells may originate in the thymus.

Adult↗
PubMed1998

Diagnostic difficulties in myasthenia gravis.

Four patients with myasthenia gravis presented with severe, largely isolated, bulbar and respiratory muscles weakness. Tensilon tests were positive and antiacetylcholine receptor (anti-AChR) antibody titers were negative in all patients. Only 1 patient had a greater than 10% decremental response during the period of respiratory failure. Although routine nerve conduction studies were normal, all had very low-amplitude diaphragmatic compound muscle action potentials. Three patients had abundant fibrillation potentials and positive sharp waves largely restricted to respiratory muscles. Clinical and electrophysiological findings improved with corticosteroids, and surprisingly, decremental responses became positive in all patients. The assessment of patients with largely isolated bulbar and respiratory muscle weakness due to myasthenia gravis may be difficult and misleading, as anti-AChR antibody titers may be negative, decremental responses may be absent, and electrophysiological assessment atypical. Due consideration of clinical symptomatology, a Tensilon test, and a trial of immunosuppression may be necessary to establish the diagnosis.

Adult↗
PubMed2002

Sensitivity to vecuronium in seropositive and seronegative patients with myasthenia gravis.

UNLABELLED: Patients with myasthenia gravis (MG) are hypersensitive to nondepolarizing neuromuscular blocking drugs. Although antibodies to the acetylcholine receptor (AChR) often are observed in MG patients, 10% to 30% of patients do not show an anti-AChR antibody. Little is known about differences in sensitivity to nondepolarizing neuromuscular blocking drugs between MG patients with and without anti-AChR antibody. Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative MG patients and in non-MG patients (n = 8 each). During anesthesia with sevoflurane (2.5%) and nitrous oxide (60%) in oxygen, neuromuscular transmission was monitored by measuring the twitch tension of the adductor pollicis muscle with supramaximal stimulation. After baseline measurements, 10 microg/kg IV dose increments of vecuronium were administered sequentially until blockade exceeded 90%. The degree of blockade and onset time after the initial 10 microg/kg of vecuronium were assessed, and doses required to exceed 90% blockade were recorded. In addition, effective doses of 50% and 95% for vecuronium were calculated from a single data point. Both types of MG patients showed increased sensitivity to vecuronium compared with non-MG patients. IMPLICATIONS: Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative myasthenia gravis (MG) patients and in non-MG patients. They were, indeed, both equally sensitive to vecuronium.

Adult↗
PubMedDate not supplied

Immuno-suppressive peptides for a human T cell clone autoreactive to a unique acetylcholine receptor alpha subunit peptide presented by the disease-susceptible HLA-DQ6 in infant-onset myasthenia gravis.

Infant-onset myasthenia gravis, an autoimmune disease specific to Asians predominantly affects neuromuscular junctions in ocular muscles. An AChR alpha peptide (p71-91) specific autoreactive CD4+ alpha beta T cell clone was established by stimulating PBMC from a patient heterozygous for two disease-susceptible HLA-DR9-DQ9 and DR13-DQ6 haplotypes with a mixture of overlapping peptides covering AChR alpha. The T cell clone recognized the AChR alpha peptide in the context of the HLA-DQ6 molecule and produced a large amount of IFN-gamma and a trace amount of IL-4. A part (p75-83) of the core epitope of the autoantigenic peptide (p75-87) is encoded for by an exon P3A of the AChR alpha gene which can be alternatively spliced. The T cell clone responded to the recombinant AChR alpha protein with a P3A exon product, but not without a P3A exon product. We investigated responses of the T cell clone to 114 analogue peptides carrying single residue substitutions of the core AChR alpha peptide. The majority of analogues substituted at residues Phe-77, Leu-80 and Asn-82 stimulated proliferation of the T cell clone. Conversely, the majority of analogue peptides substituted at either Gln-81 or Glu-83 did not stimulate proliferative responses, and all exhibited strong or intermediate inhibitory effects on proliferative responses of the T cell clone to the wild type peptide, possibly by TCR antagonism. Thus, an HLA class II allele specific to Asians may directly control susceptibility to the Asian-specific type of myasthenia gravis. Analogues of the auto-antigenic AChR alpha peptide may prove effective for new immunosuppressive therapy.

Antibodies, Blocking↗
PubMed2005

Does this patient have myasthenia gravis?

CONTEXT: Clinicians must be able to diagnose myasthenia gravis, since delays in establishing the diagnosis may put patients at risk for complications from this treatable disease. OBJECTIVE: To determine if items in the history and examination or results of simple tests change the likelihood of myasthenia gravis as a diagnosis. DATA SOURCES: MEDLINE search of English-language articles (January 1966-January 2005) using the terms myasthenia gravis, diagnosis, and test, and a search of bibliographies of retrieved articles. STUDY SELECTION: Studies evaluating a particular symptom or sign in patients both with and without myasthenia gravis. Of 640 articles retrieved, 33 were eligible for review. Of these, 15 met inclusion criteria and form the basis of this review. DATA EXTRACTION: Two authors independently reviewed each study to determine eligibility, abstracted data using a standardized instrument, and classified study quality using previously published criteria. DATA SYNTHESIS: A history of "speech becoming unintelligible during prolonged speaking" and the presence of the peek sign increase the likelihood of myasthenia gravis (likelihood ratio [LR], 4.5; 95% confidence interval [CI], 1.2-17.0 and LR, 30.0; 95% CI, 3.2-278.0, respectively). Their absence does not significantly reduce the likelihood of myasthenia gravis. The identified studies only assessed 1 other historical feature and sign each ("food remaining in the mouth after swallowing" and quiver eye movements, respectively), and neither of these significantly changes the likelihood of myasthenia. The ice test is useful when the response is abnormal (summary positive LR, 24.0; 95% CI, 8.5-67.0) and diminishes the likelihood of myasthenia gravis when the response is normal (summary negative LR, 0.16; 95% CI, 0.09-0.27). A positive response to an anticholinesterase medication (mainly edrophonium test) increases the probability of a diagnosis of myasthenia gravis (summary positive LR, 15.0; 95% CI, 7.5-31.0), and a negative response reduces the diagnostic probability of myasthenia (summary negative LR, 0.11; 95% CI, 0.06-0.21). An abnormal sleep test result is useful in confirming the diagnosis (LR, 53.0; 95% CI, 3.4-832.0). The rest and sleep tests make the probability of myasthenia unlikely when results are normal (LR, 0.52; 95% CI, 0.29-0.95 and LR, 0.01; 95% CI, 0.00-0.16, respectively). CONCLUSIONS: Items in the history and physical examination along with results of certain simple tests performed in the office (ice test, sleep test, and edrophonium test) are useful in predicting the likelihood of myasthenia gravis. These results must be interpreted with caution, however, given the high prevalence of disease in the populations reported in clinical studies. This review is limited by the small number of signs and symptoms scientifically studied and reported in the literature. Future studies evaluating the value of common historical features and easy maneuvers commonly known and practiced by experts in the clinical diagnosis of myasthenia are needed.

Cholinesterase Inhibitors↗
PubMed2002

Anti-p110 autoantibodies identify a subtype of "seronegative" myasthenia gravis with prominent oculobulbar involvement.

Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness and pathogenetic autoantibodies directed against the nicotinic acetylcholine receptor (seropositive myasthenia gravis; SPMG). Nearly 15% to 20% of MG patients do not have these antibodies (seronegative myasthenia gravis; SNMG), but several evidence indicate that these patients have circulating pathogenic autoantibodies directed against other muscle antigens. Using the TE671 rhabdomyosarcoma cell line as an antigen source, we analyzed sera from 63 SNMG and 26 SPMG patients and 26 healthy blood donors by FACS analysis. We found that 40 of 63 SNMG patients and only 1 of 26 SPMG patients had IgG binding to the TE671 cell line. None of the sera bound to the unrelated MRC5 cell line. To identify the antigen, we analyzed sera immunoreactivity in more detail by immunoprecipitation of biotinylated membrane proteins from TE671 cells. When the immunoprecipitated proteins were separated by SDS-PAGE electrophoresis and then transferred to nitrocellulose membranes, we found that SNMG IgG identify a band corresponding to a protein with a molecular weight of 110 kDa (P110), which is not recognized by seropositive MG sera. This anti-P110 immunoreactivity is significantly associated with a distinct clinical picture characterized by a prominent involvement of ocular and bulbar muscles, with frequent respiratory problems (p < 0.005), and is recognized by a specific antimuscle specific kinase (MuSK) antiserum. In a recent article, the presence of anti-MuSK antibodies was described in SNMG. Our results confirm the presence of these antibodies in SNMG and suggest that anti-P110/MuSK autoantibodies identify a subtype of SNMG in which the different pathogenesis induces the distinct clinical picture.

Adolescent↗
PubMed1996

Myasthenia gravis and upper airway obstruction.

Respiratory impairment in myasthenia gravis is usually attributed to weakness of the diaphragm and thoracic chest wall muscles, and is rarely attributed to upper airway obstruction. Myasthenia gravis is characterized by weakness of the striated muscles and usually affects those innervated by the bulbar cranial nerves. Weakness of these bulbar and upper airway muscles can lead to upper airway obstruction. To our knowledge, there are only five case reports in the literature associating upper airway obstruction with myasthenia gravis. Therefore, we attempted to further define its occurrence in myasthenia gravis patients by reviewing their flow volume loops. We present a case of upper airway obstruction causing respiratory symptoms in a myasthenia gravis patient. We then surveyed a total of 61 patients with myasthenia gravis who were tested in our pulmonary function laboratory between February 1990 and August 1993. Of these 61 patients, 12 had flow volume loops and 7 of these 12 disclosed a pattern of extrathoracic upper airway obstruction. The FVC was 80% or more in five of seven patients. Our data suggest that upper airway obstruction is much more common in patients with myasthenia gravis than previously recognized. In conclusion, we recommend the performance of flow volume loops in patients with myasthenia gravis to evaluate their respiratory impairment.

Adult↗
PubMed2006

[Case report of simultaneous coronary artery bypass grafting with cardiopulmonary bypass and total thymectomy in patient with myasthenia gravis].

In this article we want to describe the successful simultaneous operation of coronary artery bypass grafting with cardiopulmonary bypass and thymectomy in patient with ischemic heart disease and myasthenia gravis. Myasthenia gravis complicates the course of anesthesia and operation, because of the inadequate restoration of muscle function, especially of respiratory and swallowing muscles, inducing the prolonged mechanical ventilation, gastrooesophageal reflux and pulmonary infection. There are lot of different techniques of the anesthesia during myasthenia gravis - no use of any myorelaxantes, restriction of opioids, use an inhalation anaesthetics and propofol, and continuous monitoring of neuromuscular junction function. Till now it is discussable question of necessity and the time of thymectomy. This case from clinical practice shows, that the correct choice of tactics of pre- and postoperative treatment makes simultaneous coronary artery bypass grafting with cardiopulmonary bypass and thymectomy possible.

Anesthesia, General↗