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PubMed2005

Ocular Myasthenia Gravis.

Myasthenia gravis (MG) is an autoimmune disorder characterized clinically by proximal weakness and bulbar symptoms and pathologically by damage to the post-synaptic membrane at the neuromuscular junction. Ocular myasthenia gravis (ocular MG) is a form of myasthenia gravis whereby the patients' weakness is limited to the muscles of the eyes and eyelids (levator palpebrae superioris). Although not life-threatening, the limitations posed by ocular myasthenia gravis can prove disabling and distressing to patients. Acetylcholinesterase inhibitors such as pyridostigmine or neostigmine are the preferred first-line treatment for ocular myasthenia gravis, with mild cases requiring no additional intervention. However, in moderate or severe cases, treatment must be tailored to the needs and desires of the patient. Intravenous immunoglobulin, although costly, is safe and effective at treating MG. Corticosteroids are effective at reducing or eliminating symptoms and may modify the long-term course of the illness. Steroid-sparing agents such as azathioprine and mycophenolate mofetil are reasonably safe and well-tolerated alternatives to steroids. Surgical interventions such as strabismus surgery and eyelid suspension serve to correct impairments refractory to medical management. Thymectomy, although less frequently recommended, is a reasonable consideration, especially for young adults, given the potential for long-term benefit.

Journal Article↗

PubMed2002

Limb-girdle myasthenia: clinical, electrophysiological and morphological features in familial and autoimmune cases.

Limb-girdle myasthenia is an uncommon disease and includes familial and autoimmune forms. Patients present proximal muscle weakness and wasting, and sometimes fatigability, without cranial nerve involvement and fluctuations. We observed, during a 15-year period, nine subjects with limb-girdle myasthenia, (24-55 years; 8 males, 1 female) who constituted 3.2% of 281 myasthenic patients attending our department. All had previously received a diagnosis different from myasthenia. Diagnosis of limb-girdle myasthenia was established by clinical, muscle biopsy and electrophysiological assessment including repetitive nerve stimulation and single fiber electromyography. Five patients had the familial form with tubular aggregates in skeletal muscle; four patients had the autoimmune form. Patients with the familial form had a good response to acetylcholinesterase inhibitors, and the patients with the autoimmune form responded to immunotherapy. Our findings reinforce the opportunity to suspect limb-girdle myasthenia in unclassifiable proximal myopathies and to differentiate familial from autoimmune cases, especially for therapeutic implications.

Action Potentials↗

PubMed2005

Treatment of myasthenia gravis exacerbation with intravenous immunoglobulin: a randomized double-blind clinical trial.

BACKGROUND: The optimal dose of intravenous immunoglobulin (IVIG) in acute exacerbation of myasthenia gravis remains unknown. Increasing the treatment duration might provide added efficacy. OBJECTIVE: To determine the optimal dose of IVIG for treating myasthenia gravis exacerbation. DESIGN: Randomized double-blind placebo-controlled multicenter trial designed to demonstrate superiority of the 2 g/kg dose over the 1 g/kg dose of IVIG, conducted between November 13, 1996, and October 26, 2002. PARTICIPANTS: One hundred seventy-three patients aged 15 to 85 years with acute exacerbation of myasthenia gravis. INTERVENTION: Participants were randomly assigned to receive 1 g/kg of IVIG on day 1 and placebo on day 2 (group 1) vs 1 g/kg of IVIG on 2 consecutive days (group 2). MAIN OUTCOME MEASURE: Improvement in the myasthenic muscular score after 2 weeks. RESULTS: The mean improvements in the myasthenic muscular scores after 2 weeks were 15.49 points (95% confidence interval, 12.09-18.90 points) in group 1 and 19.33 points (95% confidence interval, 15.82-22.85 points) in group 2. However, the difference between the 2 groups was not significant (effect size, 3.84 [95% confidence interval, -1.03 to 8.71]; P = .12). CONCLUSION: This trial found no significant superiority of 2 g/kg over 1 g/kg of IVIG in the treatment of myasthenia gravis exacerbation.

Adolescent↗

PubMed2003

Evidence of underdiagnosis of myasthenia gravis in older people.

BACKGROUND: Myasthenia gravis is a potentially serious but treatable muscle disease caused by autoantibodies directed at the acetylcholine receptor (AChR) on the postsynaptic membrane of the neuromuscular junction. There is anecdotal evidence that the diagnosis is sometimes missed in older patients. OBJECTIVE: To examine the incidence and age distribution of positive AChR antibodies in samples referred to diagnostic laboratories in the UK, and the prevalence of positive AChR antibodies in samples from a cohort of older individuals. METHODS: Positive AChR antibody tests were identified from all UK centres registered for the assay with the European quality assurance scheme (EQAS) during 1997-99, and the age and sex specific incidence was calculated, based on the UK population. The prevalence of AChR antibodies in sera from a sample of 2000 individuals aged > or =60 years was determined. RESULTS: 3183 individuals had positive AChR antibody tests on routine screening during the years 1997 to 1999 in the UK, giving an annual incidence of 1.8/100 000. In both sexes, the age specific incidence rose steeply between the ages of 45 and 74, reaching 9.9/100 000 in men, and then fell, with a sharp decline above the age of 80. In the prevalence study, whereas only one serum from individuals aged 60-74 years was positive for AChR antibodies (0.12%), sera from eight individuals aged > or =75 years were positive (0.7%). Only one had a previous clinical diagnosis of myasthenia gravis but four others had histories of stroke or transient ischaemic attacks. CONCLUSIONS: The sharp fall in the incidence of clinically recognised myasthenia gravis in people over 80 years of age in our national AChR antibody incidence study, and the high prevalence of previously unrecognised positive AChR antibodies in those > or =75 years old, suggest that myasthenia gravis may be substantially underdiagnosed in older people.

Aged↗

PubMed2004

Myasthenia in a patient with sarcoidosis and schizophrenia.

A 44-year-old male patient was hospitalised with paranoid schizophrenia in 1985. Depot neuroleptic treatment was started which successfully prevented further psychotic relapses for the next ten years. His myasthenia gravis started with bulbar signs in 1997 and the symptoms soon became generalized. The diagnosis of myasthenia gravis was confirmed by electromyography, by positive anticholinesterase test and by the detection of anti-acetylcholine receptor antibodies in the serum. Mediastinal CT examination showed enlarged hilar lymph nodes on the left but no thymic pathology was observed. Mediastinoscopy was performed and biopsies were obtained from the affected nodes. Histology revealed sarcoidosis. The patient suffered respiratory crisis following the thoracic intervention (in September 1998). Combined oral corticosteroid (64 mg methylprednisolone/e.o.d.) and azathioprine (150 mg/day) treatment regimen was initiated and complete remission took place in both the myasthenic symptoms and the sarcoidosis. The follow-up CT scans showed no mediastinal pathology (January 2000). During steroid treatment a transient psychotic relapse occurred which was successfully managed by supplemental haloperidol medication added to his regular depot neuroleptics. The patient currently takes 150 mg/day azathioprine and receives 40 mg/month flupentixol depot i.m. His physical and mental status are stable and he has been completely symptom free in the last 24 months. The association of myasthenia gravis and sarcoidosis is very rare. To our best knowledge no case has been reported of a patient suffering from myasthenia gravis, sarcoidosis, and schizophrenia at the same time.

Adult↗

PubMed1980

Familial infantile myasthenia.

Familial infantile myasthenia is a rare type of myasthenia that usually occurs in connection with respiratory depression. The condition is characterized by (1) absence of myasthenia in the mother, (2) occurrence of a similar disorder among siblings, (3) respiratory depression at birth, (4) episodic weakness and apnea during the first two years of life, and (5) improvement with age. Since the condition responds to anticholinesterase medication, early diagnosis is important. Familial infantile myasthenia is a potential cause of sudden infant death and should be considered in infants with unexplained respiratory distress.

Adolescent↗

PubMed1982

Thymectomy in late-onset myasthenia gravis.

Between 1977 and 1979, 12 consecutive patients with myasthenia gravis who were over the age of 55 years were treated by thymectomy. In all, their conditions improved clinically; 11 of the 12 became free of the generalized features of myasthenia gravis. Nine patients required no further medication. Acetylcholine-receptor antibody titers did not change significantly. Although five patients had atrophic thymus glands, their conditions also improved. We conclude that (1) thymectomy is a safe and effective therapy for patients with myasthenia gravis who are over the age of 55 years; (2) steroids and anticholinesterase agents are not essential in the management of late-onset myasthenia gravis; and (3) reduction in acetylcholine-receptor antibody titer is not essential for beneficial clinical response.

Aged↗

PubMed2005

Striational antibodies in myasthenia gravis: reactivity and possible clinical significance.

Myasthenia gravis is an autoimmune disease caused, in most cases, by antibodies attaching to the acetylcholine receptor. Some myasthenia gravis patients have antibodies that bind in a cross-striational pattern to skeletal and heart muscle tissue sections (striational antibodies). These antibodies react with epitopes on the muscle proteins titin and ryanodine receptor, are found mainly in sera of patients with thymoma and late-onset myasthenia gravis, and may correlate with myasthenia gravis severity. Their presence may predict an unsatisfactory outcome after thymectomy. The detection of titin and ryanodine receptor antibodies provides more specific clinical information than the immunofluorescent demonstration of striational antibodies.

Autoantibodies↗

PubMed1993

Thymectomy for myasthenia gravis.

OBJECTIVES: To assess the change in clinical status of patients with generalized myasthenia gravis treated with thymectomy and to identify prognostic variables that may be of significance in optimizing patient selection. DESIGN: Retrospective review. Mean follow-up period was 41 months. SETTING: Large community hospital. PATIENTS: Thirty-seven patients (11 male and 26 female) with generalized myasthenia gravis who were referred for thymectomy if they were refractory to medical treatment or had a thymoma. This represents all patients undergoing thymectomy for myasthenia gravis between January 1982 and December 1991. INTERVENTIONS: Each patient underwent staging before and after thymectomy using a modified Osserman classification. Medication requirements were also recorded. All patients underwent transsternal thymectomy and complete mediastinal dissection. MAIN OUTCOME MEASURES: Changes in clinical stage and medication requirement before and after thymectomy; effect of patient age, sex, duration of disease, stage of disease, antibody status, histologic characteristics of the thymus, and duration of follow-up on outcome. RESULTS: Improvement after thymectomy was noted in all 37 patients. Complete remission was achieved in three patients (8%) and pharmacologic remission in 23 (62%). The remainder improved in stage, medication requirement, or both. Patients in preoperative stages IIb and IIc showed the greatest improvement. Age, sex, duration of disease, antibody status, histologic characteristics of the thymus, and duration of follow-up were not significant factors in assessing improvement. CONCLUSIONS: Transsternal thymectomy was found to be beneficial to all patients with generalized myasthenia gravis. Complete or pharmacologic remission was achieved in most patients (70%) following the procedure. Patients in preoperative stages IIb and IIc showed the greatest degree of postoperative improvement.

Adolescent↗

PubMed1999

Predictable recovery from myasthenia gravis crisis with plasma exchange: thirty-six cases and review of current management.

Adult, acquired, idiopathic, autoimmune myasthenia gravis has a well-characterized IgG anti-acetylcholine striated-muscle receptor antibody. Removal by plasma exchange is effective, established therapy to augment anti-cholinesterase and immunosuppressive therapy and is the treatment of choice for myasthenia gravis crisis. We report 36 consecutive patients referred and accepted for plasma exchange, 32 of whom were in or entering myasthenia crisis, over a 10 year period. An average of 7.8 (range 1 to 16) plasma exchange procedures were done, with uniform, significant improvement, including extubation of 13 in myasthenic crisis and discharge from hospital in all. We conclude that this is the best treatment for myasthenia gravis crisis in hospital. From recent cases, most, if not all, crises can be prevented by IVIgG or plasma exchange as out-patients with use of corticosteroid and or azathioprine.

Adolescent↗

PubMed2000

Maximal bite force and surface EMG in patients with myasthenia gravis.

Masticatory muscle strength was quantified in patients with bulbar myasthenia gravis and compared with that of patients with ocular myasthenia gravis, patients in clinical remission (whether or not pharmacological) who previously suffered from bulbar myasthenia gravis, and healthy subjects. Maximal bite force and maximal activity of the masseter and temporalis muscles and of the submental muscle complex were measured. Bite force was decreased in the patients with bulbar myasthenia gravis, but was normal in the patients in the clinical remission group and in the ocular group. These findings were consistent with the results of electromyographic data. Although subjective reports of masticatory muscle weakness provide valuable information, quantitative measurements provide more information about the degree of muscle weakness of individual muscles. This is especially important for longitudinal evaluation of therapy in individual patients and for pharmacotherapeutic research.

Adult↗

PubMed1981

A comparison of stapedial reflex fatigue with repetitive stimulation and single-fiber EMG in myasthenia gravis.

The pattern of stapedial reflex fatigue in response to pulsed acoustic stimulation was measured and compared to results of repetitive nerve stimulation and single-fiber electromyography (EMG) in 89 patients with myasthenia gravis. Studies were also made on 22 patients with other neuromuscular disorders and 40 control subjects with no evidence of neuromuscular impairment. Stapedial reflex fatigue exceeded normal control values in 84% of the patients with myasthenia gravis. Repetitive stimulation and single-fiber EMG measurements were abnormal in 56% and 91% of this same population, respectively. Stapedial reflex abnormalities were most prevalent in patients with mild forms of myasthenia (predominantly ocular or oropharyngeal weakness). Of 22 nonmyasthenic patients with neuromuscular disease tested, 6 had abnormal stapedial reflex fatigue according to our normal values, indicating that this form of testing also detects other diseases of the motor unit. The measurement of stapedial reflex fatigue is painless, is easy to perform, and requires minimal patient cooperation. Due to the relatively high occurrence of abnormal stapedial reflex fatigue in patients with myasthenia gravis, this procedure appears to have considerable potential value in screening and monitoring patients for the presence of defects in neuromuscular transmission.

Acoustic Stimulation↗

PubMed1982

Immune regulation in myasthenia gravis: evidence for an increased suppressor T-cell population.

The production of anti-acetylcholine receptor antibodies in myasthenia gravis represents a persistent and unexplained break in self-tolerance. The studies reported here demonstrate an altered regulatory T-cell population with an increase in the percentage of circulating T-suppressor cells as defined by two independently developed murine monoclonal antibody markers. Leu 2a- and OKT8a-positive cells were significantly increased within the T-cell population in myasthenia gravis (25.0 +/- 6.4% versus 20.7 +/- 2.9% and 34.9 +/- 7.0% versus 26.0 +/- 3.2%, respectively) compared to an age- and sex-equivalent group. In addition, the circulating total T-cell population was reduced in myasthenia gravis. Patients with symptomatically uncontrolled disease (with or without immunosuppression) demonstrated significantly altered ratios of helper to suppressor T-cells, while patients whose myasthenia symptoms were controlled did not differ from normal subjects.

Adolescent↗

PubMed1984

Enzyme-linked immunosorbent assay for antibody against the nicotinic acetylcholine receptor in human myasthenia gravis.

Antibody against acetylcholine receptor (AChR) of human skeletal muscle was measured using enzyme-linked immunosorbent assay and found in 23 (74%) of 31 Japanese patients with generalized myasthenia gravis. In 15 patients with generalized myasthenia gravis who had not undergone thymectomy and who were not receiving adrenocorticosteroids, the antibody was found in 13 (87%). Antibody was also found in 13 (54%) of 24 patients with myasthenia gravis against AChR fractions obtained from fetal calf thymus. Based on the subunit structures of the AChR protein, the double precipitation assay using iodine 125-alpha-bungarotoxin is also capable of detecting antibody against the toxin binding site, by cross reactivity. This is among the first reports of experiments in which enzyme-linked immunosorbent assay was used to measure the antibodies in human myasthenia gravis and provides evidence of anti-AChR antibody against antigens from fetal calf thymus.

Autoantibodies↗

PubMed1992

Ryanodine receptor autoantibodies in myasthenia gravis patients with a thymoma.

Sera from patients with myasthenia gravis were examined by Western blot for the presence of antibodies to proteins of the sarcoplasmic reticulum from rabbit skeletal muscle. Fourteen of 30 patients with myasthenia gravis and a thymoma had IgG autoantibodies to the calcium release channel of the sarcoplasmic reticulum (the ryanodine receptor), which plays a crucial role in the mechanism of excitation-contraction coupling in striated muscle. Ryanodine receptor autoantibodies were not detected in any of the 45 sera from patients with myasthenia gravis without a thymoma. Ryanodine receptor autoantibodies may have pathogenetic relevance in thymoma-associated myasthenia gravis.

Autoantibodies↗

PubMed1994

Organ-specific autoantigens induce transforming growth factor-beta mRNA expression in mononuclear cells in multiple sclerosis and myasthenia gravis.

Multiple sclerosis (MS) is characterized by patchy accumulations of inflammatory cells combined with demyelination. There are mononuclear cells in blood and cerebrospinal fluid of patients with MS that produce interferon-gamma and interleukin-4 in response to myelin basic protein (MBP) and proteolipid protein (PLP). Here we describe autoantigen-induced production of transforming growth factor-beta (TGF-beta). This multifunctional cytokine has inhibitory effects on the growth, differentiation, and effector functions of activated T cells. Blood and cerebrospinal fluid cells were exposed in short-term cultures to MBP and PLP and, after hybridization with complementary DNA oligonucleotide probes, they were evaluated for TGF-beta mRNA expression. Patients with MS had higher numbers of MBP- and PLP-responsive TGF-beta mRNA expressing cells in blood compared with control patients with other neurological diseases or myasthenia gravis and a five- and threefold further increment in their cerebrospinal fluid. In blood of patients with myasthenia gravis, where the acetylcholine receptor (AChR) is a target for autoaggressive immunity, there were increased levels of AChR-responsive TGF-beta mRNA expressing cells. Thymectomized myasthenia gravis patients showed higher levels of TGF-beta mRNA expressing cells compared with patients not thymectomized. Numbers of cells responding to AChR in MS and MBP in myasthenia gravis did not differ from numbers found in absence of antigen. Patients with other neurological diseases showed infrequent and low responses to MBP, PLP, and AChR. Diseases with presumed autoimmune pathogenesis are associated with organ-specific autoantigen-induced TGF-beta production, which is increased after thymectomy.

Adult↗

PubMed2003

Ryanodine receptor antibodies in myasthenia gravis: epitope mapping and effect on calcium release in vitro.

Patients with myasthenia gravis can have antibodies against skeletal muscle ryanodine receptor (Ry1), the sarcoplasmic reticulum calcium-release channel, which plays a crucial role in excitation-contraction coupling. We have screened a panel of overlapping Ry1 fusion proteins with Ry1 antibody-containing myasthenia gravis sera to identify the main immunogenic region. The pc2 Ry1 fusion protein representing a Ry1 region close to the N-terminus (residues 799-1172) was identified as the main immunogenic region for the antibodies. The binding kinetics of the Ry1 antibodies to the pc2 Ry1 fusion protein were tested using an optical biosensor. Ry1 antibodies in the IgG fraction from sera of patients with myasthenia gravis bound with high affinity and with a stoichiometry of 1:1. The functional effect of these Ry1 antibodies was tested in an in vitro Ca2+-release assay. The Ry1 antibodies induced a twofold increase of the half-maximal concentration for 4-Cl-m-cresol-induced Ca2+ release from terminal cisternae vesicles but had no effect on V(max). The effect on 4-Cl-m-cresol-induced Ca2+ release was specific, as preincubation of the active IgG fraction with the pc2 Ry1 fusion protein abolished the inhibition. These data suggest that the Ry1 sequence defined by residues 799-1172 is involved in the regulation of Ry1 function, and that this regulation could be functionally affected in vivo in patients with myasthenia gravis.

Autoantibodies↗

PubMed1994

Variable effect of calcium channel blockers on the decremental response in experimental autoimmune myasthenia gravis.

We tested the effect of intravenous administration of verapamil and nimodipine on the decremental response in rabbits with experimental autoimmune myasthenia. Nimodipine produced an immediate augmentation of the decremental response to 3-Hz nerve stimulation, which lasted about 30 min. In contrast, verapamil caused marked amelioration of the decrement beginning 30 min after injection. Our findings are consistent with previous reports suggesting that verapamil has a presynaptic effect of enhanced acetylcholine release at the neuromuscular junction. Since evaluation of a drug effect in vivo in animals with experimental autoimmune myasthenia gravis may be more pertinent to its effect on patients with myasthenia gravis (MG), verapamil might prove to be safer in MG than nimodipine. However, due to the additional effects of calcium channel blockers, the safety of their use in myasthenia gravis cannot be inferred from the experimental results.

Action Potentials↗