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PubMed1980

Stapedius reflexometry. A diagnostic test of myasthenia gravis.

Contraction of the stapedius muscle can be measured by electroacoustic impedance bridge. Muscle weakness and easy fatiguability which are cardinal features of myasthenia gravis (MG) are manifested by increased threshold and early decay of the stapedius reflex. This can be used as an objective test in the diagnosis of myasthenia gravis. Stapedius reflex was measured using Madsen Zo72 electroacoustic impedance bridge in 10 patients with myasthenia gravis and in an equal number of controls. The test was done before and 30 min after intramuscular injection of neostigmin. All patients with myasthenia gravis showed an elevated reflex threshold and 5 patients showed reflex decay. These findings reverted to normal after neostigmin injection. Stapedius reflexometry is a simple objective test for the diagnosis of myasthenia gravis.

Acoustic Impedance Tests↗

PubMed1981

The pathogenesis of myasthenia gravis--a hypothesis.

We have suggested that a thymic factor plays a critical role in the pathogenesis of myasthenia gravis. The presence of specific ACh R antibodies in more than 90% of patients with myasthenia gravis has provided us with a marker for this disorder and has greatly increased our understanding of the pathophysiology. These antibodies can induce physiological parameters similar to those seen in myasthenia gravis following passive transfer to experimental animals and can accelerate degradation of ACh R in myotube culture. However, clinical studies suggest that additional factors of thymic origin are necessary for the development of the clinical features of myasthenia gravis. While the nature of the thymic factor(s) is speculative, this hypothesis has a significant clinical implication as it argues for an early, total thymectomy as the treatment of choice for myasthenia gravis.

Antibodies↗

PubMed1995

Coexistence of scleromyositis associated with PM-Scl antibody and myasthenia.

Myasthenia gravis coexists in about 15% of the cases with other autoimmune diseases. Association with polymyositis or dermatomyositis is very rare, although myasthenic reaction is not infrequent in typical polymyositis and myopathic changes may occur in cases of myasthenia. This is the first case of coexistence of myasthenia and scleromyositis, associated with PM-Scl antibody as an immune marker. The patient was found to have persistent thymus. Myasthenia preceded scleromyositis for 9 yr, was at periods asymptomatic, and recurred simultaneously with development of scleromyositis. Scleromyositis should be added to the list of autoimmune disorders coexistent with myasthenia.

Autoantibodies↗

PubMed2004

Ocular myasthenia gravis.

Myasthenia gravis may be limited solely to the eyes (ocular myasthenia) or may have systemic manifestations (generalized myasthenia). Most patients display blepharoptosis or ophthalmoparesis, resulting in diplopia, but the ocular motility disorder may take many forms. The diagnosis is often elucidated by variable muscle weakness with fatigability noted in the history and on examination. The ice test has supplanted the need for the edrophonium (Tensilon) test in many cases of ocular myasthenia. Therapy may be challenging, because many ocular myasthenics do not achieve significant clinical improvement with acetylcholinesterase inhibitors alone. Immunomodulatory treatment,such as systemic corticosteroids, is frequently effective, and emerging data suggest that this type of therapy may reduce the likelihood of ocular myasthenia becoming generalized.

Humans↗

PubMed2005

Dental management of patients with myasthenia gravis: a literature review.

Myasthenia gravis is a chronic neuromuscular disease characterized by muscular weakness and fatigability. Dental management of patients diagnosed with myasthenia gravis presents a challenge to the dental profession. A MEDLINE search of the English medical (limited to provision in dental care) and dental literature on myasthenia gravis and dental management published between 1975 and 2004 was conducted. In the dental literature, 12 articles were found, and only a few focused on myasthenia gravis and dental care. The purpose of this article was to review and summarize the clinical signs and symptoms associated with myasthenia gravis, highlighting the role of the dental profession in the process of the diagnosis and management of the oral and dental complications that might be associated with the disease, while avoiding myasthenic crisis.

Anesthetics, Local↗

PubMed1996

Extended thymectomy for myasthenia gravis patients: a 20-year review.

BACKGROUND: Since 1973 we have performed extended thymectomy for myasthenia gravis because of the presence of thymic tissue in the anterior mediastinal fatty tissue. Follow-up results were reviewed and influencing factors were investigated. METHODS: Three hundred seventy-five patients with myasthenia gravis (286 nonthymomatous and 89 thymomatous) who have undergone extended thymectomies were reviewed. The status of the patients was evaluated as follows: A (remission), B (improvement), C (no change), D (deterioration), E (death due to myasthenia gravis). Evaluation was performed at 3 and 6 months, and at 1, 3, 5, 10, 15, and 20 years. The effectiveness of the operation was estimated by the remission rate (RR = A/Total number of patients evaluated) and the palliation rate (PR = A + B/Total number of patients evaluated) at each point. RESULTS: Remission rates of the nonthymomatous patients were 15.2% (3 months), 15.9% (6 months), 22.4% (1 year), 36.9% (3 years), 45.8% (5 years), 55.7% (10 years), 67.2% (15 years), and 50.0% (20 years). Remission rates in the thymomatous patients were 13.6% (3 months), 17.5% (6 months), 27.5% (1 year), 32.4% (3 years), 23.0% (5 years), 30.0% (10 years), 31.8% (15 years), and 37.5% (20 years). Absence of thymoma, younger age, and short duration of the disease were favorable prognostic factors. Thymectomy was effective also in patients with ocular myasthenia gravis. Preoperative steroid administration did not improve the outcome. CONCLUSIONS: Extended thymectomy is an excellent operative procedure for myasthenia gravis in both nonthymomatous and thymomatous patients.

Adult↗

PubMed1996

Delayed remission after thymectomy for myasthenia gravis of the purely ocular type.

Twenty-two cases of purely ocular myasthenia gravis were reviewed to evaluate the long-term effects of thymectomy. Remission rate increased gradually with time (11.8% at 3 years, 23.1% at 5 years, and 33.3% at 10 years). Analysis of factors influencing remission with time showed that patients with short duration of illness attained remission significantly earlier (p = 0.035 at 5-year follow-up). One of 22 patients with purely ocular myasthenia gravis (4.5%) had disease progression. Because ocular myasthenia gravis often progresses to the generalized type and because duration of illness before operation is one of important factors influencing remission, we conclude that thymectomy in the earlier stages of the disease is the preferred treatment for ocular myasthenia gravis, just as for generalized myasthenia gravis.

Adolescent↗

PubMed2001

Myasthenia gravis with autoimmune autonomic neuropathy.

The autoantibodies that impair neuromuscular junction transmission in myasthenia gravis are specific for the nicotinic acetylcholine receptor (AChR) of muscle. Antibodies specific for AChRs in ganglionic neurons are found in a majority of patients with subacute autonomic neuropathy. Dysautonomia is not a recognized feature of myasthenia gravis, but there have been rare reports of myasthenia gravis coexisting with autonomic failure, usually in association with thymoma. Here we report seven patients who had myasthenia gravis with subacute autonomic failure. Their autonomic dysfunction ranged from isolated gastroparesis to severe panautonomic failure. Gastrointestinal dysmotility was a common feature. All had antibodies against muscle AChR, and three (all of whom had thymoma) had antibodies against neuronal ganglionic AChRs. In several patients, gastrointestinal function improved clinically after administration of an acetylcholinesterase inhibitor. These observations support a rare but definite clinical association between myasthenia gravis and autonomic failure and strengthen the concept that subacute autonomic neuropathy is an autoimmune disorder.

Adult↗

PubMed2001

Active management in patients with ocular manifestations of myasthenia gravis.

PURPOSE: Myasthenia gravis can cause variable strabismus with disabling diplopia and/or poor cosmesis. A retrospective study of a group of patients with myasthenia gravis or 'myasthenia gravis like' syndromes was made. METHODS: The study group consisted of patients who had undergone botulinum toxin treatment and/or surgery for disabling diplopia, poor cosmesis or both. Surgical treatment was by conventional techniques including recess/resect, posterior fixation, superior oblique tenotomy and adjustable sutures. RESULTS: There were 9 patients in the study group (8 female, 1 male). Age at surgery ranged from 21 to 59 years (mean 46 years). Six were symptom-free following treatment. Two, although symptomatically improved, had occasional diplopia. One patient failed treatment and required an occlusive contact lens. CONCLUSIONS: The ocular manifestations of myasthenia gravis or 'myasthenia gravis like' syndromes may respond to surgery and/or botulinum toxin injection. Active intervention should be considered when deviations become stable. To our knowledge this is the first report of the use of botulinum toxin in such patients.

Adolescent↗

PubMed1976

Studies of human myasthenia gravis: electrophysiological and ultrastructural evidence compatible with antibody attachment to acetylcholine receptor complex.

Neuromuscular junctions from patients with early onset and chronic myasthenia gravis were examined by electrophysiological and ultrastructural techniques. Acetylcholine (AcCh) sensitivities were reduced by 34-63% in early onset myasthenia and 60-80% in chronic myasthenia. Ultrastructural analysis revealed that virtually all junctional folds of the early onset patients were intact but that the AcCh-receptor-rich crests of these folds were uniformly covered by an attached layer of 30 X 70 A particles arranged in small tufts or rosettes. In chronic myasthenic endplates, however, junctional fold crests were destroyed, apparently being replaced by vesicular membrane debris similarly labeled by tufts of 30 X 70 A particles. Thus, the initial reduction in junctional AcCh sensitivity observed in early onset myasthenia gravis may be attributed at least in part to in situ masking or inactivation of AcCh receptors, whereas the marked decrease in AcCh sensitivity observed in the chronic myasthenic patient may represent a combination of two factors: (a) in situ masking of AcCh receptors and (b) destruction of the receptor-containing crests of the junctional folds. These observations are compatible with an autoimmune etiology of myasthenia gravis initially involving an apparent antibody attachment to one or more components of the functional AcCh receptor complex, followed by systematic destruction and removal of junctional folds by both humoral and cell-mediated autoimmune responses.

Action Potentials↗

PubMed1994

Involvement of human muscle acetylcholine receptor alpha-subunit gene (CHRNA) in susceptibility to myasthenia gravis.

The muscle acetylcholine receptor is the major target of the autoimmune response in generalized myasthenia gravis. To investigate the role of the gene encoding the alpha subunit of the receptor (CHRNA), two stable polymorphic d[(GT).(CA)]dinucleotide repeats, designated HB and BB, were characterized within the first intron of CHRNA. The HB*14 allele conferred a relative risk for myasthenia gravis of 2.5 in 81 unrelated patients compared with 100 control subjects. Very significantly, family analysis based on haplotype segregation data indicated that parental haplotypes associated with HB*14 always segregated to the child with myasthenia gravis (P < 0.0002 for the comparison with the transmission of haplotypes not bearing HB*14), whereas their transmission to unaffected siblings was equilibrated. Myasthenia gravis patients also showed a high frequency of microsatellite variants unseen in controls. These findings implicate the CHRNA in susceptibility to myasthenia gravis.

Adolescent↗

PubMed2001

Difference in sensitivity to vecuronium between patients with ocular and generalized myasthenia gravis.

Patients with myasthenia gravis show sensitivity to non-depolarizing neuromuscular blocking drugs, but little is known about differences in this sensitivity between types of myasthenia. In 10 patients with ocular myasthenia gravis and 10 with generalized myasthenia gravis, twitch tension was monitored in the adductor pollicis muscle by supramaximal train-of-four stimulation of the ulnar nerve during anaesthesia with sevoflurane 2.5% and nitrous oxide 60%. After baseline measurement, an initial dose of vecuronium 10 microg kg(-1) was given. When the twitch height stabilized (maximum block after the first 10 microg kg(-1)), the next incremental dose of 10 microg kg(-1) was given and repeated until block, defined as [1-(first twitch/baseline first twitch)] x 100 reached 90%. Maximum block after the first dose of vecuronium in ocular patients was significantly less than that in generalized patients (median 51 vs 91%; P<0.05). Onset of block after the first dose of vecuronium was significantly slower in ocular than in generalized myasthenic patients (mean 300 vs 200 s; P<0.05). Doses required to attain a block of 90% or more were significantly higher in ocular than in generalized patients (median 20 vs 10 microg kg(-1); P<0.05). Clinicians should consider the type of disease according to the Osserman classification when using non-depolarizing neuromuscular. blocking drugs in patients with myasthenia gravis.

Adult↗

PubMed1997

Mapping of the familial infantile myasthenia (congenital myasthenic syndrome type Ia) gene to chromosome 17p with evidence of genetic homogeneity.

Familial infantile myasthenia is an autosomal recessive disorder, recently classified as congenital myasthenic syndrome type Ia. Onset of symptoms is at birth to early childhood with significant myasthenic weakness and possible respiratory distress, followed later in life by symptoms of mild to moderate myasthenia. Thirty-six patients of 12 families, seven of them consanguineous, were used to map the familial infantile myasthenia gene. A combination of linkage search through the genome, DNA pooling and homozygosity mapping were employed resulting in the localisation of this disease locus to the telomeric region of chromosome 17p. A maximum lod score of 9.28 at theta = 0.034 was obtained between the disease locus and marker locus D17S1537. Haplotype analysis showed all families to be consistent with linkage to this region thus providing evidence for genetic homogeneity of familial infantile myasthenia. Multipoint linkage analysis mapped the disease gene in the approximately 4.0 cM interval between marker loci D17S1537 and D17S1298 with a maximum multipoint lod score of 12.07. Haplotype analysis and homozygosity by descent in affected individuals of the consanguineous families revealed results in agreement with the confinement of the familial infantile myasthenia region within the interval between marker loci D17S1537 and D17S1298.

Chromosome Mapping↗

PubMed2005

Myasthenia gravis: lessons for the emergency physician.

We describe three patients with myasthenia gravis who presented to the emergency department - one with a previously established diagnosis and two others who were newly diagnosed as a result of workup initiated in the emergency department. Differential diagnosis of conditions causing neuromuscular weakness is broad; however, a key aspect of myasthenia gravis is fluctuating muscle weakness that increases with repeated use and improves with rest. Both newly diagnosed patients presented with ocular complaints, a common finding in myasthenia gravis. The third patient presented with a potentially life-threatening myasthenic crisis. Key points of discussion include: bedside tests to diagnose myasthenia gravis; distinction between cholinergic versus myasthenic crisis; and emergency department considerations when intubating a myasthenia gravis patient becomes necessary.

Aged↗

PubMed1975

Antibodies against nicotinic acetylcholine receptor and skeletal muscle in human and experimental myasthenia gravis.

Using rocket immunoelectrophoresis and indirect haemagglutination tests, antibodies to nicotinic acetylcholine receptor (n-AChR) from Torpedo marmorata were detected in sera from rabbits with experimental myasthenia but not in sera from patients with myasthenia gravis or in rabbit antisera to a partly purified skeletal muscle antigen. Antibodies to this antigen were demonstrated in sera from patients with myasthenia gravis but not in sera from rabbits with experimental myasthenia. The results indicate that there is no immunological cross-reaction between the muscle antigen and n-AChR from Torpedo marmorata, and little or no cross-reactivity between these n-AChR antibodies and possible muscle n-AChR antibodies in myasthenia gravis patients.

Acetylcholine↗

PubMed1992

The T-cell repertoire in myasthenia gravis involves multiple cholinergic receptor epitopes.

Antibodies against the alpha-subunit of the acetylcholine receptor (AChR) are found in most patients with myasthenia gravis and are considered to contribute to the receptor damage which leads to the characteristic signs and symptoms of the disease. This B-cell response is T-cell driven. Elevated T-cell reactivities to AChR and its alpha-subunit have been described in myasthenia gravis, and AChR alpha-subunit peptide reactive T-cell lines and clones preferentially recognizing certain defined sequence segments have been reported, thereby disclosing the possibility of specific immunotherapy. We have defined the T-cell repertoire to AChR, its alpha-subunit and the synthetic peptide sequences 100-117, 113-130, 143-163, 161-179, 207-225, 221-240, and 235-255 of the alpha-subunit in an immunospot assay which is based on secretion of interferon-gamma (IFN-gamma) by individual memory T cells upon stimulation with specific antigen in short-term cultures. Most patients with myasthenia gravis displayed T-cell reactivities to 1 to 6 different peptides. The mean numbers of T cells recognizing individual peptides varied in the myasthenia gravis patients between 1 per 77,000 and 1 per 167,000 peripheral blood mononuclear cells. None of the seven peptides evaluated could be identified as an immunodominant T-cell epitope, and any of them was found to dominate in individual patients. The numbers of T cells reacting with AChR and recombinant human AChR alpha-subunit were slightly higher (mean numbers 1 per 26,000 and 1 per 50,000 mononuclear cells, respectively). Such cells, as well as AChR alpha-subunit peptide reactive T cells, were also found in patients with other neurological diseases and in healthy subjects, but at lower frequencies and numbers. In myasthenia gravis, the elevated numbers of memory T cells recognizing multiple AChR alpha-subunit peptides may be crucial for the development of the disease, and the IFN-gamma released by such T cells might be important for its perpetuation.

Adolescent↗

PubMed2006

Epidemiology of myasthenia gravis with anti-muscle specific kinase antibodies in The Netherlands.

The epidemiology of myasthenia gravis subtypes and the frequency of antibodies to muscle-specific kinase (MuSK) was studied in patients with generalised myasthenia gravis without anti-acetylcholine receptor antibodies who had an onset of symptoms between 1990 and 2004 in a well-defined region in The Netherlands. The nationwide prevalence and incidence of myasthenia gravis with anti-MuSK antibodies were also studied. MuSK antibodies were found in 22% of patients with generalised myasthenia gravis without anti-acetylcholine receptor antibodies. Nationwide, 35 patients with MuSK myasthenia gravis were identified, yielding a prevalence of 1.9 per million (95% confidence interval (CI) 1.22 to 2.59) and an annual incidence 0.10 per million person-years (95% CI 0.06 to 0.14).

Adolescent↗

PubMed1972

A genetic study of infantile and juvenile myasthenia gravis.

From the present study, and from reports in the literature, two forms of childhood myasthenia emerge. There is an early-onset form (with onset of symptoms under 2 years of age) where the illness is milder but more persistent, and where there is frequent occurrence of myasthenia in sibs. Such cases are likely to be inherited as an autosomal recessive, although it is possible that they represent the extreme edge of a multifactorial distribution of combined genetic and environmental aetiology. The second group (with onset of symptoms between the age of 2 and 20 years) clinically resembles adult myasthenia, which is associated with autoimmunity and an increased incidence of thyroid dysfunction. Some genetic contribution occurs in this form but it is less marked than with the early-onset cases and there is no recognizable pattern of inheritance. As secondary cases are even less common among the families of adult myasthenics, it is likely that individuals with most genetic predisposition to myasthenia tend to develop symptoms early, and that non-genetic factors are relatively more important for the development of myasthenia in adults.

Adolescent↗