Edrophonium responsiveness not necessarily diagnostic of myasthenia gravis

Uneqivocally positive edrophonium tests, both clinically and electrophysiologically, were observed in a classic case of the Lambert-Eaton myasthenic syndrome. A review of the literature revealed that a positive edrophonium response has been reported in a majority of cases of myasthenia gravis (MG) and overlap myasthenic syndrome and in some cases of the Lambert-Eaton myasthenic syndrome, botulism, congenital myasthenic syndrome, drug-induced myasthenic syndrome, the Guillain-Barre syndrome, and amyotrophic lateral sclerosis. From this, we conclude that an unequivocally positive edrophonium test alone is not necessarily diagnostic of MG and that the diagnosis of MG should be based on the clinical features together with edrophonium-responsiveness and other laboratory findings.     

SFEMG in ocular myasthenia gravis diagnosis.

BACKGROUND AND OBJECTIVE: In typical cases, the patient's history and clinical examination make it possible to diagnose ocular myasthenia gravis (OMG). But, in many cases a clear clinical picture is not present and OMG diagnosis is very difficult because gold diagnostic standard tests are not available. The diagnostic tests for OMG are usually unable to display a good sensitivity and specificity simultaneously. In this paper, we studied 86 cases submitted for suspected OMG. METHODS: The patients were studied clinically and with various other tests used in OMG diagnosis (SFEMG, repetitive nerve stimulation, Ab anti AChR titration, tensilon test). RESULTS AND CONCLUSION: SFEMG showed the highest sensitivity (100%) while Ab anti AChR showed the highest specificity (100%). To our knowledge this is the largest population of suspected OMG studied using most of the diagnostic parameters, reported in the literature.     

Masseteric repetitive nerve stimulation in the diagnosis of myasthenia gravis.

OBJECTIVE: (1) to develop a method for masseteric repetitive nerve stimulation (RNS) and to obtain normative data for amplitude and area decrement of the muscle (M) response. (2) To investigate myasthenia gravis (MG) patients with masseteric RNS. Masticatory muscles are frequently affected in MG, but no RNS test is available to investigate this district. METHODS: Fifteen healthy subjects and 17 MG patients were examined. The masseteric nerve was stimulated by a monopolar needle (cathode), inserted between the mandibular incisure and the zygomatic arch, and a surface electrode (anode), on the contralateral cheek. Masseteric M response was recorded using surface electrodes on the muscle belly and below the mandibular angle. Stimuli were delivered at 3 Hz in trains of 9, at rest and after isometric effort. RESULTS: Normal subjects: mean amplitude decrement was 0.3+/-1.2% at rest, and 1.9+/-1.3% after isometric effort. Patients: 15 patients (88%) were positive on masseteric RNS; in 3 of these it was the only positive RNS test. The extent of decrement observed in masseter muscle was significantly greater than in trapezius muscle. CONCLUSIONS: Masseteric RNS is a simple and well-tolerated procedure; it offers a new possibility in testing the cranial muscles in disorders of neuromuscular transmission.     

The diagnosis of thymoma in myasthenia gravis

Between 10 and 15 per cent of patients with myasthenia gravis (MG) have a thymoma. We have evaluated the possibility of detecting such tumours on the basis of clinical features, radiological findings and immunological tests in a group of 70 MG patients. The mean age at onset of myasthenic symptoms was 67.6 years in the thymoma group and 33.8 years in the non-thymoma group. Otherwise, the clinical picture was similar. Radiological examination revealed a mediastinal mass in 2 patients. Six of the 70 MG sera contained antibodies to a citric acid (CA) extract of striated muscle. At thymectomy, a thymoma was found in these 6 patients. None of the remaining 64 patients had evidence of a thymoma. Antibodies to AChR were detected in 52 of the 70 MG sera. There was no relation between titres of AChR and CA antibodies. Three out of 5 sera from non-MG patients with a thymoma contained CA antibodies. Apparently, this assay is a valuable technique for the identification of a thymoma at an early stage.     

重症肌无力胸腺异常的影像学诊断(附120例临床分析)

评价重症肌无力胸腺异常的影像学检查手段。方法：对经手术病检证实的１２０例重症肌无力伴胸腺异常患者的影像学改变与病诊断进行对比研究。结果：ＣＴ和ＭＲＩ诊断胸腺瘤、胸腺增生的灵敏度明显高于传统Ｘ线检查（Ｃ线平片及体层摄影）（Ｐ〈０．０５）,而ＣＴ和ＭＲＩ之间无明显差异;     

The stapedius reflex in the diagnosis of myasthenia gravis

The contralateral stapedius reflex, elicited by a clearly-defined auditory stimulus, was studied in 3 patients with myasthenia gravis. The reflex was assessed by recording the change which occurred in the acoustic impedance of the middle ear. In all patients a decay (decrement) of the reflex was found, interpreted as a sign of increased fatiguability at the neuromuscular junction of the stapedius muscle. The reflex recovered rapidly after the intravenous injection of a cholinesterase inhibitor (Tensilone?g;).It is concluded that the stapedius reflex test can be of value in the diagnosis of myasthenia gravis, since it can be well-standardized, involves a muscle innervated by the facial nerve and is not disturbing to the patient, whose active cooperation is not necessary.     

Electrophysiologic diagnosis of myasthenia gravis and the regional curare test.

Two hundred and fifty consecutive patients were evaluated for myasthenia gravis with repetitive supramaximal stimulation of peripheral nerves and regional curare administration when necessary. Among patients with definite generalized myasthenia gravis, 72 percent had abnormal responses to repetitive supramaximal stimulation alone and another 17 percent had abnormal responses after regional curare administration. Among those with possible generalized myasthenia gravis, 15 percent had abnormal responses to repetitive supramaximal stimulation and another 12 percent had abnormal responses after regional curare administration. Of those with only ocular symptoms, 46 percent had abnormal responses to repetitive supramaximal stimulation before or after regional curare administration, suggesting generalized involvement. Myasthenia gravis has not developed subsequently in any of the equivocal patients with negative electric tests. We have found these electric procedures to be simple, safe, and at least as effective as other methods in diagnosing myasthenia gravis.     

Saccadic eye movements analysis in the early diagnosis of myasthenia gravis.

Saccadic eye movements were examined by electro-oculography in 21 patients with suspected myasthenia gravis. The presence of dissociated nystagmus and quiver eye movements was also assessed. The aim of the study was to assess the diagnostic value of saccadic abnormalities in the early stage of the disease. Pathological oculographic findings consisted of intra and post saccadic disorders and intersaccadic variability. A fatigue test was useful in detecting latent disorders in most patients. A Tensilon test was positive in 11 out of 16 patients with oculographic abnormalities. Diagnostic problems, apparently paradoxical findings and differential involvement of extraocular muscle fibers are discussed.     

The laboratory diagnosis of mild myasthenia gravis

We report our experience with single-fiber electromyogrphy (SF-EMG), acetylcholine receptor antibody assays, and Lancaster Red-Green tests of ocular motility with edrophonium chloride in the diagnosis of myasthenia gravis (MG). Over a period of almost 3 years, 43 patients in whom repetitive-stimulation nerve conduction tests were nondiagnostic had SF-EMG studies; 34 (79%) were positive. Examination of more proximal muscles yielded a higher likelihood of positive results. Anti-acetylcholine receptor antibodies were detected in 25 (71%) of 35 patients whose sera were assayed, and Lancaster Red-Green tests of ocular motility were positive in 13 (81%) of 16 patients studied. No single test was superior in diagnosing MG, but the three were complementary. If patients with mild MG are tested by all three methods, at least 95% should have laboratory confirmation of MG.     

Arthritis in myasthenia gravis.

Seven patients with myasthenia gravis developed clinical signs of arthropathy. In two patients, the symptoms were due to a deforming rheumatoid arthritis and the myasthenic symptoms appeared as a transitory phase during the course of the disease. Muscle antibodies of IgG class were demonstrated with sera from both patients. Autoreactivity between muscle antibodies and rheumatoid factor was detected in one patient. Both patients died from sudden cardiac failure. Necropsy was performed in one and revealed a spotty myocardial necrosis. One patient had juvenile rheumatoid arthritis. Two patients had mild articular symptoms with indices of multivisceral disease and serological findings indicating a systemic lupus erythematous. One patient had classical ankylosing spondylitis, and one, unspecified arthropathy.     

Open-loop and closed-loop optokinetic nystagmus (OKN) in myasthenia gravis and nonmyasthenic subjects

Optokinetic nystagmus (OKN) eye movements of myasthenia gravis (MG) and nonmyasthenic ocular palsies, and normal subjects were examined under closed-loop and open-loop conditions. The open-loop OKN condition was achieved by adding the signal of eye-movement velocity of OKN to the computer-generated signal controlling the stimulus grating moving. The OKN was recorded by means of electromagnetic search scleral coil technique. In MG patients, the open-loop gains of OKN increased significantly after the intramuscular injection of an acetylcholinesterase inhibitor, neostigmine, while the closed-loop OKN gains were not significantly changed. Both the closed-loop and open-loop OKN gains of normal subjects and nonmyasthenic patients were not increased for the administration of neostigmine. The experimental results indicated that the open-loop OKN gain could be sensitive to reflect the changes of the function of neuromuscular junction in MG patients.     

Familial myasthenia gravis.

A family is reported in which myasthenia gravis and thyroid disease occur over three generations. The grandmother and granddaughter have ocular myasthenia and an aunt in the second generation had generalised myasthenia gravis with a thymoma. The pattern of histocompatibility antigens (HLA) haplotypes, anti-AChR antibodies, anti-striate muscle antibodies and thyroid disease is described. The haplotype HLA-A1, B8 was found in affected members of the first and third generation but the family study showed that this was not the same haplotype because the HLA-A1, B8 haplotype in the third generation was contributed by an unaffected person marrying into the family in the second generation.     

Concentric-needle single-fiber electromyography for the diagnosis of myasthenia gravis

The goal of this study was to estimate the accuracy of concentric-needle single-fiber electromyography (CN-SFEMG) for the diagnosis of myasthenia gravis (MG). A consecutive series of patients referred for CN-SFEMG was evaluated by an investigator blinded to the results of CN-SFEMG in order to determine the presence or absence of MG using an independent reference standard. Sensitivity, specificity, predictive values, and likelihood ratios were calculated. The study population included 51 patients (21 with MG). CN-SFEMG was normal in 34 patients (67%) and abnormal in 17 (33%). The sensitivity of CN-SFEMG for the diagnosis of MG was 0.67 and the specificity was 0.96. The positive likelihood ratio was 16.8 and the negative likelihood ratio was 0.34. The positive and negative predictive values were 0.93 and 0.76, respectively. These results indicate that CN-SFEMG showing abnormal jiggle is extremely useful for confirming the diagnosis of MG, but that CN-SFEMG showing normal jiggle has limited utility in excluding the diagnosis.     

Late onset forms of myasthenia gravis. Comparison with early-onset myasthenia gravis

INTRODUCTION: The incidence of myasthenia gravis appears to be increasing in elderly but few studies have been devoted to late onset myasthenia gravis. PATIENTS AND METHODS: We retrospectively compared myasthenic patients with an age at onset above or below 35 years which were observed in two departments of Neurology from 1980 to 2002. RESULTS: 81 cases were included, 28 of which were late onset myasthenia gravis. The two populations were similar in terms of sex-ratio, clinical symptoms, course of the disease and therapeutic response. There was a trend for older patients to present more frequently at onset with dysphagia and axial or proximal involvement, and to have extra-ocular symptoms more quickly. Antibodies against acetylcholine receptor and striated muscle were statistically more frequent in elder patients. CONCLUSIONS: A late onset is not a factor of poor prognosis in myasthenia gravis and older patients must be treated in the same way than younger ones.     

Facilitation phenomenon in electrophysiological diagnosis of myasthenia gravis]

A group of 10 patients with atypical result of repetitive stimulation was selected out of the patients examined in our EMG Laboratory. The diagnosis of myasthenia was clinically confirmed. In all those 10 patients no essential amplitude decrement was found on stimulation, so the electrophysiological confirmation of the diagnosis was lacking. On repetitive stimulation (3 Hz) all increment of the response was observed and also post-tetanic facilitation was present. In SFEMG moderate neuromuscular transmission disturbances were found in those patients. It suggests that, sometimes, facilitation may reflect disturbed neuromuscular transmission even despite the absence of the typical amplitude decrement.