Direct comparison of median and ulnar repetitive nerve stimulation in generalized myasthenia gravis.

INTRODUCTION/AIMS: Ulnar nerve repetitive nerve stimulation (RNS) has been traditionally used in the electrophysiological evaluation of myasthenia gravis (MG). However, its low diagnostic sensitivity remains a limitation. Existing data may suggest that median nerve RNS outperforms that of the ulnar nerve, but a direct comparison is currently lacking. The aim of this study was to directly compare the diagnostic yields between median and ulnar nerve RNS in patients with generalized MG. METHODS: We performed a retrospective analysis of patients with MG who underwent median and ulnar nerve RNS at a single tertiary center. RESULTS: RNS studies of median nerve recording from the abductor pollicis brevis and ulnar nerve recording from the adductor digiti minimi were completed in 28 patients with generalized MG. Abnormal RNS was more frequently observed in the median compared with the ulnar nerve (60.7% vs 35.7%, P = .046). The average magnitude of decrement was higher in the median nerve compared with the ulnar nerve (17.3% vs 9.6%, P = .017). Differences between the median and ulnar nerve RNS studies were restricted to patients with mild manifestations (Myasthenia Gravis Foundation of America class II). DISCUSSION: Median nerve RNS has superior diagnostic sensitivity as compared with ulnar nerve RNS in the assessment of mild generalized MG.

Tonifying spleen and replenishing kidney method of traditional Chinese medicine for myasthenia gravis: A protocol for systematic review and meta-analysis.

BACKGROUND: Myasthenia gravis (MG) is an autoimmune antibody-mediated disorder caused by dysfunction at the neuromuscular junction spreads. The main clinical features of this disease are fluctuating fatigue, and weakness of the skeletal muscles of the eyes and limbs. At present, the tonifying the spleen and replenishing the kidney method in traditional Chinese medicine has been widely used for MG. The present study was conducted to evaluate the efficacy and safety of the tonifying the spleen and replenishing the kidney method in traditional Chinese medicine for MG. METHODS: The following 10 databases were searched from inception to March 2021: PubMed, Cochrane Library, EMBASE, Web of Science, Springer, China National Knowledge Infrastructure (CNKI), Wan fang, VIP Chinese Science and Technique Journals Database, the Chinese Bio Medical Database (CBM), and Baidu Scholar. The language was limited to the Chinese and English language. Merely randomized controlled trials (RCTs) were included. The Cochrane Collaboration risk-of-bias tool was used for the methodological quality assessment and risk of bias. The meta-analysis was assessed using the Cochrane RevMan 5.3 software. RESULTS: In the present study, a meta-analysis was conducted, and RCTs that met the eligibility criteria were included. Furthermore, the different outcome indicators of different methods were objectively compared. The main outcome indicators included the effective rate, quantitative myasthenia gravis (QMG) scores, adverse events, and quality of life (QOL). The secondary outcome indicators included AchRAb, serum-related immune cells (such as CD3+CD4+cells and CD4+/CD8+cells), the traditional Chinese medicine syndrome score scale (TCMSSS), the serum interleukin-6 level, the level of IFN-γ and its mRNA, and the clinical score that contains the clinical absolute score (CAS) and clinical relative score (CRS). CONCLUSION: This study would provide credible evidence to determine whether the tonifying the spleen and replenishing the kidney method in traditional Chinese medicine is an effective treatment method for MG. TRIAL REGISTRATION NUMBER: INPLASY202110097.

Respiratory Muscle Training Improves Functional Outcomes and Reduces Fatigue in Patients with Myasthenia Gravis: A Single-Center Hospital-Based Prospective Study.

BACKGROUND: Myasthenia gravis (MG) is an immune-mediated disorder characterized by muscle fatigue and fluctuating weakness. Impairment in respiratory strength and endurance has been described in patients with generalized MG. We tested the hypothesis that respiratory muscle training (RMT) can improve functional outcomes and reduce fatigue in patients with MG. METHODS: Eighteen patients with mild to moderate MG participated in this study. The training group underwent home-based RMT three times a week for 12 weeks. Sixteen patients with MG without RMT were enrolled as a disease control group. Lung function, autonomic testing, Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF), and functional outcome measurement by using quantitative myasthenia gravis (QMG) score and myasthenia gravis composite (MGC) scale were measured before and after the 12-week RMT. RESULTS: The 12-week RMT significantly increased forced vital capacity (FVC) from 77.9 ± 12.6% to 83.8 ± 17.7% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (p = 0.03), forced expiratory volume in one second (FEV1) from 75.2 ± 18.3% to 83.3 ± 19.0% (. CONCLUSION: The home-based RMT is an effective pulmonary function training for MG patients. The RMT can not only improve short-term outcomes but also reduce fatigue in patients with mild to moderate generalized MG.

Acupuncture for ocular myasthenia gravis: A protocol for systematic review and meta-analysis.

BACKGROUND: The aim of this systematic review with meta-analysis is to determine the efficacy and security of acupuncture in treatment of ocular myasthenia gravis and find out whether or not the quick short-term efficacy of acupuncture exists. METHODS: The following electronic databases will be searched by 2 independent reviewers: PubMed, Cochrane Library, EMBASE, Springer, China National Knowledge Infrastructure, Wanfang, and Chinese Biomedical Literature Database. All randomized controlled trials on acupuncture for ocular myasthenia gravis published in electronic databases from inception to March 1, 2020, with language restricted in Chinese and English will be included in the study.Methodologic quality is assessed by 2 blinded reviewers independently screen and score the articles using the PEDro scale and the Cochrane Collaboration risk of bias tool. A meta-analysis was performed when there is sufficient clinical homogeneity in at least 2 studies. The Grading of Recommendations Assessment, Development and Evaluation approach is used to rate the body of evidence in each meta-analysis. When the quantitive evaluation is not available, a qualitative description of the results of single study is provided. RESULTS: An evidence of variety of acupuncture treatment methods for treating ocular myasthenia gravis will be illustrated using subjective reports and objective measures of performance. The primary outcomes consisted of effective rate, MGFA PIS, QMG, and MG-composite. Secondary outcomes involve clinical absolute and relative score, titers of AchR antibodies, and the side effects. The treatment frequency and courses will be measured. CONCLUSION: This protocol will present the evidence of whether acupuncture is an effective and safe intervention for ocular myasthenia gravis. TRIAL REGISTRATION NUMBER: CRD42019141325.

Study on variation trend of repetitive nerve stimulation waveform in amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease involving both upper and lower motor neurons with no effective cure. Electrophysiological studies have found decremental responses during low-frequency repetitive nerve stimulation (RNS) except for diffused neurogenic activities. However, the difference between ALS and generalized myasthenia gravis (GMG) in terms of waveform features is unclear. In the current study, we explored the variation trend of the amplitudes curve between ALS and GMG with low-frequency, positive RNS, and the possible mechanism is discussed preliminarily. METHODS: A total of 85 ALS patients and 41 GMG patients were recruited. All patients were from Peking Union Medical College Hospital (PUMCH) between July 1, 2012 and February 28, 2015. RNS study included ulnar nerve, accessory nerve and facial nerve at 3 Hz and 5 Hz stimulation. The percentage reduction in the amplitude of the fourth or fifth wave from the first wave was calculated and compared with the normal values of our hospital. A 15% decrease in amplitude is defined as a decrease in amplitude. RESULTS: The decremental response at low-frequency RNS showed the abnormal rate of RNS decline was 54.1% (46/85) in the ALS group, and the results of different nerves were 54.1% (46/85) of the accessory nerve, 8.2% (7/85) of the ulnar nerve and 0% (0/85) of the facial nerve stimulation, respectively. In the GMG group, the abnormal rate of RNS decline was 100% (41/41) at low-frequency RNS of accessory nerves. However, there was a significant difference between the 2 groups in the amplitude after the sixth wave. CONCLUSIONS: Both groups of patients are able to show a decreasing amplitude of low-frequency stimulation RNS, but the recovery trend after the sixth wave has significant variation. It implies the different pathogenesis of NMJ dysfunction of these 2 diseases.

Effects of long-term respiratory muscle endurance training on respiratory and functional outcomes in patients with Myasthenia gravis.

BACKGROUND: Myasthenia gravis (MG) is characterized by reduced muscle endurance and often leads to respiratory complications. OBJECTIVE: A long-term respiratory muscle endurance training (RMET) based on normocapnic hyperpnea was introduced for the first time in MG patients. We investigated RMET effects on respiratory endurance (RE), MG symptoms, lung function and physical fitness and compared the results with a control group (CG). METHODS: The training period consisted of four weeks intensive training (IT; five 30-min training sessions per week) followed by twelve months maintenance training (MT; five 30-min training sessions over two weeks). Eighteen patients with mild to moderate MG participated as the training group (TG), six patients served as CG. RE, lung function, MG score and physical fitness were tested before and after IT and after three to twelve months of MT. RESULTS: Only 12 TG patients completed the entire training period. Thirteen months of training significantly increased RE measured as time until exhaustion (Tlim) to 412% of baseline (P < 0.001). The MG score improved from 0.67±0.09 to 0.41 ± 0.1 (p = 0.004), and the number of squats per minute as a measure of physical fitness increased in the TG to 160% of baseline (p = 0.015). While lung function did not change during the training period, we observed a modulation in the breathing pattern at rest with prolonged expiration (122% of baseline, p = 0.028). In addition, TG reported subjective improvements in MG symptoms, respiratory symptoms and physical fitness by 49%, 58% and 64%, respectively (P < 0.001). No significant changes were observed in the CG. CONCLUSION AND SIGNIFICANCE: This is the first controlled long-term RMET study in MG patients. The results demonstrated that this normocapnic hyperpnea training is feasible and beneficial for patients with mild to moderate MG and is a valuable supplement to conventional drug treatment.

[Decrement pattern of M-response amplitude in the low-frequency repetitive nerve stimulation in the muscles of patients with myasthenia gravis and Lambert-Eaton myasthenic syndrome]. / Dekrement amplitudy M-otveta pri nizkochastotnoi stimulyatsii myshts bol'nykh miasteniei i miastenicheskim sindromom Lamberta­Itona.

AIM: To investigate the pattern of decrement in the muscles of patients with myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS). MATERIAL AND METHODS: Twenty-seven patients with MG and 39 patients with LEMS were studied using low frequency repetitive nerve stimulation (3/ sec). RESULTS AND CONCLUSION: The decrease of safety factor of neuromuscular transmission was equal in both groups. At the same time, a significant difference in the decrease of pattern of the amplitude compound of muscle action potential (CMAP) was found. In LEMS, by contrast with MG, another sequence of amplitude variability of CMAP from the second stimulus to the first and from the fifth stimulus to the fourth was noted. In LEMS patients, progressive decrement, manifesting by increasing ratios of late A9/A1 to early A4/A1 was found, whereas the MG patients showed retrogressive decrement expressed by the reduction in decrement ratio (from late to early). These differences reflect the mechanisms and status of acetylcholine mobilization and release from the axon terminal.

Repetitive facial nerve stimulation in myasthenia gravis 1min after muscle activation is inferior to testing a second muscle at rest.

OBJECTIVES: To explore the increased diagnostic yield of repetitive nerve stimulation (RNS) following activation for myasthenia gravis (MG) diagnosis, and compare with testing an additional muscle at rest only. METHODS: We performed a retrospective chart review of patients diagnosed with MG attending the neuromuscular clinic from 2013 to 2015 and extracted data on electrophysiological studies, including frequency of decrement of 10% or above, with facial RNS at rest, and following activation. RESULTS: The total cohort included 102 patients with MG, 65 with generalized, and 37 with ocular MG. Facial RNS sensitivities for diagnosing MG were 32-46% and 14-19% respectively. The increase in RNS sensitivity following muscle activation was 6-8% for frontalis muscle recordings, and 0-2% for nasalis muscle recordings. Recording from both muscles at rest only, increased the sensitivity by 9-15%. CONCLUSION: RNS is a valid method for confirming a clinical diagnosis of MG. The increased diagnostic yield of RNS following activation is controversial. Our study shows that the increased diagnostic yield of facial RNS following activation is modest, and is less than performing facial RNS in a second muscle. SIGNIFICANCE: Performing facial RNS in an additional muscle at rest appears to be more sensitive than facial RNS in a single muscle after activation.

Modelling the response to low-frequency repetitive nerve stimulation of myasthenia gravis and Lambert-Eaton myasthenic syndrome.

Myasthenia gravis (MG) is an autoimmune postsynaptic disorder of neuromuscular transmission caused, in most patients, by antibodies against postsynaptic acetylcholine receptors. Lambert-Eaton myasthenic syndrome (LEMS) is a presynaptic autoimmune disease in which there is a reduction in Ca2+ entry with each impulse due to the action of antibodies against Ca2+ channels. These diseases have a distinct pattern of response to low-frequency repetitive nerve stimulation which allows its recognition in a particular subject. Nevertheless, the physiologic basis of this response is not entirely known. A model of the time-course of release probability of neuromuscular junctions that incorporates facilitation and a depression-recovery mechanism has been developed with the aim to investigate these response patterns. When the basal value of release probability was in the physiologic range, as in MG, release probability showed an increment after its initial decrease only if the recovery from depression was accelerated by presynaptic residual Ca2+. Otherwise, when the basal release probability was low, as in LEMS, a progressive reduction in the release probability without any late increase was only obtained if the efficacy of Facilitation and Ca2+-dependent recovery from depression were reduced.

The clinical absolute and relative scoring system-a quantitative scale measuring myasthenia gravis severity and outcome used in the traditional Chinese medicine.

Myasthenia gravis (MG) is a chronic autoimmune disease caused by autoantigen against the nicotine acetylcholine receptor at the neuromuscular junction. With modern treatment facilities, the treatment effect and outcome for MG has been greatly improved with MG and non-MG patients enjoying the same life expectancy. Many classifications of disease distribution and severity have been set up and tested all over the world, mainly in the western world. However, the absolute and relative scoring system for evaluating the severity and treatment effect of MG in China where traditional Chinese medicine (TCM) has been practiced for thousands of years has not been introduced worldwide. The TCM has achieved a great success in the treatment of MG in the country with a huge population. This article serves to introduce this scoring system to the world.

Electrophysiological profile of the patients with MuSK positive myasthenia gravis.

OBJECTIVES: To determine the electrophysiological profile of our cohort of patients with muscle-specific tyrosine kinase (MuSK) positive myasthenia gravis (MG). METHODS: Repetitive nerve stimulation test (RNS) and jitter analysis using concentric needle electrode were performed in 31 MuSK and in 28 acetylcholine receptor (AChR) positive MG patients. RESULTS: Pathological RNS was verified in 16 (51.6%) MuSK and 26 (92.9%) AChR MG patients (P < 0.01). Pathological jitter analysis was registered in 28 (90.3%) MuSK and 26 (92.9%) AChR MG patients (P > 0.05). Increased jitter was present in extensor digitorum communis (EDC) in 23 (74.2%) MuSK and in 25 (89.3%) AChR MG patients (P > 0.05) as well as in orbicularis oculi (OO) muscle in 24 (85.7%) MuSK and 22 (81.5%) AChR MG patients (P > 0.05). Lower mean value of mean consecutive difference (MCD) and fewer potential pairs with increased jitter were registered in MuSK MG compared to AChR MG patients only in EDC muscle (P < 0.05). In MuSK MG patients, increased jitter was observed to be more frequent in patients with longer disease duration (P < 0.05) and also in those patients exhibiting more severe disease forms (P < 0.01) only in EDC muscle. DISCUSSION: Repetitive nerve stimulation test has low sensitivity in MuSK MG patients, while jitter analysis shows high sensitivity, especially in facial muscles. The EDC muscle in MuSK MG patients usually shows increased jitter in more severe disease forms and later in the course of the disease.

Clinical treatment of myasthenia gravis with deficiency of spleen and kidney based on combination of disease with syndrome theory.

OBJECTIVE: To study the use of Jianjining in the treatment of myasthenia gravis (MG) patients with a deficiency of both spleen and kidney via the theory on the combination of disease with syndrome. METHODS: Sixty MG patients with a deficiency of both spleen and kidney were randomly divided into an treatment group (n = 30) treated with Jianjining granules and Western Medicine (prednisone or pyridostigmine bromide) and a control group (n = 30) treated with Jianjining granules. The dosage of the three drugs was reduced over the course of treatment. After 3 and 6 months of treatment, the curative effect was evaluated with the muscle weakness severity scale (MWSS). RESULTS: The MWSS score after treatment declined significantly in both groups. The score in the treatment group was much lower tha that in the control group (P < 0.05). The total effective rate was 63.33% (19/30) in the treatment group and 36.67% (11/30) in the control group after 3 months of treatment, and 80.00% (24/30) and 50.00% (15/30), respectively, after 6 months of treatment. The obvious and total effective rates in the treatment group were much higher than those in the control group (P < 0.05). After 6 months of treatment, there were no obvious differences (P > 0.05) in the obvious and effective rates between the 2 groups. However, the total effective rate in the treatment group was much higher than that in the control group (P < 0.01). CONCLUSION: Using the theory on the combination of disease with syndrome, we found that the curative effect of Jianjining and Western Medicine on MG patients with deficiency of both spleen and kidney is worth further exploration.

A cohort study on myasthenia gravis patients in China.

Clinical classification and age distribution in myasthenia gravis (MG) cases seem different between Oriental and Caucasian populations, but there have rarely been any clinical studies on MG patients from mainland China. The goal of the current study was to perform a comprehensive survey of myasthenia gravis in a hospital in China, establishing contemporary cohort data and clinical features. 1,108 unselected patients with MG attending the 309th Hospital of PLA, Beijing, China were studied during a 36-month period from July 2008 to June 2011. The sex ratio was 1:1 (F:M). 62.5 % of patients presented as adolescents and adults. Ocular MG cases accounted for 65.6 % childhood MG patients. A positive response was observed in 96.8 % of the patients for neostigmine tests, whereas a positive decremental response to low frequency repetitive nerve stimulation (RNS) was observed in 77.4 % of the patients. The highest stimulating positive rate was 65.3 % in stimulated facial nerve. Thymoma was significantly increased in those patients with severe MG, especially in the cohort involving the respiratory muscles (p < 0.001). The study revealed higher frequency of ocular and childhood MG compared to other studies in USA and European countries, which can be a result of optimum case ascertainment, increased disease duration, or application of complex diagnostic tests. The relative increase in the prevalence of ocular myasthenia can be attributed to the impact of an aging population.

Treatment strategies for myasthenia gravis: an update.

INTRODUCTION: New treatments for immune mediated diseases have increased notably in the last 10 years. Monoclonal antibodies directed against different components of the immune system have appeared, along with new drugs from the haematology field. In the case of myasthenia gravis (MG), many of these new treatments have been used in experimental animal models and also in patients. AREAS COVERED: This manuscript reviews the progress in the field of MG treatment achieved in the last 5 years. Firstly, our current treatment protocol is introduced. Secondly, new data from recent randomized trials and case series of patients treated with methotrexate, cyclophosphamide, rituximab or improved systems of apheresis is reported. Finally, all future treatments are discussed that are currently under evaluation in preclinical animal models of experimental autoimmune MG. EXPERT OPINION: Evidence supporting the use of methotrexate and rituximab in MG has been published recently, in addition to conflicting randomized trials that were not successful, evaluating the use of tacrolimus as a steroid sparing agent. New promising treatments are currently under evaluation in clinical trials, such as belimumab and eculizumab.

Decremental responses to repetitive nerve stimulation (RNS) in motor neuron disease.

OBJECTIVE: To clarify the features of decremental responses following repetitive nerve stimulation in patients with motor neuron diseases (MNDs), in comparison with myasthenia gravis (MG). METHODS: The subjects consisted of 48 MND, 39 generalized MG and 19 ocular MG patients. Six muscles, both proximal and distal muscles, were tested. RESULTS: Significant decrements (>5%) in at least one muscle were observed in 83% of the MND patients, and 74% and 47% of the generalized MG and ocular MG patients, respectively. Decrements were more frequently observed in the proximal muscles both in MND and MG patients (deltoid 76% and 62%, and trapezius 71% and 51% for MND and generalized MG, respectively), suggesting lower safety factors in neuromuscular transmission in those muscles. Decrements in the nasalis were rare in MND (8%) in comparison with generalized MG (54%). CONCLUSIONS: Decremental responses were frequently observed in MND patients. There were small differences between MND and MG regarding the distribution and other features of decrements, such as the degree of the U-shape or the responses to different stimulus frequencies and to brief exercise. SIGNIFICANCE: These results imply that the underlying mechanism regulating the decrements is common to MND and MG.

[Effective reversal of muscle relaxation by rocuronium using sugammadex in a patient with myasthenia gravis undergoing laparoscopic cholecystectomy].

As myasthenia gravis affects neuromuscular transmission, these patients show various responses to neuromuscular blocking drugs. We report a successful use of the sugammadex in a myasthenic patient to reverse rocuronium-induced neuromuscular block. A 69-year-old woman was scheduled for laparoscopic cholecystectomy and total of rocuronium 20 mg was administered. After spontaneous recovery of T1, we administered sugammadex 200mg intravenously, reversing neuromuscular blockade to a train-of-four ratio (T4/T1) of 100% within 30 sec. Sugammadex can be used to reverse rocuronium-induced neuromuscular blockade in patients with myasthenia gravis, thereby avoiding the need for reversal with acetylcholinesterase inhibitors.

[Analysis of the clinical manifestations and electrophysiological changes in 32 patients with atypical myasthenia gravis].

OBJECTIVE: To study the clinical characteristics and electrophysiological changes in patients with atypical myasthenia gravis (MG). METHODS: The characteristics of the clinical symptoms and electrophysiological changes were investigated in 32 patients with atypical MG diagnosed in our hospital from January 2004 to December 2008. RESULTS: The ages of the patients ranged from 7 to 70 years. Five patients were diagnosed to have ocular MG (OMG), among whom 2 patient only complained of eye discomfort and blurred vision. Twenty-seven patients had generalized MG, and 6 of them showed muscle weakness of the limbs with or without mild difficulty in swallowing or respiratory muscles, but free of muscle dysfunctions in muscles of eyes, head, neck or face. Another 2 patients manifested muscular atrophy. Twenty-three patients (71.9%) displayed both fluctuating symptoms and positive results of fatigue test. Twenty-nine patients (90.6%) have positive results in the neostigmine test. Two patients in the OMG group (40.0%) showed positive results in the low frequency repetitive nerve stimulation (LFRNS), as compared with the 21 patients in the generalized MG group (71.9%) showing positive results. The total positivity rate of LFRNS was 71.9% in the total patients, consistent with the published data. CONCLUSIONS: In MG patients with atypical clinical symptoms, negative results of neostigmine test and fatigue test, LFRNS test can be an indispensable method to increase detection rate of MG and reduce erroneous or missed diagnosis.

The difficulty in confirming clinical diagnosis of myasthenia gravis in a seronegative patient: a possible neurophysiological approach.

In seronegative myasthenia gravis repetitive nerve stimulation and single-fibre EMG have a crucial diagnostic value but they may be negative, particularly in repetitive nerve stimulation studies. We report the case of a 43-year-old patient with generalized seronegative myasthenia gravis with negative 3 Hz repetitive nerve stimulation at Erb's point and voluntary single-fibre EMG in the orbicularis oculi. We also performed 6 and 12 Hz repetitive nerve stimulation at Erb and stimulated single-fibre EMG in the extensor digitorum communis and our findings were pathological. Our data suggest that, for individual patients with an atypical picture characterised by dissociation between a severe clinical pattern and no definite neurophysiological findings on conventional tests, repetitive nerve stimulation with a stimulation rate higher than 3 Hz and/or stimulated single-fibre EMG with an increasing stimulation rate may be helpful.

Comparison of amplitude and area decrement in repetitive nerve stimulation.

OBJECTIVE: To access the percentage of the patients whose repetitive nerve stimulation (RNS) studies were negative for 10% amplitude decrement but positive for 10% area decrement and to compare these disagreed results with specialist physician's diagnosis. STUDY DESIGN: Retrospective descriptive study. SETTING: Electrodiagnosis laboratory, Department of Rehabilitation Medicine, King Chulalongkorn Memorial Hospital. MATERIAL AND METHOD: All of the electromyography (EMG) reports of RNS studies were reviewed Both 10% amplitude and area decrement were used as criteria for diagnosis in each patient. The disagreed results would be compared to final diagnosis of the specialist physicians that were recorded in out-patient medical records. RESULTS: Eighty-three reports were included in the present study. Nineteen records (22.9%) were negative for 10% amplitude decrement but positive for 10% area decrement. Three records (3.6%) were positive for 10% amplitude decrement but negative for 10% area decrement. Twenty-two patients had disagreed results. Sixteen disagreed out-patient medical records (72.7%) were available for review the final specialist doctors' diagnosis. About 69% of patients, whose test was negative for 10% amplitude decrement but positive for 10% area decrement, were diagnosed as myasthenia gravis (MG) or suspected MG. All of the patients, whose test was negative for 10% area decrement but positive for 10% amplitude decrement, were diagnosed as MG. The use of both 10% amplitude and area decrement instead of 10% amplitude decrement alone will provide additional diagnostic yields in about 13% of the cases. CONCLUSION: Twenty-three percent of patients had disagreed RNS results that were negative for 10% amplitude decrement but positive for 10% area decrement. When these disagreed results were compared to the final diagnosis of specialist doctors, 69% of these patients were diagnosed or suspected and treated as MG. Using both 10% amplitude and area decrement may improve sensitivity of MG diagnosis in about 13% of the cases.

[The effect of tripterygium wilfordii polyglycosidium on the compound action potential of skeletal muscle in experimental animals with myasthenia gravis].

OBJECTIVE: To observe and analyze the direct effect of tripterygium wilfordii polyglycosidium (TWP) on the activity of skeletal muscle in experimental animals with myasthenia gravis (EAMG). METHODS: C57BL/6 mice were used. After sieving EAMG animals, we observed and compared the variation of the attenuation percentage of compound action potential of gastrocnemius muscle and pronator teres muscle of EAMG before and after the muscle specimens being immersed in the breeding ground of TWP solution. Such variation of attenuation percentage was taken as an indicator of the direct effect of TWP on skeletal muscle. RESULTS: 1. Evident influence of TWP on the attenuation percentage of compound action potential of gastrocnemius muscle was observed (P < 0.05), and apparent decrease of the attenuation percentage could be seen one and a half hours after the muscle was immersed [(14 +/- 36)% before treatment, (-40 +/- 24)% after treatment]; 2. The influence of TWP on the attenuation percentage of compound action potential of pronator teres muscle was noted (P < 0.05), and an apparent decline of the attenuation percentage could be observed one and a half hours after the muscle was immersed[(17 +/- 25)% before treatment, (-17 +/- 10)% after treatment]; 3. There was no distinctive difference between the gastrocnemius muscle and pronator teres muscle in respect of their attenuation percentages of compound action potential. CONCLUSION: TWP has direct remedial effect on the activity of skeletal muscle of EAMG.