Sensitivity Of Repetitive Nerve Stimulation Research Articles

Different Muscles, Lower Cutoff Values: Does it Truly Improve the Diagnostic Sensitivity of Repetitive Nerve Stimulation in Myasthenia Gravis?

ABSTRACT Context: This study evaluated the diagnostic accuracy of repetitive nerve stimulation (RNS) compared with single-fiber electromyography (SF-EMG) in generalized myasthenia gravis (MG). Aims: The aim of the study was to determine the diagnostic sensitivity of RNS in various muscles and assess the effect of varying decrement cutoff values on diagnostic efficacy. Setting and Design: This was a prospective study of 34 confirmed generalized MG patients. Subjects and Methods: RNS was performed on five muscles. Clinical features, autoantibody presence, and SF-EMG jitter rates recorded from the frontalis muscle were analyzed. Patients were classified according to the MG Foundation of America classification. Statistical Analysis: SPSS version 23 was used for descriptive statistics, comparisons of categorical and quantitative data, and correlation analysis, with the significance level set at P < 0.05. Results: Among the patients (58.8% males and mean age = 59.47 ± 13.37 years), SF-EMG detected increased jitter in 91.2%, whereas RNS identified a significant decrease of 50% across at least one muscle. The decremental response was >10% in the abductor digiti minimi (ADM), trapezius, nasalis, abductor pollicis brevis, and extensor indicis proprius muscles in 5.9%, 26.5%, 29.4%, 11.8%, and 29.4% of patients, respectively. A sensitivity improvement at lower decrement values was observed only in the ADM muscle. A significant correlation was found between decreases in the trapezius muscle and seropositivity. Conclusions: Optimal muscle selection improves RNS diagnostic accuracy in MGs. The study recommends incorporating the spinal accessory and radial nerves in RNS due to their high sensitivity, although modifying the decrement cutoff value has a limited overall effect.

Unveiling Myasthenia Gravis: A Comprehensive Analysis of Diagnostic Tools and Clinical Insights

Objective: This research offers a comprehensive analysis of Myasthenia Gravis (MG), uncovering the remarkable accuracy of spinal accessory, ulnar, and facial nerve repetitive nerve stimulation (RNS), along with the precision of single fiber electromyography (SF-EMG) in MG diagnosis. We also embark on an exploration of clinical features and autoantibody test results in generalized MG patients.
 Methods: In this prospective study, we welcomed 31 individuals definitively diagnosed with generalized MG into our quest. The categorization of patients was conducted in accordance with the criteria set by the Myasthenia Gravis Foundation of America (MGFA). We examined patients' trapezius, nasalis, and abductor digiti minimi (ADM) muscles using RNS. We meticulously recorded the presence of MG autoantibodies, clinical subtypes based on affected muscle groups, and SF-EMG jitter rates.
 Results: The mean age of the 31 patients of whom 19 (61.3%) were male, was 64 ± 13.9 years. Among them, 20 showed positivity in the Anti-AChR antibody test. In 28 patients, accounting for 90.3% of the study group, single fiber electromyography (EMG) displayed increased jitter. There were 4 (12.9%), 24 (77.4%) and 12 (38.7%) patients featuring a decremental response of exceeding 10% in ADM, trapezius and nasalis muscles, respectivelyOur investigation revealed notable findings, such as the absence of substantial correlations between decremental response rates and age, gender, duration of complaints, antibody test results, thymus abnormalities, affected muscle types, familial history, or increased jitter rates in SF-EMG (p>0.05).
 Conclusion: As our findings clearly show, we can confidently attest to the remarkable sensitivity of RNS in MG diagnosis when muscle selection is precise. A gem discovered on our study is the high sensitivity of the spinal accessory nerve, a revelation that should guide the course of routine RNS studies, particularly for those facing ocular-onset myasthenia.

Sensitivity and specificity of repetitive nerve stimulation with lower cutoffs for abnormal decrement in myasthenia gravis.

The sensitivity of repetitive nerve stimulation (RNS) in myasthenia gravis (MG) is dependent on the cutoff for abnormal decrement. RNS data of adults with and without MG from 2014 to 2017 were reviewed retrospectively. The maximum reliable RNS amplitude/area decrement before and after exercise from facial, spinal accessory (SA), ulnar, and fibular nerves was recorded. Sensitivity/specificity using 5%, 7%, and 10% cutoffs were calculated. Seventy-nine of 141 patients had MG (46 generalized, 21 ocular, 12 bulbar). A total of 608 unique RNS recordings were analyzed. Overall RNS sensitivity/specificity at ≥5%, ≥7%, and ≥10% amplitude cutoffs were as follows: SA, 65.6%/86.3%, 49.2%/94.1%, and 29.5%/96.1%; facial, 51.0%/82.5%, 43.1%/95.0%, and 37.3%/100%; ulnar, 43.6%/100%, 41.0%/100%, and 41.0%/100%; and fibular, 52.6%/89.5%, 42.1%/94.7%, and 42.1%/100%. Lowering amplitude cutoff from 10% to 7% increased or maintained sensitivity with little loss in specificity. Post-exercise and area analysis resulted in increased sensitivity in some circumstances.

What's in the Neuromuscular Junction Literature?

Four retrospective studies from the United States, Europe, and Asia address outcomes in juvenile myasthenia gravis. Common features include earlier onset with ocular myasthenia gravis (MG) and generally good outcomes overall. Patients who were seronegative, had equivocal acetylcholine receptor (AChR) antibodies, or had only clustered AChR antibodies had better outcomes. An article highlighting the utility of median nerve slow-repetitive stimulation is reviewed and another showing the high sensitivity of repetitive nerve stimulation in myasthenic crisis is covered. Two articles address the thymus and thymectomy in non-AChR antibody-positive autoimmune MG. Longer term data on eculizumab as well as studies of cyclophosphamide, rituximab, and tacrolimus are summarized. Other topics include the possible role of statins in MG and central nervous system autoimmune comorbidities.

Repetitive nerve stimulation: Relative muscles sensitivity in generalized myasthenia gravis

Objectives The diagnosis of myasthenia gravis (MG) is established through the medical history and examination and confirmed by the clinical response to anti-cholinesterase medication, the detection of anti-acetylcholine receptor antibodies (AchR) and especially electrodiagnostic testing using repetitive nerve stimulation (RNS) [3] . However, the sensitivity of RNS depends on the distribution of clinically affected muscles and its severity [2] . We aimed to investigate the decrement of RNS of various muscles in patients with generalized MG in order to test the nerve-muscle sensitivity. Methods We performed a retrospective study of patients with clinical diagnosis of MG, who attended our neurology department [2011–2018] (n:33) and we included those with generalized MG to investigate their neurophysiological outcomes. All patients had a neurological examination. Patients who have not a detailed neurophysiological study including RNS within these 3 spots (facial-nerve, accessory-nerve, upper limbs nerves) were excluded. Results Among the 33 patients with MG, we selected 27 patients (M/F:8/19) who had generalized MG with fluctuating motor weakness and oculo-bulbar involvement. Their age ranged from 14 to 77 years (mean, 47.77 years) and the average age at onset was 44.18 years. Forty-four percent had thymus abnormality and 83.33% had positive antibody testing to AchR. RNS studies showed at least one abnormal muscle response (significant decrement > 10% in low frequencies) in 96.29%. Decrement was most detected in the facial nerve (77.77%). An abnormal trapezius response was observed in 55.55%. However, hand muscles abnormalities tested using the ulnar, medial and radial nerves stimulation were detected respectively in 48.14%, 37.03% and 14.81%. The facial nerve was significantly more sensitive than any other nerve (P Conclusion RNS is a commonly used technique to evaluate patients with MG, through multiple nerve-muscle testing [1] . Therefore, the facial nerve seems to be the most sensitive one.

T37. Electrodiagnostic criteria for neuromuscular transmission disorders suggested by a European consensus group

Despite advances in antibody testing, electrodiagnostic testing still plays a crucial role in diagnosing disorders of the neuromuscular transmission (NMT). Existing criteria for NMT disorders are derived from consensus, while no evidence-based criteria have been published. The aim of this study was to derive evidence-based criteria for the electrodiagnosis of NMT disorders, supported on clinical diagnosis as agreed by consensus (gold standard) in an expert group. A group of experienced physicians in the European multicentre project ESTEEM representing six different European countries reviewed samples of their patients diagnosed with NMT disorder. A total of 164 examinations obtained a consensus diagnosis of definite (105), probable (44), or possible (15) NMT disorder. In these examinations 405 repetitive nerve stimulation (RNS) and 116 single fibre electromyography (SFEMG) studies were performed. The average numbers of abnormal RNS and SFEMG studies in the patients with a probable consensus diagnosis of NMT disorder served as basis for recommendation of minimal electrodiagnostic criteria. The average number of performed RNS studies per patient from each of eight physicians ranged from 1.9 to 5.2, while the average number of abnormal RNS studies ranged from 0.7 to 3.2. For SFEMG the average number ranged from 0.09 to 1.6 for performed studies and from 0.09 to 1.5 for abnormal studies. In the 99 patients diagnosed with generalised myasthenia, the sensitivity of RNS varied from 43% (abductor digiti minimi muscle) to 78% (nasalis muscle), while the sensitivity of SFEMG ranged from 80% (orbicularis oculi muscle) to 100% (anconeus and frontalis muscles). As minimal electrodiagnostic criteria, the ESTEEM group recommends that either (a) 2 abnormal RNS studies, or (b) 1 abnormal RNS study and 1 abnormal SFEMG study, or (c) 2 abnormal SFEMG should be required to diagnose a NMT disorder. To evaluate the electrodiagnostic tests, the routinely used limits for decrement at the different centres should be applied. Electrodiagnostic consensus recommendations for the minimum number of RNS and SFEMG studies to diagnose disorders of the neuromuscular junction are suggested. The recommendations encourage use of different limits according to the muscle examined and the relevant age group (e.g. children vs. adults), preferably obtained locally at each diagnostic centre. These are the first electrodiagnostic criteria for NMT based on clinical evidence of diagnosis as agreed by consensus.

S12-1. Diagnostic sensitivity and specificity of the laboratory tests in myasthenia gravis

The diagnostic sensitivity of repetitive nerve stimulation (RNS) in patients with myasthenia gravis (MG) varies as the choice of muscles studied and method used as “gold standard” to judge sensitivity and specificity. Many research in MG-RNS studies for more high sensitivity were reported previously, almost generalized MG RNS sensitivity was from 60% to 80% slight more sensitive than serological study. We recommend RNS examination of at least 3 muscles, nasalis, trapezius, and deltoid. Sensitivity of RNS in generalized seropositive MG were 54%, 51%, 62%. The seronegativity of AChR frequency reported subsequently has ranged from 7% to 40% for all acquired MG patients, and from 6% to 30% for generalized MG. We hope RNS and SFEMG for diagnosis of MG could help to pick up from seronegative patients. SFEMG is one of the key, and combination of selection of examination for RNS is another key of diagnosis for MG. Pitfall of specificity of RNS is misdiagnosis of motor neuron disease decrement as same as neuromuscular transmission dysfunction. We should be aware of sensitivity of RNS for ALS is higher than MG except nasalis muscle.

New strategy for improving the diagnostic sensitivity of repetitive nerve stimulation in myasthenia gravis.

The diagnostic sensitivity of repetitive nerve stimulation (RNS) in patients with myasthenia gravis (MG) varies as a function of the number of muscles or the choice of muscles studied. By exploring 12 muscles bilaterally, we evaluated the global sensitivity of RNS at rest, the sensitivity in different clinical forms, and the sensitivity of different combinations of muscles studied. The global sensitivity of RNS was 82%, and specificity was 100%. The sensitivity in the MG subgroups was as follows: ocular (O) = 67%; oculobulbar (OB) = 86%; and generalized (G) = 89%. The most sensitive muscles were the anconeus in group O, orbicularis oculi (OO) or nasalis in group OB, and the trapezius in group G. Maximum sensitivity was obtained by exploring OO, trapezius, and anconeus bilaterally. We recommend bilateral exploration of at least 3 muscles, a facial muscle, trapezius, and anconeus. Muscle Nerve 55: 532-538, 2017.

Electrophysiological and immunological study in myasthenia gravis: Diagnostic sensitivity and correlation

Objective To determine the diagnostic sensitivity of repetitive nerve stimulation (RNS), single fiber electromyography (SFEMG) and acetylcholine receptor antibody (AChRAb) in myasthenia gravis (MG), and to compare the degree of SFEMG abnormality between ocular and generalized MG and between seronegative and seropositive patients. Methods The sensitivities of RNS, SFEMG and AChRAb were estimated. SFEMG abnormality was compared between ocular and generalized MG and between seronegative and seropositive patients. Results Abnormal RNS, abnormal SFEMG and AChRAb were detected in 62%, 93% and 38% of 42 ocular, and 80%, 99% and 73% of 70 generalized cases, respectively. The degree of SFEMG abnormality was significantly greater in the generalized than ocular patients and was significantly greater in the seropositive than seronegative patients in both extensor digitorum communis and orbicularis oculi muscles. Conclusion SFEMG is a very sensitive and useful test for MG. A correlation between SFEMG abnormality and clinical phenotype or severity and between SFEMG abnormality and AChRAb seropositivity was demonstrated. Significance The sensitivities of RNS, SFEMG and AChRAb in the diagnosis of MG were documented. The differences in severity between the ocular and generalized MG and between the seronegative and seropositive MG were confirmed and quantitatively determined by SFEMG.

Sensitivity of repetitive facial‐nerve stimulation in patients with myasthenia gravis

Repetitive stimulation of the facial nerve is commonly performed in cases of suspected myasthenia gravis (MG) because bulbar weakness is often present, but the most sensitive facial muscle is unknown. We compared the sensitivity of repetitive nerve stimulation (RNS) to the frontalis and nasalis muscles in 244 patients with suspected MG. We found no difference in sensitivity of RNS when recording from these muscles in both ocular and generalized MG. In addition, we confirmed the low sensitivity of RNS for ocular (18%) or generalized (47%) MG. The specificity of facial RNS for both muscles was 100% and, in certain circumstances, may obviate the need for further diagnostic testing.

Repetitive nerve stimulation for the evaluation of peripheral nerve hyperexcitability

Objective: To examine the utility of repetitive nerve stimulation (RNS) in the evaluation of peripheral nerve hyperexcitability (PNH). Background: PNH describes a group of disorders characterized by muscle cramps, twitching and stiffness. When severe, PNH may be characterized by the presence of continuous muscle fiber activity on routine needle electromyography (EMG). In milder forms of the disease, nerve hyperexcitability may be evidenced by the presence of after-discharges or cramp potentials following RNS. Methods: Fifty-four patients were prospectively recruited and classified into one of three groups—PNH, other neuromuscular disease and controls. We recorded and quantified the after-discharges and cramp potentials following RNS at 1, 5, 10 and 30 Hz. Results: The proportion of nerves with after-discharges and/or cramp potentials was significantly greater in the PNH group than the control group at both 5 Hz ( p=0.03) and 10 Hz ( p=0.01), as well as in the neuromuscular disease group compared to controls at 5 Hz ( p=0.02). There was also a significant concordance between complaints of muscle cramps and fasciculations and the finding of after-discharges and/or cramp potentials at both 5 Hz ( p=0.005) and 10 Hz ( p=0.004). At a stimulation frequency of 10 Hz, the sensitivity of RNS for the diagnosis of PNH (primary or secondary) was 79% and the specificity was 88%. Conclusion: Our findings suggest that RNS at or below a stimulation frequency of 10 Hz (when positive) is a useful test for the diagnosis of PNH, whether it is primary or secondary.

Electrodiagnostic studies in myasthenia gravis : Z.G. Bagabaldo, S. Lim-Lopez, L.D. Renales, C.M. Danguilan, M.C. Perez (University College of Medicine, Manila Philippines)

Forty-three patients with myasthenia gravis (MG) were studied to compare the sensitivity of repetitive nerve stimulation (RNS) test with single fiber electromyography (SFEMG) in the diagnosis of MG. SFEMG was abnormal in 81% (35 of 43 cases), while RNS test was abnormal in 53% (23 of 43 cases). In ocular MG, SFEMG showed a much higher positive rate (70%, 16 of 23 cases) than RNS test (22%, 5 of 23 cases). Both studies had similar abnormal rates in the generalized group. In patients studied with SFEMG in the EDC muscle, the clinical severity was closely correlated with jitter abnormality. We conclude that SFEMG is more sensitive than RNS test in the diagnosis of MG, especially in the ocular group.