Concentric Needle Jitter in 97 Myasthenia Gravis Patients

Kouyoumdjian, João Aris; Paiva, Gabriel Pina; Stålberg, Erik

doi:10.3389/fneur.2020.600680

Cited by 4 publications

(4 citation statements)

References 38 publications

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“…41 Jitter measurement is the most sensitive test NT function in MG, 18,44,45 being abnormal in up to 99% of cases. 17,18,35,46 For patients without abnormal decrement and negative antibodies, the increased jitter will support the MG diagnosis in cases responsive to prednisone. Despite the localized weakness, as in OMG, Weinberg et al 47 found a 70% increased jitter in the ED muscle, emphasizing abnormal jitter in non-symptomatic muscles.…”

Section: Myasthenia Gravismentioning

confidence: 98%

“…53 In a high suspicion of MG with a seronegative AChR-Ab, the jitter measurement should be done in the facial muscles. 52,54,55 The sensitivity of a given electrophysiological test in 97 MG cases, 46 either OMG or GMG, is shown in ►Table 4. The sensitivity of the LFRNS increases by careful muscle selection depending on the most involved territory, ocular, bulbar, or generalized.…”

Section: Myasthenia Gravismentioning

confidence: 99%

“…The sensitivity of a given electrophysiological test in 97 MG cases, 46 either OMG or GMG, is shown in Table 4 . The sensitivity of the LFRNS increases by careful muscle selection depending on the most involved territory, ocular, bulbar, or generalized.…”

Section: Neuromuscular Junction Disordersmentioning

confidence: 99%

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Electrophysiological evaluation of the neuromuscular junction: a brief review

Kouyoumdjian,

Estephan

2023

Arq Neuropsiquiatr

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The nerve terminal and muscle membrane compose the neuromuscular junction. After opening the voltage-gated calcium channels, action potentials from the motor axons provoke a cascade for the acetylcholine release from synaptic vesicles to the synaptic cleft, where it binds to its receptor at the muscle membrane for depolarization. Low amplitude compound muscle action potential typically presents in presynaptic disorders, increasing by more than 100% after a 10-second effort in the Lambert-Eaton myasthenic syndrome and less in botulism. Needle electromyography may show myopathic motor unit action potentials and morphological instability (“jiggle”) due to impulse blocking. Low-frequency repetitive nerve stimulation (RNS) is helpful in postsynaptic disorders, such as myasthenia gravis and most congenital myasthenic syndromes, where the number of functioning acetylcholine receptors is reduced. Low-frequency RNS with a decrement >10% is abnormal when comparing the 4th to the first compound muscle action potential amplitude. High-frequency RNS is helpful in presynaptic disorders like Lambert-Eaton myasthenic syndrome, botulism, and some rare congenital myasthenic syndromes. The high-frequency RNS releases more calcium, increasing the acetylcholine with a compound muscle action potential increment. Concentric needle records apparent single-fiber action potentials (spikes). A voluntary activation measures the jitter between spikes from two endplates. An electrical activation measures the jitter of one spike (one endplate). The jitter is the most sensitive test for detecting a neuromuscular junction dysfunction. Most neuromuscular junction disorders are responsive to treatment.

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Section: Myasthenia Gravismentioning

confidence: 98%

Section: Myasthenia Gravismentioning

confidence: 99%

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Electrophysiological evaluation of the neuromuscular junction: a brief review

Kouyoumdjian,

Estephan

2023

Arq Neuropsiquiatr

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“…The range between the depolarization of two fibers of one single motor unit is called jitter. This is the most sensitive method of identifying a neuromuscular junction disorder, and its sensitivity ranges around 98% 23 . A normal jitter test practically excludes an abnormality in the tested muscle.…”

Section: Electrophysiologymentioning

confidence: 99%

Myasthenia gravis in clinical practice

Estephan

Baima

Zambon

2022

Arq. Neuro-Psiquiatr.

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Background: Myasthenia gravis is largely a treatable disease, but it can result in significant morbidity and even mortality, which can usually be avoided, or at least mitigated, with timely diagnosis and appropriate treatment of the disease. Objective: this review aims to summarize the main practical aspects of the diagnostic approach, treatment and care of myasthenic patients. Methods: The authors performed a non-systematic critical review summarizing the main practical aspects of myasthenia gravis. Results: Most patients with myasthenia have autoantibodies targeted at acetylcholine receptors or, less commonly, muscle-specific kinase - MuSK. Electrophysiology plays an important role in the diagnosis of neuromuscular junction dysfunction. The central clinical manifestation of myasthenia gravis is fatigable muscle weakness, which can affect eye, bulbar, respiratory, and limb muscles. With rare exceptions, patients have a good response to symptomatic treatment, but corticosteroids and/or immunosuppressants are usually also necessary to obtain good control of the manifestations of the disease. Conclusion: Knowledge of the peculiar aspects of their clinical and electrophysiological presentations is important for the diagnosis. Likewise, specific treatment and response time to each drug are crucial for proper care.

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