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

Abstract

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.

Ocular vestibular evoked myogenic potentials as a test for myasthenia gravis

“…24 In ocular MG, SFEMG is considered the diagnostic gold standard, as reflected by four studies reporting a high sensitivity of 92-97% [25][26][27][28] , although two other groups found lower sensitivities of 83% and 62%. 29,30 Comparison of different electromyographic tests in ocular MG demonstrated that the closer the measurement to the extraocular muscles, the higher the sensitivity. In contrast to SFEMG, oVEMP not only directly assess the extraocular muscles, but is also better tolerated, because it is less invasive, less cumbersome and less operator-dependent.…”

Concentric needle single fiber electromyography: normative jitter values on voluntary activated Extensor Digitorum Communis

“…The recording allows a high recording selectivity, which is further increased by filtering the low-frequency components (high pass filter) to reduce the contribution from distant muscle fibers which contains relatively more low frequency components than high frequency components compared to signals adjacent to the recording tip 2 . The use of a reusable electrode as the specific SFEMG has raised concern regarding the risk of transmission of infectious agents such as prion disease 10,11 . Because of that, attempts are being in course to use disposable concentric needle electrode (CNE) 8,10,11 .…”

“…The use of a reusable electrode as the specific SFEMG has raised concern regarding the risk of transmission of infectious agents such as prion disease 10,11 . Because of that, attempts are being in course to use disposable concentric needle electrode (CNE) 8,10,11 . The low-frequency filter should then typically be raised from 500 Hz to 1-2 kHz in order to suppress activity from distant muscle fibers 10,11 .…”

Análise do jitter com agulha concêntrica em pacientes com miastenia gravis autoimune adquirida

“…Recentemente, com a necessidade crescente de utilização de material descartável em procedimentos médicos, incluindo os eletrodos de agulha utilizados em eletroneuromiografia (ENMG), iniciou-se uma série de estudos usando eletrodos de agulha convencionais descartáveis, por exemplo, a agulha monopolar (Wiechers, 1985;Buchman, Garratt, 1992;Tutkavul, Baslo, 2010) e a agulha concêntrica (AC) (Ertaş et al, 2000;Benatar et al, 2006;Sarrigiannis et al, 2006;Kouyoumdjian, Stålberg, 2007;2008a;2008b;2013a). Em comparação com as agulhas monopolar e concêntrica, a AFU possui área de registro muito mais seletiva (King et al, 1997).…”

“…Adicionalmente à filtragem de sinais, são necessários cuidados técnicos na aceitação dos PAs obtidos com AC para análise do jitter (Sanders, Stålberg, 1996;Ertaş et al, 2000;Benatar et al, 2006;Sarrigiannis et al, 2006;Kouyoumdjian, Stålberg, 2007;Stålberg, Sanders, 2009 (Stålberg, Sanders, 2009;Stålberg et al, 2010). Além da velocidade de propagação nas fibras musculares individuais (Stålberg, 1966) e do jitter neuromuscular (Stålberg et al, 1971;Ekstedt et al, 1974), a EMGFU também permite o estudo da distribuição das fibras musculares nas unidades motoras individuais, denominado densidade de fibras (Gath, Stålberg, 1976).…”