Maria Pia Giannoccaro1,2, Vitantonio Di Stasi3, Corrado Zanesini3, Vincenzo Donadio3, Patrizia Avoni4,3, Rocco Liguori4,3. 1. Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy. mpgiannoccaro@gmail.com. 2. IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy. mpgiannoccaro@gmail.com. 3. IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy. 4. Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy.
Abstract
BACKGROUND AND PURPOSE: Single-fibre electromyography (SF-EMG) is considered as the most sensitive test for the diagnosis of MG. However, previous studies had limitations, such as a retrospective design, non-consecutive sampling, incorporation bias or were performed in small or mixed populations. Our aims were to determine the diagnostic sensitivity and specificity of SF-EMG of the orbicularis oculi in OMG and the utility of this test in relation to patients' clinical presentation. MATERIALS AND METHODS: We studied 232 consecutive patients referred to the SF-EMG laboratory for a suspected OMG. Stimulated SF-EMG was performed on the orbicularis oculi muscle. RESULTS: OMG was diagnosed in 165 cases and other disorders (OD) in 67. SF-EMG showed a sensitivity of 0.79 (95% CI 0.73-0.85) and a specificity of 0.80 (95% CI 0.71-0.90). False negative results were associated with mild symptoms and with isolated diplopia. Comparison of the diagnostic yield among patients with different clinical presentations showed a similar diagnostic accuracy of SF-EMG in patients with ptosis and in patients with ptosis and diplopia, significantly higher than in patients with isolated diplopia (P < 0.0001). Twenty-two patients with OMG presenting with isolated ptosis or diplopia, who initially tested negative, were re-tested in relation to a worsening of their symptoms showing a positivisation in 91% of cases. CONCLUSIONS: SF-EMG on the orbicularis oculi muscle is very sensitive in patients with ptosis. In contrast, in patients with isolated diplopia SF-EMG does not exclude OMG. Therefore, the interpretation of the results of the test should take into account the patients' clinical presentation.
BACKGROUND AND PURPOSE: Single-fibre electromyography (SF-EMG) is considered as the most sensitive test for the diagnosis of MG. However, previous studies had limitations, such as a retrospective design, non-consecutive sampling, incorporation bias or were performed in small or mixed populations. Our aims were to determine the diagnostic sensitivity and specificity of SF-EMG of the orbicularis oculi in OMG and the utility of this test in relation to patients' clinical presentation. MATERIALS AND METHODS: We studied 232 consecutive patients referred to the SF-EMG laboratory for a suspected OMG. Stimulated SF-EMG was performed on the orbicularis oculi muscle. RESULTS: OMG was diagnosed in 165 cases and other disorders (OD) in 67. SF-EMG showed a sensitivity of 0.79 (95% CI 0.73-0.85) and a specificity of 0.80 (95% CI 0.71-0.90). False negative results were associated with mild symptoms and with isolated diplopia. Comparison of the diagnostic yield among patients with different clinical presentations showed a similar diagnostic accuracy of SF-EMG in patients with ptosis and in patients with ptosis and diplopia, significantly higher than in patients with isolated diplopia (P < 0.0001). Twenty-two patients with OMG presenting with isolated ptosis or diplopia, who initially tested negative, were re-tested in relation to a worsening of their symptoms showing a positivisation in 91% of cases. CONCLUSIONS: SF-EMG on the orbicularis oculi muscle is very sensitive in patients with ptosis. In contrast, in patients with isolated diplopia SF-EMG does not exclude OMG. Therefore, the interpretation of the results of the test should take into account the patients' clinical presentation.
Authors: Donald B Sanders; Kimiyoshi Arimura; LiYing Cui; Mustafa Ertaş; Maria Elena Farrugia; James Gilchrist; João Aris Kouyoumdjian; Luca Padua; Matthew Pitt; Erik Stålberg Journal: Clin Neurophysiol Date: 2019-04-27 Impact factor: 3.708
Authors: Yew Long Lo; Raymond P Najjar; Kelvin Y Teo; Sharon L Tow; Jing Liang Loo; Dan Milea Journal: J Neurol Sci Date: 2017-03-14 Impact factor: 3.181