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.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. 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. 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.
Sensitivity and specificity of single-fibre EMG in the diagnosis of ocular myasthenia varies accordingly to clinical presentation / Giannoccaro, Maria Pia; Di Stasi, Vitantonio; Zanesini, Corrado; Donadio, Vincenzo; Avoni, Patrizia; Liguori, Rocco. - In: JOURNAL OF NEUROLOGY. - ISSN 0340-5354. - ELETTRONICO. - 267:(2020), pp. 739-745. [10.1007/s00415-019-09631-3]
Sensitivity and specificity of single-fibre EMG in the diagnosis of ocular myasthenia varies accordingly to clinical presentation
Giannoccaro, Maria Pia
;Di Stasi, Vitantonio;Donadio, Vincenzo;Avoni, Patrizia;Liguori, Rocco
2020
Abstract
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.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. 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. 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.