Sensitivity and specificity of single-fibre EMG in the diagnosis of ocular myasthenia varies accordingly to clinical presentation.
J Neurol
; 267(3): 739-745, 2020 Mar.
Article
en En
| MEDLINE
| ID: mdl-31734908
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 ANDMETHODS:
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.Palabras clave
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Base de datos:
MEDLINE
Asunto principal:
Electromiografía
/
Miastenia Gravis
Tipo de estudio:
Diagnostic_studies
Idioma:
En
Revista:
J Neurol
Año:
2020
Tipo del documento:
Article