Utility of single fiber electromyography in the diagnostic evaluation of patients with isolated ocular symptoms

Objective: Ptosis and diplopia are frequent presentation symptoms in the emergency rooms, ophthalmology and neurology clinics. Most of these cases are referred for single fiber electromyographic (SFEMG) to confirm or rule out ocular myasthenia gravis (OMG). The aim of this study is to investigate the clinical utility of SFEMG/jitter analysis with concentric needle electrode (CNE) in the assessment of patients with ocular symptoms and signs. Material and methods: The clinical and electrophysiological data of patients with isolated ocular symptoms, who were referred for CNE-jitter analysis to our laboratory for the last 3 years, were retrospectively reviewed. Results: A total of 122 cases (78 female, 44 male) were included in the study. In retrospective review of the follow-up charts, 62.3% of them were found to have non-myasthenic disorders. Only 37.7% of the patients had the final diagnosis of OMG. The presence of both ptosis and diplopia, diurnal fluctuation and alternating patern were likely to be indicative of OMG (p<0,001). CNE-jitter analysis in the frontalis muscle was found to have a sensitivity of 80.4%, specificity of 90.8%, positive predictive value of 84.1%, and negative predictive value of 88.5% in the diagnosis of OMG. Conclusion: This study confirms the favorable diagnostic accuracy of CNE-jitter analysis in OMG, in concordance with the literature. However, it draws attention to the overutilization of SFEMG and frequent misdiagnosis/overestimation of OMG in clinical practice. Key words: Ocular myasthenia gravis, single fiber electromyography, ptosis, diplopia, misdiagnosis