Diagnostic value of orbicularis oculi muscle electromyography in functional epiphora.

BACKGROUND Functional epiphora is a clinical condition which is not due to an anatomic defect. Most studies agree that it involves the action of the orbicularis oculi muscle, particularly its deeper segment (Horner's muscle), but the exact mechanism is not clear. AIM To evaluate the orbicularis oculi muscle in functional epiphora patients using electromyography (EMG). METHODS A total of 8 Chinese patients (16 eyes) with functional epiphora were enrolled in this study, and ten volunteers (10 eyes) were included as normal controls. Five epiphora patients (five eyes) with facial palsy served as positive controls. Quantitative EMG was performed in the deeper segment of orbicularis oculi muscle. The average duration of each EMG waveform was measured. RESULTS The average duration of EMG waveforms in the normal control group, the functional epiphora group, and the facial palsy group were 6.39 +/- 0.73 ms, 9.39 +/- 1.32 ms and 11.2 +/- 1.42 ms, respectively. The duration of EMG waveforms was significantly longer in the functional epiphora group than in the normal control group (P< 0.05), and shorter than that in the facial palsy group (P< 0.05). CONCLUSION These data indicate the presence of neurogenic orbicularis oculi muscle damage in epiphora patients, which may be the cause of functional epiphora. The etiology of neurogenic damage in the orbicularis oculi muscle requires further investigation.