Electroneurography in the acute stage of facial palsy as a predictive factor for the development of facial synkinesis sequela

Abstract

Objective: We investigated whether the value of ENoG is a predictive factor for the development of facial synkinesis in patients with facial palsy.

Methods: The degree of oral-ocular synkinesis was evaluated quantitatively by an asymmetry of the interpalpebral space width during the mouth movement (% eye opening). Twenty healthy volunteers without a history of facial palsy (12 men and 8 women; 25-65 years old; mean age: 42.3±9.7years) were included in the study to examine the normal range of % eye opening. Fifty-one patients with facial palsy including 38 with Bell palsy and 15 with herpes zoster oticus (28 men and 25 women; 11-86 years old; mean age: 54±19years) were enrolled to examine the relationship between the ENoG value 10-14days after the onset of facial palsy, and the % eye opening 12 months later. Receiver operating characteristic (ROC) curve for the ENoG value was then used to decide the optimum cut-off value as a predictor of the development of oral-ocular synkinesis.

Results: We defined a % eye opening inferior to 85% as an index of the development of oral-ocular synkinesis. There was a significant correlation between the values of ENoG 10-14days after the onset of facial palsy and those of % eye opening 12 months later (ρ=0.81, p<0.001). The area under the ROC curve for the ENoG value was the predictor for the development of oral-ocular synkinesis at 0.913 (95%CI: 0.831-0.996, p<0.001). The optimum cut-off value of ENoG 10-14days after the onset of facial palsy was 46.5% to predict the development of oral-ocular synkinesis 12 months after the onset of facial palsy (sensitivity 97.1% and specificity 77.5%).

Conclusion: The value of ENoG 10-14days after the onset of facial palsy is a predictive factor for the development of facial synkinesis 12 months later. Since facial palsy patients with a ENoG value inferior to 46.5% have a high risk of developing synkinesis, they should receive the facial biofeedback rehabilitation with a mirror as a preventive therapy.

Keywords: % eye-opening; Electroneurography; Facial palsy; Facial synkinesis; Predictive factor.