Background: Synkinesis is an involuntary movement accompanying a voluntary one. These unintentional movements are caused by an undifferentiated regeneration of the facial nerve that occurs after being compressed or partially damaged. Synkinesis can affect eating, drinking, and speaking and can be socially distressing because of facial asymmetry and disruption of intended emotional expressions.
Objective: This study aims to describe the frequency and location of synkinesis in patients with peripheral facial nerve paresis.
Methods: Patients were observed on video and analyzed using a standardized Synkinesis Scoring Form. Five voluntary expressions, derived from the Sunnybrook Facial Grading Scale, were tested: brow lift, eye closure, smile, snarl, and lip pucker. The Kruskal-Wallis test, 95% confidence intervals, and analysis of variance were used to analyze data.
Results: Patients with a facial nerve paresis (n = 103) were observed, and all showed synkineses. Lifting-mouth-corner-synkinesis coupled to voluntary brow lift movements (89%) or eye closure (85%) occurred most frequently. The voluntary movement lip puckering evoked the most synkineses of the eye (narrowing, 82%). During all voluntary expressions lifting-brow-synkineses occurred the least (17%). A significant effect for sex and age (p < 0.05) was found but not for side and duration of the paresis (p > 0.05).
Conclusion: Mouth-corner-synkinesis is most common in brow lift and eye movements, whereas eye synkinesis is coupled to mouth movements. These are important facts for rehabilitation of facial nerve pareses, to refine and intensify the inhibition and control of synkineses so that facial symmetry and expressions may improve.