Synkinetic Spread and Hyperexcitability: Orbicularis Oris Recovery in Post-facial Synkinesis

Abstract

Objective: Synkinesis after peripheral facial palsy is seen during spontaneous movements or reflex activity. The aim of the study was to investigate the recovery of the blink reflex (BR) R2-locked response on orbicularis oris (O.or) muscle, which is assumed to be caused by synkinetic spread of R2 recorded on orbicularis oculi (O.oc) in post-facial synkinesis. Materials and Methods: A group of 20 patients who had post-facial synkinesis (5 males, 15 females and mean age: 38.1±18.0 years) and 20 healthy individuals (9 males, 11 females and mean age: 42.7±11.8 years) were included. Responses following single and paired electrical stimulations of the supraorbital nerve were recorded over bilateral O.oc in all participants and over O.or on the symptomatic side of patients. Latencies (for R1, R2 and R2-locked response on O.or) and area under the curve [(AUC), for R2 and R2-locked response on O.or] were measured. Recovery rates of R2 and R2-locked responses recorded over O.or at interstimulus intervals of 200, 600, and 1000 ms were calculated and compared. Results: R1 and R2 latencies were longer and R2 AUC was smaller on the symptomatic side; however, the recovery rate of BR-R2 AUC was higher on the symptomatic side in the patient group. The recovery rate of R2-locked responses on O.or was also high and early, which was statistically similar to the recovery of R2. Conclusion: In the presence of postparalytic facial syndrome, there is a R2-locked response on the O.or exhibiting high recovery rates similar to R2, suggesting a similar behavior and increased excitability of O.oc and O.or motoneurons or related circuits.

Keywords

• facial synkinesis
• blink reflex recovery
• orbicularis oris
• r2-locked response