Does Electrical Stimulation Therapy Influence Synkinesis in Facial Paralysis? A Systematic Review

Objective: Facial paralysis (FP) has aesthetic, social, and functional consequences. While electrical stimulation (ES) shows promise for peripheral nerve injury, its role in FP remains controversial due to concerns about increasing synkinesis. Data Sources: A literature review was conducted using Medline/PubMed, Cochrane, and Web of Science databases. Review Methods: Included studies evaluated the incidence or severity of synkinesis after ES in FP patients. Extracted data included demographics, ES parameters, FP etiology, synkinesis outcomes, and treatment duration. Results: Of 601 identified articles, 6 met inclusion criteria, comprising 243 patients (92 female, reported in 5 studies). Bell's palsy was the most common FP etiology (76.5%), followed by iatrogenic facial nerve injury (20.2%). Time to treatment ranged from 1 week to 7 years post-onset. Treatment durations varied from 2 weeks to 29 months, with inter-impulse gaps of 30 to 3000 milliseconds, phase durations of 10 to 700 milliseconds, and amplitudes of 0.5 to 27 mA. All ES was transcutaneous. Three of 5 studies reported no differences in synkinesis scores between ES and control groups. Two studies found no differences in synkinesis incidence. Only one study showed reduced synkinesis in the ES group. Conclusions: This study represents an up-to-date review of synkinesis in FP patients receiving ES. Evidence suggests a benefit in overall facial function for patients without significant additional risk of synkinesis. Inconsistencies in synkinesis outcomes and measurement underscore the need for further research in this area.