Too much or too little? A systematic review of postparetic synkinesis treatment.

Synkinesis is a negative sequela of facial nerve recovery. Despite the need for effective treatment, controversy exists regarding optimal management and outcome reporting measures. The goals of this study were to evaluate the current synkinesis literature and compare the effectiveness of treatment modalities. A search of biomedical databases was performed in May 2019. Full-text English language articles of cohort studies or randomized controlled trials on synkinesis treatment were eligible for inclusion. Reviews, animal studies, and those without assessment of treatment effect were excluded. We found 592 unique citations; 33 articles were included in the final analyses. Nine studies focused on botulinum toxin (BTX-A), 7 on surgery, 5 on physical therapy (PT), and 12 on multimodal therapy. The Sunnybrook Facial Grading System was the most frequently used outcome measure (17 studies, 51.5%). All treatment modalities improved outcomes. Chemodenervation studies showed an average improvement of 17.8% (range 11-33.3%) in the respective outcome measures after treatment. PT improved by 29.7% (range 14.6-41.2%), surgery by 16.6% (range 4.7-41%), and combination therapy by 20.4% (range 5.13-37.5%). Only 21 studies (63.6%) provided data on adverse outcomes. There is lack of high-evidence level data for robust comparisons of postparetic synkinesis treatments; however, this condition is likely effectively treated nonsurgically and requires the support of a specialized multidisciplinary team. Adoption of standardized patient evaluation and outcome reporting methods is necessary for robust comparative effectiveness studies.