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Background: The purpose of this review is to provide an overview of the available literature assessing the treatment of botulinum toxin injections for the treatment of synkinesis of the buccinator muscle in patients with peripheral facial palsy (PFP)., Materials and Methods: A multi database search was performed, including the following databases: Pubmed, Medline, Embase, and the Cochrane Library. Each database was searched from its earliest date until 8 June 2023. The following outcome measures were extracted from the articles when available: subjective, somatic, and psychological effects on the patients and objective outcomes such as the House-Brackmann, Sunnybrook and Sydney scores. The methodological quality of the included studies was rated using the Newcastle-Ottawa scale for nonrandomised trials., Results: The primary literature search generated 37 articles. After removing duplicates, 25 articles remained for abstract appraisal, of which 20 underwent full-text appraisal, resulting in 3 studies for analysis. All of these studies showed (significant) improvement in synkinesis either measured using the Synkinesis Assessment Questionnaire or subjectively measured by asking treated patients., Conclusion: The available literature supports the finding that botulinum toxin treatment of the buccinator muscle could be a welcome addition to facial synkinesis treatment and could significantly improve patient outcomes. In future studies, the efficacy of EMG-guided buccinator injections, optimal dose, and a validated measuring method could be beneficial in optimising treatment for patients with a PFP and synkinesis., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

Background: Synkinesis is defined as involuntary movements accompanying by voluntary movements and can occur during the aftermath of peripheral facial palsy, causing functional, aesthetic and psychological problems in the patient. Botulinum toxin A (BTX-A) is frequently used as a safe and effective treatment; however, there is no standardized guideline for the use of BTX-A in synkinesis. The purpose of this article is to review and summarize studies about the BTX-A treatment of synkinesis in patients with a history of peripheral facial palsy; including given dosages, injection sites and time intervals between injections., Materials and Methods: A multi-database systematic literature search was performed in October 2020 using the following databases: Pubmed, Embase, Medline, and The Cochrane Library. Two authors rated the methodological quality of the included studies independently using the 'Newcastle-Ottawa Quality Assessment Scale' for non-randomised studies' (NOS)., Results: Four-thousand-five-hundred-and-nineteen articles were found of which 34 studies met the inclusion criteria, in total comprising 1314 patients. Most studies were assessed to be of 'fair' to 'good' methodological quality. The Cohen's kappa (between author FJ and AS) was 0.78. Thirty-one studies investigated the reported dosage injected, 17 studies reported injection location and 17 studies investigated time intervals. A meta-analysis was performed for three studies comprising 106 patients, on the effects of BTX-A treatment on the Synkinesis Assessment Questionnaire (SAQ) scores. The mean difference was 11.599 (range 9.422-13.766), p < 0.01. However, due to inconsistent reporting of data of the included studies, no relationship with the dosage and location could be assessed., Conclusions: Many treatment strategies for synkinesis exist, consisting of varying BTX-A brands, dosages, time intervals and different injection locations. Moreover, the individual complaints are very specific, which complicates creating a standardized chemodenervation treatment protocol. The BTX-A treatment of long-term synkinesis is very individual and further studies should focus on a patient-tailored treatment instead of trying to standardize treatment., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)