Masseteric-to-Facial Nerve Transfer and Selective Neurectomy for Rehabilitation of the Synkinetic Smile

Synkinesis is the involuntary movement of 1 area of the face accompanying volitional movement of another; it is commonly encountered in patients affected by facial palsy. Current treatments for synkinesis include biofeedback for muscular retraining and chemodenervation via the injection of botulinum toxin. Chemodenervation is effective in reducing unwanted muscle movement, but it requires a commitment to long-term maintenance injections and may lose effectiveness over time. A permanent solution for synkinesis remains elusive.

To evaluate masseteric-to-facial nerve transfer with selective neurectomy in rehabilitation of the synkinetic smile.

In this case series, 7 patients at a tertiary care teaching hospital underwent masseteric-to-facial nerve transfer with selective neurectomy for synkinesis between September 14, 2015, and April 19, 2018. The medical records of these patients were retrospectively reviewed and demographic characteristics, facial palsy causes, other interventions used, and changes in eFACE scores were identified.

Masseteric-to-facial nerve transfer.

Changes in eFACE scores (calculated via numeric scoring of many sections of the face, including flaccidity, normal tone, and hypertonicity; higher scores indicate better function and lower scores indicate poorer function) and House-Brackmann Facial Nerve Grading System scores (range, 1-6; a score of 1 indicates normal facial function on the affected side, and a score of 6 indicates absence of any facial function [complete flaccid palsy] on the affected side).

Among the 7 patients in the study (6 women and 1 man; median age, 49 years [range, 41-63 years]), there were no postoperative complications; patients were followed up for a mean of 12.8 months after surgery (range, 11.0-24.5 months). Patients experienced a significant improvement in mean (SD) eFACE scores in multiple domains, including smile (preoperative, 65.00 [8.64]; postoperative, 76.43 [7.79]; P = .01), dynamic function (preoperative, 62.57 [15.37]; and postoperative, 75.71 [8.48]; P = .03), synkinesis (preoperative, 52.70 [4.96]; and postoperative, 82.00 [6.93]; P < .001), midface and smile function (preoperative, 60.71 [13.52]; and postoperative, 78.86 [14.70]; P = .02), and lower face and neck function (preoperative, 51.14 [16.39]; and postoperative, 66.43 [20.82]; P = .046). Preoperative House-Brackmann Facial Nerve Grading System scores ranged from 3 to 4, and postoperative scores ranged from 2 to 3; this change was not significant.

This study describes the application of masseteric-to-facial nerve transfer with selective neurectomy for smile rehabilitation in patients with synkinesis, with statistically significant improvement in smile symmetry and lower facial synkinesis as measured with the eFACE tool. This technique may allow for long-term improvement of synkinesis and smile. This study is only preliminary, and a larger cohort will permit more accurate assessment of this therapeutic modality.

4.