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Functional Outcomes in Facial Animation: Comparison of Innervation Sources
Alison Snyder-Warwick, MD; Leanne Zive; Adel Fattah; William Halliday; Gregory Borschel; Ronald Zuker; The Hospital for Sick Children
The Hospital for Sick Children, Toronto, Canada
Purpose: Facial paralysis carries significant functional and psychosocial implications. Free muscle transfer to the face is the standard treatment for dynamic smile reconstruction when reinnervation of native musculature is not feasible. Transferred muscle may be neurotized via two-stage procedures utilizing a cross-face nerve graft (CFNG) from the contralateral facial nerve or a single-stage procedure utilizing the motor nerve to the masseter muscle. We compare axonal counts and our results utilizing these two techniques.
Method: A retrospective review of patients undergoing dynamic smile reconstruction at our institution over a 7-year period was performed. Intraoperative neural biopsies were obtained for morphometric analysis for the donor nerve(s) (contralateral facial and CFNG or masseter) and compared with changes in oral commissure excursion and position postoperatively for each technique utilizing the Scaled Measurement in Lip Excursion software.
Results: Data for intraoperative neural biopsies were available in 45 two-stage procedures and 23 single-stage procedures, and photographs were analyzed in 47 patients. No significant differences were noted between the two groups for patient age at time of muscle transplantation or weight of the muscle segment utilized. For the two-stage technique, the downstream CFNG demonstrated a 74% decrease in axonal number(1647) from the donor branch of the contralateral facial nerve(6757). The motor branch to the masseter displayed over 3-fold greater myelinated axons(5289) compared to the CFNG. The improvement in oral commissure excursion was 2-fold greater when the motor nerve to the masseter (8.1mm) was utilized compared to the CFNG group (4.1mm). Symmetry in oral commissure excursion improved by 6.2mm in the CFNG group and 10.6mm in the motor nerve to the masseter group after reconstruction. Both techniques resulted in improved symmetry of the vertical height of the oral commissure.
Conclusions: Both single-stage and two-stage facial animation techniques are effective. The motor branch to the masseter has more axons available to power a free muscle transfer compared to a CFNG, and this correlates clinically with improved oral commissure excursion, symmetry, and vertical height.
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