Dual Versus Single Innervation of Gracilis Free Functional Muscle Transfer in Facial Paralysis - Long-Term Resting and Dynamic Outcomes.

BACKGROUND: Comparing long-term tone and excursion between single- versus dual-innervated free functional muscle transfer (FFMT) in patients with longstanding facial paralysis.

METHODS: Longstanding facial palsy patients treated with a FFMT innervated either by a nerve-to-masseter (single-innervation group) or by nerve-to-masseter and cross-facial-nerve graft (dual-innervation group) were included. One year minimal follow up was required. Outcome measures, based on standardized photos, included excursion, smile angle, teeth exposure, commissure height deviation, and upper lip height deviation in repose and in closed and open teeth smile preoperatively, and at 3-months, 1-year, and 3-years postoperatively. Emotrics software (Massachusetts Eye and Ear Infirmary, Boston, MA) and ImageJ (Rasband, W.S., ImageJ, U.S, National Institutes of Health, Bethesda, MD) were used for measurements. Between group and within group longitudinal comparisons were analyzed.

RESULTS: At three years (single=24, dual=13), significance was found between groups in commissure position (single=26.42mm, dual=31.51mm, p<0.0001) and excursion with open mouth smile (single=31.32mm, dual=26.59mm, p<0.001). Single-innervation FFMT within group analysis lacked significant improvement in commissure height deviation and upper lip height deviation at 3 years in repose, while dual-innervation group revealed significant improvements (3.67mm and p<0.001, 3.17mm and p<0.001 respectively). Teeth exposure revealed an increase in the dual-innervation group (single=35.753 mm 2, dual=64.177 mm 2), albeit significance was not observed.

CONCLUSIONS: Dually innervated FFMT revealed improvements in resting tone and teeth exposure with minimal decrease in smile excursion compared with single innervated FFMT.