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Outcomes of Mini-Hypoglossal Nerve Transfer and Direct Muscle Neurotization for Restoration of Lower Lip Function in Facial Palsy

Background: Most reconstructions for lower lip palsy focus on paralyzing the contralateral normal lip or providing static support on the affected side. The authors’ unit has reported dynamic strategies for lower lip reanimation and use of 40 percent of the hypoglossal nerve (mini-hypoglossal) in facial reanimation. They report their experience with mini-hypoglossal nerve transfer for lower lip palsy. Methods: Between 1987 and 2005, 29 patients with unilateral facial palsy had lower lip reanimation with the mini-hypoglossal as the motor donor. Twenty patients had transfer of the mini-hypoglossal to the cervicofacial branch of the facial nerve and nine had direct depressor muscle neurotization. Five patients had a mean denervation time of 14.60 ± 4.50 months (<2 years), and the rest had a mean denervation time of 10.63 ± 9.23 years. In late cases, the facial nerve was in-continuity, and preoperative needle electromyographs of depressors showed at least fibrillations. Standardized videos taken preoperatively and at 2 years postoperatively were available for 27 patients and assessed by three independent reviewers. Needle electromyographic results were analyzed. Results: Thirteen patients (48.15 percent) achieved excellent and good results, nine (33.33 percent) had moderate results, and five (18.52 percent) obtained fair results. The difference between the averaged preoperative and postoperative scores was statistically significant, as was the difference in electromyographic outcomes (p < 0.0001, Wilcoxon signed rank test). The nerve transfer and direct neurotization groups had no statistically significant difference in clinical and electromyographic outcomes. Four patients required muscle transfer for further outcome upgrading. Conclusion: Use of the mini-hypoglossal either for nerve transfer or for direct muscle neurotization of lower lip depressors can provide reinnervation and satisfactory clinical function, even for muscles with prolonged partial denervation.