Using the Post-Descendens Hypoglossal Nerve in Hypoglossal-Facial Anastomosis: An Anatomic and Histologic Feasibility Study

BACKGROUND: Hypoglossal-facial anastomosis (HFA) is a popular facial reanimation technique. Mobilizing the intratemporal segment of the facial nerve and using the postdescendens hypoglossal nerve (ie, the segment distal to the take-off of descendens hypoglossi) have been proposed to improve results. However, no anatomic study has verified the feasibility of this technique. OBJECTIVE: To assess the anatomic feasibility of HFA and the structural compatibility between the 2 nerves when the intratemporal facial and post-descendens hypoglossal nerves are used. METHODS: The facial and hypoglossal nerves were exposed bilaterally in 10 sides of 5 cadaveric heads. The feasibility of a side-to-end (ie, partial end-to-end) HFA with partial sectioning of the post-descendens hypoglossal nerve and the mobilized intratemporal facial nerve was assessed. The axonal count and cross-sectional area of the facial and hypoglossal nerves at the point of anastomosis were assessed. RESULTS: The HFA was feasible in all specimens with a mean (standard deviation) 9.3 (5.5) mm of extra length on the facial nerve. The axonal counts and cross-sectional areas of the hypoglossal and facial nerves matched well. Considering the reduction in the facial nerve cross-sectional area after paralysis, the post-descendens hypoglossal nerve can provide adequate axonal count and area to accommodate the facial nerve stump. CONCLUSION: Using the post-descendens hypoglossal nerve for side-to-end anastomosis with the mobilized intratemporal facial nerve is anatomically feasible and provides adequate axonal count for facial reanimation. When compared with use of the predescendens hypoglossal nerve, this technique preserves C1 fibers and has a potential to reduce glottic complications.