Anatomic Study of the Peripheral Motor Branches of the Swine Facial Nerve

Introduction: Our face represents one of the most unique aspects of an individual. Facial paralysis can lead to both functional and psychosocial consequences. New surgical approaches and medical devices for this disease can be developed with the help of large animal models. However, current literature lacks information about the anatomy of the facial nerve in swine. Hence, the purpose of this study was to investigate the branching pattern and histologic characteristics of the swine facial nerve to establish a preclinical animal model for future studies. Materials and Methods: The anatomic course of the peripheral motor branches of the facial nerve was carefully dissected in 30 hemifaces of fresh swine cadavers. Starting from the stylomastoid foramen, the branching pattern was recorded, and histology samples were taken. All samples were epoxy embedded and stained with toluidine blue for histomorphologic analysis. Results: The dissections regarding the branching pattern demonstrated consistent anatomy of the buccal and marginal mandibular branch in contrast to the temporal and zygomatic branch. The buccal branch had the largest mean diameter of 1.34 mm (+/- 0.26), whereas the marginal mandibular branch had the largest fascicular area of 536,823,268.63 μm2 (+/- 68,594,056.81) and highest axon count with 3,636.35 axons (+/- 526.36). The zygomatic branch appeared to be the smallest branch with a diameter of 0.74 mm (+/- 0.25) and a fascicular area of 133,018,365.40 μm2 (+/- 108,968,870.33). Conclusion: Swine models are a useful pre-clinical animal model, as pig facial nerve anatomy presented similarly to human anatomy. General anatomic knowledge about the facial nerve and its branching pattern in pigs will serve as a baseline for future facial paralysis research.