Surgical Anatomy of the Facial Nerve Trunk

Objective: To gain accurate knowledge of the location of the facial nerve trunk with reference to the plane, depth, and its branching pattern. This information is necessary during surgery of the parotid, mastoid, and temporomandibular joints and in reconstruction of the facial nerve.Materials and Methods: Twenty-eight cadaver head halves of both genders aged 28 to 85 years were dissected. The position of the bifurcation of the facial nerve trunk and distance from several anatomical landmarks to the facial nerve were collected to assess the depth of the facial nerve.Results: The facial nerve emerged from the stylomastoid foramen and was found to lie medial to the posterior belly of the digastric muscle. In 2 cases (7%), the bifurcation was proximal to the glandular substance. The shortest distances from the tragal point to the facial nerve trunk and to the bifurcation were 10.08 ± 2.34 mm and 13.97 ± 2.72 mm, respectively. The distance from the bifurcation to the mastoid tip was 16.28 ± 2.87 mm, from the bifurcation to the most caudal point of the external auditory meatus was 19.64 ± 2.98 mm and from bifurcation to the lowest point of the postglenoid tubercle was 23.83 ± 3.28 mm. The length of the facial nerve trunk from the stylomastoid foramen to the bifurcation was 18.51 ± 3.80 mm and the diameter at the stylomastoid foramen was 1.78 ± 0.31 mm.Conclusions: The results of this study will be useful in locating the facial nerve with higher accuracy during relevant surgery.