Chapter 11: Head and Neck
Which intraoperative technique during parotidectomy is used to locate the main trunk of the extracranial facial nerve?
(A) Identification of posterior aspect of the sternocleidomastoid muscle
(B) Identification of the anterior belly of the digastric muscle
(C) Retrograde tracking of the marginal mandibular nerve
(D) Retrograde tracking of the greater auricular nerve
(E) Identification of the tympanosquamousal suture line
(C) The facial nerve begins as the fascioacoustic primordium during the third week of gestation, and by the eleventh week, most of its branching is complete. The facial nerve is the most superficial structure to pass through the parotid gland, dividing it into superficial and deep lobes. The nerve first exits the skull base at the stylomastoid foramen and then courses anteriorly and somewhat inferiorly toward the posterior surface of the parotid gland. The pes anserinus is the point at which the facial nerve divides into its temporozygomatic (upper) and cervicofacial (lower) divisions within the parotid gland (see Fig. 11-7). Once the anterior border of the parotid is reached, the nerve will have divided into its five branches: temporal, zygomatic, buccal, marginal mandibular, and cervical (see Fig. 11-8). In children under age 3, the mastoid bone is poorly developed, and the facial nerve courses much more superficially and caudally.
FIGURE 11-7. Intraoperative photograph of the pes anserinus in the parotid gland.
FIGURE 11-8. Identification of the main trunk of the facial nerve and Stensen's duct. From Brunicardi F, Andersen DK, Billiar TR, et al. (eds.), Schwartz's Principles of Surgery, 10th ed. New York, NY: McGraw-Hill; 2014:Fig. 18-44.
A superficial parotidectomy begins with a preauricular incision that curves around the lobule of the ear to the mastoid extending into the neck past the angle of the mandible in a natural skin crease. Anterior and posterior skin flaps are developed to ensure exposure of the entire gland. The mastoid and anterior border of the sternocleidomastoid (SCM) are located. The posterior belly of the digastric is then located, which marks the level of the nerve from a superficial to deep plane. The gland is then separated by blunt dissection from the cartilage of the external auditory canal, and the tragal pointer (the medial-most aspect of the cartilaginous portion of the external auditory canal [EAC]) is exposed. The main trunk of the facial nerve is identified approximately 1 cm medial and anterior the tragal pointer, exiting the stylomastoid foramen immediately posterior to the styloid process entering the parotid gland immediately anterior to the insertion of the digastric muscle into ...