Surgical anatomy of the facial nerve

(1) The temporal branch of the facial nerve emerges within the parotid gland to cross the zygomatic arch at the deep surface of the temporoparietal fascia. The nerve is separated from the deep temporal fascia immediately above the zygomatic arch by a loose areolar plane; this plane may be obliterated when previous surgical procedures have been performed in this region. (2) The temporal branch can be found within a trajectory that has been described relating the lower portion of the auricle to the lateral aspect of the eyebrow. However, one must be aware that these surface landmarks may vary with respect to the underlying skeleton and from one individual to the next. (3) Recent studies indicate that the temporal branch consists of not one, but multiple rami that cross the zygomatic arch. Because there are multiple rami to the temporal branch of the facial nerve, any single trajectory can describe only a portion and not the entirety of the temporal branch. (4) The zygomatic, buccal, and marginal mandibular branches of the facial nerve innervate the mimetic muscles of the face from either their superficial or deep surfaces. Several mimetic muscles are innervated by two or more branches of the facial nerve. (5) Interconnections between the zygomatic and buccal branches are noted in over 70% of cases, whereas interconnections between the temporal or marginal mandibular branches to other facial nerve branches occur in less than 15% of cases. (6) The zygomatic, buccal, and marginal mandibular branches lie in intimate relationship with the retaining ligaments of the face. Surgical dissection for release of the zygomatic ligament, the masseteric cutaneous ligament, or the mandibular ligament should be performed meticulously and with extreme caution.