Branches of the Facial Nerve
The facial nerve (CN VII) divides into five terminal branches after exiting the stylomastoid foramen and traversing the parotid gland: temporal, zygomatic, buccal, marginal mandibular, and cervical branches. 1
Anatomical Course and Segments
The facial nerve follows a complex path from its origin to its terminal branches 1:
Intracranial segments: The nerve originates from nuclei in the pons, courses superiorly along the pontine surface, exits at the pontomedullary sulcus (root exit point), traverses the cerebellopontine angle (cisternal segment), enters the internal auditory canal (meatal segment), and courses through the temporal bone 1
Intratemporal segments: Within the temporal bone, the nerve passes through the labyrinthine, tympanic, and mastoid segments, with the geniculate ganglion located at the sharp posterior turn 1
Extracranial segment: The nerve exits the temporal bone at the stylomastoid foramen and courses through the parotid gland, where it divides into its terminal branches 1
Terminal Branches and Their Functions
The five terminal branches innervate the muscles of facial expression 2:
Temporal branch: Innervates muscles of the forehead and upper face; crosses the zygomatic arch at the deep surface of the temporoparietal fascia 3
Zygomatic branch: Supplies muscles around the eye and upper cheek region 4, 5
Buccal branch: Innervates muscles of the mid-face and cheek 4, 5
Marginal mandibular branch: Supplies muscles of the lower lip and chin 4, 5
Cervical branch: Innervates the platysma muscle of the neck 4, 5
Functional Components
The facial nerve is one of the most complex cranial nerves, containing four functional components 1, 2, 1:
Branchial motor fibers: Innervate muscles of facial expression (the primary clinical focus) 2
Visceral motor (parasympathetic) fibers: Provide parasympathetic innervation to most glands of the head, including lacrimal and salivary glands 2
General sensory fibers: Supply surface sensation to a small portion of the external ear and tympanic membrane 2
Special sensory fibers: Mediate taste sensation to the anterior two-thirds of the tongue via the chorda tympani nerve 2
Branching Pattern Variations
The facial nerve trunk typically bifurcates into temporofacial (upper) and cervicofacial (lower) divisions approximately 13.0 ± 2.8 mm from the stylomastoid foramen 6:
Bifurcation pattern: Occurs in 86.7% of cases, with the nerve dividing into two main divisions 6
Trifurcation pattern: Occurs in 13.3% of cases 6
Interconnections: The zygomatic and buccal branches show interconnections in over 70% of cases, while the temporal and marginal mandibular branches interconnect with other branches in less than 15% of cases 3
Clinical Significance of Neural Communications
The facial nerve forms extensive communications with other cranial nerves, particularly branches of the trigeminal nerve (CN V) 7:
Communications with the auriculotemporal nerve (a branch of CN V) occur in 93.3% of cases 6
Additional communications occur with branches of CN VIII (vestibulocochlear), CN IX (glossopharyngeal), CN X (vagus), and cervical plexus nerves 7
These neural interconnections have importance during facial reconstructive surgery, neck dissection, and nerve transfer procedures 7
Important Surgical Landmarks
The stylomastoid foramen lies approximately 21.0 ± 3.1 mm deep from the skin surface 6:
The temporal branch trajectory extends from the lower auricle to the lateral eyebrow, though surface landmarks vary between individuals 3
Multiple rami of the temporal branch cross the zygomatic arch, not a single trajectory 3
The zygomatic, buccal, and marginal mandibular branches lie in intimate relationship with the retaining ligaments of the face, requiring meticulous surgical dissection 3