Facial nerve anatomy
Supranuclear pathways
Somatomotor cortex: Broadmann area 4, 6, 8
Volitional component: bilateral cortico-nuclear tract innervation
Emotional component: basal ganglia and limbic system control
Other inputs: visual system (involved in blink reflex), trigeminal nerve and nuclei (involved in corneal reflex), auditory nuclei (involuntary closure of eye in response to loud noise)
- wrinkling forehead: frontal branch components of facial nucleus receives innervation from the cortex of both the sides
- involuntary vs voluntary smile are different paths
Course
Pontomedullary junction → Posterior cranial fossa → Internal acoustic meatus → Fundus of Internal acoustic meatus → Bony facial canal → Stylomastoid foramen
- nucleus: motor, salivatory, and solitary
- IAC: 7up, coke down
Upper temporofacial division gives: Temporal and Zygomatic
Lower cervicofacial division gives: Buccal, Marginal mandibula, Cervical
Facial Nerve Subdivision and Functions
Branchial motor: Muscles of facial expression, Posterior belly of digastric muscle, Stylohyoid muscle, Stapedius muscle
Visceral motor: Salivation (lacrimal, submandibular, and sublingual), Nasal mucosa or mucous membrane
General sensory: Sensory to auricular concha, External auditory canal, Tympanic membrane
Special sensory Chorda tympani nerve (taste to anterior 2/3 of the tongue)
Donor nerve
The most common donor nerve for facial nerve grafting is sural and greater auricular nerves.
