Facial Nerve (CN VII): Course and Branches
The facial nerve is complex, carrying motor, sensory, and parasympathetic fibers. It exits the posterior cranial fossa via the internal acoustic meatus.
Key Intracranial/Intratemporal Branches:
- Greater Petrosal Nerve: Parasympathetic to lacrimal, nasal, and palatine glands.
- Nerve to Stapedius: Motor to the stapedius muscle (dampens sound).
- Chorda Tympani: Taste to anterior 2/3 of tongue; parasympathetic to submandibular/sublingual glands.
| Terminal Branch (Exiting Parotid) | Innervated Area |
|---|---|
| Temporal | Frontalis, orbicularis oculi (superior). |
| Zygomatic | Orbicularis oculi (inferior). |
| Buccal | Buccinator, muscles of upper lip. |
| Marginal Mandibular | Lower lip muscles (depressors). |
| Cervical | Platysma. |
High-Yield Clinical Pearls:
- Upper vs. Lower Motor Neuron: Upper motor neuron (central) lesions spare the forehead (bilateral innervation). Lower motor neuron (Bell palsy) lesions affect the entire ipsilateral half of the face.
- Mnemonic: “Ten Zebras Bit My Cheek.”