The Mask of Expression:
• Mixed nerve (GSE, GVE, SVA, GSA); Origin: Medulla; Exit: Stylomastoid Foramen
• Intracranial: Enters Internal Acoustic Meatus (with CN VIII), travels through Facial Canal in petrous temporal bone
• Geniculate Ganglion: Sensory for taste; gives off Greater Petrosal Nerve (parasympathetic to lacrimal/nasal glands)
• Chorda Tympani: Crosses middle ear, joins Lingual Nerve (V3)—carries taste from rostral 2/3 tongue
• Major Branches: Auriculopalpebral (eyelid/ear motor), Dorsal/Ventral Buccal (lips/cheeks), Cervical
• Ox vs Horse: Ox has rich plexus between buccal branches over masseter; Horse has widely separated branches

Cranial Nerve VII: The Facial Nerve

The Facial nerve dictates the animal's ability to blink, move its ears, and flare its nostrils. It is the nerve of facial expression and parasympathetic supply to salivary and lacrimal glands.

Intracranial Course

Enters the Internal Acoustic Meatus (with CN VIII), then travels through the Facial Canal in the petrous temporal bone—an extremely tortuous path making it vulnerable to middle ear infections.

Key Intracranial Structures:

• Geniculate Ganglion: Located at the "knee" (geniculum) of the facial canal. Contains sensory neurons for taste from rostral tongue.
• Greater Petrosal Nerve: Parasympathetic fibers to lacrimal and nasal glands (secretomotor).
• Chorda Tympani: Branches off inside the canal, crosses the middle ear (tympanic cavity), and joins the Lingual Nerve (V3). Carries taste from rostral 2/3 of tongue AND parasympathetic supply to submandibular/sublingual salivary glands.

Exit and Branching

Exit: Stylomastoid Foramen, then enters Parotid Salivary Gland where it forms a plexus.

Angiology Note: The nerve intertwines with the Transverse Facial Artery and vein within the parotid.

Major Branches

1. Auriculopalpebral Nerve:

• Ascends over the zygomatic arch.
• Motor to eyelids (Orbicularis oculi) and ear muscles.
• Clinical: Target for auriculopalpebral block to stop eyelid closure (akinesia) during eye examination.

2. Dorsal and Ventral Buccal Branches:

• Run across masseter muscle to the face.
• Motor to lips (Orbicularis oris), cheeks (Buccinator), and nostrils.
• Ox vs Horse: In the horse, these branches are widely separated. In the ox, there is a rich plexus (anastomosis) between dorsal and ventral branches over the masseter muscle, providing collateral innervation.

3. Cervical Branch: Supplies cutaneous colli muscle.

Clinical Pathology

Facial Paralysis: Drooping ear, drooping lip (commissure), absent palpebral reflex (cannot blink), widened palpebral fissure, food impaction in cheek (buccinator paralysis), and dry cornea (lacrimal paralysis). Common in Listeriosis (asymmetric deficits).