Facial nerve: course, branches and site of the lesion

Applied anatomy

The facial nerve moves the face and also carries tears, saliva, taste and the stapedius reflex; where it is damaged decides which of these fail.

Updated Nov 5, 2026

See it in 3D: Facial nerve (VII) · Facial nerve branches · Stylomastoid foramen

Key points

Peripheral (lower motor neuron) palsy paralyses the whole half of the face, forehead included; a central (upper motor neuron) lesion spares the forehead because it has input from both hemispheres.
The labyrinthine segment is the shortest and narrowest part of the canal; the mastoid segment is the most common site of surgical injury.
Branches inside the temporal bone: greater petrosal nerve (tears), nerve to stapedius (dampens loud sound), chorda tympani (taste of the anterior two-thirds of the tongue, submandibular and sublingual saliva).
Five terminal branches in the parotid: temporal, zygomatic, buccal, marginal mandibular, cervical.
Bell palsy is the most common cause in healthy people, but otitis media, cholesteatoma, parotid tumours, Lyme disease, sarcoidosis and stroke must be considered.

What it is

The facial nerve (VII) leaves the pons, enters the internal acoustic meatus with the vestibulocochlear nerve, runs through the temporal bone past the middle ear and mastoid, exits at the stylomastoid foramen and fans out inside the parotid gland. Along the way it gives off branches for tears, the stapedius muscle and taste. This long bony course explains why ear infections, cholesteatoma, temporal bone fractures and parotid tumours can paralyse the face, and why the forehead tells a central from a peripheral lesion.

Applied anatomy

Origin: motor nucleus in the pons; sensory and parasympathetic fibres travel in the intermediate nerve.
Internal acoustic meatus: shared with the vestibulocochlear nerve (a tumour here can cause hearing loss and facial weakness).
Labyrinthine segment to the geniculate ganglion, where the greater petrosal nerve leaves for the lacrimal gland.
Tympanic segment across the middle ear; mastoid segment down to the stylomastoid foramen, giving the nerve to stapedius and the chorda tympani.
After the stylomastoid foramen: posterior auricular, digastric and stylohyoid branches, then the parotid plexus and five terminal branches.

Which function is lost tells you where the lesion is (proximal lesions affect everything below them)

Lesion site	Face	Tears	Sound sensitivity (stapedius)	Taste, anterior two-thirds
Cortex or internal capsule (central)	Lower face only, opposite side	Normal	Normal	Normal
Internal acoustic meatus or above the geniculate ganglion	Whole half of face	Reduced	Louder sounds	Lost
Between geniculate ganglion and stapedius branch	Whole half of face	Normal	Louder sounds	Lost
Between stapedius branch and chorda tympani	Whole half of face	Normal	Normal	Lost
At or below the stylomastoid foramen, or in the parotid	Whole half of face, or only some branches	Normal	Normal	Normal

Clinical correlation

Bell palsy: sudden one-sided weakness peaking in 2 to 3 days, sometimes with pain behind the ear, taste loss or louder sound in one ear.
Facial palsy with ear discharge, a retraction pocket or a mass behind the drum suggests otitis media, cholesteatoma or a tumour, not Bell palsy.
A slowly progressive palsy, or one affecting single branches, with a parotid lump suggests a parotid tumour.
An eye that does not close is at risk of dryness, corneal ulcer and vision loss.

Next step / Initial management

Examine forehead, eye closure, smile, both ears (otoscopy), the parotid and the other cranial nerves; look for vesicles in the ear canal.
Bell palsy: corticosteroids started early, with or without an antiviral (for example valacyclovir); protect the eye with lubricating drops or ointment and a patch at night.
Refer as an emergency (same day) if the forehead is spared or there are other neurological signs (stroke), or if palsy follows otitis, cholesteatoma or trauma.
Refer urgently to ENT or ophthalmology if the eye does not close and is red or painful.
Refer routinely to ENT if there is no recovery after a few weeks, a slowly progressive or recurrent palsy, or a parotid mass.

Test yourself

Think of the answer, then tap the question to see it.

A patient cannot wrinkle the forehead or close the eye on the right, and the right corner of the mouth droops. Central or peripheral?

Peripheral (lower motor neuron) right facial palsy: the whole half of the face is weak. A central lesion would spare the forehead.

A facial palsy comes with loss of taste on the front of the tongue and hyperacusis, but normal tears. Where is the lesion?

Between the geniculate ganglion (tears spared) and the nerve to stapedius (hyperacusis): in the facial canal of the temporal bone.

During a parotidectomy, what structure divides the gland surgically and must be preserved?

The facial nerve, which forms the parotid plexus inside the gland and splits into temporal, zygomatic, buccal, marginal mandibular and cervical branches.

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Elsewhere in DurgiPedia

Second pharyngeal arch (hyoid arch) and the facial nerve

Connections

See it in 3D3

The structures of Durgical's 3D anatomy where it is found.

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Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.

Sources: Bell palsy (MedlinePlus, US National Library of Medicine, 2026); Facial paralysis (MedlinePlus, US National Library of Medicine, 2025); Taste Disorders (National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, 2023); Cholesteatoma (MedlinePlus, US National Library of Medicine, 2026); Salivary gland tumors (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.