Cranial nerve VII, the motor nerve of the muscles of facial expression
Facial nerve — the seventh cranial nerve.
Anatomy · Brain & nerves
Facial nerve
Cranial nerve VII
Cranial nerves · face
The seventh cranial nerve: the motor nerve of facial expression, supplying every muscle that smiles, frowns or blinks. It also carries taste from the front two-thirds of the tongue, supplies the tear and salivary glands with secretomotor fibres, and serves the tiny stapedius muscle in the middle ear. It leaves the skull through the stylomastoid foramen and fans out through the parotid gland.
How to spot them
- ▸Leaves the brainstem at the lower border of the pons, alongside the vestibulocochlear nerve, in the cerebellopontine angle
- ▸Runs in its own winding bony canal inside the temporal bone, emerging behind the ear at the stylomastoid foramen
- ▸Fans across the cheek as five terminal branches, passing through the parotid gland without supplying it
- ▸Sends a branch (the chorda tympani) across the middle ear to join the tongue's nerve
What to know
Its five terminal branches are remembered as 'To Zanzibar By Motor Car'
Facial nerve — temporal, zygomatic, buccal, marginal mandibular, cervical.
Sudden one-sided weakness of the whole face, including the forehead, named after a Scottish anatomist who described it in 1821
Facial nerve — Bell's palsy, after Sir Charles Bell.
A stroke causes weakness of the lower face but spares the forehead, because of its bilateral cortical supply
Facial nerve — upper motor neuron lesion versus lower motor neuron lesion.
Carries taste from the front two-thirds of the tongue via a branch that crosses the middle ear
Facial nerve — the chorda tympani.
Passes through the parotid gland without supplying it, a hazard in surgery of the cheek
Facial nerve — the gland is supplied by the glossopharyngeal nerve.
Supplies the stapedius, the smallest muscle in the body, whose paralysis makes sounds uncomfortably loud
Facial nerve — hyperacusis.
Leaves the skull through a hole between the mastoid process and the styloid process
Facial nerve — the stylomastoid foramen.
Key ideas
- Bell's palsy is a lower motor neuron lesion: the whole half of the face droops, because the nucleus itself or the nerve after it is damaged.
- In a stroke, the forehead is spared because the upper part of the facial nucleus receives fibres from both hemispheres.
Quick-fire facts
- •Cranial nerve VII; the twelve pairs are olfactory (I), optic (II), oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII), glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII)
- •Mnemonic for the mixed, sensory and motor pattern: 'Some Say Marry Money, But My Brother Says Big Brains Matter More' — the seventh word, 'Brother', means the facial nerve is 'both' — mixed sensory and motor
- •Terminal branches: temporal, zygomatic, buccal, marginal mandibular and cervical ('To Zanzibar By Motor Car')
- •Passes through the internal acoustic meatus, then the facial canal, and exits at the stylomastoid foramen
- •Gives the nerve to stapedius, the chorda tympani, and the greater petrosal nerve to the lacrimal gland
- •Bell's palsy is named for Sir Charles Bell, the Scottish surgeon who described it in 1821
- •The facial nerve is the cranial nerve most often affected by palsy
- •Ramsay Hunt syndrome is shingles of the geniculate ganglion, causing facial palsy and an ear rash
- •The greater petrosal nerve carries parasympathetic fibres to the tear gland, and the chorda tympani to the submandibular and sublingual glands
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