What are the main functions of the facial nerve (CN VII)?

The facial nerve is a mixed nerve with three primary functions: motor to the muscles of facial expression, parasympathetic secretomotor to glands like the lacrimal and salivary glands, and special sensory for taste from the anterior two-thirds of the tongue.

What is the course of the facial nerve through the skull?

It arises from the pontomedullary junction with motor and sensory roots, passes through the internal acoustic meatus, unites in the facial canal of the temporal bone, and exits via the stylomastoid foramen. The canal has three segments: labyrinthine, tympanic, and mastoid.

What are the key branches of the facial nerve and what do they supply?

Major branches include the greater petrosal nerve for parasympathetic to lacrimal and nasal glands, chorda tympani for taste and parasympathetic to submandibular and sublingual glands, and five terminal branches for muscles of facial expression.

How does a lesion at different sites along the facial nerve affect function?

Lesion severity varies by location: at the stylomastoid foramen, it causes Bell's palsy with facial muscle paralysis; above the chorda tympani, it adds taste loss and decreased salivation; above the nerve to stapedius, it adds hyperacusis; and at the geniculate ganglion, it adds lacrimation loss.

What is Bell's palsy and how is it related to the facial nerve?

Bell's palsy is an infranuclear lesion, typically at the stylomastoid foramen, resulting in ipsilateral paralysis of all facial muscles. It's a common clinical presentation of facial nerve dysfunction.

What role does the facial nerve play in taste sensation?

It carries special visceral afferent fibers via the chorda tympani branch, providing taste sensation from the anterior two-thirds of the tongue, excluding the vallate papillae.

What is Ramsay Hunt syndrome and how does it involve the facial nerve?

Ramsay Hunt syndrome is a herpes zoster infection of the geniculate ganglion, causing symptoms like vesicles on the auricle, hyperacusis, taste loss, dry eye, and complete facial paralysis.

Facial Nerve (CN VII) – Expression, Taste & Parasympathetic

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