Why is the facial nerve known as the seventh cranial nerve?

The twelve cranial nerves are named in the order they emerge from the brainstem in a rostral to caudal direction.

Do all the cranial nerves have both motor and sensory function?

The specific functions of the twelve cranial nerves vary.  The olfactory, optic and vestibulocholear nerves all have sensory-only functions.  The oculomotor, trochlear, abducens, accessory and hypoglossal have only motor functions.  Where as the trigeminal, glossopharyngeal and vagus, along with the facial nerve have a mixture of both motor and sensory fibres.

Who does Bell’s palsy affect?

Although Bell's palsy can affect anyone the most commonly affected age group is 15-45. About one in 70 people will be affected by this condition at some point during their life.

How can the facial nerve affect hearing?

The facial nerve innervates the muscle of the small middle bone of the ear called the stapes as well as passing through the ear canal.  In addition the facial nerve also contains pain fibres from the ear.  Therefore damage to the facial nerve can result in an increased sensitivity to loud sound and pain in the ear. 

How can someone who has suffered a stroke that involves the corticonuclear fibers and exhibits facial paralysis still smile symmetrically?

Involuntary movement, such as smiling or laughing in response to a joke is medicated by fibres originating from the reticular formation of the brain. In this instance the innervation is not involving the corticonuclear fibres, which are necessary for voluntary movement.

If the facial nerve innervates the anterior two-thirds of the tongue then what innervates the posterior third?

Both taste and general sensations to the posterior third of the tongue are carried by the glossopharyngeal nerve– cranial nerve IX.

"I suffer with Trigeminal Neuralgia, which causes me a lot of facial pain. Is this pain related to the facial nerve?"

No.  Although facial pain is the primary symptom in this condition, affected areas of the face have sensory innervation from the Trigeminal nerve (fifth cranial nerve) therefore this is not a facial nerve disease.

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