Anatomy clinical correlates: Facial (CN VII) and vestibulocochlear (CN VIII) nerves

The facial nerve is all about supplying those facial muscles and allowing for the whole range of facial expressions that they create. But don’t just judge a nerve by its face; ‘cause that’s not all it can do! The facial nerve is also involved in salivating, secreting tears, and it even plays a role in taste.

On the other hand, the vestibulocochlear nerve is the cranial nerve that helps you hear your favorite song, so then you can use your facial nerve to smile when you hear it. And it also plays a role in balance, so you can dance along without tipping over! Understanding the anatomy of the facial and vestibulocochlear nerves is important, as damage to these nerves can cause significant impairments when it comes to facial expression, hearing and balance, among several other functions!

Let’s start with the general anatomy of the facial nerve. Remember that there are two facial nerves, one on each side, and each of them is primarily responsible for providing motor innervation to the muscles of facial expression. The facial nerve also innervates the stapedius muscle in the middle ear; gives parasympathetic innervation to the lacrimal glands, nasal glands, palatal mucosal, submandibular, and sublingual salivary glands; and also carries the special sensory information of taste from the anterior two-thirds of the tongue and the palate.

It is also involved in the corneal reflex, also known as the blink reflex, which causes involuntary blinking when the cornea is stimulated to protect the eye from foreign bodies like sand. In this reflex, the trigeminal nerve is the sensory or afferent pathway, while the facial nerve serves as the motor or efferent pathway.

Now, the clinical presentation of facial nerve damage is called facial nerve palsy. If the entire facial nerve is damaged, all of its functions are affected. Without motor innervation, facial muscles become weak or impaired. This means the affected individual will have trouble when trying to smile, frown, raise their eyebrows, puff their cheeks, or whistle.