Anatomy of the facial nerve

1. Big picture

The facial nerve, cranial nerve VII (CN VII), is not only the “nerve of facial expression.” For the exam, think of it as a mixed nerve with four clinically important functions:

1. Motor to the muscles of facial expression.

2. Parasympathetic secretomotor to lacrimal, submandibular, and sublingual glands.

3. Taste from the anterior two-thirds of the tongue.

4. Small somatic sensory component from part of the external auditory canal, eardrum, pinna, and mastoid region.

The most important exam skill is to use the anatomy to localize the lesion: facial paralysis alone versus facial paralysis + ageusia + hyperacusis + dry eye + vestibulocochlear symptoms.