Anatomy of cranial nerve VII

The facial nerve arises as two roots in the angle between the pons and the medulla.

The medial motor root supplies the muscles of the face, scalp, auricle, buccinator, platysma, stapedius, stylohyoid and the posterior belly of digastric.

The lateral root has:

• fibres which carry taste from the anterior two thirds of the tongue, the floor of the mouth and the soft palate
• parasympathetic secretomotor fibres to the submandibular and sublingual salivary glands

The facial and vestibulocochlear nerve pass together into the internal acoustic meatus.

At the bottom of the internal acoustic meatus the facial nerve enters the facial canal and then runs laterally, above the vestibule of the labyrinth until it reaches the medial wall of the tympanic cavity. Here the nerve expands to form the geniculate ganglion.

The nerve now passes posteriorly and laterally becoming closely related to the mastoid antrum.

The facial nerve leaves the skull through the stylomastoid foramen. The facial nerve passses through the middle of the parotid gland and goes on to supply the muscles of facial expression.

Knowledge of the intrapetrous branches of the facial nerve may be useful in localising a facial nerve lesion caused by ear pathology.