Applied Anatomy

The facial nerve (Figures 14.1 and 14.2) is the motor nerve to the muscles of facial expression. Smiling, frowning and expressing emotions are dependent on its normal function. It begins in the facial nucleus in the brainstem (the pons), passes close to the internal auditory meatus to run in the middle ear and mastoid and then exits the skull at the stylomastoid foramen just in front of the mastoid process. It then runs in the parotid gland. It breaks into two divisions, the zygomatic-temporal and the mandibulo-cervical, which between them have five branches (Figure 14.1) supplying the muscles of facial expression.

The nerve has a long course and is vulnerable to injury at several sites (Figure 14.2). Facial paralysis (Figure 14.3) can be a devastating condition for the patient.

Facial Palsy

A patient suffering stroke will often have a facial palsy but the forehead muscles are spared as they have innervations from both sides (supranuclear/upper motor neurone palsy). If the nerve is injured below the pons (infranuclear/lower motor neurone palsy), the paralysis can be complete and involves the forehead and the facial muscles.

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