A thorough medical history is important in establishing the differential diagnoses of facial paralysis. Pertinent historical features are listed in Table 13-2 (see Chapter 3). Since facial paralysis can be a sign of systemic diseases, complete physical examination with thorough otolaryngologic and neurotologic assessment should be performed. A detailed cranial nerve examination is essential because facial paralysis might be due to cranial polyneuropathy, multiple sclerosis, or tumors at the cerebellopontine angle. Ear examination includes assessment of the external ear canal (Ramsay Hunt syndrome, trauma, or infection), and the middle ear (acute or chronic otitis media, cholesteatoma, mass, hemotympanum). The remaining head and neck examination includes palpation of the parotid (to rule out a mass lesion), assessment of facial nerve function, and search for traumatic or infectious lesions.

The extent of facial paralysis and the degree of voluntary function deficit should be determined (Fig. 13-1). It is important to assess the five divisions of the facial nerve (frontal, zygomatic, buccal, mandibular, and cervical). A peripheral lesion, such as a tumor or trauma in the parotid gland may spare some branches. The forehead sparing, however, might be due to a supranuclear lesion (often seen with strokes) since the facial nerve nucleus receives bilateral cortical innervation. Incomplete eyelid closure results in corneal drying, which can lead to exposure keratitis, eventual ulceration, and blindness. Buccinator muscle weakness may result in drooling and difficulty with chewing.

Successive examinations of the facial nerve may demonstrate progressive paralysis. Slow progression over several weeks or persistence beyond 3 months suggests a neoplasm. Recurrent facial paralysis may occur in Melkersson-Rosenthal syndrome, sarcoidosis, idiopathic facial paralysis, and some tumors. Acute onset of paralysis without any other symptoms might be secondary to idiopathic paralysis (Bell’s palsy), inflammatory disease, or vascular process.

The intracranial portion of the facial nerve includes segments involving the voluntary motor cortex, genu of internal capsule, extrapyramidal system, upper midbrain, lower brainstem,
pontine-facial nerve nucleus, and the cerebellopontine angle. The extracranial facial nerve has four anatomic segments (meatal/canalicular, labyrinthine, tympanic, and mastoid) prior to its exit from the stylomastoid foramen. After the cerebellopontine angle segment (approximately 15.8 mm), the meatal/canalicular segment (approximately 8 to 10 mm) traverses the internal auditory canal with the eighth cranial nerve, and exits as the labyrinthine segment (approximately 3 to 5 mm), which ends at the geniculate ganglion. From here, the greater superficial petrosal nerve (first branch of the facial nerve) branches off and carries preganglionic parasympathetic fibers destined for the lacrimal gland and the glands within the nasal and palatal mucosa. The geniculate ganglion also houses the cell bodies of gustatory neurons of the chorda tympani. From the geniculate ganglion, the tympanic segment (approximately 11 mm) courses horizontally and posteriorly through its bony canal along the medial wall of the middle ear and above the oval window. The facial nerve then turns inferiorly and descends toward the stylomastoid foramen as the mastoid segment (approximately 13 mm), which gives off a branch innervating the stapedius muscle. Prior to exiting the stylomastoid foramen, the facial nerve also gives off the chorda tympani nerve, which courses superiorly between the maleus and incus before leaving the middle ear to join the lingual nerve. The chorda tympani carries the preganglionic parasympathetic fibers for the submandibular gland, as well as taste fibers to the anterior two-thirds of the tongue. After exiting the stylomastoid foramen, the facial nerve arbitrarily divides the parotid gland into two lobes (superficial and deep), and branches into five major divisions described earlier.