Signs

Facial weakness may occur in select or all branches of the facial nerve. Decreased blink reflex, incomplete eye closure, or lower eyelid rounding may be observed. Deviation of nasal base and philtrum, loss of melolabial fold definition, or a drooped oral commissure are common. Patients may have periauricular vesicles, a body rash, or other neurologic deficits.

Symptoms

A detailed history is the key to identifying the etiologic cause of the facial weakness. A history of preceding illnesses, surgery, or trauma should be elucidated. Travel patterns, particularly in locations endemic with Lyme disease, or a tick bite may be reported. Facial weakness may be described as rapid onset (< 72 hours), delayed onset, progressive, fluctuating, unilateral, or bilateral. It may involve the entire hemiface or select branches. Associated pain or mass raises a concern for malignancy. A full assessment of other neurologic symptoms and a general review of systems should be undertaken.

Differential Diagnosis

There are a myriad of potential causes of facial paralysis. Bell′s palsy (idiopathic) is the most common cause and is generally self-limited, with the majority of patients showing complete resolution (see Chapter 3.1.3). Other common causes are viral reactivation (Bell′s palsy, Ramsay Hunt′s syndrome), infection (Lyme disease, otitis media), or injury. Facial paralysis due to nerve injury may be iatrogenic or traumatic.

Intracranial nerve injuries most commonly occur during resection of vestibular schwannoma or other cerebellopontine angle (CPA) tumors. The incidence of facial nerve injury following CPA tumor surgery is reported to be 2.3%. Intratemporal facial nerve injury is usually encountered in patients following external head trauma with skull base fractures or iatrogenic injury during or following otologic surgery. Most temporal bone fractures result from motor vehicle accidents and violent encounters. Seven to 10% of these fractures result in facial nerve dysfunction, with paralysis more common in transverse fractures. Extratemporal injury to the facial nerve may occur during parotid surgery, temporomandibular joint procedures, or facelift procedures or following traumatic lacerations of the face. Patients at higher risk for facial nerve injury during parotid surgery include children and those undergoing a total parotidectomy. The differential may be narrowed by history, exam, and studies as indicated.

Physical Exam

A general neurologic evaluation, complete head and neck exam, and a detailed cranial nerve exam should be performed, as findings may help narrow the differential diagnosis. At a minimum, the degree of facial impairment should be graded by the House–Brackmann Facial Nerve Grading System ( Table 3.3 in Chapter 3.1.3), although more detailed and updated grading systems now exist ( Table 9.2 ; Fig. 9.11 ).