DEFINITION
Bell’s palsy is an idiopathic, isolated, usually unilateral facial weakness in the distribution of the seventh cranial nerve; less than 1% are bilateral.

PHYSICAL FINDINGS AND CLINICAL PRESENTATION
● Unilateral paralysis of the upper and lower facial muscles (asymmetrical eye closure, brow, and smile; Fig. 49–1).
● Ipsilateral loss of taste
● Ipsilateral ear pain, usually 2 to 3 days before presentation
● Increased or decreased unilateral eye tearing
● Hyperacusis
● Subjective ipsilateral facial numbness
● In about 8% of cases, other cranial neuropathies may occur.

CAUSE
● Most cases are idiopathic, although the cause is often viral (herpes simplex).
● Herpes zoster can cause Bell’s palsy in association with herpetic blisters affecting the outer ear canal or the area behind the ear (Ramsay-Hunt syndrome).
● Bell’s palsy can also be one of the manifestations of Lyme disease.
DIFFERENTIAL DIAGNOSIS
● Neoplasms affecting the base of the skull or the parotid gland
● Infectious process (meningitis, otitis media, osteomyelitis of the skull base)
● Brainstem stroke
● Multiple sclerosis
● Head trauma, temporal bone fracture
● Other: sarcoidosis, Guillain-Barré syndrome, carcinomatous or leukemic meningitis, leprosy, Melkersson-Rosenthal syndrome
LABORATORY TESTS
● Consider CBC, fasting glucose, VDRL, ESR, angiotensinconverting enzyme (ACE) level in select patients.
● Lyme titer in endemic areas.

IMAGING STUDIES
● Contrast-enhanced MRI to exclude neoplasms is indicated only in patients with atypical features or course.
● Chest x-ray may be useful to exclude sarcoidosis or rule out TB in select patients before treating with steroids.
TREATMENT
● Reassure patient that the prognosis is usually good and the disease is most likely a result of a virus attacking the nerve, not a stroke.
● Avoid corneal drying by patching the eye. Ophthalmic ointment at night and artificial tears during the day are also
useful to prevent excessive drying.
● A short course of oral prednisone is commonly used, although the evidence from randomized controlled trials
demonstrating its efficacy is inadequate. If used, prednisone therapy should be started within 24 to 48 hours of symptom onset. Optimal steroid dose is unknown.
● Combination therapy with acyclovir and prednisone may be effective in improving clinical recovery, although robust evidence from high-quality, randomized controlled trials is lacking.
● Botulinum toxin may be helpful for treatment of synkinesis and hemifacial spasm, two late sequelae of Bell’s palsy.