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Bell's palsy
Last reviewed: 04.07.2025
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Bell's palsy is an idiopathic sudden unilateral peripheral paralysis of the facial nerve (VII pair).
The diagnostic symptom of Bell's palsy is hemifacial paresis of the upper and lower parts of the face. There are no specific methods of examination. Treatment of Bell's palsy includes glucocorticoids, lubricants, and eye patches.
[ What causes Bell's palsy?
The cause of Bell's palsy is unknown, the mechanism is associated with swelling of the facial nerve due to immune or viral damage (possibly herpes simplex virus). The nerve passes through a narrow canal in the temporal bone and is very easily compressed with the development of ischemia and paresis. With peripheral (but not central!) damage, paralysis of the orbicularis oculi muscle and the frontal belly of the occipitofrontal muscle, which receive innervation from the left and right nuclei of the VII pair, develops.
Symptoms of Bell's Palsy
Paresis is often preceded by pain behind the ear. Symptoms of Bell's palsy include paresis or complete paralysis, which develops over several hours and usually reaches its maximum after 48-72 hours. Patients complain of numbness and/or a feeling of heaviness in the face. The affected side is smoothed out, loses expressiveness, the ability to wrinkle the forehead, blink and make other movements of the facial muscles decreases or disappears. In severe cases, the palpebral fissure is widened, the eye does not close, the conjunctiva is irritated, the cornea is dry. Sensitivity testing does not reveal any disturbances, with the exception of the external auditory canal and a small area behind the auricle. If the proximal segment is affected, salivation, lacrimation and taste sensitivity of the anterior 2/3 of the tongue are impaired, hyperalgesia appears in the area of the external auditory canal.
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Diagnosis of Bell's Palsy
There are no specific diagnostic tests for Bell's palsy. Bell's palsy is distinguished from central lesion of the seventh cranial nerve (eg, stroke or tumor), in which weakness of the facial muscles develops only in the lower parts of the face. Causes of peripheral facial nerve lesions include herpetic ganglionitis of the geniculate ganglion (Ramsay Hunt syndrome in herpes zoster), infection of the middle ear or mastoid process, sarcoidosis (especially in African Americans), Lyme disease (especially in endemic areas), fractures of the petrous pyramid, carcinomatosis or leukemic invasion of the nerve, chronic meningitis, or tumor of the pontine-cerebellar angle or jugular glomus. These diseases progress more slowly than Bell's palsy, and there are other differences. If the diagnosis is in doubt, MRI with contrast is done; CT scans are usually normal in Bell's palsy and are performed if a fracture or stroke is suspected. In areas where Lyme disease is endemic, serologic testing is performed during the acute or convalescent phase. Chest X-rays are performed to rule out sarcoidosis.
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Prognosis and treatment of Bell's palsy
The outcome is determined by the degree of nerve damage. If any function is preserved, then usually complete recovery occurs within a few months. In case of complete paralysis, electromyography and nerve conduction studies are useful for prognosis. If normal excitability to electrical stimulation is preserved, then the probability of complete recovery is 90%, and if electrical excitability is absent - 20%.
During recovery, nerve fiber growth may go in the wrong direction, so that the facial muscles of the lower face can innervate the periocular fibers and vice versa. As a result, attempts at voluntary facial movements lead to unexpected results (syncinesis), and "crocodile tears" appear during salivation. Chronic inactivity of the facial muscles can lead to contractures.
There are no proven treatments for idiopathic Bell's palsy. Treatment of Bell's palsy consists of early administration of glucocorticoids (within the first 48 hours of onset) which somewhat reduces the duration and extent of residual paralysis. Prednisolone is prescribed 60-80 mg orally once a day for 1 week with subsequent dose reduction over 2 weeks. Antiviral drugs effective against the herpes simplex virus are usually prescribed (eg, valacyclovir 1 g 3 times a day for 7-10 days, famciclovir 500 mg orally 3 times a day for 5-10 days, acyclovir 400 mg orally 5 times a day for 10 days).
To prevent corneal dryness, frequent instillation of natural tears, isotonic solution or drops with methylcellulose, periodic application of a bandage covering the affected eye, especially during sleep, is prescribed. Sometimes tarsorrhaphy (complete or partial suturing of the edges of the eyelids) is required.
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