June 22, 2022
Years published: 1985, 1990, 1993, 1997, 2001, 2005, 2022
NORD gratefully acknowledges Catriona Neville, Extended Scope Practitioner, Facial Therapist, Facial Palsy Team, Queen Victoria Hospital NHS Foundation Trust, for assistance in the preparation of this report.
Bell’s palsy is a non-progressive neurological disorder of the facial nerve (7th cranial nerve). This disorder is characterized by the sudden onset of facial paralysis that may be preceded by a slight fever, pain behind the ear on the affected side and weakness on one side of the face. Paralysis results from decreased blood supply (ischemia) and/or compression of the 7th cranial nerve. The exact cause of Bell’s palsy is not known. Viral (e.g., herpes zoster virus) and immune disorders are frequently suggested as a cause for this disorder. There may also be an inherited tendency toward developing Bell’s palsy.
The early symptoms of Bell’s palsy may include a slight fever, pain behind the ear and weakness on one side of the face. The symptoms may begin suddenly and progress rapidly over several hours and sometimes follow a period of stress or reduced immunity. The whole side of the face is affected.
In most cases of Bell’s palsy, only facial muscle weakness occurs, and the facial paralysis is temporary. Most cases resolve in two to three weeks. Approximately 80% of cases resolve within three months. However, some cases persist.
In severe cases of Bell’s palsy, the facial muscles on the affected side are completely paralyzed, causing that side of the face to become smooth, expressionless and immobile. Often the opening between the upper and lower eyelids (palpebral fissure) is enlarged and remains open during sleep. This may result in the inability to close the eye on the affected side. People with Bell’s palsy may not have a corneal reflex, which means that the eye on the affected side does not close when the cornea is touched.
If the compressed region of the facial nerve is higher than certain facial nerve branches, there may be a decrease in saliva and/or tear production. Some people with Bell’s palsy experience a loss of the sense of taste on one side of the mouth, drooling and an increased sensitivity to sound (hyperacusis) on the affected side of the head. In some cases, an affected individual’s response to a pinprick behind the ear is also decreased.
Recovery from Bell’s palsy depends on the extent and severity of damage to the 7th cranial nerve. If facial paralysis is only partial, complete recovery can be expected. The affected muscles usually regain their original function within one to two months. If, as recovery proceeds, the nerve fibers regrow to muscles other than the ones they originally supplied, there may be voluntary muscle movements of the face accompanied by involuntary contractions of other facial muscles (synkinesia). Crocodile tears (tears not brought on by emotion) associated with facial muscular contractions occasionally develop in the aftermath of Bell’s palsy, particularly when eating.
The exact cause of Bell’s palsy is not known. Viral and immune disorders are often suggested as a cause for this disorder. There may also be an inherited tendency toward developing Bell’s palsy. Symptoms develop due to deficiency of blood supply and pressure on the 7th cranial nerve as a result of nerve swelling.
Bell’s palsy affects males and females in equal numbers. It is estimated that 25-35 per 100,000 people in the United States are affected with Bell’s palsy. Approximately 40,000 individuals are diagnosed with Bell’s palsy in the United States each year.
Elderly individuals are more likely to develop Bell’s palsy than children, but the disorder may affect individuals of any age. Pregnant women or individuals with diabetes or upper respiratory ailments are affected more often than the general population
A preliminary diagnosis may be made by the physician upon looking at the patient’s face and noticing the difficulty the patient has in moving the facial muscles. Electromyography, a test that measures the electrical conductivity of the nerve, may be used to confirm the diagnosis and to measure the extent of the nerve damage.
Patients often worry that they have suffered a stroke. Stroke can cause facial weakness but following a stroke most people are still able to move their forehead and eye, whereas after facial palsy the forehead and eye areas are unable to move.
Most people with Bell’s palsy recover fully without treatment. Massage can maintain the mobility of the facial muscles and prevent the loss of muscle function as the nerve recovers. Treatment with oral corticosteroid drugs such as prednisone has been more successful than surgical attempts to widen the facial canal. Steroids must be given within the first 72 hours of onset of facial palsy to have optimal benefit. It is best to avoid exercise while the face is flaccid as this can cause overactivity of the face following recovery and worsen synkinesis.
Preservative free eye drops and/or eye ointment, taping, and eyeglasses or goggles may help to protect the exposed eye of people with Bell’s palsy if they cannot close the eye. In extremely severe cases, partial or total surgical closure (tarsorrhaphy) or chemical closure (with botulinum toxin) of the eyelid on the affected side may protect the eye from permanent damage. In those rare cases when Bell’s palsy has caused permanent paralysis of one side of the face, the peripheral facial nerve can be surgically connected to adjacent cranial nerves to allow some eventual return of muscle function. If the paralysis has continued for more than two years, the existing facial muscles may not be able to recover, in which case surgery may be used to transfer muscles from other parts of the body to restore function such as smiling.
Patients with long-term complications such as synkinesis may benefit from specialist facial therapy including muscle release, relaxation retraining and neuromuscular retraining as well as adjunctive treatments such as botulinum toxin to reduce problematic muscle overactivity. There are also surgical options to reduce synkinesis and improve function if conservative options are unsuccessful. Patients with long term complications often benefit from counseling and support groups to reduce anxiety and social isolation.
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