Bell's palsy is a non-progressive neurological disorder of one of the facial nerves (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, a stiff neck, and weakness and/or stiffness 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 implicated 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, a stiff neck, and weakness and/or stiffness on one side of the face. The symptoms may begin suddenly and progress rapidly over several hours, and sometimes follow exposure to cold or a draft. Part or all of the face may be affected.
In most cases of Bell’s palsy, only facial muscle weakness occurs and the facial paralysis is temporary. Most cases resolve with two to three weeks. Approximately 80 percent of cases are resolved within three months. However, some cases persist. Occasionally, only the upper or lower half the face is affected.
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; the eye on the affected side does not close when the cornea is touched.
If the compressed region of the facial nerve is next to the branching of other nerves, 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 also is decreased.
Recovery from Bell’s palsy depends on the extent and severity of damage to the seventh 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 innervated, 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.
The exact cause of Bell’s palsy is not known. Viral and immune disorders are often implicated 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 is a fairly prevalent disorder that affects males and females in equal numbers. It is estimated that between 25 and 35 in 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. However, 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 measure the electrical conductivity of the nerve, may be administered to confirm the diagnosis and to measure the extent of the nerve damage.
Most people with Bell's palsy recover fully without treatment. Massage and mild electrical stimulation of the paralyzed muscles can help maintain facial muscle tone and prevent the loss of muscle function. Treatment with oral corticosteroid drugs, such as prednisone, has been more successful than surgical attempts to widen the facial canal.
Methylcellulose eye drops, eyeglasses or goggles, and/or temporary patching 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 of the eyelid on the affected side (tarsorrhaphy) 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 with the spinal accessory or hypoglossal nerves to allow some eventual return of muscle function.
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ARTICLES REPORTING THE RESULTS OF CLINICAL TRIALS
Lagalla G, Logullo F, Di Bella P, et al. Influence of early high-dose steroid treatment on Bell’s palsy evolution. Neurol Sci. 2002;23:107-12.
Koriyama T, Inafuku S, Kimata K, et al. Recent-onset Bell’s palsy complicated by diabetes: comparison of steroid and lipoprostaglandin E(1) therapy. Arch Otolaryngol Head Neck Surg. 2001;127:1338-40.
Salman MS, MacGregor DL. Should children with Bell’s palsy be treated with corticosteroids? A systematic review. J Child Neurol. 2001;16:565-68.
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