Bell's Palsy - From Wikipedia, the free encyclopedia

Bell's palsy is a paralysis of cranial nerve VII (the facial nerve) resulting in inability to control facial muscles on the affected side. Several conditions can cause a facial paralysis, e.g., brain tumor, stroke, and Lyme disease. However, if no specific cause can be identified, the condition is known as Bell's Palsy. Named after Scottish anatomist Charles Bell, who first described it, Bell's palsy is the most common acute mononeuropathy (disease involving only one nerve), and is the most common cause of acute facial nerve paralysis.

Bell's palsy is defined as an idiopathic unilateral facial nerve paralysis, usually self-limiting. The trademark is rapid onset of partial or complete palsy, usually in a single day. Symptoms typically subside after 2-6 days and full facial function is usually returned within 2-3 weeks. Although rare, residual paralysis or dysfunction is possible and chances of this increase with age.^[1]

It is thought that an inflammatory condition leads to swelling of the facial nerve (nervus facialis). The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to lead to nerve inhibition, damage or death. No readily identifiable cause for Bell's palsy has been found, but clinical and experimental evidence suggests herpes simplex type 1 infection may play a role.

Doctors may prescribe anti-inflammatory and anti-viral drugs. Early treatment is necessary for the drug therapy to have effect. The effect of treatment is still controversial. Most people recover spontaneously and achieve near-normal to normal functions. Many show signs of improvement as early as 10 days after the onset, even without treatment.

Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea may be permanently damaged resulting in impaired vision.

Recovery

Even without any treatment, Bell's palsy tends to carry a good prognosis. In a 1982 study^[19], when no treatment was available, of 1,011 patients, 85% showed first signs of recovery within 3 weeks after onset. For the other 15%, recovery occurred 3–6 months later. After a follow-up of at least 1 year or until restoration, complete recovery had occurred in more than two thirds (71%) of all patients. Recovery was judged moderate in 12% and poor in only 4% of patients. Another study^[1] finds that incomplete palsies disappear entirely, nearly always in the course of one month. The patients who regain movement within the first two weeks nearly always remit entirely. When remission does not occur until the third week or later, a significantly greater part of the patients develop sequelae. A third study^[7] found a better prognosis for young patients, aged below 10 years old, while the patients over 61 years old presented a worse prognosis.