Bell's palsy is a type of paralysis (or weakness) of the muscles in the face, thought to be due to inflammation of the seventh cranial nerve, also known as the facial nerve. While it can strike anyone, it seems to occur more frequently in individuals recovering from viral infections and people with diabetes. Bell's palsy affects only one side of the face at a time, and rarely recurs.
Bell's palsy tends to come on very suddenly. You may go to bed one night with no noticeable symptoms, only to peer in the mirror the next morning and notice that your face appears to be drooping. Some people notice pain behind their ear a day or two before they notice any weakness. Others comment that sounds seem abnormally and uncomfortably loud several days before the development of paralysis. Within a day or two, the paralysis usually reaches its peak. Most people start to recover within a couple of weeks and are completely recovered within three months. Some people who develop Bell's palsy have a longer recovery period or have some permanent symptoms of the condition.
Many people with Bell's palsy worry that they are having a stroke. This is unlikely, because a stroke that affects the face muscles would also cause muscle weakness in other parts of the body.
What Causes Bell's Palsy?
The exact cause of Bell's palsy has not been pinpointed. Most doctors assume that some process causes swelling of the facial nerve. Because the facial nerve passes through a narrow, bony area within the skull, any swelling of the nerve causes it to be compressed against the skull's hard surface. This interferes with the nerve's functioning.
Researchers have long believed that viral infections may be involved in the development of Bell's palsy. Scientists have found evidence suggesting that the herpes simplex 1 virus (a common cause of cold sores) may be responsible for a large percentage of Bell's palsy cases.
Paralysis of the facial muscles where a cause is pinpointed is called a facial palsy. Known causes include viral infections such as shingles, Lyme disease, ear infections, or compression of the facial nerve by a benign tumor called an acoustic neuroma. Facial nerve damage can also be caused by progressive nerve diseases such as multiple sclerosis.