Bell’s palsy is the most common cause of facial paralysis, affecting up to 30,000 – 40,000 people each year in the United States. It develops when the nerve that controls facial muscles (7th cranial nerve) becomes inflamed and swollen in the area where it travels through the bones of the skull.
What causes Bell’s palsy? More often than not, the cause of Bell’s palsy is never determined. Many cases appear to be related to a herpes simplex virus infection, the same virus that causes cold sores and genital herpes, although there may be no evidence of an active infection. Lyme disease, a bacterial infection transmitted through tick bites, is a less common cause, affecting up to 10% of untreated victims. A neurological complication of diabetes mellitus known as “mononeuropathy” has also been implicated as a cause in diabetics.
What are the symptoms of Bell’s palsy? Weakness or paralysis on one side of the face, making it difficult to smile or close the eye, is the most common feature. In addition, Bell’s palsy may have one or more of the following features:
- Up to half of people affected with Bell’s palsy will complain of pain behind the ear, often prior to the development of the facial weakness.
- Drooling from the corner of the mouth or difficulty eating or drinking
- Increased sensitivity to sound
- Difficulty closing the eye with decreased tearing
- Decreased ability to taste
- Facial numbness or twitching
How is Bell’s palsy diagnosed? There is no specific laboratory test to confirm the diagnosis of Bell’s palsy. Doctors make a tentative diagnosis of Bell’s palsy by noting the facial asymmetry and asking patients to move the facial muscles by smiling, closing the eyes, and showing the teeth. Usually, no specific testing is required. If the diagnosis is uncertain or the paralysis lasts longer than 6-8 weeks, testing to confirm the underlying cause could include:
- Nerve conduction study/Electromyelogram to assess the severity of nerve damage by measuring electrical activity in the facial muscles.
- CT/ MRI Scan to evaluate the possibility that a brain tumor or stroke is responsible for the paralysis.
- Blood sugar testing to check for diabetes
- Lyme disease titers
Can surgery help? Rarely, surgery to remove bony impingement of the facial nerve may be considered. This is only appropriate in those cases involving complete paralysis and markedly abnormal electrical testing of the facial muscles.
What is the outlook for recovery? Whether specific treatment is given or not, 85% of individuals with Bell’s palsy begin to get better within 2 weeks, and most recover completely within 3 months. In some instances, long-term changes can persist, such as weakness or spasms in the facial muscles, excessive tearing (“crocodile tears”), or persistent changes in taste.
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