Bell's palsy is a form of temporary facial paralysis resulting from damage or trauma to one of the two facial nerves that is known as the seventh cranial nerve. The paralysis causes distortion of facial features and interferes with normal facial function, such as closing the eyes, chewing, and eating.
Overview of Bell's Palsy
The onset of Bell's palsy usually is sudden. Many people wake up in the morning and find that one side of their face is paralyzed. Patients often fear that they have suffered a stroke, but Bell's palsy is not related to stroke. Milder symptoms include tingling around the lips or a dry eye, and usually progress quickly, reaching maximum severity in 48 hours or less.
Bell's palsy is named for Sir Charles Bell, a Scottish surgeon who studied the nerve and its innervation of the facial muscles approximately 200 years ago.
Facial Nerve Anatomy
The facial nerve controls the muscles that move the eyebrows, close the eyes, and move the mouth and lips. It also controls the tear glands, one of the salivary glands, and the taste buds in the front of the tongue.
Electrochemical signals are relayed between the brain and many facial muscles by 7000 nerve fibers that comprise the facial nerve. When the facial nerve is damaged, as in Bell's palsy, the action of each nerve fiber is disrupted. Because the facial nerve controls several functions, several symptoms occur.
Incidence & Prevalence of Bell's Palsy
Bell's palsy affects about 40,000 people in the United States every year. It affects approximately 1 person in 65 during a lifetime. Worldwide statistics indicate a frequency of about .02% of the population.
Bell's palsy is more commonly seen in young adults, and persons of Japanese descent have a slightly higher incidence of the condition. Bell's palsy is the most common cause of facial paralysis worldwide and one of the most common neurological disorders involving a cranial nerve.
Incidence of Bell's palsy in males and females, as well as in various races, is approximately the same. The severity of the condition (e.g., mild, severe), and the rate of recovery also is equal.