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By Adrienne Onofri

What Doctors Know About Bell's Palsy

The Noun Project

“Classic Bell's palsy typically occurs out of the blue,” says Steven L. Lewis, MD, FAAN, physician in chief at the Lehigh Valley Fleming Neuroscience Institute in Allentown, PA. It strikes men and women in similar numbers, at any age, with an apparent peak in incidence among people in their forties, fifties, and sixties, says Gary Gronseth, MD, FAAN, chair of the neurology department at the University of Kansas Medical Center, who had Bell's palsy at age 43.

It's usually treated with a short course of the steroid prednisone, and about 95 percent of people recover fully, says Dr. Gronseth. Permanent disfigurement and facial asymmetry are rare.

While Bell's palsy is believed to be triggered by damage in the seventh cranial nerve (also known as the facial nerve), the cause is unknown.

“We think that Bell's palsy occurs mainly due to some kind of inflammation affecting the facial nerve, possibly related to a virus,” says Dr. Lewis. “The nerve has a long course through the temporal bone, so it gets swollen and then pinched, and that causes the damage that results in paralysis,” says Dr. Gronseth. “The question is, What causes the swelling?”

The answer may be reactivation of the herpes simplex virus, which people might have without knowing, since it can be transmitted between people by casual contact, Dr. Gronseth says.

Lyme disease also can be a cause of the nerve inflammation that leads to Bell's palsy, says Dr. Gronseth. “If people present with facial paralysis that looks like Bell's palsy and they live in an area where Lyme disease is endemic, we would look for evidence of Lyme disease [using an FDA-approved test]. In places where Lyme disease isn't common, we would not test for Lyme disease [because in these circumstance positive tests for Lyme disease are usually false positives.]”

Facial paralysis also is a sign of stroke, but stroke usually affects just the lower part of the face, whereas Bell's palsy typically affects one entire side (left or right) of a face. Bell's palsy is not life-threatening, but it's still “important to see a medical provider urgently when this symptom occurs,” says Dr. Lewis. The steroid prednisone “seems to work better the sooner it's given,” Dr. Gronseth says.

People with Bell's palsy whose eyelid won't close are encouraged to use eye drops to protect the eye—and to tape their eyelid shut and wear an eye patch at night so they don't scratch the cornea if they turn their head while sleeping. Doctors also may prescribe an antiviral, such as acyclovir (Zovirax) or valacyclovir (Valtrex). “Antiviral medications added to the steroid may give some small additional benefit,” says Dr. Gronseth.

Imaging is normally not necessary for diagnosis. “Neurologists can tell just by performing a neurologic exam,” says Dr. Gronseth. “They would check taste—if taste is affected, they would be very confident it was Bell's palsy. They would look in the ear to make sure there are no blisters suggestive of shingles.” Hearing also may be affected because Bell's palsy can affect a tiny branch of the facial nerve involved in the mechanism of hearing, says Dr. Lewis. “Some people experience difficulty with sounds seeming too loud in the ear on the side of the facial weakness.”

Pregnancy, diabetes, and high blood pressure increase the risk for Bell's palsy, and the latter two may contribute to a slower or incomplete recovery, says Dr. Gronseth. Among pregnant women who get Bell's palsy, it generally occurs during the third trimester, he says. The reason for this is another mystery. “We don't know for sure the connection to pregnancy,” says Dr. Gronseth. “There's a lot of fluid retention [in the third trimester of pregnancy], so the nerves tend to swell up during that time.” Or, he says, it could be that “women's immune systems become suppressed during the third trimester so they don't have an immune reaction and ‘reject’ the baby—[which] increases the risk of reactivation of a common virus like herpes simplex.”

Bell's palsy sometimes results in synkinesis, a “miswiring” of nerves when they regrow that causes an involuntary movement to accompany an unrelated voluntary movement—an eye tearing up while a person is eating, for example, or squinting when smiling. Another possible but less likely complication is “called hemifacial spasm, where the muscles will start to contract spontaneously,” says Dr. Gronseth.

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