Bell’s palsy is perhaps best known for its hallmark symptom, the drooping of one side of the face from a partial or complete paralysis of the facial muscles on that side. The disorder is usually temporary, and most people fully recover—even without treatment. But the likelihood of full recovery improves if steroid treatment is initiated within two or three days of symptom onset.
What causes Bell’s palsy?
The symptoms of Bell’s palsy are a result of damage to one of the two facial nerves—the seventh cranial nerves—which control muscle movement on either side of the face. Weakness or paralysis of the facial muscles occurs when one of the nerves becomes inflamed and swollen. The swelling can also cause compression of the nerve, resulting in further damage.
Bell’s palsy is most likely caused by a viral infection. Most scientists believe the herpes simplex virus—the same virus that leads to cold sores and genital herpes—is the most common of the viruses that cancause Bell’s palsy. Other infectious agents such as cytomegalovirus (a common herpes virus), Epstein-Barr virus (the virus that can cause mononucleosis), and herpes zoster (shingles) are also suspect.
Bell’s palsy gets its name from the 19th-century surgeon Sir Charles Bell, who first described the seventh cranial nerve and its involvement in facial palsy.
Sudden onset of symptoms
Bell’s palsy onset can be sudden, and symptoms typically worsen over 48 hours. Symptoms range from mild to severe and can vary from person to person. In rare cases, symptoms can affect both sides ofthe face. In addition to facial weakness or paralysis, symptoms may include:
- A drooping eyebrow, eyelid, or corner of the mouth on one side of the face
- Facial twitching
- Excessive tearing
- Inability to close one eye, squint, or blink, which can lead to dry eye
- Difficulty eating and drinking
- Difficulty making facial expressions, such as smiling and frowning
- Dry mouth
- Taste or hearing impairment
The symptoms, which can be distressing and cause some patients to avoid social interaction, typically begin to subside within three weeks. The more nerve damage you have, the longer it usually takes to recover. If your symptoms start to improve within three weeks, it’s a good indicator that you’ll fully recover. Most people regain full facial function within three to six months of symptom onset. An estimated 7 to 15 percent of people do not fully regain facial muscle strength.
Bell’s palsy strikes about 40,000 Americans each year, according to the National Institute of Neurological Disorders and Stroke. It can appear at any age but is less common after age 60. Having diabetes or an upper-respiratory infection like the cold of flu or being pregnant is associated with an increased risk of developing Bell’s palsy.
A South Korean study published in January 2020 in JAMA Otolaryngology–Head and Neck Surgery suggests that people younger than 40 and those with moderate symptoms are more likely to recover fully from Bell’s palsy. People who have diabetes or uncontrolled high blood pressure are less likely to have favorable outcomes.
Treating Bell’s palsy
Mild cases of Bell’s palsy don’t always require drug therapy. But undergoing early short-term steroid treatment of about one week increases your probability of a full recovery from Bell’s palsy. Guidelines from the American Academy of Neurology advise that you take oral steroids, such as prednisone, within two to three days of symptom onset.
Steroids used short term are usually effective, safe, and tolerable for most people with Bell’s palsy. For some people, though, steroid treatment may be risky. Your doctor may advise against taking steroids because of potential complications if, for example, you have uncontrolled diabetes, are morbidly obese (a body mass index of 40 or higher), or have a history of problematic steroid treatment.
Some doctors may additionally prescribe an antiviral drug such as valacyclovir (Valtrex, generic) if facial paralysis is severe, but research is mixed as to whether it can help improve recovery. Side effects from antivirals are rare, but the drugs are known to interact with other medications.
Sometimes, if damage is severe, the nerve may not heal properly, resulting in the inability to control facial movements. For example, one eye may completely close when you smile, or your mouth may twitch when you blink. In rare cases, reconstructive plastic surgery may be considered to correct facial deformities. Some patients may benefit from Botox injections to reduce facial muscle spasms.
If symptoms affect your ability to blink or fully close your eye, you need to take special precautions to prevent dry eye and possible permanent damage to your cornea. Administering hourly drops of artificial tears and applying a protective ointment at bedtime can help keep your eye lubricated. Your doctor may also suggest that you wear eyeglasses or goggles during the day, and an eyepatch while you sleep.
There’s no diagnostic test for Bell’s palsy, so doctors use certain clinical criteria to diagnose the condition. However, if your symptoms don’t improve within four months, another underlying condition may be causing facial paralysis instead. Lyme disease is a common culprit since its symptoms of facial paralysis mimic those of Bell’s palsy.
This article appeared in the May 2020 issue of UC Berkeley Health After 50.