What Is Bell's Palsy?

Bell's palsy is a condition that causes partial or complete weakness of one side of the face. The symptoms of Bell’s palsy, such as a sagging eyebrow or drooping mouth corner, develop pretty quickly and can dramatically change one's appearance. Symptoms of Bell's palsy usually improve on their own within a few months. Corticosteroids are typically prescribed to optimize a person's chance for a full recovery.

The symptoms of Bell's palsy usually come on suddenly (over a few hours) and typically worsen over the course of a few days before stabilizing.

Bell's palsy affects one side of the face. It can cause partial or complete facial weakness, including in the forehead, eyelid, cheek, and mouth. Common findings (on the affected side) include:

• A sagging eyebrow
• Disappearance of the nasolabial fold (so-called "smile line")
• Drooping of the corner of the mouth

In addition, Bell’s palsy can cause difficulties eating and drinking, and patients may notice some drooling. Problems with the ability to taste food may also occur. A person's speech can also sound a bit slurred due to difficulty controlling the muscles of their mouth.

Bell's palsy can also cause dryness and even redness of the eye due to decreased blinking, incomplete eyelid closing, and diminished facial tears.

Lastly, some people with Bell’s palsy experience ear discomfort with loud noises (i.e., hyperacusis).

Bell's palsy is more common in adults than in children, and it is not a sign of any serious health problem. It is a peripheral neuropathy (nerve disease) of the facial nerve, which is the seventh cranial nerve. This nerve comes off the brain stem and controls facial movement. When the facial nerve is inflamed and swollen (as in Bell's palsy), it cannot properly communicate with the facial muscles, which leads to weakness.

Sometimes Bell's palsy is triggered by a viral infection, like the herpes simplex virus (HSV). Diabetes and pregnancy have also been associated with a higher incidence of Bell's palsy. But most of the time, it is impossible to pinpoint the exact cause of the condition, and so the "why" behind a person's Bells palsy is often considered idiopathic (without a known cause).

Bell's palsy is usually diagnosed based on a person's symptoms and physical exam. That said, Bell's palsy is generally considered a diagnosis of exclusion, meaning additional diagnostic studies are often needed to rule out mimicking conditions.

Some of these possibilities are very serious, so referral to a neurologist or otolaryngologist as soon as possible is warranted.

If one side of your face is weak, your doctor will examine you to check for serious, brain-related causes of facial weakness, such as a stroke.

The good news is that there are some distinct physical exam characteristics of Bell's palsy that differentiate it from facial weakness caused by a problem in the brain.

This distinction is due to the way nerves run from the brain to the face. Basically, your forehead receives connections from both sides of the brain, whereas the lower part of the face receives connections from just one side of the brain.

This means that a person with a problem in the brain (stroke) would have preserved forehead movement while a person with a problem with the facial nerve (Bell's palsy) would have a loss of forehead movement.

In the end, while Bell's palsy is not as serious a condition as brain disorders that can cause like symptoms, the facial weakness with Bell's is usually more severe.

Since one-sided facial weakness may result from a bacterial infection of the middle ear, or as a complication of herpes zoster infection (shingles)—called Ramsay Hunt syndrome—your doctor will also examine your ear.

Various imaging tests, such as brain magnetic resonance imaging (MRI) and computed tomography (CT scan), can be helpful in teasing out alternative diagnoses like stroke, tumor, multiple sclerosis, and an uncommon inflammatory disease called sarcoidosis.

Sometimes blood tests are warranted to rule out other causes of facial paralysis, most commonly Lyme disease and less commonly, HIV infection or an autoimmune disease like Sjögren's syndrome.

For people with more severe cases of Bell's palsy, like complete paralysis of the facial nerve, a doctor may recommend an electromyography (EMG) to help predict prognosis and/or provide guidance on a treatment plan.

While there is no medication or therapy that can cure Bell's palsy, corticosteroids (e.g., prednisone) have been found in various studies to improve both speed of recovery and chances for a full recovery.

An antiviral medication, such as Valtrex (valacyclovir), is sometimes prescribed along with corticosteroids for the treatment of Bell's palsy. However, the effectiveness of antiviral therapy for this purpose is highly debated, as most studies show no benefit compared with placebo.

One major concern associated with Bell's palsy is the affected eye. Due to incomplete eyelid closure and impaired eye tearing, the eyeball can become dry, red, or itchy.

This is why those with Bell's palsy should use artificial tears, which are available over the counter. Your doctor may also recommend using an eye patch at night to prevent irritation.

A few different complementary therapies, such as electrical nerve stimulation, acupuncture, and facial exercises, may also be useful in the management of Bell's palsy, although research backing these therapies is scant.

If any part of your face becomes weak or droopy, you should see a doctor right away—even if it seems that you have a classic Bell's palsy presentation. Your symptoms could be caused by a variety of neurological conditions, and it is important to exclude the serious ones.