An Overview of Bell's Palsy

The most common cause of facial weakness

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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 they can be stressful and frightening due to the dramatic change in the appearance of the face.

While a physical and neurological exam is usually sufficient to diagnose Bell's palsy, sometimes additional tests, like a brain magnetic resonance imaging (MRI), are needed to confirm the diagnosis or rule out mimicking conditions.

The upside of Bell's palsy is that symptoms often improve on their own within three weeks; although, corticosteroids are usually prescribed to optimize a person's chance for a full recovery.

Symptoms

Bell's palsy affects one side of the face, and it can cause partial or complete facial weakness, including the forehead, eyelid, cheek, and mouth. Due to this one-sided weakness, common findings (on the affected side) include:

  • Sagging eyebrow
  • Disappearance of the nasolabial fold
  • Drooping of the corner of the mouth

In addition, Bell’s palsy often impairs chewing, so a person may notice that they drool, particularly when drinking water. 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 (called hyperacusis).

Residual Symptoms

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.

For most people, their symptoms resolve within three weeks to a few months. Sometimes after an episode of Bell's palsy is largely resolved, though, a person may continue to experience mild facial tingling for months, or even slight weakness of their face, which can last for years.

Causes

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 7th 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, leading 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).

Diagnosis

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.

Important Note

Due to the fact that several diagnoses, some very serious, can mimic the symptoms of Bell's palsy, referral to a neurologist or otolaryngologist as soon as possible is warranted.

Physical Exam

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.

Peripheral (Bell's Palsy) Versus Central Nervous System (Stroke)

Bell's palsy causes weakness of the lower and upper parts of the face, while a lesion of the brain (like a stroke) causes weakness of the lower part of the face.

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 as facial weakness caused by a disorder in the brain, the facial weakness is usually more severe.

Ear Exam

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.

Imaging Tests

Various imaging tests, such as a brain MRI or CT scan, can be helpful in teasing out alternative diagnoses like stroke, tumor, multiple sclerosis, and an uncommon inflammatory disease called sarcoidosis.

Blood Tests

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 Sjogren's syndrome.

Electromyography (EMG)

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

Bottom Line

Much of the time, weakness of one side the face turns out to be Bell's palsy. But it is important for you to know that weakness of the face can be a stroke or another neurological condition, so be sure to seek medical attention.

Treatment

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 a person's 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 is highly debated, as most studies show no benefit compared with placebo.

Eye Care

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 when diagnosed with Bell's palsy, it's important to use artificial tears, which are available over-the-counter. Your doctor may also recommend using an eye patch at night to prevent irritation.

Complementary Therapies

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

A Word From Verywell

If any part of your face becomes weak or droopy, you should see a doctor. Even if you look up your symptoms on the Internet or if a friend or family member tells you that you look like you have Bell's palsy, you should still make sure to get medical attention right away. Your symptoms could be caused by a variety of neurological conditions, and it is important to exclude serious causes.

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