Bell’s Palsy: The Most Common Cause of Facial Paralysis


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By Alisa Yamasaki, MD

Bell’s palsy is a facial nerve disorder that causes paralysis or weakness on one side of the face.

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It is the most common cause of facial paralysis and occurs when the facial nerve — which controls the muscles of your face — becomes injured or stops working properly.

At Penn Medicine Princeton Health, doctors have several non-surgical and surgical techniques to help treat Bell’s palsy and restore facial symmetry.

Affects Both Men and Women

Though the exact cause of the nerve injury associated with Bell’s palsy is not clear, doctors believe that the condition may could be triggered by several different factors, including:

  • A viral infection, such as herpes simplex, that gets reactivated.
  • Inflammation of the facial nerve from other viruses or autoimmune conditions.
  • Impaired blood flow to the facial nerve.
  • Pregnancy-related inflammation and swelling.
  • Other genetic factors.

Bell’s palsy affects an estimated 40,000 people in the United States each year, according to the National Institutes of Health (NIH). Bell’s palsy affects both men and women, and while it can occur at any age, it is most common in young adults aged 15 to 45.

Sudden Symptoms

Bell’s palsy occurs as a sudden weakness or paralysis that occurs within 72 hours. It typically occurs on one side of the face, though may very rarely occur on both sides. You may notice:

  • Problems smiling, frowning, or making facial expression.
  • Trouble eating or drinking and/or drooling from one side of the mouth.
  • Difficulty closing the eye.
  • Droopy eyebrow.
  • Twitching or weakness in the muscles of your face.

Other symptoms from Bell’s palsy may include:

  • Facial pain, tightness, and/or numbness and tingling.
  • Dry eye, which can lead to eye ulcer or infections.
  • Excessive tearing.
  • Changes in taste.
  • Pain around the ear or jaw.

Diagnoses and Treatment

Often, doctors can diagnose Bell’s palsy by taking a medical history and performing a complete physical exam. In some cases, blood tests and imaging studies may be recommended to rule out other causes of facial paralysis, such as Lyme disease, autoimmune conditions, brain tumor, or stroke.

Treatment for Bell’s palsy is time sensitive, and prompt medical attention is critical. Treatment should be started within 72 hours and may include steroid and antiviral medications to reduce inflammation and improve the chances of recovering full facial nerve function.

Facial Reanimation: Restoring Symmetry After Bell’s Palsy

While most people with Bell’s palsy will regain facial function within six months, some patients may be left with persistent facial asymmetry as well as facial pain and tightness.

During the healing process, the nerves may undergo abnormal regrowth — think of electrical wires becoming tangled — that is called synkinesis. Synkinesis causes involuntary contraction of muscles in the face. This causes facial muscles to become too taut, leading to tightness and pain as well as facial asymmetry.

Incomplete recovery from Bell’s palsy can have a significant impact — both physically and emotionally. Fortunately, there are several techniques to help restore more natural movement and symmetry to the face.

In many instances, routine Botox injections can help relax the muscles and restore balance to the face. This is done as a quick procedure in the office with no downtime.

As an alternative to Botox, procedures can be used to more permanently correct asymmetries in parts of the face. For example, surgery can be used to lift the brow or the eyelid or reduce activity of tight smile muscles.

In more severe cases, surgery called selective neurectomy may be used.

Selective neurectomy targets specific facial nerve branches that are causing abnormal contractions of the muscles and leading to facial asymmetry. The surgeon then cuts those nerves, which ultimately allows the overactive muscles to relax.

The procedure typically takes several hours under general anesthesia. Surgeons typically use a facelift approach to keep incisions and scars well camouflaged. An overnight hospital stay may be required for observation, and most patients recover from the procedure within one to two weeks.

Recovery from Bell’s palsy is a collaborative journey that you embark on with your physician. The most important thing is to have patience and open communication with your doctor regarding your treatment.

To find a physician affiliated with Penn Medicine Princeton Health, call 888-742-7496 or visit

Alisa Yamasaki, MD, is a fellowship-trained facial plastic and reconstructive surgeon on the Medical Staff at Penn Medicine Princeton Health.

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