Overview

Bell's palsy causes sudden weakness in your facial muscles. This makes half of your face appear to droop. Your smile is one-sided, and your eye on that side resists closing.

Bell's palsy, also known as facial palsy, can occur at any age. The exact cause is unknown, but it's believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of your face. It may be a reaction that occurs after a viral infection.

For most people, Bell's palsy is temporary. Symptoms usually start to improve within a few weeks, with complete recovery in about six months. A small number of people continue to have some Bell's palsy symptoms for life. Rarely, Bell's palsy can recur.

Symptoms

Signs and symptoms of Bell's palsy come on suddenly and may include:

  • Rapid onset of mild weakness to total paralysis on one side of your face — occurring within hours to days
  • Facial droop and difficulty making facial expressions, such as closing your eye or smiling
  • Drooling
  • Pain around the jaw or in or behind your ear on the affected side
  • Increased sensitivity to sound on the affected side
  • Headache
  • A decrease in your ability to taste
  • Changes in the amount of tears and saliva you produce

In rare cases, Bell's palsy can affect the nerves on both sides of your face.

When to see a doctor

Seek immediate medical help if you experience any type of paralysis because you may be having a stroke. Bell's palsy is not caused by a stroke.

See your doctor if you experience facial weakness or drooping to determine the underlying cause and severity of the illness.

Causes

Although the exact reason Bell's palsy occurs isn't clear, it's often linked to exposure to a viral infection. Viruses that have been linked to Bell's palsy include the virus that causes:

  • Cold sores and genital herpes (herpes simplex)
  • Chickenpox and shingles (herpes zoster)
  • Mononucleosis (Epstein-Barr)
  • Cytomegalovirus infections
  • Respiratory illnesses (adenovirus)
  • German measles (rubella)
  • Mumps (mumps virus)
  • Flu (influenza B)
  • Hand-foot-and-mouth disease (coxsackievirus)

With Bell's palsy, the nerve that controls your facial muscles, which passes through a narrow corridor of bone on its way to your face, becomes inflamed and swollen — usually related to a viral infection. Besides facial muscles, the nerve affects tears, saliva, taste and a small bone in the middle of your ear.

Risk factors

Bell's palsy occurs more often in people who:

  • Are pregnant, especially during the third trimester, or who are in the first week after giving birth
  • Have an upper respiratory infection, such as the flu or a cold
  • Have diabetes

Also, some people who have recurrent attacks of Bell's palsy, which are rare, have a family history of recurrent attacks. In those cases, there may be a genetic predisposition to Bell's palsy.

Complications

A mild case of Bell's palsy normally disappears within a month, but recovery from a more severe case involving total paralysis varies. Complications may include:

  • Irreversible damage to your facial nerve
  • Misdirected regrowth of nerve fibers, resulting in involuntary contraction of certain muscles when you're trying to move others (synkinesis) — for example, when you smile, the eye on the affected side may close
  • Partial or complete blindness of the eye that won't close due to excessive dryness and scratching of the cornea, the clear protective covering of the eye
Dec. 16, 2014
References
  1. Bope ET, et al. Conn's Current Therapy. Philadelphia, Pa.: Saunders Elsevier; 2014. http://www.clinicalkey.com. Accessed Nov. 14, 2014.
  2. Glass GE, et al. Bell's palsy: A summary of current evidence and referral algorithm. Family Practice. In press. Accessed Nov. 14, 2014.
  3. Ferri FF. Ferri's Clinical Advisor 2015: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2015. https://www.clinicalkey.com. Accessed Nov. 14, 2014.
  4. Bell's palsy fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/bells/detail_bells.htm. Accessed Nov. 14, 2014.
  5. Ronthal M. Bell's palsy: Pathogenesis, clinical features, and diagnosis in adults. http://www.uptodate.com/home. Accessed Nov. 15, 2014.
  6. Ronthal M. Bell's palsy: Prognosis and treatment in adults. http://www.uptodate.com/home. Accessed Nov. 15, 2014.
  7. Facial nerve palsy. The Merck Manual Professional Edition. http://www.merckmanuals.com/professional/neurologic_disorders/neuro-ophthalmologic_and_cranial_nerve_disorders/facial_nerve_palsy.html?qt=&sc=&alt=. Accessed Nov.16, 2014.
  8. AskMayoExpert. What is the initial therapy recommended for patients with Bell palsy? Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2014.