Peripheral Facial Paralysis or Bell's Palsy

What is it?

Bell's palsy, or peripheral facial paralysis, is a condition in which the facial nerve that controls the muscles of the face becomes inflamed, leading to partial or complete loss of function

The inflammation causes swelling of the nerve and the small blood vessels around it. Since these structures are surrounded by the bones of the skull, they become compressed, impairing the nerve's ability to conduct electrical impulses. This results in the nerve being unable to communicate with the facial muscles, causing facial paralysis

Incidence

An American estimate suggests an average of 40,000 cases per year in the U.S. Statistics in Brazil are likely similar. Bell's palsy affects all races and both sexes equally. Diabetes and pregnancy increase the risk of developing Bell's palsy

Symptoms and Diagnosis

Common signs and symptoms of Bell's palsy include: weakness of the muscles on one side of the face, with paralysis of the upper eyelid, leading to difficulty closing the eye and blinking. This can cause eye dryness and corneal damage. The mouth may also be pulled to the opposite side of the paralysis (crooked mouth), as it shifts toward the healthy side where the muscles still contract

Other symptoms may include decreased taste on the front part of the tongue and excessive salivation, causing drooling. Pain behind the ear may occur, and loud noises may cause discomfort in the affected ear—a condition known as hyperacusis. The changes caused by Bell's palsy affect facial appearance, including how you smile. These changes are often noticeable to others and may cause distress and social withdrawal

A major concern for patients with Bell's palsy is the fear of having a stroke. Some clinical clues make a stroke less likely, such as the absence of paralysis in other parts of the body. In Bell's palsy, the upper part of the face is affected, while in a stroke, the mouth typically droops without affecting the eye. Despite these clues, it is important to seek urgent medical attention to rule out serious neurological conditions and begin early treatment. The diagnosis of Bell's palsy is clinical and does not rely on additional tests. Imaging is not necessary in emergency settings. Complementary tests are reserved for cases that take longer to improve. A CT scan is not needed; if imaging is chosen, MRI is the best option. Some viral and bacterial serologies may be useful. Electroneuromyography can help assess nerve condition in cases that take longer to recover, especially those lasting more than three months

Most people with Bell's palsy recover completely, usually within three weeks to nine months. A small number may have lasting effects. If you show signs of Bell's palsy, you should see a doctor immediately, as treatment is available and should begin within two to three days of symptom onset. Early treatment shortens symptom duration and reduces the risk of long-term effects

Cause

The cause of Bell's palsy has long been debated. There is a popular belief that it may be caused by “thermal shocks” or “drafts of air,” but this has no scientific basis

The most accepted theory today is that the inflammation of the facial nerve, which interrupts its function, is caused by various viral infections. The virus most commonly associated with Bell's palsy is herpes simplex—the same virus that causes cold sores and genital herpes. Other viruses that may cause Bell's palsy include herpes zoster (which causes chickenpox), cytomegalovirus, and Epstein-Barr virus (which causes mononucleosis)

Treatment

Treatment does not reverse facial paralysis but helps speed up recovery, especially if started within the first few days of symptoms

Eye care – You will need to take care of your eyes if you cannot close them. There is a risk of permanent corneal damage if the eye becomes too dry. Artificial tears can help keep the eye moist. If your eye does not close completely, you should protect it during the day with glasses. Tape the upper eyelid shut while sleeping to prevent corneal injury

Medication – Most people diagnosed with Bell's palsy (within two to three days of symptom onset) are treated with steroids (e.g., prednisone). Steroids, also known as corticosteroids, can reduce swelling and improve the chances of full recovery. These medications work best when started early (within three days of symptom onset). Antiviral medications (e.g., acyclovir, valacyclovir) are sometimes used alongside corticosteroids, especially in cases of severe facial weakness. Some controlled trials have shown additional benefits from these agents in patients with very severe symptoms. Other treatment methods are not proven

By the Einstein Editorial Board