Bell's Palsy Diagnosis and Chance of Recovery

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When half of the face loses its ability to move, it is often a sign of a stroke. One side of the mouth droops, and it may be impossible to fully close the eye on that side as well. A smile is transformed into what looks more like a lopsided smirk.

The appearance of these symptoms is always a reason to get medical help as soon as possible, because you do not want to miss the chance to get the best medical treatment for what could be a stroke.

There’s no reason to despair entirely, though. Facial droop can also be caused by Bell’s palsy, which is much less serious than a stroke.

bell's palsy
 Verywell / JR Bee

What Is Bell’s Palsy?

Bell’s palsy is named after Dr. Charles Bell, a Scottish surgeon who described the disorder in 1821. Dr. Bell was focusing on the facial nerve, also known as cranial nerve VII. Bell’s palsy is due to a sudden loss of facial nerve function, which leads to acute paralysis of half of the face and possibly other symptoms as well.

There is no clear cause of Bell’s palsy. Most people believe that it results from a viral infection that leads to inflammation of the nerve.

Bell’s palsy affects about one in 5,000 people every year. It is more common as we age. Diabetes and pregnancy also seem to increase the risk of Bell’s palsy.

The Function of the Facial Nerve

The facial nerve does more than just signal for facial muscles to move. Parasympathetic nerve fibers for eye tearing and some salivation run through the facial nerve. The facial nerve helps control the stapedius muscle, which adjusts the mechanics of hearing in the middle ear. The facial nerve also carries taste fibers from the foremost two-thirds of the tongue.

The fibers that do all these different nerve functions break away from the nerve at different points. It may be possible for a neurologist to determine just where in the course of the nerve the trouble lies by noting what nerve functions have been lost.

Due to a quirk in the way nerves run from the brain to the face, the top part of the face receives connections from both sides of the brain, and the bottom half of the face receives connections from just one side of the brain. This fact is important in making a diagnosis of Bell’s palsy because whereas a lesion of the nerve will usually affect both the top and bottom half of the face, a disease of the brain like a stroke will normally lead to paralysis of only the lower face.


Very often, a physician can diagnose Bell’s palsy just by hearing your story and doing a thorough physical exam. The doctor may examine your hearing as well as your sense of taste to see if those parts of the facial nerve have been affected. If they have, the problem is more likely Bell’s palsy than stroke. The most important thing is to see if the upper and lower parts of the face are equally affected. If so, the facial droop is more likely Bell’s palsy than a problem with the brain itself.

Sometimes a doctor may order specific imaging tests, like magnetic resonance imaging (MRI), in order to rule out a stroke or other problems with the brain. Occasionally, an electromyogram or nerve conduction study may be done on the face in order to confirm that the nerve is not working well, and to ensure that it is healing properly.

Differential Diagnosis of Facial Droop

One of the most serious things that can cause a facial droop is a stroke. Other diseases that cause facial drooping include Lyme disease, neurosarcoidosis, Ramsay-Hunt syndrome, and some seizures.


The chances of recovering from Bell’s palsy are very good. Many people recover in as soon as 10 days. About 85% of people will recover within three weeks, although recovery can take months in some cases. Only about 5% of patients have a poor recovery. Younger patients tend to recover more often than older patients. Only about 7% of people with Bell’s palsy will ever have another attack.

About 12% of patients who get Bell’s palsy have related symptoms afterward. Some patients may suffer from facial pain or spasm even after the ability to move recovers. Loss of taste may result as well. Unless care is taken to protect the affected eye, it may be damaged from remaining open. Sometimes when the facial nerve regenerates, branches may grow into different destinations than those with which they originally connected. The result is called synkinesis, when attempting to move one part of the face, such as the mouth, results in movement of another part of the face as well, such as the eyelid. In crocodile tear syndrome, the regenerated nerve connects the tearing of the eyes with the muscles of the mouth, so that the eyes tear whenever someone eats.

Although the chances of recovering from Bell’s palsy are good, it is important to see a doctor as soon as possible if you notice a facial droop. Bell’s palsy is a diagnosis of exclusion, meaning that more serious disorders must be ruled out before the diagnosis can be made. If that diagnosis of Bell’s palsy is made, it generally means that you are already on the road to recovery.

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Additional Reading
  • Bell C, Romberg MH. Karl Bells Physiolog. u. Patholog. Untersuchungen d. Nervensystems. Berlin.

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By Peter Pressman, MD
Peter Pressman, MD, is a board-certified neurologist developing new ways to diagnose and care for people with neurocognitive disorders.