Bell's palsy is a type of facial paralysis that results in a temporary inability to control the

facial muscles The facial muscles are a group of striated skeletal muscles supplied by the facial nerve (cranial nerve VII) that, among other things, control facial expression. These muscles are also called mimetic muscles. They are only found in mammals, alth ...

on the affected side of the face. In most cases, the weakness is temporary and significantly improves over weeks. Symptoms can vary from mild to severe. They may include muscle twitching, weakness, or total loss of the ability to move one or, in rare cases, both sides of the face. Other symptoms include drooping of the eyebrow, a change in

taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste. Taste is the perception stimulated when a substance in the mouth biochemistry, reacts chemically with taste receptor cells l ...

, and pain around the ear. Typically symptoms come on over 48 hours. Bell's palsy can trigger an increased sensitivity to sound known as

hyperacusis Hyperacusis is an increased Hearing, sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it often revolves around damage to or dysfunction of the Stapes, ''stapes'' bone, stapedius ...

. The cause of Bell's palsy is unknown and it can occur at any age. Risk factors include

diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...

, a recent

upper respiratory tract infection An upper respiratory tract infection (URTI) is an illness caused by an acute infection, which involves the upper respiratory tract, including the nose, sinuses, pharynx, larynx or trachea. This commonly includes nasal obstruction, sore throat ...

, and

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

. It results from a dysfunction of

cranial nerve VII The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tast ...

(the facial nerve). Many believe that this is due to a viral infection that results in swelling. Diagnosis is based on a person's appearance and ruling out other possible causes. Other conditions that can cause facial weakness include

brain tumor A brain tumor (sometimes referred to as brain cancer) occurs when a group of cells within the Human brain, brain turn cancerous and grow out of control, creating a mass. There are two main types of tumors: malignant (cancerous) tumors and benign ...

stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

, Ramsay Hunt syndrome type 2,

myasthenia gravis Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, ...

, and

Lyme disease Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of ''Borrelia'' bacteria, Disease vector, transmitted by blood-feeding ticks in the genus ''Ixodes''. It is the most common disease spread by ticks in th ...

. The condition normally gets better by itself, with most achieving normal or near-normal function.

Corticosteroids Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invol ...

have been found to improve outcomes, while antiviral medications may be of a small additional benefit. The eye should be protected from drying up with the use of

eye drops ''Eye Drops'' is a television program on TechTV that showcased short computer animation movies and clips made using off the shelf 3D animation software. The show claimed to showcase all different types of animation, but only a very small number ...

or an eyepatch. Surgery is generally not recommended. Often signs of improvement begin within 14 days, with complete recovery within six months. A few may not recover completely or have a recurrence of symptoms. Bell's palsy is the most common cause of one-sided facial nerve paralysis (70%). It occurs in 1 to 4 per 10,000 people per year. About 1.5% of people are affected at some point in their lives. It most commonly occurs in people between ages 15 and 60. Males and females are affected equally. It is named after Scottish surgeon

Charles Bell Sir Charles Bell (12 November 177428 April 1842) was a Scottish surgeon, anatomist, physiologist, neurologist, artist, and philosophical theologian. He is noted for discovering the difference between sensory nerves and motor nerves in the ...

(1774–1842), who first described the connection of the facial nerve to the condition. Although defined as a mononeuritis (involving only one nerve), people diagnosed with Bell's palsy may have "myriad neurological symptoms", including "facial tingling, moderate or severe headache/neck pain, memory problems, balance problems, ipsilateral limb paresthesias, ipsilateral limb weakness, and a sense of clumsiness" that are "unexplained by facial nerve dysfunction".

Signs and symptoms

Bell's palsy is characterized by a one-sided facial droop that comes on within 72 hours. In rare cases (<1%), it can occur on both sides resulting in total facial paralysis. The facial nerve controls many functions, such as blinking and closing the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

s, smiling,

frowning A frown (also known as a scowl) is a facial expression in which the eyebrows are brought together, and the forehead is wrinkled, usually indicating displeasure, sadness or worry, or less often confusion or concentration. The appearance of a fr ...

, lacrimation, salivation, flaring

nostrils A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, ...

and raising

eyebrow An eyebrow is an area of short hairs above each eye that follows the shape of the lower margin of the Supraorbital ridge, brow ridges of some mammals. In humans, eyebrows serve two main functions: first, human communication, communication thro ...

s. It also carries

sensations from the anterior two thirds of the

tongue The tongue is a Muscle, muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper s ...

, through the

chorda tympani nerve Chorda tympani is a branch of the facial nerve that carries gustatory (taste) sensory innervation from the front of the tongue and parasympathetic ( secretomotor) innervation to the submandibular and sublingual salivary glands. Chorda tympani ...

(a branch of the facial nerve). Because of this, people with Bell's palsy may present with loss of taste sensation in the anterior two thirds of the tongue on the affected side. The facial nerve innervates the

stapedius muscle The stapedius is the smallest skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous syste ...

of the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles (malleus, incus, and stapes), which transfer the vibrations ...

(through the

tympanic branch The tympanic nerve ( Jacobson's nerve) is a branch of the glossopharyngeal nerve passing through the petrous part of the temporal bone to reach the middle ear. It provides sensory innervation for the middle ear, the Eustachian tube, the paroti ...

), which reflexively dampens the conduction of loud sounds. Thus, Bell's Palsy may cause normal sounds to be perceived as very loud (

), and dysacusis is possible but hardly ever clinically evident.

Cause

The cause of Bell's palsy is unknown. Risk factors include

, a recent

, and

. Some viruses are thought to establish a persistent (or latent) infection without symptoms, e.g., the

varicella zoster virus Varicella zoster virus (VZV), also known as human herpesvirus 3 (HHV-3, HHV3), is one of nine known herpes viruses that can infect humans. It causes chickenpox (varicella) commonly affecting children and young adults, and shingles (herpes zos ...

and the

Epstein–Barr virus The Epstein–Barr virus (EBV), also known as human herpesvirus 4 (HHV-4), is one of the nine known Herpesviridae#Human herpesvirus types, human herpesvirus types in the Herpesviridae, herpes family, and is one of the most common viruses in ...

, both of the herpes family. Reactivation of an existing (dormant) viral infection has been suggested as a cause of acute Bell's palsy. As the facial nerve swells and becomes inflamed in reaction to the infection, it causes pressure within the Fallopian canal, resulting in the restriction of blood and oxygen to the nerve cells. Other viral and bacterial infections that have been linked to the development of Bell's palsy include

HIV The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the im ...

and

. This new activation could be triggered by trauma, environmental factors, and metabolic or emotional disorders. Familial inheritance has been found in 4–14% of cases. There may also be an association with

migraines Migraine (, ) is a complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea, and light and sound sensitivity. Other characterizing symptoms may includ ...

. In December 2020, the U.S.

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

recommended that recipients of the

Pfizer Pfizer Inc. ( ) is an American Multinational corporation, multinational Pharmaceutical industry, pharmaceutical and biotechnology corporation headquartered at The Spiral (New York City), The Spiral in Manhattan, New York City. Founded in 184 ...

and

Moderna COVID-19 vaccine The Moderna COVID19 vaccine, sold under the brand name Spikevax, is a COVID-19 vaccine developed by the American company Moderna, the United States National Institute of Allergy and Infectious Diseases (NIAID), and the Biomedical Advanced ...

s should be monitored for symptoms of Bell's palsy after several cases were reported among clinical trial participants, though the data were not sufficient to determine a causal link.

Genetics

A meta-analysis of genome-wide association study (GWAS) identified the first unequivocal association with Bell's palsy.

Pathophysiology

Bell's palsy is the result of a malfunction of the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

(

cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

VII), which controls the

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

s of the face. Facial palsy is typified by an inability to move the muscles of facial expression. The paralysis is of the infranuclear/lower motor neuron type. It is thought that as a result of

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

of the facial nerve, pressure is produced on the nerve where it exits the skull within its bony canal (the

stylomastoid foramen The stylomastoid foramen is a foramen between the styloid and mastoid processes of the temporal bone of the skull. It is the termination of the facial canal, and transmits the facial nerve, and stylomastoid artery. Facial nerve inflammation in th ...

), blocking the transmission of neural signals or damaging the nerve. Patients with facial palsy for which an underlying cause can be found are not considered to have Bell's palsy ''per se''. Possible causes of facial paralysis include

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...

diabetes mellitus Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or th ...

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inj ...

and inflammatory diseases of the cranial nerves (

sarcoidosis Sarcoidosis (; also known as Besnier–Boeck–Schaumann disease) is a disease involving abnormal collections of White blood cell, inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph n ...

brucellosis Brucellosis is a zoonosis spread primarily via ingestion of raw milk, unpasteurized milk from infected animals. It is also known as undulant fever, Malta fever, and Mediterranean fever. The bacteria causing this disease, ''Brucella'', are small ...

, etc.). In these conditions, the neurologic findings are rarely restricted to the facial nerve. Babies can be born with facial palsy. In a few cases, bilateral facial palsy has been associated with acute HIV infection. In some research, the

herpes simplex virus Herpes simplex virus 1 and 2 (HSV-1 and HSV-2) are two members of the Herpesviridae#Human herpesvirus types, human ''Herpesviridae'' family, a set of viruses that produce Viral disease, viral infections in the majority of humans. Both HSV-1 a ...

type 1 (HSV-1) has been identified in a majority of cases diagnosed as Bell's palsy through endoneurial fluid sampling. Other research, however, identified, out of a total of 176 cases diagnosed as Bell's palsy, HSV-1 in 31 cases (18%) and

herpes zoster Shingles, also known as herpes zoster or zona, is a viral disease characterized by a painful skin rash with blisters in a localized area. Typically the rash occurs in a single, wide mark either on the left or right side of the body or face. T ...

in 45 cases (26%). In addition, HSV-1 infection is associated with demyelination of nerves. This nerve damage mechanism is different from the above-mentioned—that edema, swelling, and compression of the nerve in the narrow bone canal are responsible for nerve damage. Demyelination may not even be directly caused by the virus but by an unknown

immune In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization. Innate and adaptive ...

response.

Diagnosis

Bell's palsy is a

diagnosis of exclusion A diagnosis of exclusion or by exclusion (''per exclusionem'') is a diagnosis of a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from history, examination o ...

, meaning it is diagnosed by the elimination of other reasonable possibilities. By definition, no specific cause can be determined. There are no routine lab or imaging tests required to make the diagnosis. The degree of nerve damage can be assessed using the House-Brackmann score. One study found that 45% of patients are not referred to a specialist, which suggests that Bell's palsy is considered by physicians to be a straightforward diagnosis that is easy to manage. Other conditions that can cause similar symptoms include

, and

Differential diagnosis

Once the facial paralysis sets in, many people may mistake it as a symptom of a stroke; however, there are a few subtle differences. A stroke will usually cause a few additional symptoms, such as numbness or weakness in the arms and legs. And unlike Bell's palsy, a stroke will usually let patients control the upper part of their faces. A person with a stroke will usually have some wrinkling on their forehead. In areas where

is common, it accounts for about 25% of cases of facial palsy. In the U.S., Lyme is most common in the

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

and Mid-Atlantic states and parts of

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

and

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

. The first sign of about 80% of Lyme infections, typically one or two weeks after a tick bite, is usually an expanding rash that may be accompanied by headaches, body aches, fatigue, or fever. In up to 10–15% of Lyme infections, facial palsy appears several weeks later, and may be the first sign of infection that is noticed as the Lyme rash typically does not itch and is not painful. The likelihood that the facial palsy is caused by Lyme disease should be estimated, based on the recent history of outdoor activities in likely tick habitats during warmer months, a recent history of rash or symptoms such as headache and fever, and whether the palsy affects both sides of the face (much more common in Lyme than in Bell's palsy). If that likelihood is more than negligible, a serological test for Lyme disease should be performed, and if it exceeds 10%, empiric therapy with antibiotics should be initiated, without

corticosteroids Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invol ...

, and reevaluated upon completion of laboratory tests for Lyme disease. Corticosteroids have been found to harm outcomes for facial palsy caused by Lyme disease. One disease that may be difficult to exclude in the

differential diagnosis In healthcare, a differential diagnosis (DDx) is a method of analysis that distinguishes a particular disease or condition from others that present with similar clinical features. Differential diagnostic procedures are used by clinicians to di ...

is the involvement of the facial nerve in infections with the

virus. The major differences in this condition are the presence of small blisters, or ''vesicles'', on the external ear, significant pain in the jaw, ear, face, and/or neck, and hearing disturbances, but these findings may occasionally be lacking ( zoster sine herpete). Reactivation of existing

infection leading to facial paralysis in a Bell's palsy type pattern is known as Ramsay Hunt syndrome type 2. The prognosis for Bell's palsy patients is generally much better than for Ramsay Hunt syndrome type 2 patients.

Treatment

Steroids are effective at improving recovery in Bell's palsy while antivirals have not. In those who are unable to close their eyes, eye-protective measures are required. Management during pregnancy is similar to management in the non-pregnant.

Steroids

Corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

s such as

prednisone Prednisone is a glucocorticoid medication mostly used to immunosuppressive drug, suppress the immune system and decrease inflammation in conditions such as asthma, COPD, and rheumatologic diseases. It is also used to treat high blood calcium ...

improve recovery at 6 months and are thus recommended. Early treatment (within 3 days after the onset) is necessary for benefit with a 14% greater probability of recovery. There is some debate regarding the optimal dosing strategy which is generally physician dependent.

Antivirals

One review found that

antivirals Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Antiviral drugs are a class of antimicrobials ...

(such as

aciclovir Aciclovir, also known as acyclovir, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include the prevention of cytomegalovirus infections following tran ...

) are ineffective in improving recovery from Bell's palsy beyond steroids alone in mild to moderate disease. Another review found a benefit when combined with corticosteroids but stated the evidence was not very good to support this conclusion. In severe disease, it is also unclear. One 2015 review found no effect regardless of severity. Another review found a small benefit when added to steroids. They are commonly prescribed due to a theoretical link between Bell's palsy and the

herpes simplex Herpes simplex, often known simply as herpes, is a viral disease, viral infection caused by the herpes simplex virus. Herpes infections are categorized by the area of the body that is infected. The two major types of herpes are Cold sore, ora ...

and

. There is still the possibility that they might result in a benefit less than 7% as this has not been ruled out.

Eye protection

When Bell's palsy affects the blink reflex and stops the eye from closing completely, frequent use of tear-like eye drops or eye ointments is recommended during the day, and protecting the eyes with patches or taping them shut is recommended for sleep and rest periods.

Physiotherapy

Physiotherapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

can be beneficial to some individuals with Bell's palsy as it helps to maintain

muscle tone In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles, or the muscle's resistance to passive stretch during resting state.O’Sullivan, S. B. (2007) ...

of the affected

and stimulate the

. It is important that muscle re-education exercises and soft tissue techniques be implemented before recovery to help prevent permanent contractures of the

paralyzed Paralysis (: paralyses; also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, r ...

facial muscles. To reduce

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

, heat can be applied to the affected side of the face. There is no high-quality evidence to support the role of electrical stimulation for Bell's palsy.

Surgery

Surgery may be able to improve outcomes in facial nerve palsy that has not recovered. A number of different techniques exist. Smile surgery or smile reconstruction is a surgical procedure that may restore the smile for people with facial nerve paralysis. Adverse effects include hearing loss which occurs in 3–15% of people. A Cochrane review (updated in 2021), after reviewing applicable randomized and quasi-randomized controlled trials was unable to determine if early surgery is beneficial or harmful. As of 2007 the

American Academy of Neurology The American Academy of Neurology (AAN) is a professional society representing over 40,000 neurologists and neuroscientists. As a medical specialty society it was established in 1948 by A.B. Baker of the University of Minnesota to advance the a ...

did not recommend surgical decompression.

Alternative medicine

The efficacy of

acupuncture Acupuncture is a form of alternative medicine and a component of traditional Chinese medicine (TCM) in which thin needles are inserted into the body. Acupuncture is a pseudoscience; the theories and practices of TCM are not based on scientif ...

remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices). There is very tentative evidence for

hyperbaric oxygen therapy Hyperbaric medicine is medical treatment in which an increase in barometric pressure of typically air or oxygen is used. The immediate effects include reducing the size of gas emboli and raising the partial pressures of the gases present. Initial ...

in severe disease.

Prognosis

Most people with Bell's palsy start to regain normal facial function within three weeks—even those who do not receive treatment. In a 1982 study, when no treatment was available, of 1,011 patients, 85% showed first signs of recovery within three weeks after onset. For the other 15%, recovery occurred 3–6 months later. After a follow-up of at least one year or until restoration, complete recovery had occurred in more than two-thirds (71%) of all patients. Recovery was judged moderate in 12% and poor in only 4% of patients. Another study found that incomplete palsies disappear entirely, nearly always in one month. The patients who regain movement within the first two weeks nearly always remit entirely. When remission does not occur until the third week or later, a significantly greater part of the patients develop

sequela A sequela (, ; usually used in the plural, sequelae ) is a pathological condition resulting from a disease, injury, therapy, or other trauma. Derived from the Latin word meaning "sequel", it is used in the medical field to mean a complication or ...

e. A third study found a better prognosis for young patients, aged below 10 years old, while the patients over 61 years old presented a worse prognosis. Major possible complications of the condition are chronic loss of taste (

ageusia Ageusia (from negative prefix ''a-'' and Ancient Greek ''γεῦσις'' geûsis 'taste') is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami (meaning 'savory t ...

), chronic facial

spasm A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ, such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a musc ...

, facial pain, and corneal infections. Another complication can occur in case of incomplete or erroneous regeneration of the damaged facial nerve. The nerve can be thought of as a bundle of smaller individual nerve connections that branch out to their proper destinations. During regrowth, nerves are generally able to track the original path to the right destination—but some nerves may sidetrack leading to a condition known as synkinesis. For instance, the regrowth of nerves controlling muscles attached to the eye may sidetrack and also regrow connections reaching the muscles of the mouth. In this way, the movement of one also affects the other. For example, when the person closes the eye, the corner of the mouth lifts involuntarily. Around 9% of people have some sort of ongoing problems after Bell's palsy, typically the synkinesis already discussed, or spasm, contracture,

tinnitus Tinnitus is a condition when a person hears a ringing sound or a different variety of sound when no corresponding external sound is present and other people cannot hear it. Nearly everyone experiences faint "normal tinnitus" in a completely ...

, or hearing loss during facial movement or crocodile-tear syndrome. This is also called gustatolacrimal reflex or Bogorad's syndrome and results in shedding tears while eating. This is thought to be due to faulty regeneration of the facial nerve, a branch of which controls the lacrimal and salivary glands. Gustatorial sweating can also occur.

Epidemiology

The number of new cases of Bell's palsy ranges from about one to four cases per 10,000 population per year. The rate increases with age. Bell's palsy affects about 40,000 people in the United States every year. It affects approximately 1 person in 65 during a lifetime. A range of annual incidence rates have been reported in the literature: 15, 24, and 25–53 (all rates per 100,000 population per year). Bell's palsy is not a reportable disease, and there are no established registries for people with this diagnosis, which complicates precise estimation.

Frequency

About 40,000 people are affected by Bell's palsy in the United States every year. It can affect anyone of any gender and age, but its incidence seems to be highest in those in the 15- to 45-year-old age group.

History

The Persian physician

Muhammad ibn Zakariya al-Razi Abū Bakr al-Rāzī, also known as Rhazes (full name: ), , was a Persian physician, philosopher and alchemist who lived during the Islamic Golden Age. He is widely regarded as one of the most important figures in the history of medicine, and a ...

(865–925) detailed the first known description of peripheral and central facial palsy. Cornelis Stalpart van der Wiel (1620–1702) in 1683 gave an account of Bell's palsy and credited the Persian physician

Ibn Sina Ibn Sina ( – 22 June 1037), commonly known in the West as Avicenna ( ), was a preeminent philosopher and physician of the Muslim world, flourishing during the Islamic Golden Age, serving in the courts of various Iranian peoples, Iranian ...

(980–1037) for describing this condition before him. James Douglas (1675–1742) and (1761–1836) also described it. Scottish neurophysiologist Sir

read his paper to the

Royal Society of London The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, r ...

on July 12, 1821, describing the role of the facial nerve. He became the first to detail the neuroanatomical basis of facial paralysis. Since then, idiopathic peripheral facial paralysis has been referred to as Bell's palsy, named after him. A notable person with Bell's palsy is former

Prime Minister of Canada The prime minister of Canada () is the head of government of Canada. Under the Westminster system, the prime minister governs with the Confidence and supply, confidence of a majority of the elected House of Commons of Canada, House of Commons ...

Jean Chrétien Joseph Jacques Jean Chrétien (; born January 11, 1934) is a retired Canadian politician, statesman, and lawyer who served as the 20th prime minister of Canada from 1993 to 2003. He served as Leader of the Liberal Party of Canada, leader of t ...

. During the 1993 federal election, Chrétien's first as leader of the

Liberal Party The Liberal Party is any of many political parties around the world. The meaning of ''liberal'' varies around the world, ranging from liberal conservatism on the right to social liberalism on the left. For example, while the political systems ...

, the opposition Progressive Conservative Party ran an attack ad in which voice actors criticized him over images that seemed to highlight his abnormal facial expressions. The ad was interpreted as an attack on Chrétien's physical appearance and garnered widespread anger among the public, while Chrétien used the ad to make himself more sympathetic to voters. The ad had the adverse effect of increasing Chrétien's lead in the polls and the subsequent backlash clinched the election for the Liberals, who won in a landslide.

References

External links

{{DEFAULTSORT:Bell's Palsy Ailments of unknown cause Facial nerve disorders Otorhinolaryngology Wikipedia neurology articles ready to translate Wikipedia medicine articles ready to translate