Bell's palsy

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.{{cite journal | vauthors = Price T, Fife DG | title = Bilateral simultaneous facial nerve palsy | journal = The Journal of Laryngology and Otology | volume = 116 | issue = 1 | pages = 46–48 | date = January 2002 | pmid = 11860653 | doi = 10.1258/0022215021910113 | s2cid = 19276545 }}{{cite journal | vauthors = Jain V, Deshmukh A, Gollomp S | title = Bilateral facial paralysis: case presentation and discussion of differential diagnosis | journal = Journal of General Internal Medicine | volume = 21 | issue = 7 | pages = C7–10 | date = July 2006 | pmid = 16808763 | pmc = 1924702 | doi = 10.1111/j.1525-1497.2006.00466.x }}

The facial nerve controls many functions, such as blinking and closing the eyes, smiling, frowning, lacrimation, salivation, flaring nostrils and raising eyebrows. It also carries taste sensations from the anterior two thirds of the tongue, through the chorda tympani nerve (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.{{Cite book|title = Fundamentals of Neurology|url = https://archive.org/details/fundamentalsneur00mume|url-access = limited| vauthors = Mumenthaler M, Mattle H | publisher = Thieme|year = 2006|isbn = 978-3131364517|location = Germany|pages = [https://archive.org/details/fundamentalsneur00mume/page/n208 197] }}

The facial nerve innervates the stapedius muscle of the middle ear (through the tympanic branch), which reflexively dampens the conduction of loud sounds. Thus, Bell's Palsy may cause normal sounds to be perceived as very loud (hyperacusis), and dysacusis is possible but hardly ever clinically evident.{{Cite book|url=https://books.google.com/books?id=-Le5bc5F0sYC|title=Clinically Oriented Anatomy| vauthors = Moore KL, Dalley AF, Agur AM |year=2013 |publisher=Lippincott Williams & Wilkins |isbn=978-1451119459 }}

Image:Cranial nerve VII.svg: the facial nerve's nuclei are in the brainstem (represented in the diagram by "θ"). Orange: nerves coming from the left hemisphere of the brain, yellow: nerves coming from the right hemisphere. Note that the forehead muscles receive innervation from both hemispheres (yellow and orange)]]

The cause of Bell's palsy is unknown. Risk factors include diabetes, a recent upper respiratory tract infection, and pregnancy.

Some viruses are thought to establish a persistent (or latent) infection without symptoms, e.g., the varicella zoster virus[http://www.medicinenet.com/facial_nerve_problems/page3.htm Facial Nerve Problems and Bell's Palsy Information on MedicineNet.com] www.medicinenet.com {{webarchive|url=https://web.archive.org/web/20080423075504/http://www.medicinenet.com/facial_nerve_problems/page3.htm |date=2008-04-23 }} and the Epstein–Barr virus, 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.{{Cite web |title=Bell's Palsy Fact Sheet {{!}} National Institute of Neurological Disorders and Stroke |url=https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Bells-Palsy-Fact-Sheet |access-date=2022-03-22 |website=www.ninds.nih.gov}} Other viral and bacterial infections that have been linked to the development of Bell's palsy include HIV and Lyme disease.{{cite journal |vauthors=Lu H, Hu H |date=17 March 2023 |title=Bilateral facial palsy caused by HIV infection: A case report and literature review |journal=Medicine (Baltimore) |volume=102 |issue=11 |page=e33263 |doi=10.1097/MD.0000000000033263 |pmc=10019170 |pmid=36930128}}{{cite journal |vauthors=McEntire CR, Chwalisz BK |date=1 May 2024 |title=Cranial nerve involvement, visual complications and headache syndromes in Lyme disease |journal=Curr Opin Ophthalmol |volume=35 |issue=3 |pages=265–271 |doi=10.1097/ICU.0000000000001031 |pmid=38518069}} This new activation could be triggered by trauma, environmental factors, and metabolic or emotional disorders.{{cite journal | vauthors = Kasse CA, Ferri RG, Vietler EY, Leonhardt FD, Testa JR, Cruz OL |title=Clinical data and prognosis in 1521 cases of Bell's palsy |journal=International Congress Series |volume=1240 |pages=641–47 |date=October 2003 |doi=10.1016/S0531-5131(03)00757-X }}

Familial inheritance has been found in 4–14% of cases.{{cite journal | vauthors = Döner F, Kutluhan S | title = Familial idiopathic facial palsy | journal = European Archives of Oto-Rhino-Laryngology | volume = 257 | issue = 3 | pages = 117–19 | year = 2000 | pmid = 10839481 | doi = 10.1007/s004050050205 | url = http://link.springer.de/link/service/journals/00405/bibs/0257003/02570117.htm | url-status = dead | s2cid = 24403036 | archive-url = https://archive.today/20130106003939/http://link.springer.de/link/service/journals/00405/bibs/0257003/02570117.htm | archive-date = 2013-01-06 | url-access = subscription }} There may also be an association with migraines.{{cite journal | vauthors = Silberstein SD, Silvestrini M | title = Does migraine produce facial palsy? For whom the Bell tolls | journal = Neurology | volume = 84 | issue = 2 | pages = 108–09 | date = January 2015 | pmid = 25520314 | doi = 10.1212/WNL.0000000000001136 | hdl = 11566/206361 | s2cid = 35589569 | hdl-access = free }}

In December 2020, the U.S. FDA recommended that recipients of the Pfizer and Moderna COVID-19 vaccines 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.{{Cite web|last=Higgins-Dunn|first=Noah|date=2020-12-15|title=FDA staff recommends watching for Bell's palsy in Moderna and Pfizer vaccine recipients|url=https://www.cnbc.com/2020/12/15/fda-staff-recommends-watching-for-bells-palsy-in-moderna-and-pfizer-vaccine-recipients.html|access-date=2020-12-15|website=CNBC|language=en}}

A meta-analysis of genome-wide association study (GWAS) identified the first unequivocal association with Bell's palsy.{{Cite journal|last=Skuladottir|first=Astros Th|date=2021-02-18|title=A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy|journal=Scientific Reports|volume=11|issue=1|page=4188|doi=10.1038/s41598-021-82736-w|pmid=33602968|pmc=7893061|bibcode=2021NatSR..11.4188S|language=en}}

Bell's palsy is the result of a malfunction of the facial nerve (cranial nerve VII), which controls the muscles 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 of the facial nerve, pressure is produced on the nerve where it exits the skull within its bony canal (the stylomastoid foramen), 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, meningitis, stroke, diabetes mellitus, head trauma and inflammatory diseases of the cranial nerves (sarcoidosis, brucellosis, etc.). In these conditions, the neurologic findings are rarely restricted to the facial nerve. Babies can be born with facial palsy.[https://www.nlm.nih.gov/medlineplus/ency/article/001425.htm MedlinePlus Medical Encyclopedia: Facial nerve palsy due to birth trauma] {{webarchive|url=https://web.archive.org/web/20081001211231/http://www.nlm.nih.gov/medlineplus/ency/article/001425.htm |date=2008-10-01 }} retrieved 10 September 2008 In a few cases, bilateral facial palsy has been associated with acute HIV infection.

In some research, the herpes simplex virus type 1 (HSV-1) has been identified in a majority of cases diagnosed as Bell's palsy through endoneurial fluid sampling.{{cite journal | vauthors = Murakami S, Mizobuchi M, Nakashiro Y, Doi T, Hato N, Yanagihara N | title = Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle | journal = Annals of Internal Medicine | volume = 124 | issue = 1 Pt 1 | pages = 27–30 | date = January 1996 | pmid = 7503474 | doi = 10.7326/0003-4819-124-1_Part_1-199601010-00005 | s2cid = 22790049 }} 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 in 45 cases (26%).{{cite journal | vauthors = Furuta Y, Ohtani F, Chida E, Mesuda Y, Fukuda S, Inuyama Y | title = Herpes simplex virus type 1 reactivation and antiviral therapy in patients with acute peripheral facial palsy | journal = Auris, Nasus, Larynx | volume = 28 Suppl | issue = Suppl | pages = S13–17 | date = May 2001 | pmid = 11683332 | doi = 10.1016/S0385-8146(00)00105-X }}

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 response.

Bell's palsy is a diagnosis of exclusion, 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.{{cite journal | vauthors = Morris AM, Deeks SL, Hill MD, Midroni G, Goldstein WC, Mazzulli T, Davidson R, Squires SG, Marrie T, McGeer A, Low DE | display-authors = 6 | title = Annualized incidence and spectrum of illness from an outbreak investigation of Bell's palsy | journal = Neuroepidemiology | volume = 21 | issue = 5 | pages = 255–61 | year = 2002 | pmid = 12207155 | doi = 10.1159/000065645 | url = http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=ned21255 | url-status = live | s2cid = 22771896 | archive-url = https://web.archive.org/web/20090713151821/http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=ned21255 | archive-date = 2009-07-13 | url-access = subscription }}

Other conditions that can cause similar symptoms include herpes zoster, Lyme disease, sarcoidosis, stroke, and brain tumors.

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.{{Cite web|url=https://news.yahoo.com/c-tv-reporter-loses-her-smile-bells-palsy-164432652--abc-news-wellness.html|archiveurl=https://web.archive.org/web/20160305003313/http://news.yahoo.com/c-tv-reporter-loses-her-smile-bells-palsy-164432652--abc-news-wellness.html|url-status=dead|title=S.C. TV Reporter Loses Her Smile after a Bell's Palsy Attack|archivedate=March 5, 2016}}

In areas where Lyme disease is common, it accounts for about 25% of cases of facial palsy.{{cite journal | vauthors = Garro A, Nigrovic LE | title = Managing Peripheral Facial Palsy | journal = Annals of Emergency Medicine | volume = 71 | issue = 5 | pages = 618–24 | date = May 2018 | pmid = 29110887 | doi = 10.1016/j.annemergmed.2017.08.039 | doi-access = free }} In the U.S., Lyme is most common in the New England and Mid-Atlantic states and parts of Wisconsin and Minnesota.{{cite web|title=Lyme Disease Data and surveillance (datasurveillance) |url = https://www.cdc.gov/lyme/datasurveillance/ |website=Lyme Disease |publisher=Centers for Disease Control and Prevention |access-date=April 12, 2019}} 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.{{cite web|title=Lyme disease rashes and look-alikes (rashes) |url=https://www.cdc.gov/lyme/signs_symptoms/rashes.html |website=Lyme Disease |publisher=Centers for Disease Control and Prevention |access-date=April 18, 2019}} 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.{{cite journal | vauthors = Wright WF, Riedel DJ, Talwani R, Gilliam BL | title = Diagnosis and management of Lyme disease | journal = American Family Physician | volume = 85 | issue = 11 | pages = 1086–93 | date = June 2012 | pmid = 22962880 | url = http://www.aafp.org/afp/2012/0601/p1086.html | url-status = live | df = dmy-all | archive-url = https://web.archive.org/web/20130927081243/http://www.aafp.org/afp/2012/0601/p1086.html | archive-date = 27 September 2013 }}{{cite journal | vauthors = Shapiro ED | title = Clinical practice. Lyme disease | journal = The New England Journal of Medicine | volume = 370 | issue = 18 | pages = 1724–31 | date = May 2014 | pmid = 24785207 | pmc = 4487875 | doi = 10.1056/NEJMcp1314325 | url = http://portal.mah.harvard.edu/templatesnew/departments/MTA/Lyme/uploaded_documents/NEJMcp1314325.pdf | archive-url = https://web.archive.org/web/20161019142422/http://portal.mah.harvard.edu/templatesnew/departments/MTA/Lyme/uploaded_documents/NEJMcp1314325.pdf | archive-date = 19 October 2016 }} 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, 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 is the involvement of the facial nerve in infections with the herpes zoster 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 herpes zoster 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.{{Cite book |author1=Andrew E. Crouch |author2=Marc H. Hohman |author3=Claudio Andaloro |title=Ramsay Hunt Syndrome |year=2022 |publisher=StatPearls |pmid=32491341 |url=https://www.ncbi.nlm.nih.gov/books/NBK557409/ }}

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.{{cite journal | vauthors = Baugh RF, Basura GJ, Ishii LE, Schwartz SR, Drumheller CM, Burkholder R, Deckard NA, Dawson C, Driscoll C, Gillespie MB, Gurgel RK, Halperin J, Khalid AN, Kumar KA, Micco A, Munsell D, Rosenbaum S, Vaughan W | display-authors = 6 | title = Clinical practice guideline: Bell's Palsy executive summary | journal = Otolaryngology–Head and Neck Surgery | volume = 149 | issue = 5 | pages = 656–63 | date = November 2013 | pmid = 24190889 | doi = 10.1177/0194599813506835 | s2cid = 25468987 }} Management during pregnancy is similar to management in the non-pregnant.

Corticosteroids such as prednisone improve recovery at 6 months and are thus recommended.{{cite journal | vauthors = Madhok VB, Gagyor I, Daly F, Somasundara D, Sullivan M, Gammie F, Sullivan F | title = Corticosteroids for Bell's palsy (idiopathic facial paralysis) | journal = The Cochrane Database of Systematic Reviews | volume = 2016 | pages = CD001942 | date = July 2016 | issue = 7 | pmid = 27428352 | pmc = 6457861 | doi = 10.1002/14651858.CD001942.pub5 }} Early treatment (within 3 days after the onset) is necessary for benefit with a 14% greater probability of recovery.{{cite journal | vauthors = Gronseth GS, Paduga R | title = Evidence-based guideline update: steroids and antivirals for Bell palsy: report of the Guideline Development Subcommittee of the American Academy of Neurology | journal = Neurology | volume = 79 | issue = 22 | pages = 2209–13 | date = November 2012 | pmid = 23136264 | doi = 10.1212/WNL.0b013e318275978c | doi-access = free }} There is some debate regarding the optimal dosing strategy which is generally physician dependent.{{Cite journal |last1=Gupta |first1=Keshav Kumar |last2=Balai |first2=Edward |last3=Tang |first3=Ho Tsun |last4=Ahmed |first4=Abiya Amna |last5=Doshi |first5=Jayesh R. |date=2023-04-01 |title=Comparing the Use of High-Dose to Standard-Dose Corticosteroids for the Treatment of Bell's Palsy in Adults-A Systematic Review and Meta-analysis |url=https://pubmed.ncbi.nlm.nih.gov/36706448 |journal=Otology & Neurotology|volume=44 |issue=4 |pages=310–316 |doi=10.1097/MAO.0000000000003823 |issn=1537-4505 |pmid=36706448|s2cid=256326046 }}

One review found that antivirals (such as aciclovir) are ineffective in improving recovery from Bell's palsy beyond steroids alone in mild to moderate disease.{{cite journal | vauthors = Turgeon RD, Wilby KJ, Ensom MH | title = Antiviral treatment of Bell's palsy based on baseline severity: a systematic review and meta-analysis | journal = The American Journal of Medicine | volume = 128 | issue = 6 | pages = 617–28 | date = June 2015 | pmid = 25554380 | doi = 10.1016/j.amjmed.2014.11.033 }} 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 and varicella zoster virus.{{cite journal | vauthors = Sullivan FM, Swan IR, Donnan PT, Morrison JM, Smith BH, McKinstry B, Davenport RJ, Vale LD, Clarkson JE, Hammersley V, Hayavi S, McAteer A, Stewart K, Daly F | display-authors = 6 | title = Early treatment with prednisolone or acyclovir in Bell's palsy | journal = The New England Journal of Medicine | volume = 357 | issue = 16 | pages = 1598–607 | date = October 2007 | pmid = 17942873 | doi = 10.1056/NEJMoa072006 | s2cid = 3916563 | doi-access = free }} There is still the possibility that they might result in a benefit less than 7% as this has not been ruled out.

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.{{cite web| vauthors = Stephenson M |title=OTC Drops: Telling the Tears Apart |url=https://www.reviewofophthalmology.com/article/otc-drops-telling-the-tears-apart |website=Review of Ophthalmology |publisher=Jobson Medical Information LLC |date=October 4, 2012 | access-date=April 16, 2019}}

Physiotherapy can be beneficial to some individuals with Bell's palsy as it helps to maintain muscle tone of the affected facial muscles and stimulate the facial nerve.{{cite web | url = http://www.ninds.nih.gov/disorders/bells/detail_bells.htm| title = Bell's Palsy Fact Sheet | access-date = 2011-05-12 | date = April 2003 | author = National Institute of Neurological Disorders and Stroke (NINDS)| archive-url=https://web.archive.org/web/20110408004237/http://www.ninds.nih.gov/disorders/bells/detail_bells.htm | archive-date= 8 April 2011 | url-status= live}} It is important that muscle re-education exercises and soft tissue techniques be implemented before recovery to help prevent permanent contractures of the paralyzed facial muscles. To reduce pain, heat can be applied to the affected side of the face.{{cite journal | vauthors = Shafshak TS | title = The treatment of facial palsy from the point of view of physical and rehabilitation medicine | journal = Europa Medicophysica | volume = 42 | issue = 1 | pages = 41–47 | date = March 2006 | pmid = 16565685 }} There is no high-quality evidence to support the role of electrical stimulation for Bell's palsy.{{cite journal | vauthors = Teixeira LJ, Valbuza JS, Prado GF | title = Physical therapy for Bell's palsy (idiopathic facial paralysis) | journal = The Cochrane Database of Systematic Reviews | issue = 12 | pages = CD006283 | date = December 2011 | pmid = 22161401 | doi = 10.1002/14651858.CD006283.pub3 }}

Surgery may be able to improve outcomes in facial nerve palsy that has not recovered.{{cite journal | vauthors = Hazin R, Azizzadeh B, Bhatti MT | title = Medical and surgical management of facial nerve palsy | journal = Current Opinion in Ophthalmology | volume = 20 | issue = 6 | pages = 440–50 | date = November 2009 | pmid = 19696671 | doi = 10.1097/ICU.0b013e3283313cbf | s2cid = 45094564 }} 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.{{cite journal|vauthors=Tiemstra JD, Khatkhate N|date=October 2007|title=Bell's palsy: diagnosis and management|journal=American Family Physician|volume=76|issue=7|pages=997–1002|pmid=17956069}} 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.{{Cite journal|last1=Menchetti|first1=Isabella|last2=McAllister|first2=Kerrie|last3=Walker|first3=David|last4=Donnan|first4=Peter T.|date=January 26, 2021|title=Surgical interventions for the early management of Bell's palsy|journal=The Cochrane Database of Systematic Reviews|volume=1|issue=1 |pages=CD007468|doi=10.1002/14651858.CD007468.pub4|issn=1469-493X|pmid=33496980|pmc=8094225}} As of 2007 the American Academy of Neurology did not recommend surgical decompression.

The efficacy of acupuncture remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices).{{cite journal | vauthors = Chen N, Zhou M, He L, Zhou D, Li N | title = Acupuncture for Bell's palsy | journal = The Cochrane Database of Systematic Reviews | issue = 8 | pages = CD002914 | date = August 2010 | volume = 2010 | pmid = 20687071 | pmc = 7133542 | doi = 10.1002/14651858.CD002914.pub5 | veditors = He L }} There is very tentative evidence for hyperbaric oxygen therapy in severe disease.{{cite journal | vauthors = Holland NJ, Bernstein JM, Hamilton JW | title = Hyperbaric oxygen therapy for Bell's palsy | journal = The Cochrane Database of Systematic Reviews | volume = 2 | issue = 2 | pages = CD007288 | date = February 2012 | pmid = 22336830 | doi = 10.1002/14651858.CD007288.pub2 | pmc = 8406519 }}

Most people with Bell's palsy start to regain normal facial function within three weeks—even those who do not receive treatment.{{cite web| vauthors = Karnath B |title=Bell Palsy: Updated Guideline for Treatment|url=http://www.consultant360.com/article/bell-palsy-updated-guideline-treatment|work=Consultant|date=14 February 2013|publisher=HMP Communications|access-date=April 3, 2013|url-status=live|archive-url=https://web.archive.org/web/20130225095629/http://www.consultant360.com/article/bell-palsy-updated-guideline-treatment|archive-date=February 25, 2013}} 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.{{cite journal | vauthors = Peitersen E | title = The natural history of Bell's palsy | journal = The American Journal of Otology | volume = 4 | issue = 2 | pages = 107–11 | date = October 1982 | pmid = 7148998 }} quoted in {{cite journal | vauthors = Roob G, Fazekas F, Hartung HP | title = Peripheral facial palsy: etiology, diagnosis and treatment | journal = European Neurology | volume = 41 | issue = 1 | pages = 3–9 | date = January 1999 | pmid = 9885321 | doi = 10.1159/000007990 | url = http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=ene41003 | url-status = live | s2cid = 46877391 | archive-url = https://web.archive.org/web/20090713152309/http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=ene41003 | archive-date = 2009-07-13 | url-access = subscription }} 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 sequelae.{{cite journal | vauthors = Peitersen E, Andersen P | title = Spontaneous course of 220 peripheral non-traumatic facial palsies | journal = Acta Oto-Laryngologica | volume = 63 | pages = 296–300 | date = June 1966 | pmid = 6011525 | doi = 10.3109/00016486709123595 }} 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), chronic facial spasm, 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, or hearing loss during facial movement or crocodile-tear syndrome.{{cite journal | vauthors = Yamamoto E, Nishimura H, Hirono Y | title = Occurrence of sequelae in Bell's palsy | journal = Acta Oto-Laryngologica. Supplementum | volume = 446 | pages = 93–96 | year = 1988 | pmid = 3166596 | doi = 10.3109/00016488709121848 }} 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.

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.{{cite journal | vauthors = Ahmed A | title = When is facial paralysis Bell palsy? Current diagnosis and treatment | journal = Cleveland Clinic Journal of Medicine | volume = 72 | issue = 5 | pages = 398–401, 405 | date = May 2005 | pmid = 15929453 | doi = 10.3949/ccjm.72.5.398 | s2cid = 37815525 }} 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,{{cite journal | vauthors = Wolf SR | title = [Idiopathic facial paralysis] | language = de | journal = Hno | volume = 46 | issue = 9 | pages = 786–98 | date = September 1998 | pmid = 9816532 | doi = 10.1007/s001060050314 | url = http://link.springer.de/link/service/journals/00106/bibs/8046009/80460786.htm | url-status = dead | s2cid = 6740784 | archive-url = https://web.archive.org/web/20000623213041/http://link.springer.de/link/service/journals/00106/bibs/8046009/80460786.htm | archive-date = 2000-06-23 | url-access = subscription }} 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,{{cite journal|title=Annualized Incidence and Spectrum of Illness from an Outbreak Investigation of Bell's Palsy|last1=Morris|first1=Andrew M.|last2=Deeks|first2=Shelley L.|last3=Hill|first3=Michael D.|last4=Midroni|first4=Gyl|last5=Goldstein|first5=Warren C.|last6=Mazzulli|first6=Tony|last7=Davidson|first7=Ross|last8=Squires|first8=Susan G.|last9=Marrie|first9=Thomas|last10=McGeer|first10=Allison|last11=Low|first11=Donald E.|journal=Neuroepidemiology|date=September–October 2002|volume=21|issue=5|page=256|doi=10.1159/000065645|pmid=12207155|s2cid=22771896}} which complicates precise estimation.

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.

{{See also|List of people with Bell's palsy}}

File:CharlesBell001.jpg was the first author to describe the anatomical basis for facial paralysis, and has since served as the eponym for Bell's palsy.]]

The Persian physician Muhammad ibn Zakariya al-Razi (865–925) detailed the first known description of peripheral and central facial palsy.{{cite journal | vauthors = Sajadi MM, Sajadi MR, Tabatabaie SM | title = The history of facial palsy and spasm: Hippocrates to Razi | journal = Neurology | volume = 77 | issue = 2 | pages = 174–78 | date = July 2011 | pmid = 21747074 | pmc = 3140075 | doi = 10.1212/WNL.0b013e3182242d23 }}{{cite journal | vauthors = van de Graaf RC, Nicolai JP | title = Bell's palsy before Bell: Cornelis Stalpart van der Wiel's observation of Bell's palsy in 1683 | journal = Otology & Neurotology | volume = 26 | issue = 6 | pages = 1235–38 | date = November 2005 | pmid = 16272948 | doi = 10.1097/01.mao.0000194892.33721.f0 | s2cid = 12630888 }}

Cornelis Stalpart van der Wiel (1620–1702) in 1683 gave an account of Bell's palsy and credited the Persian physician Ibn Sina (980–1037) for describing this condition before him. James Douglas (1675–1742) and {{interlanguage link|Nicolaus Anton Friedreich|de}} (1761–1836) also described it.

Scottish neurophysiologist Sir Charles Bell read his paper to the Royal Society of London 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.{{cite journal|title=The Bicentenary of Bell's Description of the Neuroanatomical Basis of Facial Paralysis: Historical Remarks|last1=Cantarella|first1=Giovanna|last2=Mazzola|first2=Riccardo F.|journal=Otolaryngology–Head and Neck Surgery|date=2021-07-27|volume=166 |issue=5 |pages=907–909 |doi=10.1177/01945998211032172|pmid=34314273|s2cid=236473244}}

A notable person with Bell's palsy is former Prime Minister of Canada Jean Chrétien.{{Cite news|publisher=BBC|date=November 28, 2000|title=Jean Chretien: Veteran fighter|language=en-GB|url=http://news.bbc.co.uk/2/hi/americas/1042917.stm|access-date=November 7, 2020}} During the 1993 federal election, Chrétien's first as leader of the Liberal Party, 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.

{{Reflist}}

{{Commons category|Bell's palsy}}

{{Medical condition classification and resources

| DiseasesDB = 1303

| ICD10 = {{ICD10|G|51|0|g|50}}

| ICD9 = {{ICD9|351.0}}

| ICDO =

| OMIM =

| MedlinePlus = 000773

| eMedicineSubj = emerg

| eMedicineTopic = 56

| eMedicine_mult = {{eMedicine2|neuro|413}} {{eMedicine2|ent|719}} {{eMedicine2|oph|508}}

| MeshID = D020330

}}

{{PNS diseases of the nervous system}}

{{DEFAULTSORT:Bell's Palsy}}

Category:Ailments of unknown cause

Category:Facial nerve disorders

Category:Otorhinolaryngology

Category:Wikipedia neurology articles ready to translate

Category:Wikipedia medicine articles ready to translate