Editing Bell's palsy (section)

==Diagnosis==
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.<ref name=CPG2013/> 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.<ref name=Morris>{{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 }}</ref>

Other conditions that can cause similar symptoms include [[herpes zoster]], [[Lyme disease]], [[sarcoidosis]], [[stroke]], and [[brain tumor]]s.<ref name=CPG2013/>

===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.<ref>{{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}}</ref><ref name=garro_2018/>

In areas where [[Lyme disease]] is common, it accounts for about 25% of cases of facial palsy.<ref name=garro_2018>{{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 }}</ref> In the U.S., Lyme is most common in the [[New England]] and [[Mid-Atlantic (United States)|Mid-Atlantic]] states and parts of [[Wisconsin]] and [[Minnesota]].<ref name=CDC-Lyme-Data>{{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}}</ref> The first sign of about 80% of Lyme infections, typically one or two weeks after a tick bite, is usually an [[Erythema migrans|expanding rash]] that may be accompanied by headaches, body aches, fatigue, or fever.<ref name=CDC_Lyme_rashes>{{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}}</ref> 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.<ref name=wright_2012>{{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 }}</ref><ref name=NEJM2014>{{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 }}</ref> 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.<ref name=garro_2018/> Corticosteroids have been found to harm outcomes for facial palsy caused by Lyme disease.<ref name=garro_2018/>

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 ([[herpes zoster#Zoster sine herpete|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.<ref>{{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/ }}</ref>