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==Pathophysiology==
==Overview==
The skin of the bony ear canal is unique, in that it is not movable but is closely attached to the bone, and it is almost paper thin. For these reasons it is easily abraded or torn by even minimal physical force. Inflammation of the ear canal skin typically begins with a physical insult, most often from injury caused by attempts at self-cleaning or scratching with cotton swabs, finger nails, hair pins, keys, or other small implements. Another causative factor for acute infection is prolonged water exposure in the forms of swimming or exposure to extreme humidity, which can compromise the protective barrier function of the canal skin, allowing bacteria to flourish; hence the name, "swimmer's ear". Densely impacted wax, usually caused by enthusiastic use of cotton swabs, can put enough pressure on the ear canal skin to injure it and initiate infection. A sensation of blockage or itching can prompt attempts to clean, scratch, or open the ear canal, which potentially worsens and perpetuates the condition. The cotton fibers of a swab are abrasive to the thin, fixed canal skin. Self-manipulative measures to improve the condition often make it worse and are to be discouraged, since it is a blind exercise that can result in significant injury to the ear. Production of wax by glands in the canal may be hindered by external otitis. The exact function(s) of cerumen (earwax) is a subject that is open to speculation, since there is very little research regarding its function. Some caretakers feel strongly that earwax has a protective function with respect to infection and that a little earwax in the ear canal is a good thing. A [[folliculitis]] of one of the hairs of the outer portion of the ear canal can be the start of a bout of external otitis.  
Otitis externa develops when the external [[ear canal]] becomes susceptible to [[bacterial]] or [[fungal]] infection by various mechanisms. Sudden invasive changes in humidity from a rapid intake of water into the [[ear canal]] can predispose the external ear to [[bacterial]] infection. This occurs by thinning of the [[cerumen]] in the [[ear canal]] and weakening an important protective barrier in the ear. The [[epithelial]] surface of the skin begins to degrade, allowing easier infiltration by [[bacteria]]. The [[pH]] of the [[ear canal]] is usually maintained at 5.0 by a combination of the [[cerumen]] and the mechanical construction of the ear; when this increases it renders the ear more favorable to [[bacterial]] reproduction. Increased moisture in the [[ear canal]] can also lead to otitis externa caused by [[otomycosis]]. The buildup of fungal debris in the [[ear canal]] [[epithelium]] leads to increasing pressure and [[inflammation]]. Surfer's ear or [[exostosis]] of the [[ear canal]] predisposes to otitis externa by rendering the ear canal more prone water-bourne pathogens. Localized trauma can cause weakening of the [[ear canal]] [[epithelium]] and thinning of [[cerumen]], predisposing infection. Otitis externa is associated with infectious, [[inflammatory]] ear and head conditions. Gross pathology for otitis externa will include [[erythema]] of the [[ear canal]], along with [[eczema]]-like scaly, shedding of the skin. It also includes visible [[ear canal]] [[swelling]], as well as potentially [[cellulitis]] of the [[pinna]] and [[otorrhea]].


It is well established that in most people the top layer of the ear canal skin normally migrates toward the ear opening, essentially sweeping the canal on a continuing basis. In other words, a normal ear canal is self-cleaning. This self-cleaning physiologic feature fails in some patients, especially in late life, and periodic cleaning by a physician can be necessary. The most controlled and least painful means of cleaning impacted wax or dead skin from the ear canal is by using a binocular surgical microscope, which frees the examiner's hands to instrument the ear and provides the magnification and depth perception needed to avoid traumatizing the delicate canal skin and eardrum.
==Pathogenesis==
Otitis externa develops when the external [[ear canal]] becomes susceptible to infection due to a variety of causes.
===Moisture-bourne infection===
*Sudden invasive changes in humidity from a rapid intake of water into the [[ear canal]] can predispose the external ear to infection.<ref name="pmid16138712">{{cite journal |vauthors=Wang MC, Liu CY, Shiao AS, Wang T |title=Ear problems in swimmers |journal=J Chin Med Assoc |volume=68 |issue=8 |pages=347–52 |year=2005 |pmid=16138712 |doi=10.1016/S1726-4901(09)70174-1 |url=}}</ref>
**Prolonged exposure to moisture causes swelling of the [[stratum corneum]].
**The [[cerumen]] quantity in the [[ear canal]] decreases, weakening an important protective barrier in the ear.
**The [[epithelial]] surface of the skin begins to degrade allowing increased access for [[bacterial]] infection.
**The pH value of the [[ear canal]], usually maintained at 5.0 by a combination of the [[cerumen]] and the mechanical construction of the ear, increases and renders the ear more favorable to [[bacterial]] infection and [[otomycosis]].<ref name="pmid19999361">{{cite journal |vauthors=Kim JK, Cho JH |title=Change of external auditory canal pH in acute otitis externa |journal=Ann. Otol. Rhinol. Laryngol. |volume=118 |issue=11 |pages=769–72 |year=2009 |pmid=19999361 |doi= |url=}}</ref>
*Increased moisture in the [[ear canal]] can also lead to otitis externa caused by [[otomycosis]].<ref name="pmid24948980">{{cite journal |vauthors=Anwar K, Gohar MS |title=Otomycosis; clinical features, predisposing factors and treatment implications |journal=Pak J Med Sci |volume=30 |issue=3 |pages=564–7 |year=2014 |pmid=24948980 |pmc=4048507 |doi=10.12669/pjms.303.4106 |url=}}</ref>
**Spread of [[fungi]] results in [[inflammation]] in the [[ear canal]].<ref name="pmid24948980">{{cite journal |vauthors=Anwar K, Gohar MS |title=Otomycosis; clinical features, predisposing factors and treatment implications |journal=Pak J Med Sci |volume=30 |issue=3 |pages=564–7 |year=2014 |pmid=24948980 |pmc=4048507 |doi=10.12669/pjms.303.4106 |url=}}</ref>
**The buildup of fungal debris in the [[ear canal]] [[epithelium]] leads to increasing pressure and [[inflammation]].
**Extensive use of topical [[antibiotic]] [[ear drops]] to treat [[bacterial]] otitis externa increases predisposition to [[otomycosis]].
*For [[immunocompromised]] individuals, chronic or recurrent otitis externa from [[bacterial]] infection results from the spread of infection to the [[temporal bone]].<ref name="pmid12892351">{{cite journal |vauthors=Handzel O, Halperin D |title=Necrotizing (malignant) external otitis |journal=Am Fam Physician |volume=68 |issue=2 |pages=309–12 |year=2003 |pmid=12892351 |doi= |url=}}</ref>
**Spread of infection may proceed through the [[temporal bone]] to the [[cranium]].


There is an uncommon and serious form of external otitis called malignant or necrotizing external otitis, in which the infection extends beyond the confines of the ear canal and can involve the bone of the skull. Although the name of this condition contains the words "external otitis" it tends to follow a more severe and chronic clinical course and can lead to skull base osteomyelitis. Instead of being a condition that most people are subject to, necrotizing external otitis (also called malignant otitis externa) is a life-threatening disorder that only affects older individuals with diabetes and patients with major disorders of the immune system.<ref>{{cite journal | author = Beers S, Abramo T | title = Otitis externa review. | journal = Pediatr Emerg Care | volume = 20|issue = 4 | pages = 250-6 | year = 2004 | id = PMID 15057182}}</ref>
===Exostosis===
*Surfer's ear or [[exostosis]] of the [[ear canal]] raises the predisposition to otitis externa by rendering the ear canal more prone to trapping water and water-bourne pathogens.<ref name="pmid22695997">{{cite journal |vauthors=Trojanowska A, Drop A, Trojanowski P, Rosińska-Bogusiewicz K, Klatka J, Bobek-Billewicz B |title=External and middle ear diseases: radiological diagnosis based on clinical signs and symptoms |journal=Insights Imaging |volume=3 |issue=1 |pages=33–48 |year=2012 |pmid=22695997 |pmc=3292638 |doi=10.1007/s13244-011-0126-z |url=}}</ref>
 
===Dermatoses===
*Localized trauma can lead to otitis externa from the following [[dermatoses]]. Weakening of the [[ear canal]] [[epithelium]] and thinning of [[cerumen]] predisposes infection in the following [[dermatoses]]:<ref name="pmid24491310">{{cite journal |vauthors=Rosenfeld RM, Schwartz SR, Cannon CR, Roland PS, Simon GR, Kumar KA, Huang WW, Haskell HW, Robertson PJ |title=Clinical practice guideline: acute otitis externa |journal=Otolaryngol Head Neck Surg |volume=150 |issue=1 Suppl |pages=S1–S24 |year=2014 |pmid=24491310 |doi=10.1177/0194599813517083 |url=}}</ref>
**[[Eczema]]
**[[Seborrhea]]
**[[Psoriasis]]
**[[Contact dermatitis]]
 
==Associated Conditions==
*Otitis externa is associated with the following infectious, [[inflammatory]] ear and head conditions:
**[[Otitis media]]
**[[Osteitis]]
**[[Osteomyelitis]]<ref name="pmid23111934">{{cite journal |vauthors=Saxby A, Barakate M, Kertesz T, James J, Bennett M |title=Malignant otitis externa: experience with hyperbaric oxygen therapy |journal=Diving Hyperb Med |volume=40 |issue=4 |pages=195–200 |year=2010 |pmid=23111934 |doi= |url=}}</ref>
**[[Otorrhea]]<ref name="pmid24421666">{{cite journal |vauthors=Hui CP |title=Acute otitis externa |journal=Paediatr Child Health |volume=18 |issue=2 |pages=96–101 |year=2013 |pmid=24421666 |pmc=3567906 |doi= |url=}}</ref>
**[[Otalgia]]
 
==Gross Pathology==
*Gross pathology for otitis externa will include [[erythema]] of the [[ear canal]], along with [[eczema]]-esque scaly, shedding of the skin.<ref name="urlSwimmers ear : MedlinePlus Medical Encyclopedia">{{cite web |url=https://www.nlm.nih.gov/medlineplus/ency/article/000622.htm |title=Swimmer's ear : MedlinePlus Medical Encyclopedia |format= |work= |accessdate=}}</ref>
*[[Ear canal]] [[swelling]] will be visible.
*[[Cellulitis]] of the [[pinna]] and [[otorrhea]] may also be present upon physical examination.<ref name="pmid23198673">{{cite journal |vauthors=Schaefer P, Baugh RF |title=Acute otitis externa: an update |journal=Am Fam Physician |volume=86 |issue=11 |pages=1055–61 |year=2012 |pmid=23198673 |doi= |url=}}</ref>
<div align="left">
<gallery heights="175" widths="175">
Image:OtitisExterna001.jpg|A severe case of acute otitis externa, with visible narrowing of the external auditory channel and prominent amounts of [[exudate]] with swelling of the [[auricle]].  Case provided by Dr. James Heilman.
</gallery>
</div>


==References==
==References==
{{reflist|2}}
{{reflist|2}}


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Latest revision as of 23:30, 29 July 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S.; Tarek Nafee, M.D. [2]

Overview

Otitis externa develops when the external ear canal becomes susceptible to bacterial or fungal infection by various mechanisms. Sudden invasive changes in humidity from a rapid intake of water into the ear canal can predispose the external ear to bacterial infection. This occurs by thinning of the cerumen in the ear canal and weakening an important protective barrier in the ear. The epithelial surface of the skin begins to degrade, allowing easier infiltration by bacteria. The pH of the ear canal is usually maintained at 5.0 by a combination of the cerumen and the mechanical construction of the ear; when this increases it renders the ear more favorable to bacterial reproduction. Increased moisture in the ear canal can also lead to otitis externa caused by otomycosis. The buildup of fungal debris in the ear canal epithelium leads to increasing pressure and inflammation. Surfer's ear or exostosis of the ear canal predisposes to otitis externa by rendering the ear canal more prone water-bourne pathogens. Localized trauma can cause weakening of the ear canal epithelium and thinning of cerumen, predisposing infection. Otitis externa is associated with infectious, inflammatory ear and head conditions. Gross pathology for otitis externa will include erythema of the ear canal, along with eczema-like scaly, shedding of the skin. It also includes visible ear canal swelling, as well as potentially cellulitis of the pinna and otorrhea.

Pathogenesis

Otitis externa develops when the external ear canal becomes susceptible to infection due to a variety of causes.

Moisture-bourne infection

Exostosis

  • Surfer's ear or exostosis of the ear canal raises the predisposition to otitis externa by rendering the ear canal more prone to trapping water and water-bourne pathogens.[5]

Dermatoses

Associated Conditions

Gross Pathology

  • A severe case of acute otitis externa, with visible narrowing of the external auditory channel and prominent amounts of exudate with swelling of the auricle. Case provided by Dr. James Heilman.

    A severe case of acute otitis externa, with visible narrowing of the external auditory channel and prominent amounts of exudate with swelling of the auricle. Case provided by Dr. James Heilman.

References

  1. ↑ Wang MC, Liu CY, Shiao AS, Wang T (2005). "Ear problems in swimmers". J Chin Med Assoc. 68 (8): 347–52. doi:10.1016/S1726-4901(09)70174-1. PMID 16138712.
  2. ↑ Kim JK, Cho JH (2009). "Change of external auditory canal pH in acute otitis externa". Ann. Otol. Rhinol. Laryngol. 118 (11): 769–72. PMID 19999361.
  3. ↑ 3.0 3.1 Anwar K, Gohar MS (2014). "Otomycosis; clinical features, predisposing factors and treatment implications". Pak J Med Sci. 30 (3): 564–7. doi:10.12669/pjms.303.4106. PMC 4048507. PMID 24948980.
  4. ↑ Handzel O, Halperin D (2003). "Necrotizing (malignant) external otitis". Am Fam Physician. 68 (2): 309–12. PMID 12892351.
  5. ↑ Trojanowska A, Drop A, Trojanowski P, Rosińska-Bogusiewicz K, Klatka J, Bobek-Billewicz B (2012). "External and middle ear diseases: radiological diagnosis based on clinical signs and symptoms". Insights Imaging. 3 (1): 33–48. doi:10.1007/s13244-011-0126-z. PMC 3292638. PMID 22695997.
  6. ↑ Rosenfeld RM, Schwartz SR, Cannon CR, Roland PS, Simon GR, Kumar KA, Huang WW, Haskell HW, Robertson PJ (2014). "Clinical practice guideline: acute otitis externa". Otolaryngol Head Neck Surg. 150 (1 Suppl): S1–S24. doi:10.1177/0194599813517083. PMID 24491310.
  7. ↑ Saxby A, Barakate M, Kertesz T, James J, Bennett M (2010). "Malignant otitis externa: experience with hyperbaric oxygen therapy". Diving Hyperb Med. 40 (4): 195–200. PMID 23111934.
  8. ↑ Hui CP (2013). "Acute otitis externa". Paediatr Child Health. 18 (2): 96–101. PMC 3567906. PMID 24421666.
  9. ↑ "Swimmer's ear : MedlinePlus Medical Encyclopedia".
  10. ↑ Schaefer P, Baugh RF (2012). "Acute otitis externa: an update". Am Fam Physician. 86 (11): 1055–61. PMID 23198673.

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