Otitis externa pathophysiology: Difference between revisions

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{{Otitis externa}}
{{Otitis externa}}
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==Overview==
==Overview==
Otitis externa develops when the external [[ear canal]] becomes susceptible to infection due to a variety of causes. The primary pathogens responsible for otitis media are the bacteria ''[[Pseudomonas aeruginosa]]'' and ''[[Staphylococcus aureus]]''. Sudden, invasive changes in humidity from a rapid intake of water into the [[ear canal]] can predispose the external ear to [[bacterial]] infection: 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 easier infiltration by [[bacterial]]; 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]] reproduction. Increased moisture in the [[ear canal]] can also lead to otitis externa caused by [[otomycosis]]. The primary [[fungal]] causes of otitis externa are ''[[Candida albicans]]'' and ''[[Aspergillus niger]]''. 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]] raises the predisposition to otitis externa by rendering the ear canal more prone to trapping water and water-bourne pathogens. Localized physical trauma can cause Weakening of the [[ear canal]] [[epithelium]] and the lessening 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]]-esque scaly, shedding of the skin. It also includes visible [[ear canal]] [[swelling]], as well as potentially [[cellulitis]] of the [[pinna]] and [[otorrhea]].
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==
==Pathogenesis==
Otitis externa develops when the external [[ear canal]] becomes susceptible to infection due to a variety of causes.
Otitis externa develops when the external [[ear canal]] becomes susceptible to infection due to a variety of causes.
===Moisture-bourne infection===
===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>
*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]].
**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 [[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 [[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>
**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>
*The [[bacteria]] ''[[Pseudomonas aeruginosa]]'' and ''[[Staphylococcus aureus]]'' are the most common opportunistic pathogens of otitis externa due to increased humidity.<ref name="pmid21845055">{{cite journal |vauthors=Mösges R, Nematian-Samani M, Eichel A |title=Treatment of acute otitis externa with ciprofloxacin otic 0.2% antibiotic ear solution |journal=Ther Clin Risk Manag |volume=7 |issue= |pages=325–36 |year=2011 |pmid=21845055 |pmc=3150478 |doi=10.2147/TCRM.S6769 |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>
*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>
**The primary [[fungal]] causes of otitis externa are ''[[Candida albicans]]'' and ''[[Aspergillus niger]]''.
**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>
**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]].
**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]].
**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>
*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]].  
**Spread of infection may proceed through the [[temporal bone]] to the [[cranium]].


===Exostosis===
===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>
*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===
===Dermatoses===
*Localized physical trauma can lead to otitis externa from 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>
*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]]
**[[Eczema]]
**[[Seborrhea]]
**[[Seborrhea]]
**[[Psoriasis]]
**[[Psoriasis]]
**[[Contact dermatitis]]
**[[Contact dermatitis]]
*Weakening of the [[ear canal]] [[epithelium]] and the lessening of [[cerumen]] predisposes infection.


==Associated Conditions==
==Associated Conditions==
Line 45: Line 42:
*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>
*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.  
*[[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>  
*[[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>  
   
   
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==References==
==References==
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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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