Sandbox: Otitis externa pathophysiology
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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.
Overview
Pathogenesis
Otitis externa develops when the external ear canal becomes more 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.[1]
- 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 denegrate, 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.[2]
- The bacteria Pseudomonas aeruginosa and Staphylococcus aureus are the most common opportunistic pathogens of otitis externa due to increased humidity.[3]
- Increased moisture in the ear canal can also lead to otitis externa caused by otomycosis.[4]
- The primary fungal causes of otitis externa are Candida albicans and Aspergillus niger.
- Spread of fungi results in inflammation in the ear canal.[4]
- 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.[5]
- Spread of infection may proceed through the temporal bone to the cranium.
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.[6]
Dermatoses
- Localized physical trauma can lead to otitis externa from the following dermatoses:[7]
- Weakening of the ear canal epithelium and the lessening of cerumen predisposes infection.
Associated Conditions
- Otitis externa is associated with the following infectious, inflammatory ear and head conditions:
Gross Pathology
- Gross pathology for otitis externa will include erythema of the ear canal, along with eczema-esque scaly, shedding of the skin.Closing
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References
- ↑ 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.
- ↑ 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.
- ↑ Mösges R, Nematian-Samani M, Eichel A (2011). "Treatment of acute otitis externa with ciprofloxacin otic 0.2% antibiotic ear solution". Ther Clin Risk Manag. 7: 325–36. doi:10.2147/TCRM.S6769. PMC 3150478. PMID 21845055.
- ↑ 4.0 4.1 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.
- ↑ Handzel O, Halperin D (2003). "Necrotizing (malignant) external otitis". Am Fam Physician. 68 (2): 309–12. PMID 12892351.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Hui CP (2013). "Acute otitis externa". Paediatr Child Health. 18 (2): 96–101. PMC 3567906. PMID 24421666.