Otitis Externa in Emergency Medicine
- Author: Samuel Lee, MD, MS; Chief Editor: Pamela L Dyne, MD more...
Background
Otitis externa is an infection of the external auditory canal. Prompt diagnosis and treatment cures the majority of cases without complication. However, patients who are diabetic, immunocompromised, or untreated may develop malignant otitis externa, a potentially life-threatening infection.
Otitis externa is defined as chronic when the duration of the infection exceeds 4 weeks or when more than 4 episodes occur in 1 year.
Pathophysiology
The ear canal guards against infection by producing a protective layer of cerumen, which creates an acidic and lysozyme-rich environment. While a paucity of cerumen allows for bacterial growth, an excess can cause retention of water and debris, which can create an environment ideal for bacterial invasion. This may happen when the ear canal is regularly exposed to water as seen in swimmers and divers. Localized trauma from foreign objects placed in the ear can also lead to direct bacterial invasion in the ear canal. Once an infection becomes established, localized maceration and inflammation occur, which lead to symptoms.
Rarely, the bacterial infection can invade the deeper underlying structures of the soft tissue and destroy the underlying temporal bone. This is called malignant otitis externa and is a complication seen more often in immunocompromised patients.
The most common organism reported in otitis externa is the Pseudomonas species, followed by Staphylococcus and Streptococcus species. Fungi are a less common cause of otitis externa.[1]
Epidemiology
Frequency
United States
Acute otitis externa occurs in 4 of every 1000 people annually, and the chronic form affects 3-5% of the population.[2] The condition is most common in swimmers, divers, and those whose ears are regularly exposed to or submerged in water.
Mortality/Morbidity
If left untreated, the infection may invade the deeper adjacent structures and progress into malignant otitis externa. This complication is almost exclusively seen in immunocompromised patients such as those with diabetes, AIDS patients, those undergoing chemotherapy, and patients taking immunosuppressant medications such as glucocorticoids. Pseudomonas is the inciting organism in the vast majority of cases. When untreated, malignant otitis externa has a mortality rate approaching 50%. This complication should be suspected if tenderness, erythema, or edema of the external ear or adjacent tissues is present on physical examination.
Race
People in some racial groups have small ear canals, which may predispose them to obstruction and infection.
Sex
Rates of occurrence of otitis externa are equal in males and females.
Age
Although otitis externa is seen in all age groups, the peak incidence is in children aged 7-12 years.[1]
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