Excerpt from Otitis Externa

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Background

Otitis externa is an infection of the external ear canal and is a common problem in most EDs. Usually simple to care for, external otitis may lead to serious problems in people who are diabetic or immunocompromised. Basic treatment measures cure 90% of cases without complication.

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

Glands within the ear canal produce a layer of protective cerumen. Too little cerumen may predispose to infection, while too much cerumen may cause retention of water and debris. Most ear canal infections are caused by excessive moisture carrying bacteria into the cerumen of the ear canal, leading to maceration and inflammation. Another common cause is local trauma allowing bacteria to enter compromised skin. The most common causative organism is Pseudomonas species. Staphylococci, streptococci, and (in rare cases) fungi are other causative agents.

Otitis externa can also result from nonbacterial origins such as atopic dermatitis or allergic contact dermatitis.

Frequency

United States

Acute otitis externa occurs in 4 of every 1000 people each year, and the chronic form affects 3-5% of the population. The condition is most common in persons who are swimmers and/or divers or who have other exposures that allow contaminated water to be trapped in the external canal.

Mortality/Morbidity

Infection of the deep structures (ie, malignant external otitis) occurs almost exclusively in patients who are immunocompromised. People who are diabetic are particularly vulnerable.

• This complication should be suspected if tenderness, erythema, and edema of the external ear or adjacent tissues are present.
• This condition can lead to cellulitis and osteomyelitis, with the untreated mortality rate approaching 50%.
• When a fever, other signs of systemic toxicity, or underlying immunocompromise is present, the patient may need admission and treatment with high-dose antibiotics covering Pseudomonas species.
• Life-threatening temporal bone infection occurs in less than 0.5% of cases.

Race

People in some racial groups have small ear canals, which may predispose them to obstruction and infection.

Sex

Rates of occurrence are equal in males and females.

Age

All ages are affected, with a peak incidence in children aged 7-12 years.

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