Jacqueline Rosenjack Burchum Otitis externa is a cellulitis of the external auditory canal that may extend to the auricle (pinna).1 The condition is often referred to as swimmer’s ear, although the causes are varied. Approximately 1 in 125 people develop acute otitis externa annually, with occurrence primarily in the warmer months and in regions with high humidity.2 Chronic otitis externa affects 3% to 5% of the U.S. population.2 A smaller percentage of patients with otitis externa will progress to malignant (necrotizing) otitis externa, which is a complication that is most often seen in people who are immunocompromised or who have comorbid conditions such as diabetes mellitus.1,3 Risk factors for development of external otitis are typically those that compromise the integrity of the inherent defense mechanism against infection. These include removal of protective cerumen with damage to fragile skin that results from vigorous cleaning of the canal; maceration of skin that results from accumulation of moisture within the canal from swimming; and alterations to the tissues that result from wearing of devices such as headphones and ear plugs.1,3 In the United States, over 90% of cases have a bacterial cause. The most common causative organisms are Pseudomonas aeruginosa and Staphylococcus aureus.1,3 Fungi such as Candida and Aspergillus organisms are uncommon causes of acute otitis externa but may be present in chronic otitis externa or after antibiotic treatment of acute otitis externa.1 Patients with recurrent otitis externa should be evaluated to determine whether the episode represents a fungal infection, treatment failure, or recurrence. The usual presentation of acute otitis externa is pain of the affected ear and auricle developing over 48 hours or less. The pain is often accompanied by a feeling of fullness or itching. Other signs and symptoms that may be present include drainage from the affected ear and hearing loss.2,4 Presentation of chronic otitis externa is primarily one of intense pruritus.3 The classic finding in acute otitis externa is pain and tenderness on palpation of the tragus and on repositioning of the auricle to allow inspection of the canal.1,3–5 The canal may be erythematous and edematous. Often the canal is filled with debris and sloughed tissue. The tympanic membrane may be erythematous; alternately, it may be poorly visualized because of edema or cerumen and exudate in the canal. Advanced cases of acute otitis externa are often accompanied by complete obstruction of the canal. The cellulitis may extend to the external ear with enlargement of periauricular lymph nodes.1,4 Hearing deficits may occur in advanced cases.1 Chronic otitis externa has a very different presentation. The canal is often dry, and cerumen may be absent. Excoriations may be present secondary to use of objects inserted to relieve the itching that accompanies this condition. Discharge may be present. The canal may be narrowed, but this is secondary to thickened canal walls that occur over time rather than to the edema that is responsible for narrowed canals in acute otitis externa.5 Diagnostic testing is usually unnecessary. • A culture of canal drainage with antibiotic sensitivities is indicated if there is no improvement after 14 days of antibiotic therapy.3 • Microscopic analysis of drainage using potassium hydroxide (KOH) can identify a fungal cause. It is important to distinguish otitis externa from other conditions that cause ear pain, drainage, inflammation, or hearing loss. Patients with recurrent otitis externa should be evaluated to determine whether the episode represents a treatment failure rather than a recurrence.
Otitis Externa
Definition and Epidemiology
Pathophysiology
Clinical Presentation
Physical Examination
Diagnostics
Differential Diagnosis
Otitis Externa
Chapter 85
