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DEFINITIONS

Otitis externa (OE) or “swimmer’s ear” is commonly defined as an inflammation of the external auditory canal (EAC) or auricle. Up to 10% of all persons may experience an episode of OE during their lifetime.1,2 OE can be painful and difficult to manage because of the confines of the ear canal. Early diagnosis and a stepwise treatment approach, including debridement and ototopical therapy, and on occasion systemic antimicrobials, are critical to expedient management.

EPIDEMIOLOGY

Otitis externa is a common complaint of patients presenting to primary care, emergency, and otolaryngology providers. The yearly incidence is believed to be as high as 0.8–2.5 in 100.3–5. Among the pediatric population, children ages 5–14 are most commonly affected.4,5 Frequent swimmers are 5 times more likely to develop OE.5 Clinicians are likely to see an increased incidence in the summer when children swim more frequently.4 OE can be subcategorized into acute (<6 weeks), subacute (6 weeks–3 months), and chronic (>3 months).5 Otitis externa is typically unilateral, although 10% of cases are bilateral.4

PATHOGENESIS

The outer one-third of the EAC consists of cartilage covered by skin containing hair follicles and cerumen-producing glands.5 Cerumen forms a lipid layer that protects the skin of the EAC and has antimicrobial properties including acidic pH and lysozymes.3,6 The medial two-thirds of the canal is composed of bone covered by a very thin layer of skin that is tightly adherent to the underlying periosteum (Figure 32-1).3,5 This skin has a large number of nerve endings, leaving it very sensitive to stimuli.3 The normal EAC is a relatively narrow canal, measuring 7–9 mm in diameter in adults, but can be much smaller in children and infants.3 This warm dark tunnel can serve as a culture medium for bacterial and fungal growth if the protective cerumen or epithelial barrier is violated by aggressive cleaning, soapy water, skin conditions such as eczema, or a heavy bacterial load.1,7 Moisture trapped in the ear canal from swimming or bathing can also make the EAC more amenable to microbial growth. The highly sensitive innervation patterns can make this condition exquisitely painful.

FIGURE 32-1.

Anatomic drawing of the external ear canal depicting the proximity of cranial nerves and great vessels to the bony cartilaginous junction of the canal. The red circle represents the site where the infection originates and where granulation tissue is typically seen. The arrow represents the direction of spread of the infection into the temporal bone and explains why cranial neuropathies present in later phases of necrotizing otitis externa. [Original artwork used with permission of Steve Cook, MD.]

Almost all acute otitis externa (AOE) in North America is bacterial (90–98%).4,5,8,...

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