Otitis Externa

Otitis externa is inflammation of the skin lining the external auditory canal. Most cases are acute and diffuse, but the same process can range from a localized, painful canal infection to invasive disease involving bone and the skull base. Moisture macerates the canal epithelium and alters its protective acidic environment. Cotton-tip swabs, hearing-aid manipulation, fingernails and other instrumentation can abrade the skin, creating an entry point for organisms. Eczema, psoriasis and other dermatologic conditions weaken the barrier in a similar way. The predominant bacterial pathogens are Pseudomonas aeruginosa and Staphylococcus aureus. The experienced clinician recognizes that the canal is both inflamed and exquisitely tender. A patient may wince when the tragus is pressed or when the pinna is gently moved because these manoeuvres transmit movement directly to inflamed canal skin. That finding is more useful than the presence of ear pain alone. Necrotizing, also called malignant, otitis externa is not simply a more uncomfortable routine infection. In a susceptible patient, infection can extend from the canal into deeper soft tissue and temporal bone. Diabetes, particularly when poorly controlled, and immunocompromise...