Otitis Externa

Otitis externa includes infections and inflammation of the external auditory canal (EAC) and auricle. It may be divided into acute diffuse and malignant types.

ACUTE DIFFUSE OTITIS EXTERNA Definition and Diagnosis Also known simply as otitis externa (OE) or swimmer's ear, this infection is characterized by pruritus, pain, and tenderness of the external ear. Physical signs include erythema and edema of the EAC, which may spread to the tragus and auricle. Other signs are clear or purulent otorrhea and crusting of the EAC. As the disease progresses, the pain becomes intolerable and is present with mastication or any movement of the periauricular skin. Increasing edema eventually narrows the EAC lumen and may cause hearing impairment. In severe cases, infection may spread to the periauricular soft tissues and lymph nodes, and there may be lateral protrusion of the auricle secondary to inflammation.

Pathophysiology Predisposing factors for the development of OE are trauma to the skin of the EAC and elevation of the local pH. Constant contact with water, from swimming, bathing, or a humid environment both elevate the pH of the EAC skin and may cause maceration. Trauma is most commonly caused by scratching or by overzealous disimpaction of cerumen. Cerumen is an acidic mixture of sebaceous and apocrine gland secretions and desquamated epithelial cells. It forms a physical barrier that protects the EAC skin from violation, while the acidic pH has antimicrobial properties.

Microbiology The most common organisms implicated in OE are Pseudomonas aeruginosa and Staphylococcus aureus,15 although one study found a polymicrobial etiology in one-third of patients and an anaerobic bacterial etiology in one-quarter, with Bacteroides species predominating.16

Otomycosis, or fungal OE, accounts for approximately 10 percent of cases, with a high percentage found in tropical climates. 17 A history may reveal the presence of diabetes or other immunocompromised states or previous long-term therapy with antibiotics. Most (80 to 90 percent) of otomycosis is due to Aspergillus species, and physical examination may reveal a black, blue-green, or yellow discoloration of the EAC. The second most common fungal pathogen is Candida. 17

Noninfectious causes include contact dermatitis from topical medications or resins in hearing aids, seborrhea, and psoriasis.

Treatment The treatment of OE involves analgesia, cleansing of the EAC, acidifying agents, topical antimicrobials, and sometimes steroids. Cleansing may be done with gentle irrigation using hydrogen peroxide, and gentle debridement by the physician with a suction aspirator such as a Frasier suction.

A variety of topical agents exist that combine an antimicrobial agent with either an acid and/or a steroid. Table..,231n-6 lists the components of many otic preparations. No single agent has been shown to be more effective than the others, although the lower-pH preparations are thought to be better. 15 The burning associated with the acidic preparations may reduce compliance, however, and patients unable to tolerate the low pH of otic preparations may instead use the slightly more alkaline ophthalmic drops. Also, if there is suspected TM perforation or the TM cannot be visualized, antibiotic drops should be prescribed. Cortisporin Otic Suspension should only be used; the solution is toxic to the middle ear. The medication should be instilled into a cleansed ear while it is facing up, with this position held for 3 min. This should be done four times daily for at least 10 days or until after the resolution of symptoms. If edema of the EAC obstructs the lumen, a commercial wick or piece of gauze may be inserted into the EAC and kept moist with the otic drops.

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