3.3 Otitis Externa
3.3.1 Uncomplicated Otitis Externa
Key Features
Otitis externa (OE) is an infectious process of the external auditory canal.
The most common pathogens are Pseudomonas aeruginosa and Staphylococcus aureus.
Otomycosis is less common and caused by Aspergillus and Candida.
Treatment involves meticulous cleaning and topical preparations.
Systemic therapy is required if the infection spreads out of the confines of the canal, or the patient is immunocompromised or a poorly controlled diabetic.
Otitis externa is a localized infection of the skin of the external auditory canal (EAC). The EAC contains varying amounts of cerumen and desquamated skin. Acute OE, called “swimmer′s ear,” is most common after water exposure but may also follow EAC trauma. Retained moisture will alkalize the canal, making it prone to bacterial infection. As long as the infection is confined to the ear canal, local aural toilet and topical drops will be curative. If the infection extends outside the confines of the canal to become a periauricular cellulitis or the patient has a complicating factor that may impede the effectiveness of topical antibiotics, then oral and occasionally IV antibiotics are required.
Epidemiology
Acute otitis externa affects from 1:100 to 1:250 of the general population. A lifetime incidence may be as high as 10%. The disorder is more common in warm environments with high humidity and increased water exposure.
Clinical
Signs
Otorrhea, conductive hearing loss, and EAC swelling are all common. As the skin of the EAC swells, the periosteum is irritated and becomes very painful. Pressing on the tragus or pulling the auricle may lead to significant pain. The auricle and periauricular tissues may also become edematous and tender if the condition becomes a periauricular cellulitis. If the infection has spread to a cellulitis, then the ear may be prominent with an increased auriculocephalic angle similar to that seen with acute mastoiditis. Signs of otomycosis include itching and visible hyphae on inspection.
Symptoms
Usually present with a 48- to 72-hour history of progressive pain, itching, discharge, and aural fullness. Patients may also complain of jaw pain. If the ear canal fills with debris or swells completely, then hearing loss will also occur.
Differential Diagnosis
The differential diagnosis includes foreign body of the EAC, otitis media, malignant or necrotizing OE in a diabetic, coalescent mastoiditis, malignancy, chronic OE, and other inflammatory lesions (e.g., eosinophilic granuloma). Dermatological conditions (eczema, contact dermatitis), allergic reaction to ototopical drops, and herpes zoster oticus with painful EAC vesicles need to be excluded. A localized furuncle may also mimic OE, as can chronic otitis media or acute otitis media with otorrhea. The presence of inflammation of the TM with formation of bullae and severe pain indicates bullous myringitis; this is rare, may be associated with influenza, and may be superinfected with bacteria. The best treatment for bullous myringitis is controversial but can include pain medications, oral antibiotics (e.g., macrolides), and ototopical antibiotic preparations.
Evaluation
Physical Exam
A head and neck examination, concentrating on the otologic exam, is performed. When possible, the EAC should be débrided with an otomicroscope. Inspection may reveal eczema, otorrhea, edematous canal skin, erythema, moist cerumen, debris, or hyphae. One classic finding is pain with palpation or manipulation of the auricle or the tragus. Frequently, the skin is so swollen that the TM cannot be seen. If visible, the TM may appear inflamed but mobile (differentiating it from acute otitis media). The skin of the auricle and periauricular region may also demonstrate erythema, edema, and tenderness.
Imaging
Imaging is not needed for uncomplicated OE. However, when there is auricular or periauricular involvement with protruded auricle, a computed tomography (CT) scan of the temporal bones can help differentiate a coalescent mastoiditis from severe OE with postauricular cellulitis.
Labs
Labs are rarely indicated for uncomplicated OE. In patients with suspected uncontrolled diabetes, a blood glucose level may be helpful.
Other Tests
Cultures are recommended for recurrent, chronic, or recalcitrant OE. Cultures should be sent for routine culture and sensitivity as well as fungus. Any abnormal-appearing tissue or polyp that does not respond to medical management should be biopsied to exclude malignancy.
Pathology
The infection usually begins with moisture buildup in the EAC. The acidic and hydrophobic qualities of cerumen make it bacteriostatic. A warm, moist EAC with decreased cerumen favors bacterial overgrowth. The bacteria will readily invade the skin. Although > 90% of OE cases are bacterial, a moist alkaline environment also favors fungal growth. Pseudomonas aeruginosa and Staphylococcus aureus are most common bacteria, and Aspergillus and Candida are the most common fungi.
Treatment Options
Medical
The ear must be meticulously cleaned with an otomicroscope with complete removal of debris. This may need to be repeated in a few days. Once the ear is cleaned, otic drops should be placed. There are several preparations available, including nonantibiotic, antibiotic alone, and antibiotic plus steroid therapies ( Table 3.6 ). They may be used two or three times per day for 7 to 14 days. Dry ear precautions are recommended until the infection clears.
Placement of a wick (e.g., Pope Oto-Wick; Medtronic, Inc., Minneapolis, MN) to carry drops medially may be required, especially in canals so swollen that the TM is not easily visible. Keep in mind that placing a wick can be a very uncomfortable experience for the patient. Analgesics, even those with narcotic, may be required to control the pain. As edema regresses, the wick will usually fall out or may be removed. OE due to a foreign body will not resolve without removal of the foreign body.
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