Otitis Externa

Key Features

Essentials of Diagnosis

• Otalgia

• Erythema, edema, and purulence of the external auditory canal skin

• Diabetic or immunocompromised patients are at risk for "malignant" otitis externa (osteomyelitis of the skull base)

General Considerations

OTITIS EXTERNA

• There is often a history of recent water exposure ("swimmer's ear") or mechanical trauma (eg, scratching, cotton applicators)

• Otitis externa is usually caused by gram-negative rods (eg, Pseudomonas, Proteus) or fungi (eg, Aspergillus), which grow in the presence of excessive moisture

MALIGNANT OTITIS EXTERNA

• Usually caused by Pseudomonas aeruginosa

• Osteomyelitis begins in the floor of the ear canal and may extend into the middle fossa floor, the clivus, and even the contralateral skull base

Clinical Findings

Symptoms and Signs

OTITIS EXTERNA

• Otalgia with associated external auditory canal edema and purulent discharge

• Erythema and edema of the ear canal skin, often with a purulent exudate, as well as surrounding periauricular cellulitis

• Manipulation of the auricle elicits pain

• The lateral surface of the tympanic membrane is often erythematous

• When the canal skin is very edematous, it may be impossible to visualize the tympanic membrane

MALIGNANT OTITIS EXTERNA

• Persistent otorrhea

• Granulation tissue in the ear canal

• Deep otalgia

• In advanced cases, progressive palsies of cranial nerves, such as cranial nerve VI, VII, IX, X, XI, or XII

Differential Diagnosis

• Otitis media

• Skin cancer

• Traumatic auricular hematoma

• Cellulitis

• Chondritis or perichondritis

• Relapsing polychondritis

• Chondrodermatitis nodularis helicis

Diagnosis

Laboratory Tests

• Persistent discharge unresponsive to treatment should be cultured

• High inflammatory markers, such as erythrocyte sedimentation rate and C-reactive protein, are indicative of malignant otitis externa

Imaging Studies

• Diagnosis of malignant otitis externa is confirmed by demonstration of osseous erosion on CT scanning in addition to the presence of high inflammatory markers (see Laboratory Tests, above)

• MRI scanning is often important to rule out abscesses that may result from malignant otitis externa

Treatment

Medications

OTITIS EXTERNA

• In cases of swimmer's ear, after getting moisture into the ear, acidification with a drying agent (ie, a 50/50 mixture of isopropyl alcohol/white vinegar) is often helpful

• When infected, an otic antibiotic solution or suspension of an aminoglycoside (eg, neomycin/polymyxin B) or fluoroquinolone (eg, ciprofloxacin), with or without a corticosteroid (eg, hydrocortisone), is usually effective

• Drops should be used abundantly (5 or more drops three or four times a ...