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For further information, see CMDT Part 8-03: Diseases of the Ear Canal

Key Features

Essentials of Diagnosis

  • Painful erythema and edema of the ear canal skin

  • Purulent exudate

  • In diabetic or immunocompromised patient, may evolve into osteomyelitis of the skull base ("malignant external otitis")

General Considerations

EXTERNAL OTITIS

  • 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 EXTERNAL OTITIS

  • 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

EXTERNAL OTITIS

  • Otalgia, frequently accompanied by ear canal pruritus

  • Erythema and edema of the ear canal skin, often with a purulent exudate

  • Manipulation of the auricle often elicits pain

  • Because the lateral surface of the tympanic membrane is ear canal skin, it is often erythematous

  • In contrast to acute otitis media, the tympanic membrane in otitis externa moves normally with pneumatic otoscopy

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

MALIGNANT EXTERNAL OTITIS

  • Persistent foul aural discharge

  • Granulations in the ear canal

  • Deep otalgia

  • In advanced cases, progressive palsies of cranial nerves 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

Imaging Studies

  • Diagnosis of malignant otitis externa is confirmed by demonstration of osseous erosion on CT scanning

Treatment

Medications

EXTERNAL OTITIS

  • 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) are usually effective

  • Drops should be used abundantly (5 or more drops three or four times a day) to penetrate the depths of the canal

  • In recalcitrant cases, particularly when cellulitis of the periauricular tissue has developed, oral fluoroquinolones (eg, ciprofloxacin, 500 mg twice daily orally for 1 week) are the drugs of choice because of their effectiveness against Pseudomonas species

MALIGNANT EXTERNAL OTITIS
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