Otitis, External

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

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

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

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

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

• Prolonged antipseudomonal antibiotic administration, often for several months

• Although intravenous therapy is often required initially (eg, ciprofloxacin 200–400 mg every 12 hours), selected patients may be graduated to oral ciprofloxacin (500–1000 mg twice daily)

Surgery

• Surgical débridement of infected bone is reserved for cases of malignant external otitis that have worsened despite medical therapy

Therapeutic Procedures

• Fundamental to the treatment of external otitis is protection of the ear from additional moisture and avoidance of further mechanical injury by scratching

• Purulent debris filling the ear canal should be gently removed to permit entry of the topical medication

• When substantial edema of the canal wall prevents entry of drops into the ear canal, a wick is placed to facilitate entry of the medication

Follow-Up

MALIGNANT EXTERNAL OTITIS

• To avoid relapse, antibiotic therapy should be continued, even in the asymptomatic patient, until gallium scanning indicates a marked reduction or resolution of the inflammation

When to Refer

• Any case of persistent otitis externa in an immunocompromised or diabetic individual must be referred for evaluation by otolaryngology and infectious disease specialists