A 28-year-old competitive swimmer presents with severe otalgia, otorrhea, and aural fullness for 3 days following a swimming competition. Otoscopy reveals an erythematous, edematous external auditory canal with debris, and the tragal sign is positive. Audiometry is performed to assess hearing. The audiogram shown demonstrates the pattern marked **A**. Which of the following best explains the audiometric finding in this patient?
A. Unilateral mild-to-moderate conductive hearing loss with air-bone gap due to canal edema and debris obstruction, with normal bone conduction
B. Unilateral sensorineural hearing loss due to inner ear involvement from ototoxic topical drops
C. Bilateral mixed hearing loss indicating progression to malignant otitis externa with skull base osteomyelitis
D. Normal audiogram, as otitis externa does not typically affect hearing thresholds
Explanation
Why option 1 is correct
The clinical presentation is classic acute diffuse otitis externa (swimmer's ear) with positive tragal sign, erythematous edematous canal, and debris. The audiometric pattern marked A — unilateral mild-to-moderate conductive hearing loss with air-bone gap — is the expected finding in uncomplicated OE. The conductive loss results from mechanical obstruction of the canal by edema and debris, which impedes sound transmission to the tympanum; bone conduction remains normal because the inner ear is intact. This distinguishes OE from sensorineural or mixed losses. Per Cummings Otolaryngology 7e, the tympanic membrane is typically normal on otoscopy, confirming the loss is conductive, not due to middle ear pathology.
Why each distractor is wrong
Option 2: Sensorineural hearing loss would indicate inner ear damage. Topical otic fluoroquinolones (ciprofloxacin, ofloxacin) are specifically chosen for OE because they have NO ototoxicity and are safe even if the TM status is uncertain. Inner ear involvement is not a feature of uncomplicated acute diffuse OE.
Option 3: Bilateral mixed loss suggests malignant (necrotizing) otitis externa with skull base osteomyelitis — a severe complication seen in diabetics, elderly, or immunocompromised patients with disproportionate pain, granulation tissue at the bony-cartilaginous junction, and cranial nerve signs. This patient's presentation is uncomplicated acute OE, not malignant OE.
Option 4: Hearing loss is common in acute diffuse OE due to canal obstruction by edema and debris. A normal audiogram would be inconsistent with the clinical findings and the degree of canal edema described.
High-YieldNEET PG
Acute diffuse OE causes unilateral conductive hearing loss (air-bone gap) from canal edema/debris; bone conduction is preserved because the inner ear is unaffected. This distinguishes it from sensorineural loss and justifies the use of ototoxic-free topical fluoroquinolones.
Cummings Otolaryngology 7e, Ch 137
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