A 5-year-old boy presents with sudden hearing loss in the right ear after his sibling places a smooth plastic bead in the external auditory canal. Otoscopy confirms the bead filling the outer one-third of the canal and occluding the tympanic membrane. Tuning fork testing shows Weber lateralizing to the right and Rinne negative on the right (bone conduction > air conduction). The pure-tone audiogram demonstrates the pattern marked **A** in the diagram. Which of the following best describes the audiological finding shown at **A**?
A. High-frequency sensorineural hearing loss with air–bone gap and depressed bone conduction
B. Low-frequency sensorineural hearing loss with positive fistula sign and normal air conduction
C. Mixed hearing loss with Carhart notch at 2 kHz indicating ossicular involvement
D. Flat mild-to-moderate conductive hearing loss with air–bone gap of 25–30 dB and normal bone conduction thresholds
Explanation
Why "Flat mild-to-moderate conductive hearing loss with air–bone gap of 25–30 dB and normal bone conduction thresholds" is right
Aural foreign bodies produce a purely conductive hearing loss by mechanically obstructing sound transmission through the external auditory canal. The hallmark audiogram pattern (marked A) shows depressed air-conduction thresholds across all frequencies with normal bone-conduction thresholds, yielding an air–bone gap of 25–30 dB. The flat configuration across frequencies (not frequency-specific) and the intact bone conduction confirm the lesion is entirely in the conductive apparatus (canal/tympanum), not the inner ear. Complete canal occlusion typically yields a 30–40 dB gap, consistent with this clinical presentation. (Dhingra ENT 7e Ch 11; Cummings Otolaryngology 7e)
Why each distractor is wrong
High-frequency sensorineural hearing loss with air–bone gap and depressed bone conduction: This pattern indicates inner ear pathology (cochlear damage), not mechanical obstruction. Bone conduction would be depressed, which contradicts the normal bone thresholds seen with foreign body obstruction.
Mixed hearing loss with Carhart notch at 2 kHz indicating ossicular involvement: Carhart notch is a characteristic finding in otosclerosis (fixation of the stapes footplate), not simple foreign body impaction. The notch at 2 kHz reflects bone conduction depression, which is absent in pure conductive foreign body cases.
Low-frequency sensorineural hearing loss with positive fistula sign and normal air conduction: This pattern suggests labyrinthine fistula (e.g., from cholesteatoma or trauma), with sensorineural loss and abnormal bone conduction. Foreign bodies do not cause fistulae or sensorineural loss.
High-YieldNEET PG
Foreign body in the external auditory canal = purely conductive loss with normal bone conduction and air–bone gap; removal under operating microscope restores hearing immediately.
Dhingra ENT 7e Ch 11; Cummings Otolaryngology 7e
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