A 6-year-old child with significant middle ear effusion; which configuration on pure-tone audiometry is most likely?

• A. Normal air conduction thresholds paired with significantly depressed bone conduction thresholds
• B. Equally depressed air and bone conduction thresholds showing a high-frequency precipitous drop
• C. An air-bone gap where bone conduction is significantly poorer than air conduction
• D. Depressed air conduction thresholds with bone conduction thresholds remaining within normal limits

Answer: (D)

Middle-ear pathology like significant middle ear effusion causes a conductive hearing loss. The outer and middle ear impede sound transmission, so air-conduction thresholds become elevated. The inner ear and auditory nerve (reflected by bone-conduction testing) are typically unaffected, so bone-conduction thresholds stay normal. This creates an air–bone gap, with depressed air-conduction thresholds and normal bone-conduction thresholds.

That pattern matches the option describing depressed air-conduction with bone-conduction remaining within normal limits. The other patterns point to different issues: a normal air-conduction result with depressed bone-conduction suggests a sensorineural problem; equal depression of air and bone with a high-frequency drop indicates sensorineural loss; and bone-conduction worse than air-conduction would imply inner-ear or mixed involvement, not a pure conductive loss from middle-ear effusion.