What does a decrease in air conduction thresholds compared to bone conduction thresholds signify?

A decrease in air conduction thresholds compared to bone conduction thresholds indicates that there is a gap between these two thresholds, which is characteristic of conductive hearing loss. In conductive hearing loss, the outer or middle ear presents some obstruction or dysfunction that inhibits the transmission of sound to the inner ear. This results in poorer air conduction results as compared to bone conduction, where the sound bypasses these structures and directly stimulates the inner ear.

In a normal hearing scenario, air conduction and bone conduction thresholds should be similar, indicating that sound is being transmitted effectively through both pathways. In the case of sensorineural loss, both air conduction and bone conduction thresholds would be elevated without a significant gap between them, meaning that there is a problem in the inner ear or auditory nerve. Mixed loss presents a combination of both conductive and sensorineural elements, exhibiting both a gap and overall elevated thresholds.

Thus, when the assessment shows that air conduction results are poorer than bone conduction, it highlights that there is a conduction issue present, leading to the conclusion of conductive hearing loss.