Which of the following may cause conductive hearing loss?

Conductive hearing loss occurs when sound waves are not effectively conducted through the outer ear canal to the eardrum and the tiny bones of the middle ear. Otosclerosis is a condition characterized by abnormal bone growth in the middle ear that can lead to the stiffness of the stapes bone (the stirrup bone), preventing it from vibrating properly and transmitting sound to the inner ear. This abnormality directly impacts the conduction of sound waves, which is why otosclerosis is a well-known cause of conductive hearing loss.

In contrast, other conditions listed, such as presbycusis, noise exposure, and acoustic trauma, are typically associated with sensorineural hearing loss. Presbycusis is age-related hearing loss due to degeneration of sensory cells and neural pathways in the inner ear. Noise exposure and acoustic trauma also damage the sensory cells within the cochlea, leading to sensorineural hearing loss rather than conductive issues. Thus, otosclerosis stands out as the primary option that specifically results in conductive hearing loss.