Evaluation of inner ear damage during conditions with middle ear effusion by use of brainstem audiometry.

The method of auditory evoked brainstem responses (AEBR) was applied on an animal model with two types of well defined middle ear effusions--serous otitis media (SOM) and purulent otitis media (POM). The animals with SOM exhibited fairly normal interpeak latencies but a considerably increased auditory threshold. In contrast, POM mainly affected the latencies of the brainstem evoked potential but also caused a slight increase of the auditory threshold. The results indicate that SOM chiefly causes a conductive hearing loss, while POM also affects the neural circuit.