Hearing in chronic suppurative otitis media.

In individuals with chronic otitis media, mixed hearing impairments are common but it is unclear whether the raised bone conduction thresholds are a reflection of the pathologic process affecting the inner ear or a combination of the high prevalence of sensorineural hearing impairments in the population along with the artificial elevation of bone conduction thresholds associated with a conductive defect. A total of 395 ears with chronic otitis media but without cholesteatoma were studied. In them, once the artificial elevation (Carhart effect) of the bone conduction thresholds, which occurs whenever there is an abnormality of the sound conduction mechanism, had been taken into account, there was no difference in the bone conduction thresholds compared with those in 920 control ears. In addition, in 100 instances, the contralateral ear was normal and there was no difference in the bone conduction thresholds between the diseased and the normal ears. Raised bone conduction thresholds in chronic otitis media are considerably likely to reflect both the Carhart effect and the high prevalence of sensorineural impairments, rather than disease damage to the inner ear.