Abstract
In chronic otitis media, bone conduction hearing impairments at high frequencies are common. However, it is unclear whether the raised bone conduction thresholds are a reflection of inner ear damage or an artificial elevation of bone conduction thresholds associated with a conductive disorder. Bone conduction measurements were performed on 7 ears from patients with acute mastoiditis, on one ear from an OME patient, and on two ears from cholesterol granuloma patients. In these ears, the raised bone conduction thresholds were characteristically demonstrated at 2000Hz before treatment. After the insertion of a tympanostomy tube, the bone conduction hearing improved in a few days. Therefore, the raised bone conduction thresholds are not likely to reflect the damage to the inner ear. The characteristic findings in these cases were of purulent and mucoid effusion in the middle ear and the mastoid cavity, and granulation tissue around the incus and stapes.
The cause of the bone conduction hearing loss was considered to be related to an abnormal sound conduction mechanism, such as the suppression of the resonant point of ossicle, rather than to disease damage to the inner ear.
