CHRONIC CONDUCTIVE HEARING-LOSS IN ADULTS - EFFECTS ON THE AUDITORY BRAIN-STEM RESPONSE AND MASKING-LEVEL DIFFERENCE

Objective: To determine whether chronic conductive hearing loss in adu lts results in changes in the auditory brainstem response (ABR) simila r to those observed in children with histories of otitis media with ef fusion. Design: Test of effect of unilateral conductive hearing loss o n adult ABR using age-matched control group and subjects as their own controls. Subjects: Twelve adults with a history of unilateral conduct ive ear disease. An age-matched control group of 21 adults was also te sted. Methods: The ABR, an electrophysiologic test of auditory brainst em functioning, was used to evaluate possible brainstem abnormalities in the impaired listeners. In addition, the masking-level difference, a behavioral test of binaural auditory processing in the brainstem, wa s used. Results: When comparing the patients' diseased ears with their healthy ears, significant delays were seen for wave V as well as for the I-V and III-V interwave intervals. For comparison with the control population, significant prolongations were again seen for wave V and for the III-V interwave intervals. In addition, reduced masking-level differences and significant correlations between the masking-level dif ferences and the ABRs, independent of hearing threshold, were noted. C onclusions: The results suggest that chronic conductive impairment in adults leads to changes in the ABR similar to those observed in childr en with histories of otitis media with effusion. As such, these change s do not appear to be related to a critical period of development.