A case study of central processing following long-standing unilateral conductive hearing loss.

This single-subject study reported the audibility and speech-processing performance of a man who at age 22 had an impacted foreign body removed from the bony portion of his L ear canal, it having been there since about age 7. Otologic and audiologic assessment, records of failing school screening, and subject and family history agreed on an uncomplicated conductive hearing level of 30-40 db. Immediately on removing the block, audiograms and tympanograms were normal (HTL less than or equal to 20 db at .25-8 kc/s) and remained so for the 14 mo of the study. At 8 days and at 5 and 14 mo post-blockage, a speech-in-noise test at 50 db HL, at S/N's of 30, 20, 15, 10, 5, and 0 db was administered along with the SSW test. At 8 days, S-in-N scores (compared to 10 in-house normal controls) were abnormally low in both ears, but especially in the L ear (e.g., at S/N = 0, L ear score was only 8% correct compared to the controls' 86.4%). Distinct improvement occurred at 5 and further at 14 mo, but at 14 mo both ears were still yielding scores 1 S.D. below the control mean. Similarly, SSW scores were abnormal for both ears; at 5 mo post-blockage the L ear still yielded abnormal scores, but yielded normal scores at 14 mo post-blockage. It may be concluded that a unilateral conductive hearing loss, even though contracted well past the age thought to be crucial in auditory perceptual development, may have a deleterious effect on auditory processing of stimuli entering not only the attenuated but also the normal ear, and that though this deleterious effect may eventually be overcome it may require a surprisingly long time for it to disappear.