تغییرات هدایت استخوانی پس از بازسازی زنجیره استخوانچه‌ای گوش میانی

    Background & Aim: The most common surgically treatable causes of hearing loss are middle ear diseases among which the greatest effect is related to ossicular chain dysfunction. Successful ossicular chain reconstruction certainly improves air conduction thresholds and closes air-bone gap in audiograms, but the effect of this procedure on bone conduction thresholds has remained to be elucidated. Only few standard clinical trials have been done and most studies are retrospective with methodological faults. The aim of the present study was to determine the effect(s) of ossicular chain reconstruction on bone conduction thresholds. Patients & Method: In a controlled clinical trial, pre-and post-operative bone conduction(BC) thresholds of speech frequencies were investigated in 68 patients. In order to evaluate the effect of ossicular chain reconstruction on bone conduction, the patients were divided into two groups including 34 cases each. One group received ossicular chain reconstruction during the middle ear surgery and the other one was to receive it later. In each group, mean preoperative bone conduction thresholds of any frequencies were compared with postoperative ones using paired t-test. Results: In the reconstruction group, the results revealed a significant improvement in the postoperative BC thresholds at 1000 and 2000 Hz with the largest mean improvement observed at 2000 Hz(about 9.7 db recovery). In the group without reconstruction, no significant changes were observed at any frequencies. Conclusion: The results indicated the remarkable effect of ossicular chain on bone conduction. This effect is eliminated in ossicular disruptions due to various middle ear diseases and is reproducible by successful reconstruction of the chain. The findings showed changes in bone conduction as a mechanical phenomenon affected by ossicular chain. In other words, BC thresholds are not exclusive indicators of chochlear function. We also observed that true sensorineural hearing loss is not a common major complication of middle ear surgery.