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KMID : 0858620060100020145
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Korean Journal of Audiology
2006 Volume.10 No. 2 p.145 ~ p.149
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Bone Conduction Threshold Shift after Middle Ear Surgery
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Lee Ho-Yun
Moon Jung-Ki
Choi Myung-Su
Chang Dong-Sik
Cho Chin-Saeng
Park Kyung-You
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Abstract
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Objective: It has been known that the bone conduction threshold shift in chronic otitis media is due to loss of cochlea function. The propagation of the bone conduction sound could be consist of several routes, which are direct vibration to the encapsulated bone of cochlea and ossicular mass inertia. It makes us expect that the bone conduction threshold shift in chronic otitis media could be from loss of middle ear apparatus. The purpose of this study is to understand the mechanism of bone conduction threshold shift in chronic otitis media by comparing preoperative bone conduction threshold with postoperative bone conduction threshold shift.
Method: 111 patients with unilateral chronic otitis media who underwent tympanoplasty were reviewed in a retrospective study. Bone conduction threshold were calculated over the speech frequencies (500, 1,000, 2,000 and 4,000 Hz). 15 dB or more depression of bone conduction threshold at least in 2 frequencies between 500 and 4,000 Hz was considered to be significant.
Result: Improvement of bone conduction threshold after tympanoplasty was shown about 12% between 20 dB and 50 dB of preoperative bone conduction threshold. and the frequencies improved bone conduction threshold were mostly 1,000 and 2,000 Hz.
Conclusion: We respect partial increasing of bone conduction threshold in 20 to 50 dB. In chronic otitis media, bone conduction threshold shift could be loss of bone conduction of middle ear apparatus to some degree.
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KEYWORD
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Tympanoplasty, Bone conduction.
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