Abstract
Postoperative bone conduction threshold, as well as postoperative air conduction threshold, is frequently examined, because one of the aims of hearing improvement operation is to close the air-bone gap. We evaluated the effects of hearing improvement operation on postoperative bone conduction thresholds. A total of 207 ears of 201 patients underwent first time operations for hearing improvement from January 2007 to December 2009. Audiometric evaluation was based on pure tone audiograms, taken before and more than 6 months after surgery.
The mean postoperative bone conduction threshold at three speech frequencies and the mean postoperative air conduction threshold improved significantly by 2.8 dB and 16.6 dB compared with preoperative hearing levels. Eighty-five out of 207 (41%) cases showed more than 5 dB improvement of the mean bone conduction threshold after operation. The mean postoperative bone conduction thresholds showed significant improvements at 1000Hz and 2000Hz, but not 500Hz and 4000Hz. In bone conduction thresholds of each middle ear disease, greater than 10 dB improvement rates after operation were as follows: chronic otitis media 5/52 (9.6%), pars flaccid cholesteatoma 4/43 (9.3%), otosclerosis 10/28 (35.7%), chronic otitis media with tympanosclerosis 3/22 (13.6%), tympanosclerosis 4/14 (28.6%), ossicular malformation 3/14 (21.4%), adhesive otitis media 0/13 (0%), pars tensa cholesteatoma 2/9 (22.2%), congenital cholesteatoma 0/6 (0%), and secondary cholesteatoma 2/6 (33.3%). At 6-12 months after operation, the mean postoperative bone conduction threshold improved significantly by 1.7 dB compared with preoperative hearing levels. At more than 12 months after operation, the mean postoperative bone conduction threshold improved significantly by 3 dB.
These results showed that the postoperative air and bone conduction thresholds improved significantly compared with preoperative hearing levels in each middle ear disease, and postoperative air and bone conduction thresholds at more than 12 months after operations improved compared with at 6-12 months after operation. Thus, the evaluation of hearing improvement operation is recommended to examine air and bone conduction threshold at the same time at more than 12 months after operation.
