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Abstract
Several studies have reported contralateral hearing deficits following ear surgery. This study aimed to evaluate changes in micromechanical cochlear properties which could occur in the contralateral ear following ear surgery, using transient evoked otoacoustic emission (TEOAE) recording. Surgery involved tympanic membrane surgery in 13 cases and middle ear surgery in 16 cases. TEOAEs were recorded and compared for contralateral ears before (day 1 : Dl) and after (day 2 : D2) ear surgery. Two patients failed to show a TEOAE reproductibility >75%, and were excluded from the study, thus reducing the number of patients to 27. Results were compared to those of a control group of 12 normal hearing subjects, recorded in similar conditions also on day one (Dl) and day two (D2). The difference between Dl and D2 was not significant in either group. Pre/postsurgery variations in TEOAE amplitude for the patient group were negatively and significantly correlated with the corresponding preoperative levels in that the greater the presurgical TEOAE level, the larger the decrease in postoperative level. Compared to the variation confidence intervals in the control group, TEOAE amplitude remained stable in 15 patients, increased in four and decreased in eight. These three groups of patients differed only regarding preoperative TEOAE amplitude values, which were significantly greater in the group which presented a decrease in TEOAE amplitude than in the others. Increase in TEOAE amplitude was more frequent after tympanic membrane surgery. On the other hand, TEOAE amplitude decrease was more frequent after middle ear surgery, and is significant compared to the tympanic membrane surgery results. The results show that cochlear micromechanical properties may be reduced in the ear contralateral to surgery and that this decrease depends on the severity of the surgical procedures in the operated ear, such as drilling or opening of the oval window.