The effects of cochlear implantation on middle ear function: A prospective study.

Abstract

Although sound conduction mechanisms may influence by cochlear implantation (CI), it is not very clear whether, how, and to what extent these mechanisms may be influenced the pediatric population. Wideband tympanometry (WBT) is a sensitive tool to evaluate alternations in the middle ear mechanics in a wide frequency range. The current study aimed to explore CI's impacts on sound conduction across the middle ear cavity using WBT in pediatrics. In a prospective design, 35 unilaterally implanted children (<24 months of age) with normal temporal bone anatomy were included in this study. Traditional tympanometry (226-Hz) and WBT measures were compared for each child in the implanted and non-implanted ears preoperatively and three months postoperatively. No significant changes in the "static acoustic admittance" and "peak pressure" parameters were observed between the pre-CI and post-CI conditions in the implanted and non-implanted ears in the 226-Hz tympanometry test. Wideband absorbance recordings before CI surgery exhibited a double-peaked pattern over a frequency range of 250 to 8000Hz. The pre- and postoperative acoustic energy absorbance comparisons indicated a significantly reduced mid-frequency (1260 to 3175Hz) and high-frequency (5040 to 8000Hz) absorbance in the implanted ears. However, our results indicated no significant differences in sound absorbance between the pre- and postoperative conditions in non-implanted ears. Our findings suggested that WBT is a more sensitive method than traditional tympanometry for monitoring the mechanical status of the middle ear after cochlear implantation in pediatrics. Cochlear implantation in young children can significantly reduce mid- and high-frequency acoustic absorbance measured by WBT.