Wideband tympanometry findings in inner ear malformations.

Objective: The deficits in the cochlea which is at the one end of the ear sound transfer system, may effect middle ear functions. Wideband typanometry (WBT) is frequently used to evaluate these transfer functions which play a crucial role in setting the impedance matching between the external ear and the cochlea. To this end, the aim of this study was to investigate the ear transfer functions in inner ear malformations via WBT, and to question whether these functions change depending on the types of inner ear malformation.
Methods: This prospective case-control study was conducted in a university hospital. One hundered-fifty-seven ears (aged 3-37 years) under the groups of cochlear hypoplasia, incomplete partition I, incomplete partition II, cochlear aplasia and complete labyrinthine aplasia were evaluated. In the control group, 30 ears with normal hearing were enrolled and WBT was carried out. Tympanometric peak pressure, equivalent middle ear volume, static admittance, tympanogram width, resonance frequency, average wideband tympanometry and absorbance measurements were analyzed.
Results: The inner ear malformation groups demonstrated statistically significant differences than the control group and from each other in terms of traditional tympanometric parameters and WBT test parameters (p<0.05). The most remarkable difference was between the group of complete labyrinthine aplasia and the control group, most probably because of complete labyrinthine aplasia's structural effects. However, on some parameters, incomplete partition II and the control group showed similarities. In absorbance measurements, there was significant difference between all patient groups and the control group, especially at high frequencies (p<0.05). The largest difference was between the control group and the group of complete labyrinthine aplasia which has revealed the lowest absorbance values (p<0.05). In averaged-wideband tympanogram analysis, all patient groups obtained a lower amplitude peak than the control group; complete labyrinthine aplasia group had the flattest peaked amplitude, while the incomplete partition II group had a near-normal curve.
Conclusion: The results of the study revealed the distinctive effects of inner ear malformations in middle ear transfer functions. It is concluded that the absence of inner ear structures causes negative effects on energy absorbance and the other transfer functions of the middle ear. WBT may provide additional information on diagnosis of patients with inner ear malformations.
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