The influence of the coupling of actuation drivers of implantable hearing systems on the mechanics of the middle ear

• Published in: Cochlear implants international Vol. 10; no. 3; pp. 160 - 165
• Main Authors: Stieve, M, Winter, M, Battmer, RD, Lenarz, M, Lenarz, TH
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.09.2009
• Subjects: implantable hearing systems; multifrequency tympanometry; resonance frequency
• ISSN: 1467-0100; 1556-9152
• DOI: 10.1002/cii.377

We used multifrequency tympanometry to provide middle ear mechanics after implantation of different implantable hearing aids. A total of 34 patients were included in the investigation; 19 of them were fitted with the Otologics system and 15 with the MED‐EL Vibrant Soundbridge system. With the Otologics recipients, measurements were made preoperatively and both two months and at least 12 months postoperatively. Measurements involving the MED‐EL patients were taken at least 12 months postoperatively. For all measurements, the non‐implanted contralateral side was used as a control. Preoperatively, the resonance frequency of the Otologics patients was 904.3 ± 218.2 Hz for the implanted side and 907.1 ± 161.8 Hz for the non‐implanted side. Postoperatively, a significant increase (p < 0.01) compared with the preoperative value and the control side was observed after two months: 1111.3 ± 234.7 Hz, as opposed to 823.8 ± 274.5 Hz on the contralateral side. After 12 months, the resonance point was restored to approximately the preoperatively measured values: 975 ± 55.3 Hz (implanted side) and 901.3 ± 207.1 (control side). The resonance frequency in the Symphonix patients, as measured after at least 12 months (on average, 35 months), was 1006.3 ± 269.5 Hz on the non‐implanted side and 900.1 ± 249.3 Hz on the implanted side. It is apparent that the resonance frequency on the implanted side was higher than on the control side, although the difference was not significant (p = 0.496). Monitoring following the implantation of active hearing systems is therefore recommended in order that conclusions can be drawn regarding the adequacy of the coupling of the actuation driver to the ossicular chain. Copyright © 2008 John Wiley & Sons, Ltd.