Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Paper Audiol Neurotol 2012;17:133–138 DOI: 10.1159/000333807 Conditions for Highly Efficient and Reproducible Round-Window Stimulation in Humans Sebastian P. Schraven a Bernhard Hirt a, b Erich Goll a Andreas Heyd a Anthony W. Gummer a Hans-Peter Zenner a Ernst Dalhoff a a Department of Otolaryngology, Section of Physiological Acoustics and Communication, and b Institute of Anatomy, University of Tübingen, Tübingen, Germany Introduction Mechanical stimulation of the cochlea at the round- window (RW) membrane has gained considerable inter- est as an alternative for the coupling of an active middle- ear implant to the ossicular chain, mainly in cases with combined conductive and sensorineural hearing loss. However, current publications [Baumgartner et al., 2010; Boeheim et al., 2010; Colletti et al., 2006; Colletti et al., 2009; Cuda et al., 2009; Frenzel et al., 2009; Kiefer and Staudenmaier, 2010; Linder et al., 2009; Streitberger et al., 2009; Wollenberg et al., 2007] reveal a considerable vari- ability regarding the degree of hearing restoration. To ap- proach this issue, different methods of coupling an ac- tuator to the RW membrane have been investigated in human temporal bone experiments [Arnold et al., 2010; Nakajima et al., 2010]. Experiments included variations such as different orientation, intervening materials be- tween actuator and membrane, and overlaying materials in order to increase the mechanical source impedance of the actuator at low frequencies. However, variability shows up even within one coupling method. Recently, we investigated the stimulation of the RW membrane using metal rods 0.5 mm in diameter without intervening ma- terial [Schraven et al., 2011], and found that the coupling efficiency and its reproducibility increases if the top sur- face of the actuator is carefully aligned with respect to the Key Words Round-window stimulation  Round-window membrane pretension  Active middle-ear implants  Mixed hearing loss Abstract Round-window stimulation is a new clinical approach for the application of active middle-ear implants. To investigate fac- tors influencing the efficiency of round-window stimulation, experiments in 6 human temporal bones were performed with different actuator geometries and coupling conditions. The experiments show that the amplitude ratio between sta- pes and round-window actuator vibration is most efficient when using a 1.0-mm diameter rod with a 30° inclined tip geometry and an attached silicone pad. In this case, the am- plitude ratio is 0.34 for frequencies up to 1.5 kHz and 0.27 for frequencies up to 20 kHz, with a standard deviation of only 4–6 dB at most frequencies. The analysis of data presented here and in a companion paper suggests that control of proper round-window membrane pretension as well as the inclined tip geometry are the major requirements for maxi- mal performance. Copyright © 2011 S. Karger AG, Basel Received: August 15, 2011 Accepted after revision: September 22, 2011 Published online: November 16, 2011 Neurotology Audiology Ernst Dalhoff, PhD, Department of Otolaryngology Section of Physiological Acoustics and Communication University of Tübingen, Elfriede-Aulhorn-Strasse 5 DE–72076 Tübingen (Germany) Tel. +49 7071 298 8232, E-Mail ernst.dalhoff  @  uni-tuebingen.de © 2011 S. Karger AG, Basel 1420–3030/12/0172–0133$38.00/0 Accessible online at: www.karger.com/aud