Conditions for Highly Efficient and Reproducible Round-Window Stimulation in Humans

Abstract

Round-window stimulation is a new clinical approach for the application of active middle-ear implants. To investigate factors 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 stapes 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 amplitude 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 maximal performance.

A novel mechanism of cochlear excitation during simultaneous stimulation and pressure relief through the round window

“…On the basis of our findings reported here, we propose that the pressure shunting occurred through the area of the RW which remained exposed. This proposal is also supported by the findings of Schraven et al [32], who tested different sized actuator tips and their coupling to the RW. Schraven et al [32] found that stimulation by actuators with tip sizes well below the dimensions of the RW resulted in reduced stapedial movements compared with those tips that covered most of the RW.…”

“…This proposal is also supported by the findings of Schraven et al [32], who tested different sized actuator tips and their coupling to the RW. Schraven et al [32] found that stimulation by actuators with tip sizes well below the dimensions of the RW resulted in reduced stapedial movements compared with those tips that covered most of the RW. This result could be accounted for if the free exposed area of the RW acted as a pressure shunt.…”

Vibro-EAS

“…To guarantee reproducible positioning of the temporal bone and to control the relative position of the temporal bone and its azimuthal angle with respect to the LDV beam, the specimen was placed on an adjustment-stage setup composed of an upper section (three-axis goniometric adjustment stage) and a lower section (rotary table and an xyz-translational stage) (16,17). The spatial angle between the surface normal of the stapes footplate and the LDV laser beam was estimated to be 40 to 60 degrees.…”

Alternative Fixation of an Active Middle Ear Implant at the Short Incus Process

“…To guarantee reproducible positioning of the temporal bone and to control the relative position of the temporal bone and its azimuthal angle with respect to the LDV beam, the specimen was placed on an adjustment-stage setup composed of an upper section (3-axis goniometric adjustment stage) and a lower section (rotary table and an xyz-translational stage) [Schraven et al, 2011;Schraven et al, 2012]. The spatial angle between the surface of the stapes footplate and the LDV laser beam was 40-60°.…”