Research on coupling effects of actuator and round window membrane on reverse stimulation of human cochlea

Abstract

An active actuator of a middle-ear implant coupled to the round window membrane (RWM), which transmits vibration to the cochlea, has been used to compensate for hearing loss in patients. However, various factors affect the coupling condition between the actuator and the RWM, resulting in coupling leakage. In this study, a coupling impedance model of the human ear and the actuator was used to investigate the effect of inefficient coupling during reverse stimulation. First, the three-port circuit network model of the actuator was coupled with the acoustic impedance model of human ear reverse sound transmission. Meanwhile, the inefficient coupling impedance was estimated. Then, the effect of the actuator’s coupling on reverse stimulation was studied by comparing the reverse pressure transfer function. Furthermore, the inefficient coupling’s influence in the ear with middle-ear disorder was also investigated by simulating two typical forms of middle-ear disorder: otosclerosis and ossicular chain disarticulation. The results show that the change of the inefficient coupling impedance plays a significant role during reverse stimulation. Inefficient coupling of the actuator and the RWM deteriorates the cochlear response of reverse stimulation over the entire frequency range. Additionally, the coupling effect of the actuator does not change the influence tendency of middle-ear disorder on reverse stimulation’s performance, but changes the response amplitude of the reverse stimulation.

Round Window Stimulation of the Cochlea

“…Backside loading has been stressed as influencing the performance of an FMT in enhancing its vibratory performance and retention of long-term coupling ( 47 ). Using a coupling impedance model of the human ear, Xue et al ( 48 ) determined that poor coupling resulted in deterioration of responses across the entire frequency ranges with RW stimulation ( 48 ). Liu et al ( 49 ) using a human ear finite-element model comparison of sites of coupling of the RW membrane with that of the umbo, incus body, incus long process, and stapes demonstrated that for an equal force of stimulation applied, the RW produced more efficient cochlear response than equivalent magnitudes of force stimulating the other sites, such as the stapes footplate ( 49 ).…”

Using Stapes Velocity to Estimate the Efficacy of Mechanical Stimulation of the Round Window With an Active Middle Ear Implant

“…Despite some success from RW stimulation, individual outcomes have shown much variability. Numerous animal and human cadaver experiments have explored the AMEI-RW coupling factors that might characterize the variability seen in patient outcomes clinically (3,10,14,(20)(21)(22) and in research (16,(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). These include the angle of AMEI approach, the static loading of the RW, the effects of interposed fascia, reduction of the RW membrane niche, and the size/shape of the AMEI tip (28,(34)(35)(36).…”