Models of Cochlea Used in Cochlear Implant Research: A Review

Abstract

As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstrated much success in providing hearing to those with severe to profound hearing loss. Despite their clinical effectiveness, key drawbacks such as hearing damage, partly from insertion forces that arise during implantation, and current spread, which limits focussing ability, prevent wider CI eligibility. In this review, we provide an overview of the anatomical and physical properties of the cochlea as a resource to aid the development of accurate models to improve future CI treatments. We highlight the advancements in the development of various physical, animal, tissue engineering, and computational models of the cochlea and the need for such models, challenges in their use, and a perspective on their future directions.

Robotic assistance during cochlear implantation: the rationale for consistent, controlled speed of electrode array insertion

“…Insertion forces may be twice as high in synthetic models compared to cadaveric specimens ( 25 ). It is possible that reproducibility of results obtained from cadaveric specimens may vary given the natural variation in cochlear and intracochlear structures/dimensions between bones ( 69 ). Studies also diverge in how forces are measured, e.g., multi-axis versus single-axis measurement, the location of the force sensors, and use of open-channel models ( 69 ).…”

“…It is possible that reproducibility of results obtained from cadaveric specimens may vary given the natural variation in cochlear and intracochlear structures/dimensions between bones ( 69 ). Studies also diverge in how forces are measured, e.g., multi-axis versus single-axis measurement, the location of the force sensors, and use of open-channel models ( 69 ). Finally, studies have used a variety of speeds, electrode types, insertion techniques (e.g., standard versus advance-off stylet), and lubricating fluids.…”

New perspectives for piezoelectric material-based cochlear implants: getting to nano

“…Therefore, four major challenges to be overcome for the future piezoelectric device have been pointed out: 1) Increase the output voltage; 2) Perform a proper fixation to the basilar membrane; 3) Increase the frequency selectivity, as it is naturally performed by outer hair cells that mechanically amplify low-level sound; and, 4) Increase the thickness to improve the piezoelectric performance (Nakagawa and Kawano, 2014). However, due to the small thickness of the basilar membrane, which varies both radially and longitudinally in 0.55-1.16 μm (Liu et al, 2015;Hrncirik et al, 2023), placing a slab even thicker than that used by Inaoka et al (2011), i.e., 40 μm-thick PVDF film, is not realistic. In our opinion, developing thick membranes will not be an option, as this would generate a heavy device, difficult to be properly placed on site, thus hampering the basilar membrane vibration.…”

Impact of Insertion Speed, Depth, and Robotic Assistance on Cochlear Implant Insertion Forces and Intracochlear Pressure: A Scoping Review

“…These models provide a controlled environment for observing and measuring the IFs and transient IP changes that arise during CI insertion. However, as artificial models do not normally contain flexible membranes (basilar and Reissner’s) separating the individual scalae, the findings in these models should be accepted with caution [ 25 ]. It is important to consider data from cadaveric specimens and also from histologic examinations in order to correlate insertion trauma location with the rise of IFs and IP [ 9 , 10 , 11 , 26 ].…”