Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments

Abstract

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

Comparison of sheep and human middle-ear ossicles: anatomy and inertial properties

“…According to studies by Seibel et al ( 2006a , b ), the average size of the middle and inner ears of the sheep is approximately two-thirds the average size of the middle and inner ears of the human. Thereby, the sheep has been used for research on bone conduction (Gerhardt et al 1996 ; McFadde et al 2008 ), training of middle- and inner ear surgeries (Gocer et al 2007 ; Cordero et al 2011 ; Mantokoudis et al 2015 ), and assessment of new surgical techniques and hearing devices (Lavinsky et al 1999 ; Neudert et al 2010 ; Miller et al 2014 ; Larsson et al 2015 ; Pfiffner et al 2018 ).…”

Packaging Technology for an Implantable Inner Ear MEMS Microphone

“…This sensor is not implantable and does not feature a multi-diaphragm design but it did further validate the LEM and is frequently used for investigations of the cochlea hydrodynamics. A detailed description of the design, fabrication and testing of that sensor is published in References [13,15].…”

“…The microphone housing and the ground plane of the FCB are electrically interconnected for EMI shielding. For testing a printed circuit board (PCB) including an amplifier unit (gain = 50, type OP ADA4004, Analog Devices, Norwood, MA, USA) and a power supply circuitry was interconnected with the MEMS CMIC over the integrated FCB cable [15].…”

“…( a ) Computer-aided-design (CAD) drawing of the MEMS condenser microphone (MEMS CMIC) installed in customized Ti housing. The drawing shows the non-planar arrangement of the MEMS chip and ASIC that allows a housing geometry with an optimal form-factor to be used for ICAR insertion into the inner ear (adapted from Reference [15]) and ( b ) the assembled flexural circuit board (FCB) before installation of the microphone enclosure.…”

“…In another study, acute in vivo animal experiments were performed to verify the surgical intervention required for the implantation of the ICAR. The partially implantable prototype of the ICAR used for these experiments and the outcome of the study are published in Pfiffner et al, 2018 [15].…”