Assessment of a Direct Acoustic Cochlear Stimulator

Abstract

This study aimed to assess the functional results of a new, active, acoustic-mechanical hearing implant, the Direct Acoustic Cochlear Stimulation Partial Implant (DACS PI), in a preclinical study. The DACS PI is an electromagnetic device fixed to the mastoid by screws and coupled to a standard stapes prosthesis by an artificial incus (AI). The function of the DACS PI-aided reconstruction was assessed by determining: (1) the maximum equivalent sound pressure level (SPL) of the implant, which was obtained from measurements of the volume displacement at the round window in normal and implanted ears, and (2) the quality at the coupling interface between the AI of the DACS and the stapes prosthesis, which was quantified from measurements of relative motions between the AI and the prosthesis. Both measurements were performed with fresh temporal bones using a scanning laser Doppler interferometry system. The expected maximum equivalent SPL with a typical driving voltage of 0.3 V was about 115–125 dB SPL up to 1.5 kHz in reconstruction with the DACS PI, and decreased with a roll-off slope of about 65 dB/decade, reaching 90 dB SPL at 8 kHz. The large roll-off relative to a normal ear was presumed to be a relatively high inductive impedance of the coil of the DACS PI actuator at higher frequencies. Good coupling quality between the AI and the prosthesis was achieved below the resonance (∼1.5 kHz) of the DACS PI for all tested stapes prostheses. Above the resonance, the SMart Piston, which is composed of a shape-memory alloy, had the best coupling quality.

The Codacs™ Direct Acoustic Cochlear Implant Actuator: Exploring Alternative Stimulation Sites and Their Stimulation Efficiency

“…The output generated by the DACS PI with piston stimulation was determined by Chatzimichalis et al [ 22 ] reconstructing the integral RW volume displacement from multi-point LDV measurements. They determined an output level of approx.…”

Sound Transfer of Active Middle Ear Implants

“…A self-crimping prosthesis was recommended for the use with the DACS PI System. 65 Lenarz and colleagues 66 introduced a clinical multicenter study of 15 patients with severe to profound mixed hearing loss because of otosclerosis with the CODACS System and found a mean sound field threshold (0.25-8 kHz) improvement of 48 dB. In addition to the DACS, the VSB is suitable for otosclerosis surgery as described by Dumon.…”

Implantable Hearing Devices

“…The DACS (Phonak Acoustic Implants SA, Switzerland) is a partially implantable hearing device for moderate to severe mixed hearing loss [42,43]. Both Phonak Acoustic Implants SA and Cochlear originally collaborated on the development of the system [44].…”

“…The DACS (a.k.a. DACS-PI) was primarily investigated for use with advanced otosclerosis using the idea of applying a power-driven stapes piston to stimulate the cochlea directly rather than performing a traditional stapedectomy and then utilizing a conventional hearing aid to overcome any remaining conductive or sensorineural hearing loss [42,43,45]. Recommended audiometric criteria for bone conduction thresholds are between 40 and 80 dB [44].…”