SS06: ACTIVE MIDDLE EAR IMPLANTS AND MHL

FIRST RESULTS WITH THE DACS (DIRECT ACOUSTIC COCHLEAR STIMULATION) IMPLANTABLE HEARING SYSTEM

M. Kompis (1) C. Stieger (1), H. Bernhard (2) and  R. Haeusler (1).

(1) Department of ENT, Head, Neck Surgery, University of Berne, Switzerland; (2) Helbling Technik Bern AG, Liebefeld, Switzerland.

Results with the direct acoustic cochlear stimulator (DACS) implantable hearing system are presented. This system is based on the principle of a power-driven stapes prosthesis and intended for the treatment of severe mixed hearing loss due to advanced otosclerosis. It consists of an implantable electromagnetic transducer, which transfers acoustic energy directly to the inner ear, and an audio processor worn externally behind the implanted ear.
The device is implanted using a specially developed retromeatal microsurgical approach. After removal of the stapes, a conventional stapes prosthesis is attached to the transducer and placed in the open window to allow direct acoustical coupling to the perilymph of the inner ear. In order to restore the natural sound transmission of the ossicular chain, a second stapes prosthesis is placed in parallel to the first one into the oval window and attached to the patient’s own incus, as in a conventional stapedectomy.

Four patients were implanted with an investigational DACS device. The hearing threshold of the implanted ears before implantation ranged from 78 to 101 dB (Air conduction, pure tone average PTA, 0.5 – 4 kHz) with air-bone-gaps of 33 to 44 dB in the same frequency range.

Postoperatively, substantial improvements in sound field thresholds, speech intelligibility as well as in the subjective assessment of everyday situations were found in all patients. Two years after the implantations, monosyllabic word recognition scores in quiet at 75 dB improved by 45 to 100 percent points when using the DACS. Furthermore, hearing thresholds were already improved by the second stapes prosthesis alone by 14 to 28 dB (PTA 0.5 - 4 kHz, DACS switched off). No device related serious medical complications occurred and all patients have continued to use their device on a daily basis for over two years.