New options for rehabilitation of conductive hearing loss Tests on normal-hearing subjects with simulated hearing loss

Background Bone conduction hearing aids can be worn as noninvasive devices using a clip or soft band that exerts pressure on the skin, or they can be surgically implanted. ADHEAR (MED-EL GmbH, Innsbruck, Austria) is a novel noninvasive bone conduction hearing aid that is attached behind the ear using an adhesive adapter and does not exert pressure on the skin. ADHEAR is indicated for patients with conductive hearing loss and normal inner ear function. The aim of this study was to evaluate the achievable hearing improvement with ADHEAR. Materials and methods Twelve subjects with normal hearing participated in this study. To mimic conductive hearing loss, the participants' ear canals were occluded unilaterally with a foam ear plug. The resultant conductive hearing loss was assessed with pure tone air- and bone-conduction threshold audiometry. Hearing ability was tested with and without ADHEAR via free-field tone audiometry, number perception, and monosyllable perception, with the contralateral ear plugged depending on test requirements. Results Using ADHEAR, the free-field hearing threshold improved by 13.7dB at 500Hz, by 17.9dB at 1kHz, by 17.2dB at 2kHz, and by 9.8dB at 4kHz. In the higher frequencies, a significant pure-tone gain of 14.4dB at 6kHz and of 16.5dB at 8kHz was observed. Number perception with ADHEAR was mean 69.2% at 35dB, 97.9% at 50dB, 100% at 65dB, and 100% at 80dB. Monosyllable perception with the ADHEAR was mean 35.0% at 35dB, 72.3% at 50dB, 93.5% at 65dB, and 98.8% at 80dB. Conclusion Hearing performance was significantly better with ADHEAR under all test conditions except those where maximum perception was already achieved without ADHEAR.