Bone conductive implantation in asymmetric hearing loss (AHL)

Background: Bone conductive implants (BCI) represent one possible solution for rehabilitation of single sided deafness (SSD), being able to restore a pseudo-stereophonic hearing when the hearing threshold of the contralateral ear is normal. Objectives: The aim of the present study was to verify the efficacy of bone conduction implantation in subjects with unilateral severe-to-profound hearing loss and contralateral mild-to-moderate hearing loss, i.e. asymmetric hearing loss (AHL), and to compare it with known indications for SSD. Method: Twenty-one subjects, 9 females and 12 males, with a mean age of 55.6 years received BCI for either SSD or AHL. All of the subjects underwent a battery of audiological tests, including free-field pure tone audiometry (PTA) and free-field speech audiometry in quiet and in noise and under unaided and aided conditions. All subjects were administered subjective evaluation tests regarding quality of sound (QoS) and life (QoL), along with 2 questionnaires: the Glasgow Benefit Inventory (GBI) and the General Satisfaction for Bone Anchored Hearing Aids (proposed by the former manufacturer). Data were collected and statistically evaluated within and between the SSD group and the AHL group. Results: A PTA threshold gain was observed in AHL patients. The speech audiometry test in quiet showed an improvement in speech recognition of between 10% and 18% in AHL patients and of less than 10% in SSD patients. The speech audiometry test in noise showed improved values only in AHL patients. The two visual-analogue-scale evaluations (QoL and QoS) and the GBI showed significantly better scores in AHL patients compared to SSD patients.