Comparison of Aided and Unaided Thresholds and Selection Processes of Contralateral Routing of Signal Hearing Aids and Implantable Bone Conduction Devices in Patients with Asymmetric Hearing Loss

Abstract

Background and Objectives We reviewed the selection processes of contralateral routing of signal (CROS) hearing aids (HAs) and bone-conduction (BC) Has, and compared aided and unaided hearing thresholds. Subjects and Method Twenty-four patients with asymmetrical hearing loss who used BC HAs (n=12) and CROS HAs (n=12) were enrolled. The choice of two different HAs were compared with respect to the degree of hearing loss, the unaided hearing thresholds and functional gains. Results When the hearing thresholds of the better hearing ears were ＞30 dB HL, most (92%, 11 of 12) chose CROS rather than BC HAs, with significant difference (p=0.001). Both CROS and BC HAs groups showed significantly improved functional gains (46.6 dB and 53.4 dB, respectively). Aided air-conduction (AC) thresholds (40.2 dB HL) in the CROS group were similar to the AC thresholds (43.1 dB HL) of better hearing ears. However, the hearing threshold of Aided AC thresholds (35.8 dB HL) in BC HAs group were less than the BC thresholds (17.3 dB HL) of better hearing ears by 19 dB (p＜0.001). Conclusion Both groups showed significantly increased functional gains. CROS HAs were preferred when hearing thresholds in better hearing ears were ＞30 dB HL. The CROS group showed aided thresholds similar to the thresholds of better hearing ears, but the BC HAs group showed poorer aided thresholds than the thresholds of better hearing ears. For patients with asymmetric hearing loss, HAs should be selected based on the degree and types of hearing loss and the maximum output level of the selected device. Key words: Bone conduction ㆍ Contralateral routing of signal ㆍ Deafness ㆍ Hearing aids ㆍ Hearing loss ㆍ Single-sided