Binaural Auditory Outcomes in Patients with Postlingual Profound Unilateral Hearing Loss: 3 Years after Cochlear Implantation

Abstract

The value of cochlear implants (CI) in patients with profound unilateral hearing loss (UHL) and tinnitus has recently been investigated. The authors previously demonstrated the feasibility of CI in a 12- month outcome study in a prospective UHL cohort. The aim of this study was to investigate the binaural auditory outcomes in this cohort 36 months after CI surgery. The 36-month outcome was evaluated in 22 CI users with postlingual UHL and severe tinnitus. Twelve subjects had contralateral normal hearing (single-sided deafness - SSD group) and 10 subjects had a contralateral, mild to moderate hearing loss and used a hearing aid (asymmetric hearing loss - AHL group). Speech perception in noise was assessed in two listening conditions: the CIoff and the CIon condition. The binaural summation effect (S₀N₀), binaural squelch effect (S₀NCI) and the combined head shadow effect (SCIN₀) were investigated. Subjective benefit in daily life was assessed by means of the Speech, Spatial and Qualities of Hearing Scale (SSQ). At 36 months, a significant binaural summation effect was observed for the study cohort (2.00, SD 3.82 dB; p < 0.01) and for the AHL subgroup (3.34, SD 5.31 dB; p < 0.05). This binaural effect was not significant 12 months after CI surgery. A binaural squelch effect was significant for the AHL subgroup at 12 months (2.00, SD 4.38 dB; p < 0.05). A significant combined head shadow and squelch effect was also noted in the spatial configuration SCIN₀ for the study cohort (4.00, SD 5.89 dB; p < 0.01) and for the AHL subgroup (5.67, SD 6.66 dB; p < 0.05). The SSQ data show that the perceived benefit in daily life after CI surgery remains stable up to 36 months at CIon. CI can significantly improve speech perception in noise in patients with UHL. The positive effects of CIon speech perception in noise increase over time up to 36 months after CI surgery. Improved subjective benefit in daily life was also shown to be sustained in these patients.