Sound Source Localization and Speech Understanding in Complex Listening Environments by Single-sided Deaf Listeners After Cochlear Implantation

Abstract

Objective To assess improvements in sound source localization and speech understanding in complex listening environments following unilateral cochlear implantation for single-sided deafness (SSD). Study Design Non-randomized, open, prospective case series Setting Tertiary referral center Patients Nine subjects with a unilateral cochlear implant (CI) for SSD (SSD-CI) were tested. Reference groups for the task of sound source localization included young (n=45) and older (n=12) normal hearing (NH) subjects and 27 bilateral CI (BCI) subjects. Intervention Unilateral cochlear implantation Main outcome measures Sound source localization was tested with 13 loudspeakers in a 180 arc in front of the subject. Speech understanding was tested with the subject seated in an 8-loudspeaker sound system arrayed in a 360-degree pattern. Directionally appropriate noise, originally recorded in a restaurant, was played from each loudspeaker. Speech understanding in noise was tested using the Azbio sentence test and sound source localization quantified using root mean square error. Results All CI subjects showed poorer-than-normal sound source localization. SSD-CI subjects showed a bimodal distribution of scores - six subjects had scores near the mean of those obtained by BCI subjects, while three had scores just outside the 95th percentile of NH listeners. Speech understanding improved significantly in the restaurant environment when the signal was presented to the side of the CI. Conclusions Cochlear implantation for SSD can offer improved speech understanding in complex listening environments and improved sound source localization in both children and adults. On tasks of sound source localization, SSD-CI patients typically perform as well as BCI patients and, in some cases, achieve scores at the upper boundary of normal performance.

Binaural Perception in Single-Sided Deaf Cochlear Implant Users with Unrestricted or Restricted Acoustic Hearing in the Non-Implanted Ear

“…While there was a limited number of subjects in this study, the data consistent with previous SSD studies [Cabral et al, 2016;Dorman et al, 2016;Finke et al, 2017;Firszt et al, 2012a, b;Kuppler et al, 2013;Kitoh et al, 2016;Mertens et al, 2015aMertens et al, , 2017Nawaz et al, 2014;Rahne and Plontke, 2016;Távora-Vieira et al, 2015;Tokita et al, 2014;Van de Heyning et al, 2008;Vermeire and Van de Heyning, 2009;Zeitler et al, 2015].…”

“…Localization was significantly better with the CI on, consistent with previous studies [Dorman et al, 2016;Firszt et al, 2012a, b;Mertens et al, 2015a;Nawaz et al, 2014;Távora-Vieira et al, 2015;Vermeire and Van de Heyning, 2009;Zeitler et al, 2015]. The mean improvement in RMSE across all subjects was 13.8°, with better localization in 13 of 18 subjects.…”

“…When speech and noise were spatially separated (S CI N NH ), performance was significantly better with the CI on, consistent with previous studies [Finke et al, 2017;Mertens et al, 2017;Rahne and Plontke, 2016;Vermeire and Van de Heyning, 2009;Zeitler et al, 2015]. CI benefits were observed for all subjects except S10, who did not wear the CI every day.…”

“…Mean RMSE with the CI on (48.7°) remained much poorer than that of the NH control group (16.8°). Mean localization across all subjects was also somewhat poorer than reported in previous SSD CI studies [Arndt et al, 2011;Dorman et al, 2016;Firszt et al, 2012a;Távora-Vieira et al, 2015;Zeitler et al, 2015], possibly due to study differences in terms of the experimental setup (speaker placement and spacing, stimulus type level roving, etc.) and the inclusion of SSD subjects with mild-to-moderate hearing loss.…”

“…For SSD patients, restoration of binaural function is possible with a cochlear implant (CI). A number of studies have shown that CI can improve SSD patients' localization, speech understanding in noise, and QoL [Cabral et al, 2016;Dorman et al, 2016;Finke et al, 2017;Firszt et al, 2012a, b;Kuppler et al, 2013;Kitoh et al, 2016;Mertens et al, 2015aMertens et al, , b, 2017Nawaz et al, 2014;Rahne and Plontke, 2016;Távora-Vieira et al, 2015;Tokita et al, 2014;Van de Heyning et al, 2008;Vermeire and Van de Heyning, 2009;Zeitler et al, 2015]. Many SSD patients also are affected by debilitating tinnitus, for which there is no consistently effective intervention.…”