(PP808) Influence of Test Configuration on Performance for Cochlear Implant Users with Single-Sided Deafness

      The indications for cochlear implantation expanded to include children and adults with single-sided deafness (SSD). Benefit with the cochlear implant (CI) can be observed on spatial hearing measures, such as speech recognition in spatially-separated noise. Performance may vary as a function of the location of the masker relative to the target speech. Speech recognition of adult CI users with SSD was assessed with the masker in different locations on the horizontal plane. The largest benefit was observed when the masker was 90^o towards the CI-ear. These data may support the development of clinical test protocols for CI users with SSD.

Summary: 

Purpose: Individuals with unilateral moderate-to-profound sensorineural hearing loss, or single-sided deafness (SSD), have poorer speech recognition in noise than individuals with normal hearing (NH) bilaterally due to limited access to binaural cues. Cochlear implant (CI) recipients with SSD typically demonstrate better speech recognition in noise when listening with a CI plus the NH ear (CI+NH) as compared to listening with rerouting technologies or the NH ear alone. The clinical test battery for conventional CI recipients typically includes assessment with the target and masker co-located, which limits the ability to measure binaural hearing benefits. The present study assessed the influence of masker locations on the performance of CI+NH listeners to assist in the expansion of clinical protocols to assess binaural hearing.

Methods: Speech recognition in noise was assessed in 5 masker locations for experienced CI+NH listeners. Listeners were recruited at the 2-year post-activation visit. Participants sat in a double-walled sound booth in the center of an 180º arc of loudspeakers. The target speech was presented from the front speaker at 0º azimuth. The masker was presented either co-located with the target (SoNo), 90º towards the CI-ear (SoNci90), 45º towards the CI-ear (SoNci45), 90º towards the NH-ear (SoNnh90), or 45º towards the NH-ear (SoNnh45). Test materials included the AzBio sentences in a 10-talker masker (0 dB SNR) and the BKB-SIN. Spatial release from masking (SRM) was calculated as the difference in performance when the masker was spatially-separated versus co-located with the target speech.

Results: Sixteen adult CI users with SSD provided data. For both tests, performance was significantly better when the masker was towards the CI-ear versus when towards the NH-ear. For example, SRM ranged from 15 to 58% (mean: 35%) when the masker was 90º towards the CI-ear and from -28 to 27% (mean: 4%) when the masker was 90º towards the NH-ear for the AzBio sentences. The AzBio sentences in noise test demonstrated similar performance when the masker was 45 or 90^o toward either side. For the BKB-SIN, pairwise comparisons found a better performance when the masker was 90º towards the CI-ear compared to 45º towards the CI-ear.

Conclusions: Investigations of binaural hearing for CI+NH listeners vary in test materials and target-to-masker locations. The current study observed differences in performance as a function of the masker location for test materials included in the Minimum Speech Test Battery. For both test materials, the largest benefit was observed when the masker was 90^o towards the CI-ear. The clinical protocol at the study site was expanded to assess speech recognition in noise with the masker co-located with the target speech or 90º towards either ear to assess binaural hearing benefits with CI use.