Acoustic plus electric speech processing: Long-term results

Abstract

Objective: Few studies have investigated the stability of residual hearing and speech perception outcomes in individuals who were implanted with a shorter electrode device.

Study design: Longitudinal, single-subject design.

Methods: Fifty subjects who received a Nucleus Hybrid (Cochlear, Sydney, Australia) short electrode cochlear implant (CI) and had a minimum of 2 years (and up to 15 years) of postoperative longitudinal experience were included in this study. Twenty-three subjects received a Nucleus Hybrid S8 (S8); 14 subjects received a Nucleus Hybrid L24 (L24); and 13 received a Nucleus Hybrid S12 (S12). Audiometric thresholds and consonant-nucleus-consonant (CNC) words were collected pre- and postoperatively for up to 15 years for the S8 subjects and for up to 7 years for the S12 and L24 subjects. AzBio Sentences in multi-talker babble was collected for up to 7 years on the S12 and L24 subjects.

Results: Longitudinally, 83% of the S8 subjects, 92% of the S12 subjects, and 86% of the L24 subjects maintained a functional hearing pure-tone average (PTA) (125-500 Hz). Predicted change using a piecewise linear mixed model in PTA over time showed a postoperative linear decrease in hearing for each group until 0.5 years, after which the PTA stabilizes and is maintained. The averaged individual data for CNC and AzBio sentences show a significant improvement in scores by 0.25 to 0.5 years postimplantation, after which scores start to reach their maximum.

Conclusion: This long-term study demonstrates that acoustic-electric processing hearing and improvement in speech understanding in quiet and in noise can be accomplished and sustained for many years with a short electrode CI.

Level of evidence: 2C. Laryngoscope, 128:473-481, 2018.

Keywords: Hybrid; cochlear implant; long-term; residual hearing.

Figure 1

Individual and modeled longitudinal hearing preservation using a three-frequency pure-tone-average (PTA) from 125 to 500 Hz. Panel A shows PTAs for the S8 subjects; Panel B for the S12 subjects; and Panel C for the L24 subjects. Panel D shows the modeled PTAs for each of the Hybrid groups over time. The light gray dashed line in each of the panels represents the threshold that is considered to be non-functional hearing. The black dashed line represents the averaged PTA longitudinally.

Figure 2

Individual most recent post-operative thresholds from 125–500 Hz. Panel A shows thresholds for the S8 subjects; Panel B for the S12 subjects; and Panel C for the L24 subjects. Panel D shows the averaged preoperative and most recent postoperative thresholds from 125–500 Hz for each of the Hybrid groups.

Figure 3

Individual and modeled longitudinal speech perception outcomes for CNC words in the Combined listening condition (bilateral hearing aids and the CI). Panel A shows scores for the S8 subjects; Panel B for the S12 subjects; and Panel C shows for the L24 subjects. The gray dashed lines within each panel show the outcomes for the subjects that lost their residual hearing. These patients were tested in the Bimodal listening condition (the CI reprogrammed to provide both low- and high-frequency information in one ear and hearing aid in the contralateral ear). The black dashed line within Panels A-C show the averaged outcomes at each time point. Panel D shows the modeled preoperative CNC score using bilateral hearing aids and longitudinally in the Combined condition following implantation for each of the subjects in the Hybrid groups.

Figure 4

Individual and modeled longitudinal speech perception outcomes for AzBio Sentences in Noise in the Combined listening condition. Panel A shows scores for the S12 subjects and Panel B shows scores for the L24 subjects. The gray dashed lines within each panel show the outcomes for the subjects that lost their residual hearing. These patients were tested in the bimodal condition. The black dashed line within Panel A and B show the averaged outcomes at each time point.

Figure 5

Averaged CNC performance for Hybrid users (N=43) in the Combined condition, Hybrid subjects who lost hearing in the Bimodal condition (N=7), standard-length electrode bimodal users (N=28), simultaneous bilateral standard-length electrode users (N=33), and standard-length electrode unilateral users (n=33).