A systematic review of electric-acoustic stimulation: device fitting ranges, outcomes, and clinical fitting practices

Abstract

Cochlear implant systems that combine electric and acoustic stimulation in the same ear are now commercially available and the number of patients using these devices is steadily increasing. In particular, electric-acoustic stimulation is an option for patients with severe, high frequency sensorineural hearing impairment. There have been a range of approaches to combining electric stimulation and acoustic hearing in the same ear. To develop a better understanding of fitting practices for devices that combine electric and acoustic stimulation, we conducted a systematic review addressing three clinical questions: what is the range of acoustic hearing in the implanted ear that can be effectively preserved for an electric-acoustic fitting?; what benefits are provided by combining acoustic stimulation with electric stimulation?; and what clinical fitting practices have been developed for devices that combine electric and acoustic stimulation? A search of the literature was conducted and 27 articles that met the strict evaluation criteria adopted for the review were identified for detailed analysis. The range of auditory thresholds in the implanted ear that can be successfully used for an electric-acoustic application is quite broad. The effectiveness of combined electric and acoustic stimulation as compared with electric stimulation alone was consistently demonstrated, highlighting the potential value of preservation and utilization of low frequency hearing in the implanted ear. However, clinical procedures for best fitting of electric-acoustic devices were varied. This clearly identified a need for further investigation of fitting procedures aimed at maximizing outcomes for recipients of electric-acoustic devices.

Conflict of interest statement

Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the authorship and publication of this article.

Figures

Figure 1.

Median change in low frequency thresholds dB HL ± SD for various electrode array studies.

Figure 2.

Preoperative versus postoperative word scores in quiet (Mean ± SD) in implanted ear for various array studies. Closed symbols represent electric stimulation alone. Open symbols represent combined acoustic & electric stimulation.

Figure 3a.

EAS benefit for implanted ear in Quiet: Electric only stimulation (CI) versus Acoustic & Electric Stimulation (CI+HAi) word scores (Mean ± SD) for various electrode array studies.

Figure 3b.

EAS benefit for implanted ear in Noise: Electric only stimulation (CI) versus Acoustic & Electric Stimulation (CI+HAi) scores (Mean ± SD) for various electrode array studies.