Performance over time on adults with simultaneous bilateral cochlear implants

Abstract

Background: Maximum performance and long-term stability of bilateral cochlear implants has become an important topic because there has been increasing numbers of recipients of bilateral cochlear implants.

Purpose: To determine the performance over time (up to 6yr) of subjects with simultaneous bilateral cochlear implants (CI+CI) on word recognition and localization.

Research design: Over-time investigation of word recognition in quiet (CNC) and sound localization in quiet (Everyday Sounds Localization Test).

Study sample: The subjects were 48 adults who simultaneously received their cochlear implants at the University of Iowa.

Results: For word recognition, percent correct scores continuously improved up to 1 yr postimplantation with the most benefit occurring within the first month of implantation. In observing up to 72 mo, the averaged scores reached to the plateau of about 63% correct in CNC after 2 yr (N = 31). But, when we followed 17 subjects who have complete data set between 12 mo and 48+ months, word recognition scores were significantly different from 12 mo to 48 + months, which implies binaural advantages need more time to be developed. Localization test results suggested that the root mean square (RMS) error scores continuously improved up to 1 yr postimplantation with most benefits occurring within the first 3 mo. After 2 yr, the averaged scores reached to the plateau of about 20 degrees RMS error (N = 27). When we followed 10 subjects who have complete data set between 12 mo and 48+ months, localization scores were not improved from 12 mo to 48+ months. There were large individual differences in performance over time.

Conclusions: In general, substantial benefits in both word recognition and localization were found over the first 1-12 mo postimplantation for subjects who received simultaneous bilateral cochlear implants. These benefits were maintained over time up to 6yr postimplantation.

Figure 1

Word recognition performance over time. Results are expressed as percent correct and error bars indicate standard errors. 1A shows the average over time bilateral word recognition performance for all 48 CI+CI subjects from pre-implantation through 72 months (6 years) post implantation. 1B shows the average performance over the first 12 months for all 48 subjects with more discreet time increments. It should be noted that not all of the 48 subjects have data at each data point. 1C shows the average performance for 23 subjects who all have data at pre-implant, 6, and 12 months post-implantation. 1D shows individual results for pre-implantation, 6, and 12 months post-implantation for the same 23 subjects shown in 1C.

Figure 2

Word recognition performance overtime for 17 subjects who all have data points at every time period except pre-implantation (6 individuals do not have pre-implant data. Results are expressed as percent correct and error bars indicate standard errors.

Figure 3

Localization performance overtime. Results are expressed as RMS error scores and error bars indicate standard errors. 3A shows the average over time localization performance from a total of 47 subjects from pre-implantation through 72 months (6 years) post-implantation. 3B shows data from the same subjects as in 3A detailing in more discreet time increments the average performance over the first 12 months. It should be noted that not all of the 47 subjects have data at every time increment. 3C shows average performance for 13 subjects who all have data points at pre-implant, 6 months and 12 months post-implantation. 3D demonstrates individual performance during the first 12 months post-implantation for the same subset of 13 subjects shown in 3C.

Figure 4

Localization performance overtime for 10 subjects who all have data points in every time period except pre-implantation (6 individuals do not have pre-implant data). Results are expressed as RMS error scores and error bars indicate standard errors.