Changes in children's speech discrimination and spatial release from masking between 2 and 4 years after sequential cochlear implantation

Abstract

Objective: To document changes in speech reception thresholds (SRTs) and spatial release from masking (SRM) for sequentially implanted children at 2 and 4 years after they received their second cochlear implant (CI₂).

Methods: Participants were 17 children who consistently used two sequentially implanted and optimally programmed CIs. SRTs were measured monaurally in quiet and binaurally in noise using the adaptive McCormick toy discrimination test. Speech signals were presented from 0° azimuth and noise from 0°, +90° or −90° azimuth. SRM was calculated from SRTs in noise. Measurements were made at 2 and 4 year post-CI₂.

Results: There were significant improvements over time in SRTs in quiet, SRTs in noise and SRM. SRTs in quiet improved more for CI₂ than for the first implant (CI₁). SRTs in noise and SRM improved more when noise was presented closest to CI₁ than when closest to CI₂. Performance became more symmetrical over time.

Discussion: Despite prolonged periods of unilateral auditory deprivation sequentially implanted children exhibited continued improvement in SRT and SRM. These results are valuable in setting expectations for and counselling families of children considering sequential CIs.

Keywords:

• Cochlear implants
• Bilateral
• Spatial release from masking
• Speech Discrimination
• Sequential
• Speech reception Thresholds
• speech intelligibility

Notes

²For multiple hypotheses testing a Bonferroni-corrected significance level of P < 0.01 was used.

1 For this and all subsequent models reported here, greatest variation was seen at the measurement (within-participant) level, with only minimal variation seen at the participant (between-participant) level. This is in keeping with the longitudinal design of this study. For all models the residuals were confirmed as being normally distributed with the mean of zero.