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

Objective: To document changes in speech reception thresholds (SRTs) and spatial release from masking (SRM) for sequentially implanted children at two and four years after they received their second cochlear implant (CI2). Methods: Participants were 17 children who consistently used two sequentially implanted and optimally programmed cochlear implants. 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 two and four years 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 cochlear implants.