Sequential Bilateral Cochlear Implantation in Children: Development of the Primary Auditory Abilities of Bilateral Stimulation

Abstract

The advantages of sequential bilateral cochlear implantation were assessed in 29 children with a severe to profound hearing loss. The effect of age at second implantation and the effect of duration of bilateral implant use on the outcomes in speech perception and directional hearing were investigated. The children received their second cochlear implant at an age ranging from 2.8 to 8.5 years. Measurements were carried out preoperatively and postoperatively after 6, 12 and 24 months of bilateral implant use. A matched control group of 9 children with a unilateral implant were also measured over time and were compared with the study group after 12 and 24 months. Speech reception in both quiet and in noise and lateralization were measured. After 24 months, a minimum audible angle task was carried out. Bilateral advantages with regard to speech reception in quiet and in noise were already present after 6 months of bilateral implant use and improved thereafter. After 24 months, speech reception in noise had significantly improved with bilateral implants compared to that of children with a unilateral implant. The percentage of children that could accurately lateralize increased from 57% after 6 months to 83% after 24 months. With regard to the minimum audible angle task, loudspeakers were placed on average at ±42°. Age at second implantation did not have an influence on all outcomes. From the results it can be concluded that the advantages of bilateral hearing occur after sequential bilateral implantation and that age at second implantation does not influence the amount of bilateral advantage. Furthermore, it can be concluded that longer periods of bilateral implant use lead to greater bilateral advantages.

A Longitudinal Study in Children With Sequential Bilateral Cochlear Implants: Time Course for the Second Implanted Ear and Bilateral Performance

“…Bilateral performance was significantly better than either ear alone at the 18-month and 3-year test intervals for children receiving CI2 before 8 years of age and by the 2-year test interval for children receiving CI2 after 8 years of age. In contrast, Sparreboom et al (2011) identified an early bilateral advantage at the 6-month test interval that was no longer present at the 12-and 24-month intervals.…”

“…Studies of children receiving CI2 at a younger age have reported bilateral lateralization or localization benefit. Sparreboom et al (2011) reported significant bilateral improvement at the 24-month postbilateral interval. Sound localization improved significantly for 74%-83% of participants across visits in Asp et al (2015) and sound localization was significantly related to age at CI2.…”

“…Similar results for speech in quiet were found by Scherf et al (2009), in that children receiving a second implant by 6 years of age had similar abilities to CI1 after 2 years of bilateral experience. In contrast, two separate studies reported CI2 performance significantly poorer than CI1 at the 2-year test interval for children receiving CI2 prior to (Sparreboom, Snik, & Mylanus, 2011) or near (Strom-Roum, Laurent, & Wie, 2012) 8 years of age. Bilateral performance surpassed CI1-alone performance by 2 years of bilateral use for children receiving their second implant before or after age 6 years in the Scherf et al (2009) and Sparreboom et al (2011) studies and by 1 year of bilateral use in the Strom-Roum, Laurent, and Wie (2012) study.…”

“…In contrast, two separate studies reported CI2 performance significantly poorer than CI1 at the 2-year test interval for children receiving CI2 prior to (Sparreboom, Snik, & Mylanus, 2011) or near (Strom-Roum, Laurent, & Wie, 2012) 8 years of age. Bilateral performance surpassed CI1-alone performance by 2 years of bilateral use for children receiving their second implant before or after age 6 years in the Scherf et al (2009) and Sparreboom et al (2011) studies and by 1 year of bilateral use in the Strom-Roum, Laurent, and Wie (2012) study. Peters et al (2007) did not identify bilateral benefit at the 12-month test interval; however, scores approached ceiling and may not have allowed identification of bilateral benefit.…”

“…For 11 bilaterally implanted children tested at two sessions 7-21 months apart, four children showed some improvement (>10°root-mean-square [RMS] error) and seven children had no substantial change (Grieco-Calub & Litovsky, 2010). Sparreboom et al (2011) included a lateralization task in their longitudinal study of sequentially implanted children. After 6 months of bilateral experience, 57% of the children tested had some lateralization ability; this increased to 63% of children after 12 months.…”