Benefits of bilateral cochlear implants and/or hearing aids in children

Abstract

This study evaluated functional benefits from bilateral stimulation in 20 children ages 4 -14, 10 use two CIs and 10 use one CI and one HA. Localization acuity was measured with the minimum audible angle (MAA). Speech intelligibility was measured in quiet, and in the presence of 2-talker competing speech using the CRISP forced-choice test. Results show that both groups perform similarly when speech reception thresholds are evaluated. However, there appears to be benefit (improved MAA and speech thresholds) from wearing two devices compared with a single device that is significantly greater in the group with two CI than in the bimodal group. Individual variability also suggests that some children perform similarly to normal-hearing children, while others clearly do not. Future advances in binaural fitting strategies and improved speech processing schemes that maximize binaural sensitivity will no doubt contribute to increasing the binaurally-driven advantages in persons with bilateral CIs. KeywordsBilateral; Binaural; Cochlear implant; Hearing aid; Children; Speech; Localization Cochlear implants (CIs) have become a powerful means of providing hearing to deaf persons. Although the vast majority of CI users can understand speech in a quiet situation (Zeng, 2004;Stickney et al, 2004;Holt & Kirk, 2005), and report improvement in quality of life postimplantation (Summerfield et al, 2002), they have continued difficulties under many circumstances. For instance, most CI users have difficulty locating sounds in their environments; all sounds appear to be coming either directly from their ear, or inside their head. In addition, their ability to understand speech in everyday, noisy and reverberant environments is quite poor (e.g., Fu et al, 1998;Nelson & Jin, 2004;Stickney et al, 2004Stickney et al, , 2005. Continuous efforts are being made to improve performance with single CIs by developing better speech processing strategies (e.g., Rubinstein & Hong, 2003;Green et al, 2005;Nie et al, 2005;Yang & Fu, 2005).Bilateral CIs (BI-CIs) are also being provided to a growing number of patients in an attempt to increase quality of life and to improve listening in everyday noisy situations. This clinical approach is primarily rooted in the assumption that, since normal-hearing people rely on two ears (binaural hearing) for sound localization and speech understanding in noise, deaf individuals should also have two good ears in order to maximize their performance. Bilaterally implanted adults show some clear and significant benefits when using two CIs compared with a single CI. As in normal hearing persons, speech understanding in noise is better in bilateral NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript users when both ears are activated compared with a monaural condition (Gantz et al, 2002;Tyler et al, 2002;Muller et al, 2002;Litovsky et al, 2004;Schleich et al, 2004). The benefits are thought to arise from a combination of effects, including the head shadow effect, binaural squelch and binaural...

Lateralization of Interimplant Timing and Level Differences in Children Who Use Bilateral Cochlear Implants

“…Further, Galvin and colleagues (Galvin et al 2007) reported that children who received their second CI after 4 years of age did not show any improvement using both implants over unilateral conditions on tests of sound localization after 6-13 months of bilateral experience. Litovsky (Litovsky et al 2006a;Litovsky et al 2006b;Litovsky et al 2004) also report high degrees of variability within groups of implanted children, which could not always be attributed to duration of deafness or length of bilateral implant use. In order to better predict and promote improved outcomes with bilateral cochlear implants, further research is needed to gain understanding into what factors determine localization abilities in these children.…”

“…However, it is not currently known whether bilateral cochlear implantation is sufficient to restore the precision of the normal binaural auditory system required to make interaural sound comparisons. Previous research has shown improved sound localization in children with bilateral implants compared to unilateral implant users (Litovsky, 2004;Grieco-Calub et al, 2008;Van Deun, 2009b). Others have shown that adults with two implants can use inter-implant signal level cues to localize sounds, but are less successful at using inter-implant sound timing cues (van Hoesel and Clark, 1997;van Hoesel and Tyler, 2003;van Hoesel, 2004;Litovsky, 2004).…”

“…Previous research has shown improved sound localization in children with bilateral implants compared to unilateral implant users (Litovsky, 2004;Grieco-Calub et al, 2008;Van Deun, 2009b). Others have shown that adults with two implants can use inter-implant signal level cues to localize sounds, but are less successful at using inter-implant sound timing cues (van Hoesel and Clark, 1997;van Hoesel and Tyler, 2003;van Hoesel, 2004;Litovsky, 2004). To date, no studies have directly investigated the ability of children with bilateral CIs to interpret inter-implant level or timing differences.…”

“…The above research groups have shown that children with bilateral implants have the ability to identify differences in sound sources (Galvin et al 2008;Grieco-Calub et al 2008;Litovsky et al 2006a;Litovsky et al 2006b;Litovsky et al 2004). However, despite observed improvements over unilateral performance, many bilaterally implanted children were not able to localize sounds in space as accurately as their peers with normal hearing.…”

“…However, a number of studies have investigated behavioural measures of bilateral cochlear implant use including free-field sound localization (the identification of sound sources from one of several speakers) (Galvin et al 2007;Galvin et al 2008;Litovsky et al 2006a;Litovsky et al 2006b;Litovsky et al 2004;Van Deun et al 2009b) and measurements of minimum audible angle (MAA) (the smallest discernable change in the location of a sound that can be consistently measured) (Grieco-Calub et al 2008;Litovsky et al 2006a;Litovsky et al 2006b). These studies have shown that many children with bilateral cochlear implants are better at identifying sound sources using two CIs rather than a single CI (Galvin et al 2008;Grieco-Calub et al 2008).…”