Earlier Intervention Leads to Better Sound Localization in Children with Bilateral Cochlear Implants

Abstract

We present sound localization results from 30 children with bilateral cochlear implants. All children received their implants sequentially, at ages from 6 months to 9 years for the first implant and 1.5–12 years for the second implant, with delays of 10 months to 9 years. Localization was measured in the sound field, with a broadband bell-ring presented from 1 of 9 loudspeakers positioned in the frontal horizontal plane. The majority of the children (63%) were able to localize this signal significantly better than chance level. Mean absolute error scores varied from 9 to 51° (root mean square error scores from 13 to 63°). The best scores were obtained by children who received their first implant before the age of 2 years and by children who used hearing aids prior to implantation for a period of 18 months or longer. Age at second implantation was important in the group of children who did not use a contralateral hearing aid during the unilateral implant period. Additionally, children who attended a mainstream school had significantly better localization scores than children who attended a school for the deaf. No other child or implantation variables were related to localization performance. Data of parent questionnaires derived from the Speech, Spatial and Qualities of Hearing Scale were significantly correlated with localization performance. This study shows that the sound localization ability of children with bilateral cochlear implants varies across subjects, from near-normal to chance performance, and that stimulation early in life, acoustically or electrically, is important for the development of this capacity.

The Development of Lateralization Abilities in Children with Bilateral Cochlear Implants

“…This may indicate either that a longer duration of hearing loss leads to loss of the ability to access binaural cues, even when hearing is stimulated later on in life, or that these 2 subjects never completely developed binaural hearing. Similarly, in the study of Van Deun et al [21], the children who scored best on localization used hearing aids for 18 or more months before implantation or were first implanted before the age of 2. Steffens et al [18] suggest that initial binaural auditory experience is related to the high bilateral localization abilities of postmeningitic children reported in their study.…”

“…The authors, Bauer et al [17], suggested that this was related to the high degree of plasticity of the system, which allowed potential development of these binaural skills. A number of recent studies have confirmed and elaborated on children's potential to use bilateral CIs to achieve or recover binaural hearing advantages in speech perception and localization [18,19,20,21,22,23]. However, research by Peters et al [24] and Galvin et al [25,26,27] has reported more modest benefits for localization, if any.…”

“…Studies have shown that bilateral implantation assists in restoring mainly interaural level difference cues [28,29,30,31,32,33]. Therefore, it should, to some degree, restore binaural localization cues in adults [2,9,31,32,34] and perhaps allow for the development of such cues in children who receive bilateral CIs [18,21,23,33,34,35]. …”

Binaural Unmasking of Multi-channel Stimuli in Bilateral Cochlear Implant Users

“…Details on their hearing history and speech processors are given in Table 1. The children participated in previous research on sound localization (Van Deun et al 2010a) and single-channel binaural masking level differences ) and their IDs are similar to the ones used in those studies. Children were tested at their home; adults were tested at the hearing center of the Medical University of Hannover, Germany.…”

Predictors of pediatric cochlear implantation outcomes in South Africa

“…The benefits of bilateral implantation in children are well documented in terms of improved localization [46][47][48] and enhanced speech recognition in quiet [49,50] and in noise [46,51,52] when compared to listening with a unilateral CI. Also recently confirmed, children with bilateral CIs have significantly better language outcomes compared to children with unilateral CIs [45,53].…”