Long-term effects of second cochlear implantation with sequential bilateral cochlear implantation in Japanese children

OBJECTIVE

This study aimed to longitudinally evaluate speech perception ability and sound-field thresholds with the first, second, or bilateral cochlear implants (CIs) and MAP parameters of second CI in children.

METHODS

Eighteen children who underwent bilateral cochlear implantation at Kyoto University Hospital were included. We evaluated speech perception under quiet and noisy conditions using the first, second, or bilateral CIs, CI-aided sound-field thresholds using the first or second CI, and MAP parameter values (C-levels, T-levels, and dynamic range) of the second CI of more than 5 years after the second implantation.

RESULTS

Patients with a second CI after 7 years of age had significantly worse speech perception ability with the second CI even long after the surgery than those with a second CI before 7 years of age. CI-aided sound-field thresholds using the first or second CI were similar, regardless of the second implantation timing. Speech perception in noise with bilateral CIs was enhanced by the addition of a second CI, even after 7 years of age. Patients undergoing second cochlear implantation before 3.5 years of age showed significantly higher C-levels and wider dynamic ranges in the second CI MAP parameters.

CONCLUSIONS

When the second implantation was performed after 7 years of age, the second CI effects were limited even with long-term use, which is attributed to unstable MAP parameters. The second CI-aided sound-field threshold contributed to the better outcome of bilateral CIs in noise, even if the second implantation was performed at age of ≥7 years.

New approach in programming sequentially implanted children: Towards balanced dynamic ranges (DR)

There is a tendency for children undergoing sequential cochlear implant after a long period of unilateral implant use to have a smaller dynamic range in their second implant compared to their first implant. This study aimed to investigate if balancing the dynamic ranges between the two implants influenced functional outcomes in sequentially implanted children. Nineteen participants with long inter-implant time delays were randomly assigned to a study group or a control group. Children in the study group received progressive minimal changes to both first and second implants over a period of nine months to achieve balanced dynamic ranges, while the children in the control group received only changes to their sequential implant. Functional outcomes were collected 24-months after sequential implantation and consisted of speech discrimination scores, spatial localisation, device use and quality of life measures. Results show that spatial discrimination skills improved over time for both groups of children; however children in the study group had smaller localisation errors compared with the children in the control group. No other differences between the two groups were observed. Balanced dynamic ranges in sequentially implanted children can contribute to better performance, particularly in spatial discrimination tasks that rely in inter-aural level differences.

Sequential Bilateral Cochlear Implantation With Prolonged Time Intervals

Purpose The aim of the study was to assess whether sequential cochlear implantation (CI) with a prolonged interimplant interval (M = 15.2 years) between the first and second CIs benefited speech recognition and health-related quality of life. Method This prospective study included 14 prelingually deafened participants who received their second CI after a prolonged interimplant interval (M = 15.2 years). Additionally, speech recognition ability over a 12-month period of bilateral implant use was investigated. The results of the speech recognition test in both quiet and noisy conditions were statistically analyzed for each CI alone and both CIs together. Nijmegen Cochlear Implant Questionnaire scores were also collected at activation and at 12 months after activation. Results Improvements in speech recognition ability were observed following the use of the first implant alone and with the use of both implants together; however, progress was much slower with the use of the second implant alone, following its introduction. Furthermore, a significant difference in the trajectory of speech recognition ability was observed between the first and the second implanted ear. According to Nijmegen Cochlear Implant Questionnaire scores, all participants benefitted from bilateral CI after 12 months. Conclusions Prolonged interimplant intervals resulted in asymmetrical speech recognition abilities. A significant improvement in the speech recognition scores was observed with the first implanted ear, and much slower progress was observed with the second implanted ear. However, the "poorer" second implanted ear could provide a considerable beneficial effect on the improved speech recognition and health-related quality of life with the bilateral CI. Supplemental Material https://doi.org/10.23641/asha.12861152.

Hearing and speech benefits of cochlear implantation in children: A review of the literature

Cochlear implantation is a safe and reliable treatment for children with severe to profound hearing loss. The primary benefit of these medical devices in children is the acquisition of hearing, which promotes development of spoken language. The present paper reviews published literature demonstrating predictive effects of a number of factors on acquisition of hearing development and speech recognition. Of the many variables that contribute to an individual child's development after implantation, age at implantation, the presence of medical comorbidities, social determinants of health, and the provision of bilateral versus unilateral hearing are those that can vary widely and have consistently shown clear impacts. Specifically, age of implantation is crucial to reduce effects of deafness on the developing auditory system and capture the remarkable plasticity of early development. Language development after cochlear implantation requires therapy emphasizing hearing and oral communication, education, and other support which can be influenced by known social determinants of health; specifically, outcomes in children decline with reductions in socioeconomic status and levels of parental education. Medical co-morbidities also slow rates of progress after cochlear implantation. On the other hand, benefits of implantation increase in children who are provided with access to hearing from both ears. In sum, cochlear implants promote development of hearing in children and the best outcomes are achieved by providing early access to sound in both ears. These benefits can be limited by known social determinants of health which restrict access to needed support and medical comorbidities which add further complexity in care and outcome.

Speech Perception Growth Patterns in Prelingual Deaf Children With Bilateral Sequential Cochlear Implantation

OBJECTIVE

To evaluate speech perception following the first (CI-1) and second (CI-2) cochlear implantation (CI) in children with sequential bilateral CI.

STUDY DESIGN

Retrospective.

PATIENTS

Seventy children with follow-up for 60 months post CI-1 and 36 months post CI-2.

MAIN OUTCOME MEASURES

Word recognition score (WRS) was the main outcome. WRSs were compared by age at CI operation (group A ≤ 3.5 yr, B 3.6-8.6, for CI-1; group I ≤ 3.5 yr, II 3.6-7.0, III 7.1-13, IV > 13, for CI-2).

RESULTS

For CI-1, the WRS of group A exceeded 80% at 24 months post procedure, earlier than group B (54 mo). Group A also had a shorter period of CI-1 use up to the WRS plateau than group B. CI-2 showed an initial burst of WRS growth much earlier than CI-1. This initial burst was most robust within 3 months in group II, but modest in group IV. The periods of CI-2 use (11-17 mo) up to the WRS plateau were much shorter than CI-1 (40-64 mo). Group I did not show the best WRS at 1 month post CI but later exceeded the other groups.

CONCLUSION

Children received an immediate benefit by a burst of WRS growth from CI-2 earlier than CI-1, even within 3 months, suggesting that CI-1 gets the auditory cortex ready to foster speech processing from CI-2. The CI-2 performance depends on age at CI-2 implantation and on CI-1 performance. Our current findings will be relevant for clinicians who are counselling parents on CI-2 surgery.

Simultaneous bilateral cochlear implants: Developmental advances do not yet achieve normal cortical processing

BACKGROUND

Simultaneous bilateral cochlear implantation promotes symmetric development of bilateral auditory pathways but binaural hearing remains abnormal. To evaluate whether bilateral cortical processing remains impaired in such children, cortical activity to unilateral and bilateral stimuli was assessed in a unique cohort of 16 children who received bilateral cochlear implants (CIs) simultaneously at 1.97 ± 0.86 years of age and had ~4 years of CI experience, providing the first opportunity to assess electrically driven cortical development in the absence of reorganized asymmetries from sequential implantation.

METHODS

Cortical activity to unilateral and bilateral stimuli was measured using multichannel electro-encephalography. Cortical processing in children with bilateral CIs was compared with click-elicited activity in 13 normal hearing children matched for time-in-sound. Source activity was localized using the Time Restricted, Artefact and Coherence source Suppression (TRACS) beamformer method.

RESULTS

Consistent with dominant crossed auditory pathways, normal P1 activity (~100 ms) was weaker to ipsilateral stimuli relative to contralateral and bilateral stimuli and both auditory cortices preferentially responded to the contralateral ear. Right hemisphere dominance was evident overall. Children with bilateral CIs maintained the expected right dominance but differences from normal included: (i) minimal changes between ipsilateral, contralateral and bilateral stimuli, (ii) weaker than normal contralateral stimulus preference, (iii) symmetric activity to bilateral stimuli, and (iv) increased occipital lobe recruitment during bilateral relative to unilateral stimulation. Between-group contrasts demonstrated lower than normal activity in the inferior parieto-occipital lobe (suggesting deficits in sensory integration) and greater than normal left frontal lobe activity (suggesting increased attention), even during passive listening.

CONCLUSIONS

Together, findings suggest that early simultaneous bilateral cochlear implantation promotes normal-like auditory symmetry but that abnormalities in cortical processing consequent to deafness and/or electrical stimulation through two independent speech processors persist.

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

PURPOSE

Whether, and if so when, a second-ear cochlear implant should be provided to older, unilaterally implanted children is an ongoing clinical question. This study evaluated rate of speech recognition progress for the second implanted ear and with bilateral cochlear implants in older sequentially implanted children and evaluated localization abilities.

METHOD

A prospective longitudinal study included 24 bilaterally implanted children (mean ear surgeries at 5.11 and 14.25 years). Test intervals were every 3-6 months through 24 months postbilateral. Test conditions were each ear and bilaterally for speech recognition and localization.

RESULTS

Overall, the rate of progress for the second implanted ear was gradual. Improvements in quiet continued through the second year of bilateral use. Improvements in noise were more modest and leveled off during the second year. On all measures, results from the second ear were poorer than the first. Bilateral scores were better than either ear alone for all measures except sentences in quiet and localization.

CONCLUSIONS

Older sequentially implanted children with several years between surgeries may obtain speech understanding in the second implanted ear; however, performance may be limited and rate of progress gradual. Continued contralateral ear hearing aid use and reduced time between surgeries may enhance outcomes.

Bilateral cochlear implants in children: Effects of auditory experience and deprivation on auditory perception

Spatial hearing skills are essential for children as they grow, learn and play. These skills provide critical cues for determining the locations of sources in the environment, and enable segregation of important sounds, such as speech, from background maskers or interferers. Spatial hearing depends on availability of monaural cues and binaural cues. The latter result from integration of inputs arriving at the two ears from sounds that vary in location. The binaural system has exquisite mechanisms for capturing differences between the ears in both time of arrival and intensity. The major cues that are thus referred to as being vital for binaural hearing are: interaural differences in time (ITDs) and interaural differences in levels (ILDs). In children with normal hearing (NH), spatial hearing abilities are fairly well developed by age 4-5 years. In contrast, most children who are deaf and hear through cochlear implants (CIs) do not have an opportunity to experience normal, binaural acoustic hearing early in life. These children may function by having to utilize auditory cues that are degraded with regard to numerous stimulus features. In recent years there has been a notable increase in the number of children receiving bilateral CIs, and evidence suggests that while having two CIs helps them function better than when listening through a single CI, these children generally perform worse than their NH peers. This paper reviews some of the recent work on bilaterally implanted children. The focus is on measures of spatial hearing, including sound localization, release from masking for speech understanding in noise and binaural sensitivity using research processors. Data from behavioral and electrophysiological studies are included, with a focus on the recent work of the authors and their collaborators. The effects of auditory plasticity and deprivation on the emergence of binaural and spatial hearing are discussed along with evidence for reorganized processing from both behavioral and electrophysiological studies. The consequences of both unilateral and bilateral auditory deprivation during development suggest that the relevant set of issues is highly complex with regard to successes and the limitations experienced by children receiving bilateral cochlear implants. This article is part of a Special Issue entitled .

Unilateral cochlear implantation in children with a potentially useable contralateral ear

Increasingly, children are considered for a unilateral CI, even if the contralateral ear falls outside current audiological guidelines, especially if they are not considered to be reaching their educational potential. The primary aim was to investigate the benefit of unilateral CI in children currently outside UK [National Institute for Health and Care Excellence Technology Appraisal Guidance. 2009. Cochlear implants for children and adults with severe to profound deafness. NICE technology appraisal guidance [TAG166]. Available January 29, 2016 from http://www.nice.org.uk/ta166 ] audiological guidelines in the contralateral ear. The secondary aim was to measure compliance. A retrospective case review with standard demographic data was performed. Forty-seven children were identified as having received a unilateral CI with the contralateral ear falling outside of current UK audiological criteria. These children were allocated to two groups; with hearing between 50 and 70 dB, and 70 and 90 dB at 2 and 4 kHz in the contralateral ear, respectively. Categories of auditory performance (CAP) were assessed. Pre- and post-operative CAP scores demonstrated a statistically significant improvement in auditory perception. We would suggest that assessing candidacy in individual ears and subsequent unilateral CI, has given these children a benefit they may not otherwise have acquired if they only had bilateral hearing aid.

Long-term outcomes on spatial hearing, speech recognition and receptive vocabulary after sequential bilateral cochlear implantation in children

Sequential bilateral cochlear implantation in profoundly deaf children often leads to primary advantages in spatial hearing and speech recognition. It is not yet known how these children develop in the long-term and if these primary advantages will also lead to secondary advantages, e.g. in better language skills. The aim of the present longitudinal cohort study was to assess the long-term effects of sequential bilateral cochlear implantation in children on spatial hearing, speech recognition in quiet and in noise and receptive vocabulary. Twenty-four children with bilateral cochlear implants (BiCIs) were tested 5-6 years after sequential bilateral cochlear implantation. These children received their second implant between 2.4 and 8.5 years of age. Speech and language data were also gathered in a matched reference group of 26 children with a unilateral cochlear implant (UCI). Spatial hearing was assessed with a minimum audible angle (MAA) task with different stimulus types to gain global insight into the effective use of interaural level difference (ILD) and interaural timing difference (ITD) cues. In the long-term, children still showed improvements in spatial acuity. Spatial acuity was highest for ILD cues compared to ITD cues. For speech recognition in quiet and noise, and receptive vocabulary, children with BiCIs had significant higher scores than children with a UCI. Results also indicate that attending a mainstream school has a significant positive effect on speech recognition and receptive vocabulary compared to attending a school for the deaf. Despite of a period of unilateral deafness, children with BiCIs, participating in mainstream education obtained age-appropriate language scores.

Bilateral sequential adult cochlear implantation: who should receive priority in the context of a constrained health care system?

Resource allocation decisions have become increasingly necessary as the cost of health care habitually increases. Bilateral (second side) adult cochlear implantation (CI) is an example of a novel technology with accruing evidence of benefit, yet expense has limited universal employ. Currently at our centers, bilateral implantation is only provided under research protocol. In this article, we discuss the need for a principled approach concerning the distribution of a second device, both during this period of investigation and if ultimately an insured service. Allocation strategies, while extensively addressed in some arenas, have yet to be developed for second-side sequential adult CI. We advocate that physicians must assume an explicit role when both caring for individual patients as well as administering health care programs. We review social justice theories that inform resource allocation macrodecisions, and include a defence of age-based considerations. Our approach to patient selection for adult second-side CI sequentially considers clinical criteria (directly addressed in the article), a willingness to participate in rigorous research, and a 65 year cut-off. Ultimately, we employ random blinded selection for allocating bilateral CI among the remaining similarly situated individuals. This approach functions impartially and in a manner that is transparent for both patient and physician.

Cochlear implantation in nontraditional candidates: preliminary results in adolescents with asymmetric hearing loss

OBJECTIVE

Traditionally, children are cochlear implant (CI) candidates if bilateral severe to profound hearing loss is present and amplification benefit is limited. The current study investigated abilities of adolescents with asymmetric hearing loss (one ear with severe to profound hearing loss and better hearing contralaterally), where the poorer ear received a CI and the better ear maintained amplification.

STUDY DESIGN

Within-subject case study.

SETTING

Pediatric hospital, outpatient clinic.

PATIENTS

Participants were 5 adolescents who had not met traditional CI candidacy because of one better hearing ear but did have 1 ear that met criteria and was implanted. All maintained hearing aid (HA) use in the contralateral ear. In the poorer ear, before implant, 3 participants had used amplification, and the other 2 had no HA experience.

MAIN OUTCOME MEASURE

Participants were assessed in 3 listening conditions: HA alone, CI alone, and both devices together (bimodal) for speech recognition in quiet and noise and sound localization.

RESULTS

Three participants had CI open-set speech recognition and significant bimodal improvement for speech recognition and localization compared with the HA or CI alone. Two participants had no CI speech recognition and limited bimodal improvement.

CONCLUSION

Some adolescents with asymmetric hearing loss who are not typical CI candidates can benefit from a CI in the poorer ear, compared with a HA in the better ear alone. Additional study is needed to determine outcomes for this population, especially those who have early onset profound hearing loss in one ear and limited HA experience.

Sound localising ability in children with bilateral sequential cochlear implants

OBJECTIVES

To evaluate the sound localisation ability in children with sequential bilateral cochlear implants and the potential influence of age at the time of the first implantation, years of experience with the first implanted ear and the inter-implant interval (time between the first and the second cochlear implantation).

METHODS

Sixty-three prelingually deaf children (mean age, 11.03; range, 6.5-17 years; SD, 3.09) were tested after 12 and 24 months of using bilateral cochlear implants. Every child was tested with each ear alone and both ears together. Five loudspeakers were placed in a 180° horizontal arch with 45° of separation between each loudspeaker. The child was placed 1.5m from the speakers. For each test run, three stimuli were presented at 65dB (A) from each speaker for a total of 15 stimulus presentations. For each test run, we calculated the mean angular error (MAE) and the proportion of correct speakers identified (CSS: correct speaker score). Performance by chance for the MAE was 72° and for the CSS was 20% (1 of 5 speakers).

RESULTS

After 12 months of using bilateral CIs, the added effect of the second CI in the MAE was minor, and there was no significant difference in CSS between listening in the unilateral condition and listening in bilateral condition. After 24 months, however, the added effect of the second CI in the MAE was significant (mean diff=12.2°; 95% CI; 4.5-20.0°, p=0.003). The mean bilateral CSS increased significantly to 38% (diff=7.7%; 95% CI; 1.4-14.0%; p=0.019) while the mean unilateral CSS remained at a similar level (27%). The influence of age at the time of the first implantation on CSS after 24 months was not significant (p=0.96). However, the inter-implant interval showed a significant decrease in score by 1.4% per year between the two implants (p=0.04).

CONCLUSION

Sound localisation with two versus one CI in children with a sequential bilateral cochlear implantation was significantly improved 24 months (but not 12 months) after the second implantation. A shorter inter-implant interval showed a small but significant beneficial effect on sound localisation.

Pediatric cochlear implantation: candidacy evaluation, medical and surgical considerations, and expanding criteria

Since the first cochlear implant approved by the US Food and Drug Administration in the early 1980s, great advances have occurred in cochlear implant technology. With these advances, patient selection, preoperative evaluation, and rehabilitation consideration continue to evolve. This article describes the current practice in pediatric candidacy evaluation, reviews the medical and surgical considerations in pediatric cochlear implantation, and explores the expanding criteria for cochlear implantation within the pediatric population.

Comparison of bilateral and unilateral cochlear implants in children with sequential surgery

OBJECTIVE

The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval.

METHODS

Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months.

RESULTS

Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months.

CONCLUSIONS

A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.

Spatial hearing of normally hearing and cochlear implanted children

OBJECTIVE

Spatial hearing uses both monaural and binaural mechanisms that require sensitive hearing for normal function. Deaf children using either bilateral (BCI) or unilateral (UCI) cochlear implants would thus be expected to have poorer spatial hearing than normally hearing (NH) children. However, the relationship between spatial hearing in these various listener groups has not previously been extensively tested under ecologically valid conditions using a homogeneous group of children who are UCI users. We predicted that NH listeners would outperform BCI listeners who would, in turn, outperform UCI listeners.

METHODS

We tested two methods of spatial hearing to provide norms for NH and UCI using children and preliminary data for BCI users. NH children (n=40) were age matched (6-15 years) to UCI (n=12) and BCI (n=6) listeners. Testing used a horizontal ring of loudspeakers within a booth in a hospital outpatient clinic. In a 'lateral release' task, single nouns were presented frontally, and masking noises were presented frontally, or 90° left or right. In a 'localization' task, allowing head movements, nouns were presented from loudspeakers separated by 30°, 60° or 120° about the midline.

RESULTS

Normally hearing children improved with age in speech detection in noise, but not in quiet or in lateral release. Implant users performed more poorly on all tasks. For frontal signals and noise, UCI and BCI listeners did not differ. For lateral noise, BCI listeners performed better on both sides (within ~2 dB of NH), whereas UCI listeners benefited only when the noise was opposite the unimplanted ear. Both the BCI and, surprisingly, the UCI listeners performed better than chance at all loudspeaker separations on the ecologically valid, localization task. However, the BCI listeners performed about twice as well and, in two cases, approached the performance of NH children.

CONCLUSION

Children using either UCI or BCI have useful spatial hearing. BCI listeners gain benefits on both sides, and localize better, but not as well as NH listeners.