Relationships between bilateral auditory brainstem activity and inter-implant interval in children with cochlear implants.

PURPOSE: To investigate the effect of the interval between bilateral cochlear implantation on the development of bilateral peripheral auditory pathways as revealed by the electrically evoked auditory brainstem response (EABR). METHODS: Fifty-eight children with profound bilateral sensorineural hearing loss were recruited. Among them, 33 children received sequential bilateral cochlear implants (CIs), and 25 children received simultaneous bilateral CIs. The bilateral EABRs evoked by electrical stimulation from the CI electrode were recorded on the day of second-side CI activation. RESULTS: The latencies of wave III (eIII) and wave V (eV) were significantly shorter on the first CI side than on the second CI side in children with sequential bilateral CIs but were similar between the two sides in children with simultaneous bilateral CIs. Furthermore, the latencies were prolonged from apical to basal channels along the cochlea in the two groups. In children with sequential CIs, the inter-implant interval was negatively correlated with the eV latency on the first CI side and was positively correlated with bilateral differences in the eIII and eV latencies. CONCLUSIONS: Unilateral CI use promotes the maturation of ipsilateral auditory conduction function. However, a longer inter-implant interval results in more unbalanced development of bilateral auditory brainstem pathways. Bilateral cochlear implantation with no or a short interval is recommended.

Using a cochlear implant processor as contralateral routing of signals device in unilateral cochlear implant recipients.

PURPOSE: In unilateral cochlear implant (CI) recipients, a contralateral routing of signals (CROS) device enables to receive auditory information from the unaided side. This study investigates the feasibility as well as subjective and objective benefits of using a CI processor as a CROS device in unilateral CI recipients. METHODS: This is a single-center, prospective cohort study. First, we tested the directionality of the CROS processor in an acoustic chamber. Second, we examined the difference of speech perception in quiet and in noise in ten unilateral CI recipients with and without the CROS processor. Third, subjective ratings with the CROS processor were evaluated according to the Client Oriented Scale of Improvement Questionnaire. RESULTS: There was a time delay between the two devices of 3 ms. Connection of the CROS processor led to a summation effect of 3 dB as well as a more constant amplification along all azimuths. Speech perception in quiet showed an increased word recognition score at 50 dB (mean improvement 7%). In noise, the head shadow effect could be mitigated with significant gain in speech perception (mean improvement 8.4 dB). This advantage was reversed in unfavorable listening situations, where the CROS device considerably amplified the noise (mean: - 4.8 dB). Subjectively, patients who did not normally wear a hearing aid on the non-CI side were satisfied with the CROS device. CONCLUSIONS: The connection and synchronization of a CI processor as a CROS device is technically feasible and the signal processing strategies of the device can be exploited. In contra-laterally unaided patients, a subjective benefit can be achieved when wearing the CROS processor.

Can the use of the CROS system provide head shadow effect contribution to unilateral Cochlear Implant Users? / O Sistema CROS pode oferecer contribuição do efeito sombra da cabeça a usuários de implante coclear unilateral?

ABSTRACT Purpose The aim of this study was to evaluate the contribution of the CROS system on the head shadow effect in unilateral implant users. Methods Prospective cross-sectional study, approved by the ethics committee under protocol 2.128.869. Eleven adults with post-lingual deafness users of unilateral Advanced Bionics CI were selected. Speech recognition was evaluated with recorded words presented at 65dBA at 0o azimuth and at 90o on the side contralateral to the CI, with noise at 55dBA, using CI alone and CI + CROS system. The results were analyzed using paired t-test with a 0.05 alpha. Results The mean speech recognition scores were significantly better with CI + CROS in relation to the condition of CI alone (p <0.05, p <0.005 and p <0.005 respectively). In the presentation at 0o azimuth, no significant differences were found. Conclusion Users of unilateral CI without useful residual hearing for the use of hearing aids or unable to undergo bilateral surgery can benefit from the CROS device for speech recognition, especially when the speech is presented on the side contralateral to the CI.

RESUMO Objetivo O objetivo deste estudo foi avaliar o efeito do sistema CROS em fenômenos como efeito sombra da cabeça em usuários de implante coclear unilateral. Método Estudo transversal prospectivo, aprovado pelo conselho de ética sob protocolo 2.128.869. Onze adultos com surdez de instalação pós-lingual usuários de IC Advanced Bionics unilateral foram selecionados. O reconhecimento de fala foi avaliado com palavras gravadas apresentadas a 65dBA a 0o azimute e a (90o no lado contralateral ao IC), com ruído a 55dBA, usando somente o IC e IC+sistema CROS. Os resultados foram analisados usando teste t pareado com alfa de 0,05. Resultados Os escores médios de reconhecimento de fala foram significativamente melhores com IC + CROS em relação à condição apenas IC (p <0,05, p <0,005 e p <0,005 respectivamente). Na apresentação à frente não foram encontradas diferenças significantes. Conclusão Os usuários de IC unilateral sem resíduo útil para uso de prótese auditiva ou impossibilitados de submeter-se à cirurgia bilateral podem se beneficiar do dispositivo CROS para o reconhecimento de fala, sobretudo quando a fala for apresentada ao lado contralateral ao IC.

Effect of unilateral cochlear implant use on contralateral electrically evoked auditory brainstem responses to round window membrane electrical stimulation.

BACKGROUND: Long-term use of a unilateral cochlear implant (CI) may lead to abnormal development of contralateral auditory pathway. OBJECTIVES: To investigate the usefulness of measuring the electrically evoked auditory brainstem response (eABR) with the electrical stimulation at the round window membrane and the effect of unilateral CI use on the contralateral auditory pathway functions. MATERIALS AND METHODS: According to duration of unilateral CI use, 45 children with severe or profound sensorineural hearing loss were divided into sCI (≤12 months), lCI (≥24 months) and nCI (no CI use) groups. Intra-operative eABRs evoked by electrical stimulation at the round window membrane were recorded. RESULTS: The latencies of eIII and eV were significantly longer in lCI group than in sCI group and in nCI group, respectively, but not significantly different between sCI group and nCI group. The eABR thresholds and eIII-eV latency intervals were not significantly different among three groups. CONCLUSIONS AND SIGNIFICANCE: The eABR evoked by the electrical stimulation at the round window membrane is a reliable and effective way of evaluating functions of the auditory pathway in deaf children. Long-term use of a unilateral CI may promote the degenerative process of the contralateral auditory pathway to the level of the brainstem.

An exploration of vestibular function pre and post unilateral cochlear implantation.

Objectives: To examine the effects of unilateral cochlear implantation on the balance system for adult patients with bilateral severe to profound sensory neural hearing loss. Methods: 7 CI candidates. The function of the sacculus, utricle, and three semi-circular canals (SCCs) was assessed separately using air conduction cervical vestibular evoked myogenic potentials (VEMP), vibration ocular VEMP and the video head impulse test (vHIT) respectively on each side, pre- and post-operatively. Results: The Otoliths appear more affected by implantation than SCCs. In 3 of 7 cases VEMP was affected by implantation. In 2 cases this was associated with short-term dizziness. Discussion: Differential assessment of vestibular end organ function may elucidate how cochlear implantation affects the vestibular system. As many CI candidates have some vestibular function, pre-implant vestibular assessment may help to inform which side of implantation may best preserve that function if other audiology and surgical considerations are equal. Post-implant assessment with VEMP may help to predict short-term dizziness. More work with a larger sample will be needed to make the case for routine clinical assessment. Conclusions: There is potential benefit of conducting multimodal vestibularassessment pre and post cochlear implantation. The otoliths appear more affected by implantation than the SCC.

Comparison Between Simulated and Actual Unilateral Hearing in Sequentially Implanted Cochlear Implant Users, a Cohort Study.

Introduction: Previous studies have proven the effectiveness of bilateral cochlear implantation compared to unilateral cochlear implantation. In many of these studies the unilateral hearing situation was simulated by switching off one of the cochlear implants in bilateral cochlear implant users. In the current study we assess the accuracy of this test method. Does simulated unilateral hearing (switching off one cochlear implant) result in the same outcomes as real life unilateral hearing with one cochlear implant and a non-implanted contralateral ear? Study design: We assessed the outcomes of one arm of a multicenter randomized controlled trial. Methods: In the original trial, 38 postlingually deafened adults were randomly allocated to either simultaneous bilateral cochlear implantation or sequential bilateral cochlear implantation. In the current study we used the data of the sequentially implanted group (n = 19). The primary outcome was speech perception-in-noise from straight ahead. Secondary outcomes were speech perception-in-silence, speech intelligibility-in-noise from spatially separated sources and localization capabilities. A within-subjects design was used to compare the results of hearing with one cochlear implant and a non-implanted contralateral ear (1- and 2-year follow-up) with the results of switching off one cochlear implant after sequential bilateral implantation (3-year follow-up). Results: We found no significant differences on any of the objective outcomes after 1-, 2-, or 3-year follow-up. Conclusion: This study shows that simulating unilateral hearing by switching off one cochlear implant seems a reliable method to compare unilateral and bilateral hearing in bilaterally implanted patients. Clinical Trial Registration: Dutch Trial Register NTR1722.

Evaluation of a wireless contralateral routing of signal (CROS) device with the Advanced Bionics Naída CI Q90 sound processor.

Objectives: Cochlear implants (CIs) usually provide severe to profoundly deaf recipients with speech intelligibility in quiet. In difficult listening situations such as background noise however, communication often remains challenging. For unilateral CI recipients with a bilateral hearing loss, speech intelligibility for speech sources on the non-implanted side is further impaired by the head-shadow effect. One possibility to overcome this impairment is the use of Contralateral Routing of Signal (CROS) systems, which capture sounds from the non-implanted side and (wirelessly) transmit them to the implant processor, therefore increasing audibility. Such a CROS system was evaluated in this study. Methods: Speech intelligibility in noise was measured in several spatial listening setups using the Oldenburg matrix sentence test in ten cochlear implant users. Performance was compared between listening with the CI alone and listening with the CI in combination with a wireless CROS device. Following an extended trial phase, subjective feedback regarding the device benefit in everyday life was collected via the Bern Benefit in Single Sided Deafness (BBSS) questionnaire. Results: The addition of the wireless CROS device significantly improved speech intelligibility by 7.2 dB (median) in spatial noise. Using advanced directional microphones, a statistically significant benefit of 4.4 dB (median) could be shown in a diffuse noise field. Responses to the BBSS questionnaire revealed that subjects perceived benefit in their everyday lives when using the CROS device with their CI. Conclusion: The investigated CROS system presents a valuable addition to a unilateral CI in cases where bilateral implantation is not an option.

Clinical and logopaedic results of simultaneous and sequential bilateral implants in children with severe and/or profound bilateral sensorineural hearing loss: A literature review.

This article carries out a literature review of the advantages and limitations of the simultaneous bilateral cochlear implantation (SCI) compared to those of the sequential bilateral cochlear implantation (SBCI) and the unilateral cochlear implantation (UCI). The variables analysed in said comparison are: safety and surgical technique, SCI incidence, effectiveness, impact of the inter-implant interval, costs and financing, impact on brain plasticity, impact on speech and language development, main benefits, main disadvantages and concerns, and predictive factors of prognosis. Although the results are not conclusive, all variables analysed seem to point towards observable benefits of SCI in comparison with SBCI or UCI. This tendency should be studied in more depth in multicentre studies with higher methodological rigour, more comprehensive samples and periods and other determining variables (age at the time of implantation, duration and degree of the hearing loss, rehabilitation methodologies used, family involvement, etc.).

The role of a new contralateral routing of signal microphone in established unilateral cochlear implant recipients.

OBJECTIVES/HYPOTHESIS: To investigate whether a contralateral routing of signal (CROS) microphone combined with a unilateral cochlear implant (CI) results in hearing improvement after a prolonged trial period. STUDY DESIGN: A prospective experimental trial was undertaken on a group of 10 postlingually deafened adults who are experienced CI users. METHODS: Participants completed audiometric testing and validated questionnaires with their unilateral CI alone, followed by addition of a CROS microphone (CI-CROS). This was worn daily for the 2-week trial, after which hearing performance was reevaluated using the same measures. Objective tests included AzBio sentences in quiet and noise and consonant-vowel nucleus-consonant (CNC) words. Subjective measures included the Abbreviated Profile of Hearing Aid Benefit (APHAB); Speech, Spatial, Qualities of Hearing Index (SSQ); Hearing Implant Sound Quality Index; an institutional questionnaire; and a daily log sheet. RESULTS: There is statistically significant enhanced speech discrimination with the CI-CROS when speech is presented on the CROS side. However, scores are markedly diminished when background noise is introduced, particularly to the CROS side. Subjective results indicate lower satisfaction scores for the global and ease of communication subdomains of the APHAB with the CI-CROS, but increased scores on the spatial hearing subdomain of the SSQ (P < 0.05). CONCLUSION: The CI-CROS provides significant benefit in certain situations, particularly speech recognition in quiet. CI-CROS performance with background noise is poor, leading to low satisfaction scores. Further refinement of the device may yield a useful tool for unilateral CI users in the future.