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Bilateral Cochlear Implants in Children

This article provides a brief overview of the advantages of two-ear hearing in children and discusses the limitations, from a psychophysical and a technical perspective, which may constrain the ability of cochlear implant users to gain these benefits. The latest outcomes for children using bilateral cochlear implants are discussed, which suggest that results are more favorable for children who receive both devices before the age of 3.5 to 4 years. The available studies that have investigated electrophysiological responses for children receiving bilateral implants are discussed. These also support the notion that optimum development of binaural auditory skills may be more difficult after the age of 3.5 to 4 years. Studies that investigate the alternative for some children of using a hearing aid on the opposite ear to the cochlear implant are briefly discussed. These indicate that advantages for speech perception in noise and localization can be obtained consistently for children with significant residual hearing in the nonimplanted ear. The article concludes with an attempt to bring the available scientific evidence into the practical clinical context with suggestions that may assist clinicians in making recommendations for families considering bilateral cochlear implantation. Although the evidence remains limited at this time, it is reasonable to suggest that bilateral cochlear implantation can provide improved auditory skills over a single implant for children with severe and profound bilateral hearing loss. The available data suggest that the benefit may be maximized by introducing both implants as early as possible, at least before 3.5 to 4 years of age.

from Thieme eJournals

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Spatial hearing of normally hearing and cochlear implanted 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.

from the International Journal of Pediatric Otorhinolaryngology

Combining acoustic and electric stimulation in the service of speech recognition

The majority of recently implanted, cochlear implant patients can potentially benefit from a hearing aid in the ear contralateral to the implant. When patients combine electric and acoustic stimulation, word recognition in quiet and sentence recognition in noise increase significantly. Several studies suggest that the acoustic information that leads to the increased level of performance resides mostly in the frequency region of the voice fundamental, e.g. 125 Hz for a male voice. Recent studies suggest that this information aids speech recognition in noise by improving the recognition of lexical boundaries or word onsets. In some noise environments, patients with bilateral implants can achieve similar levels of performance as patients who combine electric and acoustic stimulation. Patients who have undergone hearing preservation surgery, and who have electric stimulation from a cochlear implant and who have low-frequency hearing in both the implanted and not-implanted ears, achieve the best performance in a high noise environment.

from the International Journal of Audiology

The Effect of Reducing the Number of Electrodes on Spatial Hearing Tasks for Bilateral Cochlear Implant Recipients

Large individual differences exist in determining maximum performance using bilateral electrodes for localization and speech perception in noise. For some bilateral cochlear implant users, as few as three to four electrodes can be used to obtain maximal performance on localization and speech-in-noise tests. However, other listeners show a gradual decrement in performance on both tasks when the number of electrodes is reduced.

from the Journal of the American Academy of Audiology

Speech detection and localization results and clinical outcomes for children receiving sequential bilateral cochlear implants before four years of age

from the International Journal of Audiology

The aim of this study was to describe the adaptation to bilateral cochlear implant use and the perceptual benefits demonstrated by 10 children who were successful users of a first implant when a second was received before four years of age. Although one subject rejected the second implant at switch-on, the nine subjects who accepted the device adapted easily to bilateral implant use and developed useful listening skills with the second implant. Tests of localization (left versus right) and speech detection in noise were administered in the unilateral and bilateral conditions, usually after six months experience. All subjects demonstrated some bilateral benefit on speech detection testing (mostly due to a headshadow effect), and the majority localized left versus right. Results suggested that outcomes may be negatively impacted by increased age at the time of second implant switch-on. The majority of the subjects adapted well to bilateral implant use within six months and demonstrated some perceptual benefit and, according to subjective parent reports, improved daily functioning; however, device rejection must be discussed pre-operatively as a possibility.

Interaural Time Discrimination of Envelopes Carried on High-Frequency Tones as a Function of Level and Interaural Carrier Mismatch

from Ear and Hearing

Abstract:
Objectives: The present study investigated interaural time discrimination for binaurally mismatched carrier frequencies in listeners with normal hearing. One goal of the investigation was to gain insights into binaural hearing in patients with bilateral cochlear implants, where the coding of interaural time differences (ITDs) may be limited by mismatches in the neural populations receiving stimulation on each side.

Design: Temporal envelopes were manipulated to present low frequency timing cues to high-frequency auditory channels. Carrier frequencies near 4 kHz were amplitude modulated at 128 Hz via multiplication with a half-wave rectified sinusoid, and that modulation was either in-phase across ears or delayed to one ear. Detection thresholds for nonzero ITDs were measured for a range of stimulus levels and a range of carrier frequency mismatches. Data were also collected under conditions designed to limit cues based on stimulus spectral spread, including masking and truncation of sidebands associated with modulation.

Results: Listeners with normal hearing can detect ITDs in the face of substantial mismatches in carrier frequency across ears.

Conclusions: The processing of ITDs in listeners with normal hearing is likely based on spread of excitation into binaurally matched auditory channels. Sensitivity to ITDs in listeners with cochlear implants may depend on spread of current that results in the stimulation of neural populations that share common tonotopic space bilaterally.

Mother outraged after NHS only agrees to fix hearing in one ear of her deaf daughter

from MailOnline

An angry mother and local GP has accused health managers of operating a postcode lottery because they will fund only one cochlear implant for her profoundly deaf child.

Evaluation of binaural functions in bilateral cochlear implant users

from the International Journal of Audiology

Abstract
Binaural abilities are difficult to assess, yet important to understand, in the course of rehabilitating bilateral cochlear implantees. One purpose of this research was to develop a binaural assessment methodology using direct electrical input to the cochlear implant, ”direct connect assessment”, pre-processed by appropriate headrelated transfer functions (HRTFs) to simulate the binaural cues for spatial release from masking and sound localization. A second purpose was to create and evaluate new, modified rules for adaptively measuring the speech reception threshold in noise with the Hearing In Noise Test (HINT) for use with cochlear implant subjects. A third purpose was to develop a new sound localization protocol whose difficulty is adjusted to the sound localization ability of the individual cochlear implant subject. These new protocols were combined with the direct connect method and evaluated in acoustic hearing subjects and cochlear implant subjects. HINT thresholds and sound localization scores measured in the sound field and with the direct connect method did not differ significantly and were highly correlated in both groups. Measures of spatial release from masking, head shadow effects, binaural squelch, and binaural summation derived from the thresholds also were comparable for both methods. The alternative adaptive rules for HINT were found to measure different points on the same performance-intensity function. These rules allowed all cochlear implant subjects in the study to be tested adaptively and their thresholds to be compared to norms. Sound localization was measured successfully in all subjects with a sector localization protocol whose difficulty is to be adjusted to the localization ability of the subject. This protocol reduced by one-third to one-half the time required to complete the assessment of the localization ability.

Unilateral and bilateral cochlear implants and the implant-plus-hearing-aid profile: Comparing self-assessed and measured abilities

from the International Journal of Audiology

Abstract
Patients fitted with one (CI) versus two (CI+CI) cochlear implants, and those fitted with one implant who retain a hearing aid in the non-implanted ear (CI+HA), were compared using the speech, spatial, and qualities of hearing scale (SSQ) (Gatehouse & Noble, 2004). The CI+CI profile yielded significantly higher ability ratings than the CI profile in the spatial hearing domain, and on most aspects of other qualities of hearing (segregation, naturalness, and listening effort). A subset of patients completed the SSQ prior to implantation, and the CI+CI profile showed consistently greater improvement than the CI profile across all domains. Patients in the CI+HA group self-rated no differently from the CI group, post-implant. Measured speech perception and localization performance showed some parallels with the self-rating outcomes. Overall, a unilateral CI provided significant benefit across most hearing functions reflected in the SSQ. Bilateral implantation offered further benefit across a substantial range of those functions.

Bilateral Cochlear Implantation: Candidacy, Outcomes, Research

from the National Library for Health

Special Guest Presenter: Susan B. Waltzman, Professor of Otolaryngology NYU School of Medicine

Abstract: The benefits of binaural hearing including speech understanding in noise and localization have been well documented and confirmed in many bilateral hearing aid and cochlear implant users. These positive results have led many unilateral cochlear implant users to explore the viability of a second implant. This talk will review the benefits of binaural hearing with sensory aids and, more specifically, examine speech perception outcomes in sequentially implanted children, adolescents and adults and explore the variables affecting post-implantation performance.

Biography: Susan B. Waltzman, PhD is Professor of Otolaryngology and Co-Director of the Cochlear Implant Center at NYU School of Medicine. Dr. Waltzman has been involved in research related to cochlear implantation for 20 years and has published books, book chapters and numerous articles in peer-reviewed journals on outcomes with cochlear implants She is also a frequent contributor and invited speaker at national and international conferences. Her research interests are focused on outcome studies with cochlear implants.

When: Thursday 26th June 2008 at 5.30 pm UK Time

Time Zone: (Note this is UK time-please convert as necessary) please go to http://www.worldtimezone.com/ for conversion

To register for this event, please go the following link:

http://www.hearingseminars.com/swaltzman0608/event/registration.html

Bilateral cochlear implants: A case when 2 are definitely superior to 1

from EurekAlert.org

A study of cochlear implant patients seen by Indiana University School of Medicine physicians is the first research to show evidence that cochlear implants in both ears significantly improves quality of life in patients with profound hearing loss and that the cost of the second implant is offset by its benefits.

The study, which appears in the May issue of the journal Otolaryngology-Head and Neck Surgery, found that improvements in factors that contribute to quality of life including such critical abilities as hearing in noisy environments, focusing on conversations, and speaking at an appropriate volume resulted when cochlear devices were implanted in both ears.

Unilateral and bilateral cochlear implants and the implant-plus-hearing-aid profile: Comparing self-assessed and measured abilities

from the International Journal of Audiology

Patients fitted with one (CI) versus two (CI+CI) cochlear implants, and those fitted with one implant who retain a hearing aid in the non-implanted ear (CI+HA), were compared using the speech, spatial, and qualities of hearing scale (SSQ) (Gatehouse & Noble, 2004). The CI+CI profile yielded significantly higher ability ratings than the CI profile in the spatial hearing domain, and on most aspects of other qualities of hearing (segregation, naturalness, and listening effort). A subset of patients completed the SSQ prior to implantation, and the CI+CI profile showed consistently greater improvement than the CI profile across all domains. Patients in the CI+HA group self-rated no differently from the CI group, post-implant. Measured speech perception and localization performance showed some parallels with the self-rating outcomes. Overall, a unilateral CI provided significant benefit across most hearing functions reflected in the SSQ. Bilateral implantation offered further benefit across a substantial range of those functions.

Comparison of Speech Recognition and Localization Performance in Bilateral and Unilateral Cochlear Implant Users Matched on Duration of Deafness and Age at Implantation

from Ear and Hearing

Objectives: The purpose of this investigation was to compare speech recognition and localization performance of subjects who wear bilateral cochlear implants (CICI) with subjects who wear a unilateral cochlear implant (true CI-only).

Design: A total of 73 subjects participated in this study. Specifically, of the 73 subjects, 64 (32 CICI and 32 true CI-only) participated in the word recognition testing; 66 (33 CICI and 33 true CI-only) participated in the sentence recognition testing; and 24 (12 CICI and 12 true CI-only) participated in the localization testing. Because of time constraints not all subjects completed all testing. The average age at implantation for the CICI and true CI-only listeners who participated in the speech perception testing was 54 and 55 yrs, respectively, and the average duration of deafness was 8 yrs for both groups of listeners. The average age at implantation for the CICI and true CI-only listeners who participated in the localization testing was 54 and 53 yrs, respectively, and the average duration of deafness was 10 yrs for the CICI listeners and 11 yrs for the true CI-only listeners. All speech stimuli were presented from the front. The test setup for everyday-sound localization comprised an eight-speaker array spanning, an arc of approximately 108[degrees] in the frontal horizontal plane.

Results: Average group results were transformed to Rationalized Arcsine Unit scores. A comparison in performance between the CICI score and the true CI-only score in quiet revealed a significant difference between the two groups with the CICI group scoring 19% higher for sentences and 24% higher for words. In addition, when both cochlear implants were used together (CICI) rather than when either cochlear implant was used alone (right CI or left CI) for the CICI listeners, results indicated a significant binaural summation effect for sentences and words.

Conclusion: The average group results in this study showed significantly greater benefit on words and sentences in quiet and localization for listeners using two cochlear implants over those using only one cochlear implant. One explanation of this result might be that the same information from both sides are combined, which results in a better representation of the stimulus. A second explanation might be that CICI allow for the transfer of different neural information from two damaged peripheral auditory systems leading to different patterns of information summating centrally resulting in enhanced speech perception. A future study using similar methodology to the current one will have to be conducted to determine if listeners with two cochlear implants are able to perform better than listeners with one cochlear implant in noise.

New research on hearing health underscores the importance of better hearing and speech month

from EurekAlert.org

Three studies published in the May 2008 edition of Otolaryngology – Head and Neck Surgery reveal substantial new findings in several areas of hearing health, including research that indicates that patients with profound hearing loss benefit substantially from having cochlear implants placed in both ears, rather than one, as is the common practice.

Speech Perception Benefits of Sequential Bilateral Cochlear Implantation in Children and Adults: A Retrospective Analysis

from Otology & Neurotology

Objective: To examine speech perception outcomes and determine the impact of length of deafness and time between implants on performance in the sequentially bilateral implanted population.

Study Design: Retrospective review.

Setting: Tertiary academic referral center.

Patients: Forty-three children (age, <18 yr) and 22 adults underwent sequential bilateral implantation with at least 6 months between surgeries. The mean age at the time of the second implant in children was 7.83 years, and mean time between implants was 5.16 years. Five children received the first side implant (C1) below 12 months of age; 16, at 12 to 23 months; 9, between the ages of 24 and 35 months; and 11, at 36 to 59 months; 2 were implanted above the age of 5 years. In adults, mean age at second implant was 46.6 years, and mean time between implants was 5.6 years.

Intervention: Sequential implantation with 6 months or more between implantations.

Main Outcome Measures: Speech perception tests were performed preoperatively before the second implantation and at 3 months postoperatively.

Results: Results revealed significant improvement in the second implanted ear and in the bilateral condition, despite time between implantations or length of deafness; however, age of first-side implantation was a contributing factor to second ear outcome in the pediatric population.

Conclusion: Sequential bilateral implantation leads to significantly better speech understanding. On average, patients improved, despite length of deafness, time between implants, or age at implantation.