Camille C. Dunn

Comparison of speech recognition and localization performance in bilateral and unilateral cochlear implant users matched on duration of deafness and age at implantation.

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° 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.

Update on bilateral cochlear implantation.

Purpose of reviewProviding a unilateral cochlear implant in a patient with a profound bilateral hearing loss has now been a standard clinical practice for more than a decade. Although results are often very good, normal hearing has not been restored. One exciting opportunity to improve hearing in this population is to provide a second implant. However, it is not obvious that bilateral electrical stimulation can be integrated by the central nervous system. This article describes binaural hearing and reviews currently published articles on binaural cochlear implants. Recent findingsControlled laboratory trials have focused on distinguishing different categories of potential binaural advantages. A potential summation effect occurs when the same stimulus is available at two ears. Listening in noise with two ears should be better than listening with one ear when the additional ear is away from the noise. This head shadow benefit results from acoustic effects, not physiologic ones. When the second ear is added near the noise source, a binaural squelch benefit can occur, requiring neural integration from both sides. Finally, two ears may improve sound localization. Binaural implantees generally benefit from head shadow effects. Only some benefit from summation and squelch effects. Most, but not all, show improved horizontal plane localization. SummaryIt is now appropriate to begin experimental studies of binaural cochlear implants. Preliminary results show promise to improve head shadow, a physical advantage, and sound localization. Some benefits have been observed for improved summation and squelch. These findings have demonstrated that the brain can integrate electrical stimulation from the two ears. Future studies will be required to maximize this binaural hearing.

Outcomes after cochlear implantation for patients with single-sided deafness, including those with recalcitrant Ménière's disease.

Objective Compare preoperative and postoperative performance in patients undergoing cochlear implantation (CI) for unilateral severe-to-profound sensorineural hearing loss (single-sided deafness, SSD). Study Design IRB-approved, prospective Setting Tertiary center Patients Twenty-nine patients have undergone CI for SSD. SSD was due to Ménière’s disease (MD) in 10 subjects; these also suffered from recalcitrant vertigo spells and in these 10 patients along with 2 others the CI was placed simultaneous with a labyrinthectomy. Intervention(s) CI with or without labyrinthectomy. Main Outcome Measure(s) CNC word and AzBio sentences in quiet were administered to the implanted ear. A multiple-loudspeaker sound localization test was administered in the bilateral listening condition. All data were collected preoperatively and 3, 6, and 12 months postoperatively with postoperative data available for 19 subjects. Additionally, a tinnitus handicap questionnaire is administered pre- and 12-months post-operatively. Results CNC word and AzBio sentence scores showed improvement in the implanted ear. Sound localization appeared to improve in an experience-dependent fashion in some patients. Most patients reported diminished tinnitus after cochlear implantation. All patients undergoing labyrinthectomy experienced resolution of vertigo attacks. Conclusion CI restores auditory function to the deafened ear. Additionally, the binaural input appears to improve sound localization for most patients. In patients with severe hearing loss and recalcitrant vertigo attacks because of MD, simultaneous labyrinthectomy and CI effectively relieves vertigo attacks and improves auditory function.

Speech Perception and Localization With Adults With Bilateral Sequential Cochlear Implants

This investigation reports measures of binaural hearing of all of our seven adults who have received sequential bilateral cochlear implants (range of time between implantation of 6 yr/8 mo and 17 yr). All subjects used both devices in everyday life. The internal array, number of channels, rate, and signal processing strategies were usually quite different between devices. Speech recognition was tested by using words in quiet and sentences in noise with the sentence stimuli presented from the front and the noise presented from the front, the right, or the left at a 90° angle. Bilateral localization was tested by using an everyday sounds test with stimuli presented from one of eight loudspeakers. Results showed that all subjects received a significant bilateral improvement on at least one speech perception test compared to either implant alone. Four of seven subjects with bilateral devices demonstrated some (root-mean-square error below 30°) localization abilities. The two subjects tested unilaterally before receiving a second implant showed a bilateral improvement on localization after implantation of the second side. We conclude that sequential implants can be beneficial even after many years of monaural use and even with very different cochlear implants.

Bilateral and Unilateral Cochlear Implant Users Compared on Speech Perception in Noise

Objective: Compare speech performance in noise with matched bilateral cochlear implant (CICI) and unilateral cochlear implant (CI only) users. Design: Thirty CICI and 30 CI-only subjects were tested on a battery of speech perception tests in noise that use an eight-loudspeaker array. Results: On average, CICI subjects performance with speech in noise was significantly better than the CI-only subjects. Conclusion: The CICI group showed significantly better performance on speech perception in noise compared with the CI-only subjects, supporting the hypothesis that CICI is more beneficial than CI only.

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

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.

Longitudinal speech perception and language performance in pediatric cochlear implant users: the effect of age at implantation.

Objectives: Few studies have examined the long-term effect of age at implantation on outcomes using multiple data points in children with cochlear implants. The goal of this study was to determine whether age at implantation has a significant, lasting impact on speech perception, language, and reading performance for children with prelingual hearing loss. Design: A linear mixed-model framework was used to determine the effect of age at implantation on speech perception, language, and reading abilities in 83 children with prelingual hearing loss who received cochlear implants by the age of 4 years. The children were divided into two groups based on their age at implantation: (1) under 2 years of age and (2) between 2 and 3.9 years of age. Differences in model-specified mean scores between groups were compared at annual intervals from 5 to 13 years of age for speech perception, and 7 to 11 years of age for language and reading. Results: After controlling for communication mode, device configuration, and preoperative pure-tone average, there was no significant effect of age at implantation for receptive language by 8 years of age, expressive language by 10 years of age, reading by 7 years of age. In terms of speech-perception outcomes, significance varied between 7 and 13 years of age, with no significant difference in speech-perception scores between groups at ages 7, 11, and 13 years. Children who used oral communication (OC) demonstrated significantly higher speech-perception scores than children who used total communication (TC). OC users tended to have higher expressive language scores than TC users, although this did not reach significance. There was no significant difference between OC and TC users for receptive language or reading scores. Conclusions: Speech perception, language, and reading performance continue to improve over time for children implanted before 4 years of age. The present results indicate that the effect of age at implantation diminishes with time, particularly for higher-order skills such as language and reading. Some children who receive cochlear implants after the age of 2 years have the capacity to approximate the language and reading skills of their earlier-implanted peers, suggesting that additional factors may moderate the influence of age at implantation on outcomes over time.

Younger- and older-age adults with unilateral and bilateral cochlear implants: speech and spatial hearing self-ratings and performance.

Objective: Compare results of cochlear implantation in younger and older adults in the domains of disability and handicap, as well as in tests of word recognition and localization, across unilateral implant (CI), bilateral (CI + CI), and CI with an acoustic hearing aid in the nonimplanted ear (CI + HA). Design: Three parts: retrospective (postimplant only) analysis; prospective (preimplant versus postimplant); correlation between age and benefit from CI versus CI + CI. Two age groups, older and younger than 60 years, for the first 2 analyses; age is a continuous variable for the third analysis. Setting: Tertiary referral hospital clinic. Patients: Postlingually severely-to-profoundly hearing-impaired adults: Totals of 68 CI, 36 CI + CI, and 38 CI + HA in the retrospective part of the study; totals of 30 CI, 18 CI + CI, and 16 CI + HA in the prospective parts. Numbers vary from these totals on individual measures. Interventions: Patients receive either 1 or 2 cochlear implants; some with 1 CI opt to retain a hearing aid in the nonimplanted ear. Outcome Measures: Principal measures: Hearing Handicap Inventory for the Elderly, Hearing Handicap Questionnaire, Speech, Spatial and Qualities of Hearing Scale, word recognition test, and soundfield localization test. The study is exploratory, but proceeding from a null hypothesis of no expected contrast as a function of patient age. Results: All patient groups show significant benefit after implantation. No significant age-related differences are observed in patients with unilateral implant, nor in CI + HA group. In the CI + CI group, the younger cohort showed very substantial increases in both performance and self-rated abilities; the older cohort provides more mixed outcomes. Conclusion: Results for the CI group confirm and extend earlier research. The result for the younger group of CI + CI patients demonstrates the consistent incremental benefit obtained from a bilateral procedure. The mixed outcome observed in the older CI + CI group might be due to individual differences in interaction between effects of aging and the ability to integrate binaural cues.

Some benefits and limitations of binaural cochlear implants and our ability to measure them

We review new recognition and localization skills in patients using one or two cochlear implant(s). We observed one unilateral patient who showed localization performance above chance. We also provide evidence for binaural processing in bilateral cochlear implant patients, even when tested with speech from the front without noise. We unsuccessfully attempted to find correlations between localization and squelch, between these variables and pre-implant threshold differences, or these variables and post-implant recognition differences. We strongly believe that new tests are needed to examine the potential benefit of two implants. We describe three tests that we use to show a binaural advantage: cued recognition, movement direction, and recognition with multiple jammers.

Hearing handicap ratings among different profiles of adult cochlear implant users.

Objective: The aim was to compare outcomes in the domain of self-reported hearing handicap across groups of patients fit with one versus two cochlear implants (CI, CI + CI), or with an implant and a hearing aid (HA) in the nonimplanted ear (CI + HA). Design: The design was retrospective, and a preliminary step was to factor analyze the two measures used, namely, the Hearing Handicap Inventory for the Elderly (HHIE) and the Hearing Handicap Questionnaire (HHQ). Longer versus shorter-term experience with a single implant profile was compared, and further analysis confined to patients fit for less than 100 mo across the three profiles. Pre- versus postimplant self-report and performance (speech test, localization) data were also compared. Results: Three factors were identified in the HHIE, labeled Emotional Distress (HHIE), Difficulty in Hearing, and Social Restriction (HHIE). Highest handicap score for Emotional Distress (HHIE) was observed in the CI + HA group. There were significantly lower scores for Difficulty in Hearing in the CI + CI group than in the CI (p = 0.02) or CI + HA (p = 0.001) groups. On the Social Restriction (HHIE) subscale, the CI + CI group reported significantly lower rating than the CI (p = 0.009) or CI + HA (p = 0.006) groups. Two factors were identified in the HHQ, labeled Emotional Distress (HHQ) and Social Restriction (HHQ). Significantly higher Emotional Distress (HHQ) score was observed in the CI + HA group than in the CI + CI group (p = 0.002); significantly lower Social Restriction (HHQ) score was found in the CI + CI group than in the CI (p = 0.02) or CI + HA (p < 0.001) groups. Pre-post speech test performance showed least contrast in the CI + HA group. Conclusions: Outcomes demonstrate an evident reduction from single or bilateral implantation in the area of emotional distress and a further advantage from bilateral implantation in the areas of hearing difficulty and social restriction.