Factors Affecting Outcomes in Cochlear Implant Recipients Implanted With a Perimodiolar Electrode Array Located in Scala Tympani

Is the spread of excitation different between adults and children cochlear implants users?

PURPOSE

While cochlea is adult size at birth, etiologies and bone density may differ between children and adults. Differences in neural response thresholds (tNRT) and the spread of excitation (SOE) width may impact the use of artificial intelligence algorithms in speech processor fitting.

AIM

To identify whether neural response telemetry threshold and spread of excitation width are similar in adults and children.

METHODS

Retrospective cross-sectional study approved by the Ethical Board. Intraoperative tNRT and SOE recordings of consecutive cochlear implant surgeries in adults and children implanted with Cochlear devices (Cochlear™, Australia) were selected. SOE was recorded on electrode 11 (or adjacent, corresponding to the medial region of the cochlea) through the standard forward-masking technique in Custom Sound EP software, which provides SOE width in millimeters. Statistical comparison between adults and children was performed using the Mann-Whitney test (p ≤ 0.05).

RESULTS

Of 1282 recordings of intraoperative evaluations, 414 measurements were selected from children and adults. Despite the tNRT being similar between adults and children, SOE width was significantly different, with lower values in children with perimodiolar arrays. Besides, it was observed that there is a difference in the electrode where the SOE function peak occurred, more frequently shifted to electrode 12 in adults implanted. In straight arrays, there was no difference in any of the parameters analyzed on electrode 11.

CONCLUSION

Although eCAP thresholds are similar, SOE measurements differ between adults and children in perimodiolar electrodes.

Loudness Balancing Optimization for Better Speech Intelligibility, Music Perception, and Spectral Temporal Resolution in Cochlear Implant Users

HYPOTHESIS

The behaviorally based programming with loudness balancing (LB) would result in better speech understanding, spectral-temporal resolution, and music perception scores, and there would be a relationship between these scores.

BACKGROUND

Loudness imbalances at upper stimulation levels may cause sounds to be perceived as irregular, gravelly, or overly echoed and may negatively affect the listening performance of the cochlear implant (CI) user. LB should be performed after fitting to overcome these problems.

METHODS

The study included 26 unilateral Med-EL CI users. Two different CI programs based on the objective electrically evoked stapedial reflex threshold (P1) and the behaviorally program with LB (P2) were recorded for each participant. The Turkish Matrix Sentence Test (TMS) was applied to evaluate speech perception; the Random Gap Detection Test (RGDT) and Spectral-Temporally Modulated Ripple Test (SMRT) were applied to evaluate spectral temporal resolution skills; the Mini Profile of Music Perception Skills (mini-PROMS) and Melodic Contour Identification (MCI) tests were applied to evaluate music perception, and the results were compared.

RESULTS

Significantly better scores were obtained with P2 in TMS tests performed in noise and quiet. SMRT scores were significantly correlated with TMS in quiet and noise, and mini-PROMS sound perception results. Although better scores were obtained with P2 in the mini-PROMS total score and MCI, a significant difference was found only for MCI.

CONCLUSION

The data from the current study showed that equalization of loudness across CI electrodes leads to better perceptual acuity. It also revealed the relationship between speech perception, spectral-temporal resolution, and music perception.

Psychoacoustic and electroencephalographic responses to changes in amplitude modulation depth and frequency in relation to speech recognition in cochlear implantees

Temporal envelope modulations (TEMs) are one of the most important features that cochlear implant (CI) users rely on to understand speech. Electroencephalographic assessment of TEM encoding could help clinicians to predict speech recognition more objectively, even in patients unable to provide active feedback. The acoustic change complex (ACC) and the auditory steady-state response (ASSR) evoked by low-frequency amplitude-modulated pulse trains can be used to assess TEM encoding with electrical stimulation of individual CI electrodes. In this study, we focused on amplitude modulation detection (AMD) and amplitude modulation frequency discrimination (AMFD) with stimulation of a basal versus an apical electrode. In twelve adult CI users, we (a) assessed behavioral AMFD thresholds and (b) recorded cortical auditory evoked potentials (CAEPs), AMD-ACC, AMFD-ACC, and ASSR in a combined 3-stimulus paradigm. We found that the electrophysiological responses were significantly higher for apical than for basal stimulation. Peak amplitudes of AMFD-ACC were small and (therefore) did not correlate with speech-in-noise recognition. We found significant correlations between speech-in-noise recognition and (a) behavioral AMFD thresholds and (b) AMD-ACC peak amplitudes. AMD and AMFD hold potential to develop a clinically applicable tool for assessing TEM encoding to predict speech recognition in CI users.

Effect of Return Electrode Placement at Apical Cochleostomy on Current Flow With a Cochlear Implant

OBJECTIVES

A method for stimulating the cochlear apex using perimodiolar electrode arrays is described. This method involves implanting an electrode (ECE1) into the helioctrema in addition to standard cochlear implant placement. One objective is to verify a suitable approach for implanting ECE1 in the helicotrema. Another is to determine how placement of ECE1 reshapes electric fields.

DESIGN

Two cadaveric half-heads were implanted, and electric voltage tomography was measured with ECE1 placed in many positions.

RESULTS

An approach for placing ECE1 was identified. Changes in electric fields were only observed when ECE1 was placed into the fluid in the helicotrema. When inside the helicotrema, electric voltage tomography modeling suggests an increased current flow toward the apex.

CONCLUSIONS

Placement of ECE1 into the cochlear apex is clinically feasible and has the potential to reshape electric fields to stimulate regions of the cochlea more apical than those represented by the electrode array.

Improving quality of life in the elderly: hearing loss treatment with cochlear implants

BACKGROUND

Hearing loss impacts health-related quality of life and general well-being and was identified in a Lancet report as one of the largest potentially modifiable factors for the prevention of age-related dementia. There is a lack of robust data on how cochlear implant treatment in the elderly impacts quality of life. The primary objective was to measure the change in health utility following cochlear implantation in individuals aged ≥ 60 years.

METHODS

This study uniquely prospectively recruited a large multinational sample of 100 older adults (mean age 71.7 (SD7.6) range 60-91 years) with severe to profound hearing loss. In a repeated-measures design, pre and post implant outcome measures were analysed using mixed-effect models. Health utility was assessed with the Health Utilities Index Mark III (HUI3). Subjects were divided into groups of 60-64, 65-74 and 75 + years.

RESULTS

At 18 months post implant, the mean HUI3 score improved by 0.13 (95%CI: 0.07-0.18 p < 0.001). There was no statistically significant difference in the HUI3 between age groups (F[2,9228] = 0.53, p = 0.59). The De Jong Loneliness scale reduced by an average of 0.61 (95%CI: 0.25-0.97 p < 0.014) and the Lawton Instrumental Activities of Daily Living Scale improved on average (1.25, 95%CI: 0.85-1.65 p < 0.001). Hearing Handicap Inventory for the Elderly Screening reduced by an average of 8.7 (95%CI: 6.7-10.8, p < 0.001) from a significant to mild-moderate hearing handicap. Age was not a statistically significant factor for any of the other measures (p > 0.20). At baseline 90% of participants had no or mild depression and there was no change in mean depression scores after implant. Categories of Auditory perception scale showed that all subjects achieved a level of speech sound discrimination without lip reading post implantation (level 4) and at least 50% could use the telephone with a known speaker.

CONCLUSIONS

Better hearing improved individuals' quality of life, ability to communicate verbally and their ability to function independently. They felt less lonely and less handicapped by their hearing loss. Benefits were independent of age group. Cochlear implants should be considered as a routine treatment option for those over 60 years with bilateral severe to profound hearing loss.

TRIAL REGISTRATION

ClinicalTrials.gov ( http://www.

CLINICALTRIALS

gov/ ), 7 March 2017, NCT03072862.

The Relationship Between Cochlear Implant Speech Perception Outcomes and Electrophysiological Measures of the Electrically Evoked Compound Action Potential

OBJECTIVE

This study assessed the relationship between electrophysiological measures of the electrically evoked compound action potential (eCAP) and speech perception scores measured in quiet and in noise in postlingually deafened adult cochlear implant (CI) users. It tested the hypothesis that how well the auditory nerve (AN) responds to electrical stimulation is important for speech perception with a CI in challenging listening conditions.

DESIGN

Study participants included 24 postlingually deafened adult CI users. All participants used Cochlear Nucleus CIs in their test ears. In each participant, eCAPs were measured at multiple electrode locations in response to single-pulse, paired-pulse, and pulse-train stimuli. Independent variables included six metrics calculated from the eCAP recordings: the electrode-neuron interface (ENI) index, the neural adaptation (NA) ratio, NA speed, the adaptation recovery (AR) ratio, AR speed, and the amplitude modulation (AM) ratio. The ENI index quantified the effectiveness of the CI electrodes in stimulating the targeted AN fibers. The NA ratio indicated the amount of NA at the AN caused by a train of constant-amplitude pulses. NA speed was defined as the speed/rate of NA. The AR ratio estimated the amount of recovery from NA at a fixed time point after the cessation of pulse-train stimulation. AR speed referred to the speed of recovery from NA caused by previous pulse-train stimulation. The AM ratio provided a measure of AN sensitivity to AM cues. Participants' speech perception scores were measured using Consonant-Nucleus-Consonant (CNC) word lists and AzBio sentences presented in quiet, as well as in noise at signal-to-noise ratios (SNRs) of +10 and +5 dB. Predictive models were created for each speech measure to identify eCAP metrics with meaningful predictive power.

RESULTS

The ENI index and AR speed individually explained at least 10% of the variance in most of the speech perception scores measured in this study, while the NA ratio, NA speed, the AR ratio, and the AM ratio did not. The ENI index was identified as the only eCAP metric that had unique predictive power for each of the speech test results. The amount of variance in speech perception scores (both CNC words and AzBio sentences) explained by the eCAP metrics increased with increased difficulty under the listening condition. Over half of the variance in speech perception scores measured in +5 dB SNR noise (both CNC words and AzBio sentences) was explained by a model with only three eCAP metrics: the ENI index, NA speed, and AR speed.

CONCLUSIONS

Of the six electrophysiological measures assessed in this study, the ENI index is the most informative predictor for speech perception performance in CI users. In agreement with the tested hypothesis, the response characteristics of the AN to electrical stimulation are more important for speech perception with a CI in noise than they are in quiet.

Evaluation of Two Spectro-Temporal Ripple Tests and Their Relation to the Matrix Speech-in-Noise Sentence Test in Cochlear Implant Recipients

OBJECTIVES

Spectro-temporal ripple tests are commonly used in cochlear implant (CI) research as language-independent indicators of speech recognition (in noise) or as stand-alone tests. Test-retest reliability of these tests has been scarcely documented. We evaluated the test-retest reliability of spectral-temporally modulated ripple test (SMRT) and spectro-temporal ripple for investigating processor effectiveness (STRIPES) and correlated their findings to the Dutch/Flemish Matrix speech-in-noise sentence test (MST) in CI recipients. This is the first time spectro-temporal ripple tests are correlated to an MST.

DESIGN

Take-home data from 15 participants over 2 test days were analyzed. Participants were fitted with their clinical speech encoding strategy (Advanced Bionics HiRes Optima) or a 14-channel non-steered monopolar strategy. Test-retest reliability was calculated through intraclass correlation coefficients and visualized through Bland Altman plots. Association of the spectro-temporal ripple tests with the MST was evaluated through linear regression analysis.

RESULTS

The SMRT and STRIPES possessed a similarly rated "good" test-retest reliability (SMRT: ICC = 0.81, confidence interval = 0.67 to 0.92; STRIPES: ICC = 0.87, confidence interval = 0.76 to 0.95) and an identical linear relationship to speech recognition in noise (SMRT: R2 = 0.28, p = 0.04; STRIPES: R2 = 0.28, p = 0.04). Both tests revealed a stable variability between session 1 and 2 outcome scores on Bland Altman plots.

CONCLUSION

On the basis of our data, both spectro-temporal ripple tests possess similar test-retest reliability and a similar association with the MST. The SMRT and STRIPES can therefore both be used equally well as a quick indicator of across-listener differences in speech recognition in noise in CI recipients.

Cochlear coverage with lateral wall cochlear implant electrode arrays affects post-operative speech recognition

OBJECTIVES

The goal was to investigate the relationship between the insertion angle/cochlear coverage of cochlear implant electrode arrays and post-operative speech recognition scores in a large cohort of patients implanted with lateral wall electrode arrays.

METHODS

Pre- and post-operative cone beam computed tomography scans of 154 ears implanted with lateral wall electrode arrays were evaluated. Traces of lateral wall and electrode arrays were combined into a virtual reconstruction of the implanted cochlea. This reconstruction was used to measure insertion angles and proportional cochlear coverage. Word recognition scores and sentence recognition scores measured 12 months after implantation using electric-only stimulation were used to examine the relationship between cochlear coverage/insertion angle and implantation outcomes.

RESULTS

Post-operative word recognition scores and the difference between post- and pre-operative word recognition scores were positively correlated with both cochlear coverage and insertion angle, however sentence recognition scores were not. A group-wise comparison of word recognition scores revealed that patients with cochlear coverage below 70% performed significantly worse than patients with coverage between 79%-82% (p = 0.003). Performance of patients with coverage above 82% was on average poorer than between 79%-82, although this finding was not statistically significant (p = 0.84). Dividing the cohort into groups based on insertion angle quadrants revealed that word recognition scores were highest above 450° insertion angle, sentence recognition scores were highest between 450° and 630° and the difference between pre- and post-operative word recognition scores was largest between 540° and 630°, however none of these differences reached statistical significance.

CONCLUSIONS

The results of this study show that cochlear coverage has an effect on post-operative word recognition abilities and the benefit patients receive from their implant. Generally, higher coverage led to better outcomes, however there were results indicating that insertion past 82% cochlear coverage may not provide an additional benefit for word recognition. These findings can be useful for choosing the optimal electrode array and thereby improving cochlear implantation outcomes on a patient-individual basis.

Assessment of cochlear synaptopathy by electrocochleography to low frequencies in a preclinical model and human subjects

Cochlear synaptopathy is the loss of synapses between the inner hair cells and the auditory nerve despite survival of sensory hair cells. The findings of extensive cochlear synaptopathy in animals after moderate noise exposures challenged the long-held view that hair cells are the cochlear elements most sensitive to insults that lead to hearing loss. However, cochlear synaptopathy has been difficult to identify in humans. We applied novel algorithms to determine hair cell and neural contributions to electrocochleographic (ECochG) recordings from the round window of animal and human subjects. Gerbils with normal hearing provided training and test sets for a deep learning algorithm to detect the presence of neural responses to low frequency sounds, and an analytic model was used to quantify the proportion of neural and hair cell contributions to the ECochG response. The capacity to detect cochlear synaptopathy was validated in normal hearing and noise-exposed animals by using neurotoxins to reduce or eliminate the neural contributions. When the analytical methods were applied to human surgical subjects with access to the round window, the neural contribution resembled the partial cochlear synaptopathy present after neurotoxin application in animals. This result demonstrates the presence of viable hair cells not connected to auditory nerve fibers in human subjects with substantial hearing loss and indicates that efforts to regenerate nerve fibers may find a ready cochlear substrate for innervation and resumption of function.

Cochlear implants: the effects of age on outcomes

INTRODUCTION

Cochlear implants (CIs) provide access to sound for children and adults who do not receive adequate benefit from hearing aids. Age at implantation is known to affect outcomes across the lifespan.

AREAS COVERED

The effects of age on CI outcomes are examined for infants, children, adolescents, and older adults. A variety of outcome measures are considered, including speech perception, language, cognition, and quality of life measures.

EXPERT OPINION/COMMENTARY

For those meeting candidacy criteria, CIs are beneficial at any age. In general, younger age is related to greater benefit when considering pre-lingual deafness. Other factors such as additional disabilities, may mitigate this effect. Post-lingually deafened adults demonstrate similar benefit regardless of age, though the oldest individuals (80+) may see smaller degrees of improvement from preoperative scores. Benefit can be measured in many ways, and the areas of greatest benefit may vary based on age: young children appear to see the greatest effects of age at implantation on language measures, whereas scores on cognitive measures appear to be most impacted for the oldest population. Future research should consider implantation at extreme ages (5-9 months or > 90 years), unconventional measures of CI benefit including qualitative assessments, and longitudinal designs.

Outcomes of Cochlear Implantation Using FLEX26 Electrode: Audiological Results and Quality of Life after 12 Months

INTRODUCTION

The electrode length is one of the many factors impacted on results of cochlear implantation. Among lateral wall flexible electrode arrays the latest one is FLEX26 (MED-EL GmbH, Innsbruck, Austria). The main aim of the study was to evaluate the preservation of residual hearing, the level of speech understanding, and quality of life after cochlear implantation with FLEX26 electrode array.

METHODS

The study was conducted in a tertiary referral centre. Fifty-two patients implanted unilaterally with FLEX26, including 10 EAS patients (electric acoustic stimulation) and 42 ES patients (electric stimulation). The intervention was minimally invasive cochlear implantation via the round window. Pure-tone audiometry (0.125-8 kHz) was performed preoperatively and at 1, 6, and 12 months postoperatively. Twelve-month hearing preservation was established using HEARRING group formula. Quality of life was measured with AQoL-8D (Assessment of Quality of Life-8 Dimensions) pre- and postoperatively.

RESULTS

Residual hearing was preserved in 88.8% EAS patients. Quality of life was significantly better postoperatively in comparison to preoperative period (the effect size for overall quality of life was 0.49). Especially, it increased in relationships and senses dimensions (the effect sizes 0.47 and 0.44, respectively).

CONCLUSION

Preservation of residual hearing can be achieved in the majority of patients implanted with FLEX26. Improvement of quality of life was also documented. FLEX26 seems to be an option for surgeons who seek an electrode providing sufficient cochlear coverage.

Extended Preoperative Audiometry for Outcome Prediction and Risk Analysis in Patients Receiving Cochlear Implants

BACKGROUND

The outcome of cochlear implantation has improved over the last decades, but there are still patients with less benefit. Despite numerous studies examining the cochlear implant (CI) outcome, variations in speech comprehension with CI remains incompletely explained. The aim of this study was therefore to examine preoperative pure-tone audiogram and speech comprehension as well as aetiology, to investigate their relationship with postoperative speech comprehension in CI recipients.

METHODS

A retrospective study with 664 ears of 530 adult patients was conducted. Correlations between the target variable postoperative word comprehension with the preoperative speech and sound comprehension as well as aetiology were investigated. Significant correlations were inserted into multivariate models. Speech comprehension measured as word recognition score at 70 dB with CI was analyzed as (i) a continuous and (ii) a dichotomous variable.

RESULTS

All variables that tested preoperative hearing were significantly correlated with the dichotomous target; with the continuous target, all except word comprehension at 65 dB with hearing aid. The strongest correlation with postoperative speech comprehension was seen for monosyllabic words with hearing aid at 80 dB. The preoperative maximum word comprehension was reached or surpassed by 97.3% of CI patients. Meningitis and congenital diseases were strongly negatively associated with postoperative word comprehension. The multivariate model was able to explain 40% of postoperative variability.

CONCLUSION

Speech comprehension with hearing aid at 80 dB can be used as a supplementary preoperative indicator of CI-aided speech comprehension and should be measured regularly in the clinical routine. Combining audiological and aetiological variables provides more insights into the variability of the CI outcome, allowing for better patient counselling.

Dynamic Current Focusing Compared to Monopolar Stimulation in a Take-Home Trial of Cochlear Implant Users

OBJECTIVES

This study compared the performance of a dynamic partial tripolar cochlear implant speech encoding strategy termed dynamic current focusing (DCF) to monopolar stimulation (MP) using spectro-temporal, temporal, and speech-in-noise recognition testing.

DESIGN

DCF is a strategy that utilizes tripolar or high partial tripolar stimulation at threshold level and increases loudness by slowly widening current spread towards most comfortable level. Thirteen cochlear implant users were fitted with DCF and a non-steered MP matched on pulse rate, pulse width, and active electrodes. Nine participants completed the single-blinded within-subject crossover trial. Repeated testing consisted of four sessions. Strategies were allocated in a DCF-MP-DCF-MP or MP-DCF-MP-DCF design. Three-week adaptation periods ended with a test session in which speech-in-noise recognition (matrix speech-in-noise sentence test), spectro-temporal ripple tests (SMRT and STRIPES) and a temporal amplitude modulation detection test were conducted. All participants recorded their subjective experiences with both strategies using the Speech, Spatial and Qualities of Hearing Scale questionnaire.

RESULTS

Participants' SMRT thresholds improved 0.40 ripples per octave ( p = 0.02, Bonferroni-corrected: p = 0.1) with DCF over MP at 65 dB SPL. No significant differences between the strategies were found on speech-in-noise recognition at conversational (65 dB SPL) and soft (45 dB SPL) loudness levels, temporal testing, STRIPES, or the SMRT at 45 dB SPL. After Bonferroni correction, a learning effect remained on the matrix speech-in-noise sentence test at both loudness levels (65 dB SPL: p = 0.01; 45 dB SPL: p = 0.02). There was no difference in learning effects over time between DCF and MP. Similarly, no significant differences were found in subjective experience on the Speech, Spatial and Qualities of Hearing Scale questionnaire. DCF reduced average battery life by 48% (5.1 hours) ( p < 0.001) compared to MP.

CONCLUSIONS

DCF may improve spectral resolution over MP at comfortable loudness (65 dB SPL) in cochlear implant users. However, the evidence collected in this study was weak and the significant result disappeared after Bonferroni correction. Also, not all spectral tests revealed this improvement. As expected, battery life was reduced for DCF. Although the current study is limited by its small sample size, considering previous studies, DCF does not consistently improve speech recognition in noise over MP strategies.

Toward neural health measurements for cochlear implantation: The relationship among electrode positioning, the electrically evoked action potential, impedances and behavioral stimulation levels

Introduction

Estimating differences in neural health across different sites within the individual cochlea potentially enables clinical applications for subjects with a cochlear implant. The electrically evoked compound action potential (ECAP) is a measure of neural excitability that possibly provides an indication of a neural condition. There are many factors, however, that affect this measure and increase the uncertainty of its interpretation. To better characterize the ECAP response, its relationship with electrode positioning, impedances, and behavioral stimulation levels was explored.

Methods

A total of 14 adult subjects implanted with an Advanced Bionics cochlear electrode array were prospectively followed up from surgery to 6 months postoperative. Insertion depth, distance to the modiolus, and distance to the medial wall were assessed for each electrode by postoperative CT analysis. ECAPs were measured intraoperatively and at three visits postoperatively on all 16 electrodes using the NRI feature of clinical programming software and characterized using multiple parameters. Impedances and behavioral stimulation levels were measured at every fitting session.

Results

Patterns in ECAPs and impedances were consistent over time, but high variability existed among subjects and between different positions in the cochlea. Electrodes located closer to the apex of the cochlea and closer to the modiolus generally showed higher neural excitation and higher impedances. Maximum loudness comfort levels were correlated strongly with the level of current needed to elicit a response of 100 μV ECAP.

Conclusion

Multiple factors contribute to the ECAP response in subjects with a cochlear implant. Further research might address whether the ECAP parameters used in this study will benefit clinical electrode fitting or the assessment of auditory neuron integrity.

Spectrotemporal Modulation Discrimination in Infants With Normal Hearing

OBJECTIVES

Spectral resolution correlates with speech understanding in post-lingually deafened adults with cochlear implants (CIs) and is proposed as a non-linguistic measure of device efficacy in implanted infants. However, spectral resolution develops gradually through adolescence regardless of hearing status. Spectral resolution relies on two different factors that mature at markedly different rates: Resolution of ripple peaks (frequency resolution) matures during infancy whereas sensitivity to across-spectrum intensity modulation (spectral modulation sensitivity) matures by age 12. Investigation of spectral resolution as a clinical measure for implanted infants requires understanding how each factor develops and constrains speech understanding with a CI. This study addresses the limitations of the present literature. First, the paucity of relevant data requires replication and generalization across measures of spectral resolution. Second, criticism that previously used measures of spectral resolution may reflect non-spectral cues needs to be addressed. Third, rigorous behavioral measurement of spectral resolution in individual infants is limited by attrition. To address these limitations, we measured discrimination of spectrally modulated, or rippled, sounds at two modulation depths in normal hearing (NH) infants and adults. Non-spectral cues were limited by constructing stimuli with spectral envelopes that change in phase across time. Pilot testing suggested that dynamic spectral envelope stimuli appeared to hold infants' attention and lengthen habituation time relative to previously used static ripple stimuli. A post-hoc condition was added to ensure that the stimulus noise carrier was not obscuring age differences in spectral resolution. The degree of improvement in discrimination at higher ripple depth represents spectral frequency resolution independent of the overall threshold. It was hypothesized that adults would have better thresholds than infants but both groups would show similar effects of modulation depth.

DESIGN

Participants were 53 6- to 7-month-old infants and 23 adults with NH with no risk factors for hearing loss who passed bilateral otoacoustic emissions screening. Stimuli were created from complexes with 33- or 100-tones per octave, amplitude-modulated across frequency and time with constant 5 Hz envelope phase-drift and spectral ripple density from 1 to 20 ripples per octave (RPO). An observer-based, single-interval procedure measured the highest RPO (1 to 19) a listener could discriminate from a 20 RPO stimulus. Age-group and stimulus pure-tone complex were between-subjects variables whereas modulation depth (10 or 20 dB) was within-subjects. Linear-mixed model analysis was used to test for the significance of the main effects and interactions.

RESULTS

All adults and 94% of infants provided ripple density thresholds at both modulation depths. The upper range of threshold approached 17 RPO with the 100-tones/octave carrier and 20 dB depth condition. As expected, mean threshold was significantly better with the 100-tones/octave compared with the 33-tones/octave complex, better in adults than in infants, and better at 20 dB than 10 dB modulation depth. None of the interactions reached significance, suggesting that the effect of modulation depth on the threshold was not different for infants or adults.

CONCLUSIONS

Spectral ripple discrimination can be measured in infants with minimal listener attrition using dynamic ripple stimuli. Results are consistent with previous findings that spectral resolution is immature in infancy due to immature spectral modulation sensitivity rather than frequency resolution.

Assessing the Relationship Between Pitch Perception and Neural Health in Cochlear Implant Users

Various neural health estimates have been shown to indicate the density of spiral ganglion neurons in animal and modeling studies of cochlear implants (CIs). However, when applied to human CI users, these neural health estimates based on psychophysical and electrophysiological measures are not consistently correlated with each other or with the speech recognition performance. This study investigated whether the neural health estimates have stronger correlations with the temporal and place pitch sensitivity than with the speech recognition performance. On five electrodes in 12 tested ears of eight adult CI users, polarity effect (PE), multipulse integration (MPI), and interphase gap (IPG) effect on the amplitude growth function (AGF) of electrically evoked compound action potential (ECAP) were measured to estimate neural health, while thresholds of amplitude modulation frequency ranking (AMFR) and virtual channel ranking (VCR) were measured to indicate temporal and place pitch sensitivity. AzBio sentence recognition in noise was measured using the clinical CI processor for each ear. The results showed significantly poorer AMFR and VCR thresholds on the basal electrodes than on the apical and middle electrodes. Across ears and electrodes, only the IPG offset effect on ECAP AGF had a nearly significant negative correlation with the VCR threshold after removing the outliers. No significant across-ear correlations were found between the mean neural health estimates, mean pitch-ranking thresholds, and AzBio sentence recognition score. This study suggests that the central axon demyelination reflected by the IPG offset effect may be important for the place pitch sensitivity of CI users and that the IPG offset effect may be used to predict the perceptual resolution of virtual channels for CI programming.

Postlingually Deafened Adult Cochlear Implant Users With Prolonged Recovery From Neural Adaptation at the Level of the Auditory Nerve Tend to Have Poorer Speech Perception Performance

OBJECTIVE

This study investigated the effects of two temporal response properties of the auditory nerve (i.e., neural adaptation and recovery from neural adaptation) on speech perception performance in postlingually deafened adult cochlear implant (CI) users.

DESIGN

Study participants included 18 postlingually deafened adults who were Cochlear Nucleus device users with a full electrode array insertion in the test ear(s). Neural adaptation and adaptation recovery of the auditory nerve (AN) were evaluated using electrophysiological measures of the electrically evoked compound action potential (eCAP). The amount of neural adaptation was quantified by the adaptation index within three time windows: 0 to 8.89 (window 1), 44.44 to 50.00 (window 2), and 94.44 to 100.00 ms (window 3). The speed of neural adaptation was estimated using a two-parameter power law function. To evaluate adaptation recovery of the AN, eCAPs to the last pulse of the 100-ms pulse train were recorded at masker-probe-intervals ranging from 1.054 to 256 ms in logarithmic steps. The amount of adaptation recovery was quantified by the adaptation recovery ratio. The time-constant of adaptation recovery was estimated using an exponential function with up to three components. Speech perception performance was evaluated by measuring consonant-nucleus-consonant (CNC) word scores presented in quiet and in speech-shaped noise at a signal-to-noise ratio (SNR) of +10 dB. One-tailed Pearson Product Moment correlation tests were used (1) to assess the associations among parameters of neural adaptation and adaptation recovery and (2) to evaluate the strength of association between these parameters and CNC word scores measured in quiet and in noise. The contributions of different parameters quantifying neural adaptation and adaptation recovery on speech perception scores were evaluated using multivariable linear regression analyses.

RESULTS

The Pearson Product Moment correlation coefficient demonstrated a moderate, negative correlation between the speed of adaptation recovery and CNC word scores measured in quiet and in noise. The speed of adaptation recovery accounted for 14.1% of variability in CNC word scores measured in quiet and 16.7% of variability in CNC word scores measured in noise. The correlation strengths between CNC word scores and the adaptation index, the adaptation recovery ratio and the speed of neural adaptation ranged from negligible to weak.

CONCLUSIONS

The speed of adaptation recovery plays a more important role than other features of neural adaptation and adaptation recovery of the AN in speech perception in postlingually deafened adult CI users. Patients with prolonged adaptation recovery tend to show poorer speech perception performance.

External Validation of Cochlear Implant Screening Tools Demonstrates Modest Generalizability

OBJECTIVE

To assess the clinical application of five recently published cochlear implant (CI) candidacy evaluation (CICE) referral screening tools through external validation.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary otology/neurotology practice.

PATIENTS

Adults who underwent CICE between December 2020 and September 2021.

INTERVENTIONS

CICE referral screening tools versus CI candidacy criteria.

MAIN OUTCOME MEASURES

CICE screening tool performance, based on the ability to identify patients who met the CI candidacy criteria, was evaluated. CI candidacy criteria were defined as best-aided AzBio sentences at +10 signal-to-noise ratio and either 60% or less accuracy to reflect traditional criteria used in clinical settings or 40% or less accuracy (only patients 65 years or older) to reflect Medicare-eligible criteria.

RESULTS

Screening criteria of proposed CICE referral tools vary widely across pure-tone average and word recognition scores. When screened by traditional criteria, the sensitivities and specificities of these referral tools varied from 40 to 77% and from 22 to 86%, respectively. When screened by Medicare-eligible criteria, sensitivities and specificities varied from 41 to 81% and from 24 to 91%, respectively. The screening tool proposed by Zwolan et al. ( Otol Neurotol 2020;41(7):895-900) demonstrated the best overall performance for traditional (Youden's J , 0.37; sensitivity, 62%; specificity, 75%) and Medicare-eligible patients (Youden's J , 0.44; sensitivity, 66%; specificity, 78%). All screening tools performed worse on the validation cohort compared with their respective development cohorts.

CONCLUSIONS

Current tools for determining CICE referral have diverse screening criteria. These combinations of pure-tone average and word recognition score are modestly successful at identifying CI candidates.

Understanding Patient Expectations Before Implantation Using the Cochlear Implant Quality of Life-Expectations Instrument

Importance

Previous research suggests that clinicians view realistic patient expectations as the most important nonaudiological factor in the decision to proceed with a cochlear implant (CI). However, clinicians have few data to determine whether patients' outcome expectations are realistic.

Objective

To address this unmet clinical need through the development and psychometric analysis of a new patient-reported outcome measure, the CI Quality of Life (CIQOL) Expectations.

Design, Setting, and Participants

This cross-sectional study was conducted at a tertiary CI center from February 26, 2020, to August 31, 2021. First, a team comprising 2 CI audiologists, a CI surgeon, a hearing scientist, and 2 psychometricians with experience in instrument development converted all items from the CIQOL-35 Profile instrument into statements reflecting expected outcomes. Then, cognitive interviews with 20 potential CI users assessed the clarity and comprehensiveness of the new instrument. Next, responses to the CIQOL-Expectations instrument for 131 potential adult CI candidates were psychometrically analyzed using confirmatory factor analysis and item response theory. Finally, degree to which patient expectations changed from before to after and their CI evaluation appointments was measured.

Intervention

The CIQOL-Expectations instrument.

Results

Of 178 participants, 85 (47.8%) were female, and there was 1 (0.6%) Asian, 26 (14.6%) Black or African American, 1 (0.6%) Latinx, and 150 (84.3%) White individuals. No major content or grammar changes were identified during the cognitive interviews. Overall, all CIQOL domains demonstrated adequate to strong psychometric properties. Several domains did not meet all a priori established indicators of model fit or ability to separate CI users based on response patterns, but all met most indicators. Potential CI users demonstrated the highest mean (SD) expectation scores for the environment (70.2 [20.8]) and social (68.4 [18.0]) domains. In addition, the entertainment (20 [15.3%]) and environment (31 [24.4%]) domains had the highest percentage of patients with expectation scores of 100. Yet, normative CIQOL-35 Profile data from experienced CI users suggested few patients obtain this high degree of functional benefit after implant.

Conclusions and Relevance

The results of this cross-sectional study suggest that the CIQOL-Expectations instrument may provide an opportunity to assess potential CI users' expected outcomes using modification of an established CIQOL instrument and a patient-centered framework. The included items and domains reflect real-world functional abilities valued by CI users and may provide opportunities for an evidence-based shared decision-making approach to the CI evaluation process. With this instrument, clinicians can compare individual patients' pre-CI outcome expectations with established normative data and provide appropriate counseling.

Normative Cochlear Implant Quality of Life (CIQOL)-35 Profile and CIQOL-10 Global Scores for Experienced Cochlear Implant Users from a Multi-Institutional Study

OBJECTIVE

Although adult cochlear implant (CI) outcomes have primarily focused on speech recognition scores, the rigorous development of a CI-specific patient-reported outcome measure provides an opportunity for a more comprehensive and ecologically valid approach to measure the real-world functional abilities of adult CI users. Here, we report for the first time normative Cochlear Implant Quality of Life (CIQOL)-35 Profile and global scores and variance for a large, multi-institutional sample of adult CI users.

STUDY DESIGN

Cross-sectional study design.

SETTING

CI centers in the United States.

PATIENTS

Seven hundred five adults with bilateral moderate to profound hearing loss with at least 1 year of CI use.

INTERVENTIONS

Cochlear implantation.

MAIN OUTCOME MEASURES

CIQOL-35 Profile and CIQOL-10 Global scores.

RESULTS

During the development of the CIQOL instruments, 1,000 CI users from all regions of the United States were invited to participate in studies. Of these, 705 (70.5%) completed all portions of the study, and their data are reported here. Mean CIQOL domain scores were highest (indicating better function) for the emotional and social domains and lowest for listening effort. The entertainment and social domains demonstrated the widest distribution of scores and largest standard deviations, indicating greatest variability in function. Overall, there were minimal ceiling and floor effects for all domains.

CONCLUSION

Normative scores from a large sample of experienced adult CI users are consistent with clinical observations, showing large differences in functional abilities and large variability. Normative CIQOL data for adult CI users have the potential to enhance preoperative discussions with CI candidates, improve post-CI activation monitoring, and establish standards for CI centers.

Guidelines for Best Practice in the Audiological Management of Adults Using Bimodal Hearing Configurations

Clinics are treating a growing number of patients with greater amounts of residual hearing. These patients often benefit from a bimodal hearing configuration in which acoustic input from a hearing aid on 1 ear is combined with electrical stimulation from a cochlear implant on the other ear. The current guidelines aim to review the literature and provide best practice recommendations for the evaluation and treatment of individuals with bilateral sensorineural hearing loss who may benefit from bimodal hearing configurations. Specifically, the guidelines review: benefits of bimodal listening, preoperative and postoperative cochlear implant evaluation and programming, bimodal hearing aid fitting, contralateral routing of signal considerations, bimodal treatment for tinnitus, and aural rehabilitation recommendations.

Assessment methods for determining small changes in hearing performance over time

Although the behavioral pure-tone threshold audiogram is considered the gold standard for quantifying hearing loss, assessment of speech understanding, especially in noise, is more relevant to quality of life but is only partly related to the audiogram. Metrics of speech understanding in noise are therefore an attractive target for assessing hearing over time. However, speech-in-noise assessments have more potential sources of variability than pure-tone threshold measures, making it a challenge to obtain results reliable enough to detect small changes in performance. This review examines the benefits and limitations of speech-understanding metrics and their application to longitudinal hearing assessment, and identifies potential sources of variability, including learning effects, differences in item difficulty, and between- and within-individual variations in effort and motivation. We conclude by recommending the integration of non-speech auditory tests, which provide information about aspects of auditory health that have reduced variability and fewer central influences than speech tests, in parallel with the traditional audiogram and speech-based assessments.

Insertion Depth and Cochlear Implant Speech Recognition Outcomes: A Comparative Study of 28- and 31.5-mm Lateral Wall Arrays

OBJECTIVES

1) To compare speech recognition outcomes between cochlear implant (CI) recipients of 28- and 31.5-mm lateral wall electrode arrays, and 2) to characterize the relationship between angular insertion depth (AID) and speech recognition.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary academic referral center.

PATIENTS

Seventy-five adult CI recipients of fully inserted 28-mm (n = 28) or 31.5-mm (n = 47) lateral wall arrays listening with a CI-alone device.

INTERVENTIONS

Cochlear implantation with postoperative computed tomography.

MAIN OUTCOME MEASURES

Consonant-nucleus-consonant (CNC) word recognition assessed with the CI-alone at 12 months postactivation.

RESULTS

The mean AID of the most apical electrode contact for the 31.5-mm array recipients was significantly deeper than the 28-mm array recipients (628° vs 571°, p < 0.001). Following 12 months of listening experience, mean CNC word scores were significantly better for recipients of 31.5-mm arrays compared with those implanted with 28-mm arrays (59.5% vs 48.3%, p = 0.004; Cohen's d = 0.70; 95% CI [0.22, 1.18]). There was a significant positive correlation between AID and CNC word scores (r = 0.372, p = 0.001), with a plateau in performance observed around 600°.

CONCLUSIONS

Cochlear implant recipients implanted with a 31.5-mm array experienced better speech recognition than those with a 28-mm array at 12 months postactivation. Deeper insertion of a lateral wall array appears to confer speech recognition benefit up to ∼600°, with a plateau in performance observed thereafter. These data provide preliminary evidence of the insertion depth necessary to optimize speech recognition outcomes for lateral wall electrode arrays among CI-alone users.

The Impact of Neurocognitive Skills on Recognition of Spectrally Degraded Sentences

BACKGROUND

 Recent models theorize that neurocognitive resources are deployed differently during speech recognition depending on task demands, such as the severity of degradation of the signal or modality (auditory vs. audiovisual [AV]). This concept is particularly relevant to the adult cochlear implant (CI) population, considering the large amount of variability among CI users in their spectro-temporal processing abilities. However, disentangling the effects of individual differences in spectro-temporal processing and neurocognitive skills on speech recognition in clinical populations of adult CI users is challenging. Thus, this study investigated the relationship between neurocognitive functions and recognition of spectrally degraded speech in a group of young adult normal-hearing (NH) listeners.

PURPOSE

 The aim of this study was to manipulate the degree of spectral degradation and modality of speech presented to young adult NH listeners to determine whether deployment of neurocognitive skills would be affected.

RESEARCH DESIGN

 Correlational study design.

STUDY SAMPLE

 Twenty-one NH college students.

DATA COLLECTION AND ANALYSIS

 Participants listened to sentences in three spectral-degradation conditions: no degradation (clear sentences); moderate degradation (8-channel noise-vocoded); and high degradation (4-channel noise-vocoded). Thirty sentences were presented in an auditory-only (A-only) modality and an AV fashion. Visual assessments from The National Institute of Health Toolbox Cognitive Battery were completed to evaluate working memory, inhibition-concentration, cognitive flexibility, and processing speed. Analyses of variance compared speech recognition performance among spectral degradation condition and modality. Bivariate correlation analyses were performed among speech recognition performance and the neurocognitive skills in the various test conditions.

RESULTS

 Main effects on sentence recognition were found for degree of degradation (p = < 0.001) and modality (p = < 0.001). Inhibition-concentration skills moderately correlated (r = 0.45, p = 0.02) with recognition scores for sentences that were moderately degraded in the A-only condition. No correlations were found among neurocognitive scores and AV speech recognition scores.

CONCLUSIONS

 Inhibition-concentration skills are deployed differentially during sentence recognition, depending on the level of signal degradation. Additional studies will be required to study these relations in actual clinical populations such as adult CI users.

Can Cochlear Implantation in Older Adults Reverse Cognitive Decline Due to Hearing Loss?

INTRODUCTION

Older adults with late-onset hearing loss are at risk for cognitive decline. Our study addresses the question of whether cochlear implantation (CI) can counteract this potential influence. We investigated whether cognitive performance in older adults with severe and profound hearing loss improves 12 months after CI to a level comparable to controls with normal hearing, matched for age, sex, and education level.

DESIGN

This cohort study was performed at two tertiary referral centers. The study included 29 patients, of age between 60 and 80 years, with adult-onset, severe to profound bilateral sensorineural hearing loss and indication for CI (study group), as well as 29 volunteers with age-adjusted hearing abilities, according to the norm curves of ISO-702 9:2000-01, (control group). Before CI and 12 months after CI, participants completed a neurocognitive test battery including tests of global cognition, verbal and figural episodic memory, and executive functions (attentional control, inhibition, and cognitive flexibility).

RESULTS

Twelve months after CI, the performance of the study group improved significantly in global cognition, compared to the situation before CI. Differences in verbal episodic memory, figural episodic memory, and executive function were not significant. Moreover, the improvement of the study group was significantly larger only in global cognition compared to the control group. Noninferiority tests on the cognitive performances of the study group after CI revealed that comparable levels to normal hearing controls were reached only in global cognition, figural episodic memory (immediate recall), and attentional control. The improvement in global cognition was significantly associated with speech recognition 3 months after CI, but not with speech recognition 12 months after CI.

CONCLUSION

One year after CI, cognitive deficits in older individuals with adult-onset hearing loss, compared to normal-hearing peers, could only improve some cognitive skills.

Brain plasticity and hearing disorders

Permanently changed sensory stimulation can modify functional connectivity patterns in the healthy brain and in pathology. In the pathology case, these adaptive modifications of the brain are referred to as compensation, and the subsequent configurations of functional connectivity are called compensatory plasticity. The variability and extent of auditory deficits due to the impairments in the hearing system determine the related brain reorganization and rehabilitation. In this review, we consider cross-modal and intra-modal brain plasticity related to bilateral and unilateral hearing loss and their restoration using cochlear implantation. Cross-modal brain plasticity may have both beneficial and detrimental effects on hearing disorders. It has a beneficial effect when it serves to improve a patient's adaptation to the visuo-auditory environment. However, the occupation of the auditory cortex by visual functions may be a negative factor for the restoration of hearing with cochlear implants. In what concerns intra-modal plasticity, the loss of interhemispheric asymmetry in asymmetric hearing loss is deleterious for the auditory spatial localization. Research on brain plasticity in hearing disorders can advance our understanding of brain plasticity and improve the rehabilitation of the patients using prognostic, evidence-based approaches from cognitive neuroscience combined with post-rehabilitation objective biomarkers of this plasticity utilizing neuroimaging.

Speech Recognition Outcomes in Adults With Slim Straight and Slim Modiolar Cochlear Implant Electrode Arrays

OBJECTIVE

To compare differences in audiologic outcomes between slim modiolar electrode (SME) CI532 and slim lateral wall electrode (SLW) CI522 cochlear implant recipients.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary academic hospital.

METHODS

Comparison of postoperative AzBio sentence scores in quiet (percentage correct) in adult cochlear implant recipients with SME or SLW matched for preoperative AzBio sentence scores in quiet and aided and unaided pure tone average.

RESULTS

Patients with SLW (n = 52) and patients with SME (n = 37) had a similar mean (SD) age (62.0 [18.2] vs 62.6 [14.6] years, respectively), mean preoperative aided pure tone average (55.9 [20.4] vs 58.1 [16.4] dB; P = .59), and mean AzBio score (percentage correct, 11.1% [13.3%] vs 8.0% [11.5%]; P = .25). At last follow-up (SLW vs SME, 9.0 [2.9] vs 9.9 [2.6] months), postoperative mean AzBio scores in quiet were not significantly different (percentage correct, 70.8% [21.3%] vs 65.6% [24.5%]; P = .29), and data log usage was similar (12.9 [4.0] vs 11.3 [4.1] hours; P = .07). In patients with preoperative AzBio <10% correct, the 6-month mean AzBio scores were significantly better with SLW than SME (percentage correct, 70.6% [22.9%] vs 53.9% [30.3%]; P = .02). The intraoperative tip rollover rate was 8% for SME and 0% for SLW.

CONCLUSIONS

Cochlear implantation with SLW and SME provides comparable improvement in audiologic functioning. SME does not exhibit superior speech recognition outcomes when compared with SLW.

Hydraulic insertions of cochlear implant electrode arrays into the human cadaver cochlea: preliminary findings

OBJECTIVES

(1) To evaluate the feasibility of a non-invasive, novel, simple insertion tool to perform automated, slow insertions of cochlear implant electrode arrays (EA) into a human cadaver cochlea; (2) to estimate the handling time required by our tool.

METHODS

Basic science study conducted in an experimental OR. Two previously anonymized human cadaver heads, three commercially available EAs, and our novel insertion tool were used for the experiments. Our tool operates as a hydraulic actuator that delivers an EA at continuous velocities slower than manually feasible.

INTERVENTION(S)

the human cadaver heads were prepared with a round-window approach for CI surgery in a standard fashion. Twelve EA insertion trials using our tool involved: non-invasive fixation of the tool to the head; directing the tool to the round window and EA mounting onto the tool; automated EA insertion at approximately 0.1 mm/s driven by hydraulic actuation. Outcome measurement(s): handling time of the tool; post-insertion cone-beam CT scans to provide intracochlear evaluation of the EA insertions.

RESULTS

Our insertion tool successfully inserted an EA into the human cadaver cochlea (n = 12) while being attached to the human cadaver head in a non-invasive fashion. Median time to set up the tool was 8.8 (7.2-9.4) min.

CONCLUSION

The first insertions into the human cochlea using our novel, simple insertion tool were successful without the need for invasive fixation. The tool requires < 10 min to set up, which is clinically acceptable. Future assessment of intracochlear trauma is needed to support its safety profile for clinical translation.

Factors Influencing Speech Perception in Adults With a Cochlear Implant

Supplemental Digital Content is available in the text.

The primary objective of this study is to identify the biographic, audiologic, and electrode position factors that influence speech perception performance in adult cochlear implant (CI) recipients implanted with a device from a single manufacturer. The secondary objective is to investigate the independent association of the type of electrode (precurved or straight) with speech perception.

Evaluation of a Tool for Measuring Temporal Modulation Detection

OBJECTIVES

A software tool (EasyMDT) that measures temporal modulation detection thresholds of a broadband noise carrier is presented. EasyMDT is designed to be both easy and quick to promote the use in environments where testing time is limited, and testers may not have extensive technical expertise to use typical research software. In addition, by providing a standardized stimulus and protocol, data collected by all groups using the software can be compared directly. Details of EasyMDT, including a description of the protocol, stimuli, interface and how to obtain the software, are provided along with representative sample data from both normal-hearing listeners and cochlear implant (CI) users. Performance with the EasyMDT is compared with speech understanding metrics as well as a metric of spectral-temporal resolution.

DESIGN

A "Full Curve" of modulation detection thresholds is measured using a three-interval forced-choice adaptive task in a single block for 7 modulation frequencies (10, 50, 75, 100, 150, 200, and 300 Hz). Similarly, the modulation detection thresholds were measured for only one modulation frequency in a block (either 100 Hz or 150 Hz). Modulation detection thresholds and block duration were recorded. In addition, performance on speech recognition tasks (CNC words, consonant identification, vowel identification, and AzBio sentences in noise) and a spectral-temporal resolution task (SMRT; Aronoff and Landsberger) were measured. Modulation detection thresholds were measured for both normal-hearing listeners and CI users. Only CI users participated in the speech and spectral-temporal tests.

RESULTS

Modulation detection thresholds measured with EasyMDT were consistent with those previously reported from other laboratories. Modulation detection thresholds at a single modulation frequency (100 Hz or 150 Hz) were predictive of modulation detection thresholds measured as part of the Full Curve consisting of all 7 modulation frequencies. Testing durations for CI users dropped from an average of over 18 minutes for the Full Curve to under 3 minutes for either of the single modulation frequency measures. Modulation detection thresholds at 100 Hz correlated with CNC words, consonant identification, and AzBio sentences in noise, but not vowel identification. No correlations were found between modulation detection and spectral-temporal resolution.

CONCLUSIONS

The EasyMDT is designed to be an easy-to-use tool that provides a nonlinguistic measure that can predict speech understanding. The test duration is short enough that it can be incorporated into clinical practice or as part of an experimental battery. The software is available for free download at https://www.ear-lab.org/software-downloads.html. The software is designed to have a minimum barrier of entry as well as provide a standardized protocol allowing direct comparison of modulation detection thresholds across studies and groups.

The Effects of GJB2 or SLC26A4 Gene Mutations on Neural Response of the Electrically Stimulated Auditory Nerve in Children

OBJECTIVES

This study aimed to (1) investigate the effect of GJB2 and SLC26A4 gene mutations on auditory nerve function in pediatric cochlear implant users and (2) compare their results with those measured in implanted children with idiopathic hearing loss.

DESIGN

Participants included 20 children with biallelic GJB2 mutations, 16 children with biallelic SLC26A4 mutations, and 19 children with idiopathic hearing loss. All subjects except for two in the SLC26A4 group had concurrent Mondini malformation and enlarged vestibular aqueduct. All subjects used Cochlear Nucleus devices in their test ears. For each subject, electrophysiological measures of the electrically evoked compound action potential (eCAP) were recorded using both anodic- and cathodic-leading biphasic pulses. Dependent variables (DVs) of interest included slope of eCAP input/output (I/O) function, the eCAP threshold, and eCAP amplitude measured at the maximum comfortable level (C level) of the anodic-leading stimulus (i.e., the anodic C level). Slopes of eCAP I/O functions were estimated using statistical modeling with a linear regression function. These DVs were measured at three electrode locations across the electrode array. Generalized linear mixed effect models were used to evaluate the effects of study group, stimulus polarity, and electrode location on each DV.

RESULTS

Steeper slopes of eCAP I/O function, lower eCAP thresholds, and larger eCAP amplitude at the anodic C level were measured for the anodic-leading stimulus compared with the cathodic-leading stimulus in all subject groups. Children with GJB2 mutations showed steeper slopes of eCAP I/O function and larger eCAP amplitudes at the anodic C level than children with SLC26A4 mutations and children with idiopathic hearing loss for both the anodic- and cathodic-leading stimuli. In addition, children with GJB2 mutations showed a smaller increase in eCAP amplitude when the stimulus changed from the cathodic-leading pulse to the anodic-leading pulse (i.e., smaller polarity effect) than children with idiopathic hearing loss. There was no statistically significant difference in slope of eCAP I/O function, eCAP amplitude at the anodic C level, or the size of polarity effect on all three DVs between children with SLC26A4 mutations and children with idiopathic hearing loss. These results suggested that better auditory nerve function was associated with GJB2 but not with SLC26A4 mutations when compared with idiopathic hearing loss. In addition, significant effects of electrode location were observed for slope of eCAP I/O function and the eCAP threshold.

CONCLUSIONS

GJB2 and SLC26A4 gene mutations did not alter polarity sensitivity of auditory nerve fibers to electrical stimulation. The anodic-leading stimulus was generally more effective in activating auditory nerve fibers than the cathodic-leading stimulus, despite the presence of GJB2 or SLC26A4 mutations. Patients with GJB2 mutations appeared to have better functional status of the auditory nerve than patients with SLC26A4 mutations who had concurrent Mondini malformation and enlarged vestibular aqueduct and patients with idiopathic hearing loss.

The Sensitivity of the Electrically Stimulated Auditory Nerve to Amplitude Modulation Cues Declines With Advanced Age

OBJECTIVES

This study aimed to investigate effects of aging and duration of deafness on sensitivity of the auditory nerve (AN) to amplitude modulation (AM) cues delivered using trains of biphasic pulses in adult cochlear implant (CI) users.

DESIGN

There were 21 postlingually deaf adult CI users who participated in this study. All study participants used a Cochlear Nucleus device with a full electrode array insertion in the test ear. The stimulus was a 200-ms pulse train with a pulse rate of 2000 pulses per second. This carrier pulse train was sinusodially AM at four modulation rates (20, 40, 100, 200 Hz). The peak amplitude of the modulated pulse train was the maximum comfortable level (i.e., C level) measured for the carrier pulse train. The electrically evoked compound action potential (eCAP) to each of the 20 pulses selected over the last two AM cycles were measured. In addition, eCAPs to single pulses were measured with the probe levels corresponding to the levels of 20 selected pulses from each AM pulse train. There were seven electrodes across the array evaluated in 16 subjects (i.e., electrodes 3 or 4, 6, 9, 12, 15, 18, and 21). For the remaining five subjects, 4 to 5 electrodes were tested due to impedance issues or time constraints. The modulated response amplitude ratio (MRAR) was calculated as the ratio of the difference in the maximum and the minimum eCAP amplitude measured for the AM pulse train to that measured for the single pulse, and served as the dependent variable. Age at time of testing and duration of deafness measured/defined using three criteria served as the independent variables. Linear Mixed Models were used to assess the effects of age at testing and duration of deafness on the MRAR.

RESULTS

Age at testing had a strong, negative effect on the MRAR. For each subject, the duration of deafness varied substantially depending on how it was defined/measured, which demonstrates the difficulty of accurately measuring the duration of deafness in adult CI users. There was no clear or reliable trend showing a relationship between the MRAR measured at any AM rate and duration of deafness defined by any criteria. After controlling for the effect of age at testing, MRARs measured at 200 Hz and basal electrode locations (i.e., electrodes 3 and 6) were larger than those measured at any other AM rate and apical electrode locations (i.e., electrodes 18 and 21).

CONCLUSIONS

The AN sensitivity to AM cues implemented in the pulse-train stimulation significantly declines with advanced age. Accurately measuring duration of deafness in adult CI users is challenging, which, at least partially, might have accounted for the inconclusive findings in the relationship between the duration of deafness and the AN sensitivity to AM cues in this study.

Examining the Relationship Between Speech Recognition and a Spectral-Temporal Test With a Mixed Group of Hearing Aid and Cochlear Implant Users

Purpose Audiology clinics have a need for a nonlinguistic test for assessing speech scores for patients using hearing aids or cochlear implants. One such test, the Spectral-Temporally Modulated Ripple Test Lite for computeRless Measurement (SLRM), has been developed for use in clinics, but it, as well as the related Spectral-Temporally Modulated Ripple Test, has primarily been assessed with cochlear implant users. The main goal of this study was to examine the relationship between SLRM and the Arizona Biomedical Institute Sentence Test (AzBio) for a mixed group of hearing aid and cochlear implant users. Method Adult hearing aid users and cochlear implant users were tested with SLRM, AzBio in quiet, and AzBio in multitalker babble with a +8 dB signal-to-noise ratio. Results SLRM scores correlated with both AzBio recognition scores in quiet and in noise. Conclusions The results indicated that there is a significant relationship between SLRM and AzBio scores when testing a mixed group of cochlear implant and hearing aid users. This suggests that SLRM may be a useful nonlinguistic test for use with individuals with a variety of hearing devices.

Association of Patient-Related Factors With Adult Cochlear Implant Speech Recognition Outcomes: A Meta-analysis

Importance

Multiple studies have evaluated associations between post-cochlear implant (CI) speech recognition outcomes and patient-related factors. Current literature often appears equivocal or contradictory, so little is known about the factors that contribute to successful speech recognition outcomes with CIs.

Objective

To use a meta-analysis to pool data from the extant literature and provide an objective summary of existing evidence on associations of patient-related factors and CI speech recognition outcomes.

Data Sources

A literature search was performed using PubMed, Scopus, and CINAHL databases in January 2019 using the following search terms: cochlear implant or cochlear implants or cochlear implantation and speech recognition or word recognition or sentence recognition. Studies of postlingually deafened adult CI recipients that reported word or sentence recognition scores were included.

Study Selection

Inclusion criteria were postlingual adult CI recipients 18 years or older with word or sentence recognition scores at minimum 6-month postimplantation. Studies that included patients undergoing revision or reimplantation surgery were excluded.

Data Extraction and Synthesis

Following the Preferred Reporting Items for Systemic Reviews and Meta-analyses (PRISMA) guidelines, 1809 unique articles underwent review by abstract, and 121 articles underwent full-text review, resulting in 13 articles of 1095 patients for a meta-analysis of correlations. Random-effects model was used when the heterogeneity test yielded a low P value (P < .05).

Main Outcomes and Measures

The planned primary outcome was the pooled correlation values between postimplant speech recognition scores and patient-related factors.

Results

Of the 1095 patients included from the 13 studies, the mean age at implantation ranged from 51.2 to 63.7 years and the mean duration of hearing loss ranged from 9.5 to 31.8 years; for the 825 patients for whom sex was reported, 421 (51.0%) were women. A weak negative correlation was observed between age at implantation and postimplant sentence recognition in quiet (r = -0.31 [95% CI, -0.41 to -0.20]). Other correlations between patient-related factors and postimplant word or sentence recognition were statistically significant, but all correlations were absent to negligible (r = 0.02-0.27).

Conclusions and Relevance

Given that most associations were weak, negligible, or absent, patient-related factors often thought to affect CI speech recognition ability offer limited assistance in clinical decision-making in cochlear implantation. Additional research is needed to identify patient-related and other factors that predict CI outcomes, including speech recognition and other important variables related to success with CIs.

Computed Tomography-Based Measurements of the Cochlear Duct: Implications for Cochlear Implant Pitch Tuning

OBJECTIVES

To determine the sources of variability for cochlear duct length (CDL) measurements for the purposes of fine-tuning cochlear implants (CI) and to propose a set of standardized landmarks for computed tomography (CT) pitch mapping.

DESIGN

This was a retrospective cohort study involving 21 CI users at a tertiary referral center. The intervention involved flat-panel CT image acquisition and secondary reconstructions of CIs in vivo. The main outcome measures were CDL measurements, CI electrode localization measurements, and frequency calculations.

RESULTS

Direct CT-based measurements of CI and intracochlear landmarks are methodologically valid, with a percentage of error of 1.0% ± 0.9%. Round window (RW) position markers (anterior edge, center, or posterior edge) and bony canal wall localization markers (medial edge, duct center, or lateral edge) significantly impact CDL calculations [F(2, 78) = 9.9, p < 0.001 and F(2, 78) = 1806, p < 0.001, respectively]. These pitch distortions could be as large as 11 semitones. When using predefined anatomical landmarks, there was still a difference between researchers [F(2, 78) = 12.5; p < 0.001], but the average variability of electrode location was reduced to differences of 1.6 semitones (from 11 semitones.

CONCLUSIONS

A lack of standardization regarding RW and bony canal wall landmarks results in great CDL measurement variability and distorted pitch map calculations. We propose using the posterior edge of the RW and lateral bony wall as standardized anatomical parameters for CDL calculations in CI users to improve pitch map calculations. More accurate and precise pitch maps may improve CI-associated pitch outcomes.

Screening Strategies for Deafness Genes and Functional Outcomes in Cochlear Implant Patients

OBJECTIVES

To review the current state of knowledge about the influence of specific genetic mutations that cause sensorineural hearing loss (SNHL) on cochlear implant (CI) functional outcomes, and how this knowledge may be integrated into clinical practice. A multistep and sequential population-based genetic algorithm suitable for the identification of congenital SNHL mutations before CI placement is also examined.

DATA SOURCES, STUDY SELECTION

A review was performed of the English literature from 2000 to 2019 using PubMed regarding the influence of specific mutations on CI outcomes and the use of next-generation sequencing for genetic screening of CI patients.

CONCLUSION

CI is an effective habilitation option for patients with severe-profound congenital SNHL. However, it is well known that CI outcomes show substantial inter-patient variation. Recent advances in genetic studies have improved our understanding of genotype-phenotype relationships for many of the mutations underlying congenital SNHL, and have explored how these relationships may account for some of the variance seen in CI performance outcomes. A sequential genetic screening strategy utilizing next-generation sequencing-based population-specific gene panels may allow for more efficient mutation identification before CI placement. Understanding the relationships between specific mutations and CI outcomes along with integrating routine comprehensive genetic testing into pre-CI evaluations will allow for more effective patient counseling and open the door for the development of mutation-specific treatment strategies.

Spectrotemporal Modulation Sensitivity in Cochlear-Implant and Normal-Hearing Listeners: Is the Performance Driven by Temporal or Spectral Modulation Sensitivity?

This study examined the contribution of temporal and spectral modulation sensitivity to discrimination of stimuli modulated in both the time and frequency domains. The spectrotemporally modulated stimuli contained spectral ripples that shifted systematically across frequency over time at a repetition rate of 5 Hz. As the ripple density increased in the stimulus, modulation depth of the 5 Hz amplitude modulation (AM) reduced. Spectrotemporal modulation discrimination was compared with subjects’ ability to discriminate static spectral ripples and the ability to detect slow AM. The general pattern from both the cochlear implant (CI) and normal hearing groups showed that spectrotemporal modulation thresholds were correlated more strongly with AM detection than with static ripple discrimination. CI subjects’ spectrotemporal modulation thresholds were also highly correlated with speech recognition in noise, when partialing out static ripple discrimination, but the correlation was not significant when partialing out AM detection. The results indicated that temporal information was more heavily weighted in spectrotemporal modulation discrimination, and for CI subjects, it was AM sensitivity that drove the correlation between spectrotemporal modulation thresholds and speech recognition. The results suggest that for the rates tested here, temporal information processing may limit performance more than spectral information processing in both CI users and normal hearing listeners.

Effect of exceeding compliance voltage on speech perception in cochlear implants

OBJECTIVES

In cochlear implants, the maximum current I (Amperes) that can be delivered on a cochlear implant electrode is determined by V = I * R, where V = compliance voltage (Volts) and R = electrode impedance (Ohms). Generally, electrode impedances are measured during each clinical visit and are used to set electrical stimulation parameters in cochlear implants. However, electrode impedances can rise during the course of cochlear implant use and lead to electrical stimulation voltage requirements exceeding the maximum compliance voltage of the medical device. Electric stimulation requirements that exceed the compliance voltage lead to clipping of the biphasic electrical pulse (current going into the cochlea) and are known to adversely affect cochlear implant outcomes.

DESIGN

Thirteen (11 unilateral and 2 bilateral) Advanced Bionics cochlear implant patients with a HiRes 90k™ cochlear implant participated in this study. Speech perception scores were measured using the patient's baseline clinical program with the most comfortable loudness levels (M-levels) and the following four test programs: (1) stimulation clipped at 15% below clinical M-levels (15%C) (2) stimulation clipped at 30% below clinical M-levels (30%C) (3) M-levels decreased by 15% (15%M) and (4) M-levels decreased by 30% (30%C). Speech perception scores were measured using AzBio sentences presented at 60 dB SPL in quiet and in the presence of multi-talker babble (+10 dB SNR).

RESULTS

Relative to the clinical baseline program, speech perception scores with the four test programs decreased in both quiet and noisy listening conditions. In quiet, speech perception scores measured with the 30%M and 30%C programs were significantly (p < 0.001) poorer than the baseline program. No significant differences in speech perception scores were measured between the baseline and the 15%C or 15%M programs. In the noisy listening condition, speech perception scores were significantly poorer than the baseline program for the 15%C (p = 0.008), 30%C (p < 0.001), and 30%M (p < 0.001) programs. No significant differences in speech perception scores were obtained between the baseline and the 15%M program in the noisy listening condition. Speech perception scores measured with the 30%C program were significantly (p < 0.001) poorer than those with the 30%M program, suggesting that clipping was more detrimental than reducing electrical stimulation levels.

CONCLUSION

Small amounts (15%) of clipping can significantly decrease speech perception in the presence of background noise. Large amounts (30%) of both clipping and M-level reduction may lead to significantly poorer speech perception in quiet and in background noise. The decrease in speech perception scores can most likely be attributed to reduced volume and poorer spectro-temporal representation. Therefore, it is important to establish comfortably loud electrical stimulation levels without exceeding the compliance voltage to maximize cochlear implant outcomes.

Neural Tissue Degeneration in Rosenthal's Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study

Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.

Simpler and effective radiological evaluations for modiolar proximity of a slim modiolar cochlear implant electrode

A new slim modiolar electrode (CI532/632) has been reported to ensure better modiolar proximity than conventional electrodes. Better modiolar proximity has been proposed to yield better electrode discrimination capability and potentially better speech outcomes, necessitating its efficient measurement. Currently, intracochlear positional index (ICPI), the most reliable indicator for evaluating modiolar proximity, has been measured exclusively through ‘metal artifact-less’ cone beam CT. However, popular use of this index is precluded due to lack of cone beam CT in many institutions. Thus, eyes are now on elucidation of easy-to-measure indicators of modiolar proximity derived from conventional CT, which is accessible in all centers. We observed that enhanced tomographic resolution significantly reduces partial volume artifacts, providing better visualization of modiolus-electrode distance. Aided by ultra-high kernel specification with high-resolution index, we developed a novel and easy-to-measure, conventional CT-specific indicator, “modified ICPI”, for evaluation of modiolar proximity. Further, we showed that it closely correlates with the previously proposed parameter of modiolar proximity, the spiral diameter, measured from post-insertion radiograph, reiterating the value of X-ray-based spiral diameter. Through this study, we have taken a step toward the stage of immediate visual feedback regarding modiolar proximity and changes in insertion technique intraoperatively, ensuring optimal modiolar proximity.

Comprehensive auditory rehabilitation in adults receiving cochlear implants: A pilot study

OBJECTIVE

In the United States, most adults who receive cochlear implants (CIs) do not undergo a comprehensive auditory rehabilitation (CAR) approach, which may result in suboptimal outcomes. The objectives of this pilot study were to demonstrate that a CAR approach incorporating auditory training (AT) by a speech-language pathologist (SLP) is feasible in adults receiving CIs and to explore whether this approach results in improved outcomes.

METHODS

Twenty-four postlingually deaf adult CI candidates were serially assigned to one of three groups: (a) a "CAR group" that received standard of care implantation, programming by an audiologist, an additional preoperative counseling session, and eight one-hour AT sessions; (b) a "passive control" standard-of-care group; and (c) an "active control" group that also received the extra preoperative counseling session. Participants were tested preoperatively and 1, 3, and 6 months after CI using measures of word and sentence recognition in quiet and in babble, as well as measures of quality of life (QOL).

RESULTS

The CAR approach was feasible, but this pilot study was underpowered to determine efficacy. Differential time courses of speech recognition improvement were seen for sentence and word recognition. All QOL measurements showed improvement from pre-CI to 1 month post-CI activation. Results revealed issues to consider for a larger-scale study of CAR revolving around participant selection, study measures, and sample size.

CONCLUSION

The CAR approach is feasible in new CI users. A larger trial is needed to investigate whether CAR leads to better outcomes or faster improvement in this clinical population.

LEVEL OF EVIDENCE

2.

Slower Speaking Rate Reduces Listening Effort Among Listeners With Cochlear Implants

OBJECTIVES

Slowed speaking rate was examined for its effects on speech intelligibility, its interaction with the benefit of contextual cues, and the impact of these factors on listening effort in adults with cochlear implants.

DESIGN

Participants (n = 21 cochlear implant users) heard high- and low-context sentences that were played at the original speaking rate, as well as a slowed (1.4× duration) speaking rate, using uniform pitch-synchronous time warping. In addition to intelligibility measures, changes in pupil dilation were measured as a time-varying index of processing load or listening effort. Slope of pupil size recovery to baseline after the sentence was used as an index of resolution of perceptual ambiguity.

RESULTS

Speech intelligibility was better for high-context compared to low-context sentences and slightly better for slower compared to original-rate speech. Speech rate did not affect magnitude and latency of peak pupil dilation relative to sentence offset. However, baseline pupil size recovered more substantially for slower-rate sentences, suggesting easier processing in the moment after the sentence was over. The effect of slowing speech rate was comparable to changing a sentence from low context to high context. The effect of context on pupil dilation was not observed until after the sentence was over, and one of two analyses suggested that context had greater beneficial effects on listening effort when the speaking rate was slower. These patterns maintained even at perfect sentence intelligibility, suggesting that correct speech repetition does not guarantee efficient or effortless processing. With slower speaking rates, there was less variability in pupil dilation slopes following the sentence, implying mitigation of some of the difficulties shown by individual listeners who would otherwise demonstrate prolonged effort after a sentence is heard.

CONCLUSIONS

Slowed speaking rate provides release from listening effort when hearing an utterance, particularly relieving effort that would have lingered after a sentence is over. Context arguably provides even more release from listening effort when speaking rate is slower. The pattern of prolonged pupil dilation for faster speech is consistent with increased need to mentally correct errors, although that exact interpretation cannot be verified with intelligibility data alone or with pupil data alone. A pattern of needing to dwell on a sentence to disambiguate misperceptions likely contributes to difficulty in running conversation where there are few opportunities to pause and resolve recently heard utterances.

Assessing the Quality of Low-Frequency Acoustic Hearing: Implications for Combined Electroacoustic Stimulation With Cochlear Implants

OBJECTIVES

There are many potential advantages to combined electric and acoustic stimulation (EAS) with a cochlear implant (CI), including benefits for hearing in noise, localization, frequency selectivity, and music enjoyment. However, performance on these outcome measures is variable, and the residual acoustic hearing may not be beneficial for all patients. As such, we propose a measure of spectral resolution that might be more predictive of the usefulness of the residual hearing than the audiogram alone. In the following experiments, we measured performance on spectral resolution and speech perception tasks in individuals with normal hearing (NH) using low-pass filters to simulate steeply sloping audiograms of typical EAS candidates and compared it with performance on these tasks for individuals with sensorineural hearing loss with similar audiometric configurations. Because listeners with NH had similar levels of audibility and bandwidth to listeners with hearing loss, differences between the groups could be attributed to distortions due to hearing loss.

DESIGN

Listeners with NH (n = 12) and those with hearing loss (n = 23) with steeply sloping audiograms participated in this study. The group with hearing loss consisted of 7 EAS users, 14 hearing aid users, and 3 who did not use amplification in the test ear. Spectral resolution was measured with the spectral-temporal modulated ripple test (SMRT), and speech perception was measured with AzBio sentences in quiet and noise. Listeners with NH listened to stimuli through low-pass filters and at two levels (40 and 60 dBA) to simulate low and high audibility. Listeners with hearing loss listened to SMRT stimuli unaided at their most comfortable listening level and speech stimuli at 60 dBA.

RESULTS

Results suggest that performance with SMRT is significantly worse for listeners with hearing loss than for listeners with NH and is not related to audibility. Performance on the speech perception task declined with decreasing frequency information for both listeners with NH and hearing loss. Significant correlations were observed between speech perception, SMRT scores, and mid-frequency audiometric thresholds for listeners with hearing loss.

CONCLUSIONS

NH simulations describe a "best case scenario" for hearing loss where audibility is the only deficit. For listeners with hearing loss, the likely broadening of auditory filters, loss of cochlear nonlinearities, and possible cochlear dead regions may have contributed to distorted spectral resolution and thus deviations from the NH simulations. Measures of spectral resolution may capture an aspect of hearing loss not evident from the audiogram and be a useful tool for assessing the contributions of residual hearing post-cochlear implantation.

A computational study to model the effect of electrode-to-auditory nerve fiber distance on spectral resolution in cochlear implant

Spectral ripple discrimination (SRD) has been widely used to evaluate the spectral resolution in cochlear implant (CI) recipients based on its strong correlation with speech perception performance. However, despite its usefulness for predicting speech perception outcomes, SRD performance exhibits large across-subject variabilities even among subjects implanted with the same CIs and sound processors. The potential factors of this observation include current spread, nerve survival, and CI mapping. Previous studies have found that the spectral resolution reduces with increasing distance of the stimulation electrode from the auditory nerve fibers (ANFs), attributable to increasing current spread. However, it remains unclear whether the spread of excitation is the only cause of the observation, or whether other factors such as temporal interaction also contribute to it. In this study, we used a computational model to investigate channel interaction upon non-simultaneous stimulation with respect to the electrode–ANF distance, and evaluated the SRD performance for five electrode–ANF distances. The SRD performance was determined based on the similarity between two neurograms in response to standard and inverted stimuli and used to evaluate the spectral resolution in the computational model. The spread of excitation was observed to increase with increasing electrode–ANF distance, consistent with previous findings. Additionally, the preceding pulses delivered from neighboring channels induced a channel interaction that either inhibited or facilitated the neural responses to subsequent pulses depending on the electrode–ANF distance. The SRD performance was also found to decrease with increasing electrode–ANF distance. The findings of this study suggest that variation of the neural responses (inhibition or facilitation) with the electrode–ANF distance in CI users may cause spectral smearing, and hence poor spectral resolution. A computational model such as that used in this study is a useful tool for understanding the neural factors related to CI outcomes, such as cannot be accomplished by behavioral studies alone.

Psychoacoustic and Demographic Factors for Speech Recognition of Older Adult Cochlear Implant Users

Purpose This study aimed to evaluate the effects of aging and cochlear implant (CI) on psychoacoustic and speech recognition abilities and to assess the relative contributions of psychoacoustic and demographic factors to speech recognition of older CI (OCI) users. Method Twelve OCI users, 12 older acoustic-hearing (OAH) listeners age-matched to OCI users, and 12 younger normal-hearing (YNH) listeners underwent tests of temporal amplitude modulation detection, temporal gap detection in noise, and spectral-temporal modulated ripple discrimination. Speech reception thresholds were measured for sentence recognition in multitalker, speech-babble noise. Results Statistical analyses showed that, for the small sample of OAH listeners, the degree of hearing loss did not significantly affect any outcome measure. Temporal resolution, spectral resolution, and speech recognition all significantly degraded with both age and the use of a CI (i.e., YNH better than OAH and OAH better than OCI performance). Although both were significantly correlated with OCI users' speech recognition, the duration of CI use no longer had a significant effect on speech recognition once the effect of spectral-temporal ripple discrimination performance was taken into account. For OAH listeners, the only significant predictor of speech recognition was temporal gap detection performance. Conclusion The preliminary results suggest that speech recognition of OCI users may improve with longer duration of CI use, mainly due to higher perceptual acuity to spectral-temporal modulated ripples in acoustic stimuli.

Matched Cohort Comparison Indicates Superiority of Precurved Electrode Arrays

OBJECTIVE

Characterize differences in adult cochlear implant outcomes and programming parameters for a straight (CI422/522) and a precurved (CI532) electrode array.

SETTING

Cochlear implant (CI) program at a tertiary otologic center.

PATIENTS

Fifty-eight adults were included in the study; 29 were implanted with CI422 or CI522 and 29 were implanted with CI532. Each CI532 recipient was matched to a CI422/522 recipient in terms of age and preoperative hearing thresholds for comparison purposes.

MAIN OUTCOME MEASURES

Consonant-Nucleus-Consonant (CNC) words, AzBio sentences, residual audiometric thresholds, and Speech Spatial Qualities (SSQ) questionnaire collected 6 months postoperatively were used to characterize outcomes. Pulse duration, maxima, impedances, and overall charge measurements were used to characterize programming parameters.

RESULTS

Postoperative unaided low frequency pure-tone average (LFPTA) was significantly better for the CI532 group. CNC scores were significantly better for the CI532 group. Impedances and pulse duration were significantly lower for the CI532 group, but there was no difference in overall charge between the groups.

CONCLUSION

The CI532 group showed either similar or statistically superior results on all measures when compared with the CI422/522 suggesting that the CI532 electrode may be an advantageous substitute for the CI522.

Validating a Quick Spectral Modulation Detection Task

OBJECTIVES

The Quick Spectral Modulation Detection (QSMD) test provides a quick and clinically implementable spectral resolution estimate for cochlear implant (CI) users. However, the original QSMD software (QSMD(MySound)) has technical and usability limitations that prevent widespread distribution and implementation. In this article, we introduce a new software package EasyQSMD, which is freely available software with the goal of both simplifying and standardizing spectral resolution measurements.

DESIGN

QSMD was measured for 20 CI users using both software packages.

RESULTS

No differences between the two software packages were detected, and based on the 95% confidence interval of the difference between tests, the difference between the tests is expected to be <2% points. The average test duration was under 4 minutes.

CONCLUSIONS

EasyQSMD is considered functionally equivalent to QSMD(MySound) providing a clinically feasible and quick estimate of spectral resolution for CI users.

Speech Perception Outcomes for Adult Cochlear Implant Recipients Using a Lateral Wall or Perimodiolar Array

AIM

To assess the speech perception outcomes of adult CI recipients with significant preimplant low frequency hearing, examining differences between perimodiolar and lateral wall electrode placement in order to provide clinical guidance for clinicians and surgeons.

METHODS

A prospective cohort study was undertaken identifying all adults who received a thin straight electrode array (TSEA) at the Royal Victorian Eye & Ear Hospital (RVEEH) from 2010 to 2015 and who had a preimplant low frequency pure tone median ≤70 dB HL (n = 63). A retrospective review was completed of the RVEEH database to identify a comparison group who had been implanted with a perimodiolar electrode array, comprising adults implanted between 2004 and 2011 (PM Group) with preimplant hearing equivalent to the TSEA group (n = 70). The TSEA Group were further divided into subgroups in which n = 19 used EAS (TSEA-EAS) and n = 44 who used electric-only hearing (TSEA-Standard).

RESULTS

There was no significant difference in median speech perception outcomes between the TSEA and PM Groups (TSEA 61.7%, PM 67.3%, p = 0.954). A significant difference was found between the TSEA-EAS and TSEA-Standard subgroups for median speech perception outcome (TSEA-EAS median 73.5%, TSEA-Standard median 58.3%, p = 0.043).

CONCLUSIONS

Significant speech perception benefit following cochlear implantation was achieved with both the perimodiolar and lateral wall electrode arrays and no significant difference was found between outcomes with those array types in this population of adults with functional low frequency hearing pre-implant. Those that received a TSEA, had preserved hearing, and utilised an EAS sound processor performed better than their peers with a TSEA and electric-only hearing.

Comparison of a Mid Scala and a Perimodiolar Electrode in Adults: Performance, Impedances, and Psychophysics

OBJECTIVES

The HiFocus Mid-Scala electrode array (HFms) is designed to sit within the scala tympani without touching either the lateral wall or the modiolus. The aim of this study was to compare the HFms to the Helix perimodiolar electrode array.

METHOD

Two groups of recipients with Helix (n = 22 ears) and HFms (n = 29 ears) electrode arrays were retrospectively identified and matched by age at implantation and duration of severe to profound deafness. Most comfortable listening levels (M), impedances, Freiburger Monosyllables in quiet, and Oldenburg sentences in adaptive noise were compared at 3, 6, and 12 months postimplant.

RESULTS

Median scores for monosyllables in quiet for the HFms group were significantly better than the Helix group at each test interval (p < 0.05). Speech perception in quiet also significantly improved from 3 to 12 months for both groups (p < 0.001). There was no significant difference between the groups for speech in noise. Impedances were significantly lower for the HFms group at 12 months (p < 0.05) except at the basal end and M levels were generally higher.

CONCLUSIONS

The HFms group had better median performance for monosyllables in quiet than the Helix group at each test interval, although performance in noise was similar. For speech in noise, the HFms group appear to reach optimum performance quicker than the Helix group. Impedances were lower in the HFms group across the array, other than at the most basal end, and support our hypothesis that the HFms assumes a more lateral position within the cochlea than the Helix electrode, although our article did not include imaging data.