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... Show moreObjectives: 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. Show less
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... Show moreObjectives: 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. Show less
Objectives: Many studies have assessed the performance of individuals with cochlear implants (CIs) with electrically evoked compound action potentials (eCAPs). These eCAP-based studies have focused... Show moreObjectives: Many studies have assessed the performance of individuals with cochlear implants (CIs) with electrically evoked compound action potentials (eCAPs). These eCAP-based studies have focused on the amplitude information of the response, without considering the temporal firing properties of the excited auditory nerve fibers (ANFs), such as neural latency and synchrony. These temporal features have been associated with neural health in animal studies and, consequently, could be of importance to clinical CI outcomes. With a deconvolution method, combined with a unitary response, the eCAP can be mathematically unraveled into the compound discharge latency distribution (CDLD). The CDLD reflects both the number and the temporal firing properties of excited ANFs. The present study aimed to determine to what extent the CDLD derived from intraoperatively recorded eCAPs is related to speech perception in individuals with CIs. Design: This retrospective study acquired data on monosyllabic word recognition scores and intraoperative eCAP amplitude growth functions from 124 adult patients with postlingual deafness that received the Advanced Bionics HiRes 90K device. The CDLD was determined for each recorded eCAP waveform by deconvolution. Each of the two Gaussian components of the CDLD was described by three parameters: the amplitude, the firing latency (the average latency of each component of the CDLD), and the variance of the CDLD components (an indication of the synchronicity of excited ANFs). Apart from these six CDLD parameters, the area under the CDLD curve (AUCD) and the slope of the AUCD growth function were determined as well. The AUCD was indicative of the total number of excited ANFs over time. The slope of the AUCD growth function indicated the increases in the number of excited ANFs with stimulus level. Associations between speech perception and each of these eight CDLD-related parameters were investigated with linear mixed modeling. Results: In individuals with CIs, larger amplitudes of the two CDLD components, greater AUCD, and steeper slopes of the AUCD growth function were all significantly associated with better speech perception. In addition, a smaller latency variance in the early CDLD component, but not in the late, was significantly associated with better speech recognition scores. Speech recognition was not significantly dependent on CDLD latencies. The AUCD and the slope of the AUCD growth function provided a similar explanation of the variance in speech perception (R-2) as the eCAP amplitude, the slope of the amplitude growth function, the amplitude, and variance of the first CDLD component. Conclusion: The results demonstrate that both the number and the neural synchrony of excited ANFs, as revealed by CDLDs, are indicative of postimplantation speech perception in individuals with a CI. Because the CDLD-based parameters yielded a higher significance than the eCAP amplitude or the AGF slope, the authors conclude that CDLDs can serve as a clinical predictor of the survival of ANFs and that they have predictive value for postoperative speech perception performance. Thus, it would be worthwhile to incorporate the CDLD into eCAP measures in future clinical applications. Show less
Objectives: Speech understanding in noise is difficult for patients with a cochlear implant. One common and disruptive type of noise is transient noise. We have tested transient noise reduction ... Show moreObjectives: Speech understanding in noise is difficult for patients with a cochlear implant. One common and disruptive type of noise is transient noise. We have tested transient noise reduction (TNR) algorithms in cochlear implant users to investigate the merits of personalizing the noise reduction settings based on a subject's own preference. Design: The effect of personalizing two parameters of a broadband and a multiband TNR algorithm (TNRbb and TNRmb, respectively) on speech recognition was tested in a group of 15 unilaterally implanted subjects in cafeteria noise. The noise consisted of a combination of clattering dishes and babble noise. Each participant could individually vary two parameters, namely the scaling factor of the attenuation and the release time (tau). The parameter tau represents the duration of the attenuation applied after a transient is detected. As a reference, the current clinical standard TNR "SoundRelax" from Advanced Bionics was tested (TNRbb-std). Effectiveness of the algorithms on speech recognition was evaluated adaptively by determining the speech reception threshold (SRT). Possible subjective benefits of the algorithms were assessed using a rating task at a fixed signal-to-noise ratio (SNR) of SRT + 3 dB. Rating was performed on four items, namely speech intelligibility, speech naturalness, listening effort, and annoyance of the noise. Word correct scores were determined at these fixed speech levels as well. Results: The personalized TNRmb improved the SRT statistically significantly with 1.3 dB, while the personalized TNRbb degraded it significantly by 1.7 dB. For TNRmb, we attempted to further optimize its settings by determining a group-based setting, leaving out those subjects that did not experience a benefit from it. Using these group-based settings, however, TNRmb did not have a significant effect on the SRT any longer. TNRbb-std did not affect speech recognition significantly. No significant effects on subjective ratings were found for any of the items investigated. In addition, at a constant speech level of SRT + 3 dB, no effect of any of the algorithms was found on word correct scores, including TNRmb with personalized settings. Conclusions: Our study results indicate that personalizing noise reduction settings of a multiband TNR algorithm can significantly improve speech intelligibility in transient noise, but only under challenging listening conditions around the SRT. At more favorable SNRs (SRT + 3 dB), this benefit was lost. We hypothesize that TNRmb was beneficial at lower SNRs, because of more effective artifact detection under those conditions. Group-averaged settings of the multiband algorithm did not significantly affect speech recognition. TNRbb decreased speech recognition significantly using personalized parameter settings. Rating scores were not significantly affected by the algorithms under any condition tested. The currently available TNR algorithm for Advanced Bionics systems (SoundRelax) is a broadband filter that does not support personalization of its settings. Future iterations of this algorithm might benefit from upgrading it to a multiband variant with the option to personalize its parameter settings. Show less
Neve, O.M.; Boerman, J.A.; Hout, W.B. van den; Briaire, J.J.; Benthem, P.P.G. van; Frijns, J.H.M. 2021
Objectives: While the costs and outcomes of cochlear implantation (CI) have been widely assessed, most of these analyses were solely performed from the perspective of healthcare costs. This study... Show moreObjectives: While the costs and outcomes of cochlear implantation (CI) have been widely assessed, most of these analyses were solely performed from the perspective of healthcare costs. This study assesses the costs and benefits of CI in the Netherlands from a broader societal perspective, including health outcomes, healthcare cost, educational cost, and productivity losses and gains. Design: The cost and benefits of CI were analyzed in this cost-benefit analysis, in which a monetary value is put on both the resources needed and the outcomes of CI. The costs and benefits were analyzed by prototypical instances of three groups, representing the majority of cochlear implant patients: prelingually deaf children implanted at the age of 1, adults with progressive profound hearing loss implanted at the age of 40 and seniors implanted at the age of 70 with progressive profound hearing loss. Costs and benefits were estimated over the expected lifetimes of the members of each group, using a Markov state transition model. Model parameters and assumptions were based on published literature. Probabilistic and one-way sensitivity analyses were performed. Results: In all three patient groups, the total benefits of CI exceeded the total cost, leading to a net benefit of CI. Prelingually deaf children with a bilateral CI had a lifetime positive outcome net benefit of euro433,000. Adults and seniors with progressive profound hearing loss and a unilateral CI had a total net benefit of euro275,000 and euro76,000, respectively. These results ensue from health outcomes expressed in monetary terms, reduced educational cost, and increased productivity. Conclusions: Based on estimates from modeling, the increased healthcare costs due to CI were more than compensated by the value of the health benefits and by savings in educational and productivity costs. In particular, for children and working adults, the societal benefit was positive even without taking health benefits into account. Therefore, CI generates an advantage for both patients and society. Show less
Objectives: Misplacement of the electrode array is associated with impaired speech perception in patients with cochlear implants (CIs). Translocation of the electrode array is the most common... Show moreObjectives: Misplacement of the electrode array is associated with impaired speech perception in patients with cochlear implants (CIs). Translocation of the electrode array is the most common misplacement. When a CI is translocated, it crosses the basilar membrane from the scala tympani into the scala vestibuli. The position of the implant can be determined on a postoperative CT scan. However, such a scan is not obtained routinely after CI insertion in many hospitals, due to radiation exposure and processing time. Previous studies have shown that impedance measures might provide information on the placement of the electrode arrays. The electrode impedance was measured by dividing the plateau voltage at the end of the first phase of the pulse by the injected current. The access resistance was calculated using the so-called access voltage at the first sampled time point after the start of the pulse divided by the injected current. In our study, we obtained the electrode impedance and the access resistance to detect electrode translocations using electrical field imaging. We have investigated how reliably these two measurements can detect electrode translocation, and which method performed best. Design: We calculated the electrode impedances and access resistances using electrical field imaging recordings from 100 HiFocus Mid-Scala CI (Advanced Bionics, Sylmar, CA) recipients. We estimated the normal values of these two measurements as the baselines of the implant placed in the cochlea without translocation. Next, we calculated the maximal electrode impedance deviation and the maximal access-resistance deviation from the respective baselines as predictors of translocation. We classified these two predictors as translocations or nontranslocations based on the bootstrap sampling method and receiver operating characteristics curves analysis. The accuracy could be calculated by comparing those predictive results to a gold standard, namely the clinical CT scans. To determine which measurement more accurately detected translocation, the difference between the accuracies of the two measurements was calculated. Results: Using the bootstrap sampling method and receiver operating characteristics-based optimized threshold criteria, the 95% confidence intervals of the accuracies of translocation detections ranged from 77.8% to 82.1% and from 89.5% to 91.2% for the electrode impedance and access resistance, respectively. The accuracies of the maximal access-resistance deviations were significantly larger than that of the maximal electrode impedance deviations. The location of the translocation as predicted by the access resistance was significantly correlated with the result derived from the CT scans. In contrast, no significant correlation was observed for the electrode impedance. Conclusions: Both the electrode impedance and access resistance proved reliable metrics to detect translocations for HiFocus Mid-Scala electrode arrays. The access resistance had, however, significantly better accuracy and it also reliably detected the electrode-location of translocations. The electrode impedance did not correlate significantly with the location of translocation. Measuring the access resistance is, therefore, the recommended method to detect electrode-array translocations. These measures can provide prompt feedback for surgeons after insertion, improving their surgical skills, and ultimately reducing the number of translocations.In the future, such measurements may allow near-real-time monitoring of the electrode array during insertion, helping to avoid translocations. Show less
Objectives: For children to understand the emotional behavior of others, the first two steps involve emotion encoding and emotion interpreting, according to the Social Information Processing model.... Show moreObjectives: For children to understand the emotional behavior of others, the first two steps involve emotion encoding and emotion interpreting, according to the Social Information Processing model. Access to daily social interactions is prerequisite to a child acquiring these skills, and barriers to communication such as hearing loss impede this access. Therefore, it could be challenging for children with hearing loss to develop these two skills. The present study aimed to understand the effect of prelingual hearing loss on children's emotion understanding, by examining how they encode and interpret nonverbal emotional cues in dynamic social situations. Design: Sixty deaf or hard-of-hearing (DHH) children and 71 typically hearing (TH) children (3-10 years old, mean age 6.2 years, 54% girls) watched videos of prototypical social interactions between a target person and an interaction partner. At the end of each video, the target person did not face the camera, rendering their facial expressions out of view to participants. Afterward, participants were asked to interpret the emotion they thought the target person felt at the end of the video. As participants watched the videos, their encoding patterns were examined by an eye tracker, which measured the amount of time participants spent looking at the target person's head and body and at the interaction partner's head and body. These regions were preselected for analyses because they had been found to provide cues for interpreting people's emotions and intentions. Results: When encoding emotional cues, both the DHH and TH children spent more time looking at the head of the target person and at the head of the interaction partner than they spent looking at the body or actions of either person. Yet, compared with the TH children, the DHH children looked at the target person's head for a shorter time (b = -0.03, p = 0.030), and at the target person's body (b = 0.04, p = 0.006) and at the interaction partner's head (b = 0.03, p = 0.048) for a longer time. The DHH children were also less accurate when interpreting emotions than their TH peers (b = -0.13, p = 0.005), and their lower scores were associated with their distinctive encoding pattern. Conclusions: The findings suggest that children with limited auditory access to the social environment tend to collect visually observable information to compensate for ambiguous emotional cues in social situations. These children may have developed this strategy to support their daily communication. Yet, to fully benefit from such a strategy, these children may need extra support for gaining better social-emotional knowledge. Show less
Objectives: 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)... Show moreObjectives: 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. Design: In a cross-sectional study design, speech perception measures and ultrahigh-resolution computed tomography scans were performed in 129 experienced CI recipients with a postlingual onset of hearing loss. Data were collected between December 2016 and January 2018 in the Radboud University Medical Center, Nijmegen, the Netherlands. The participants received either a precurved electrode (N = 85) or a straight electrode (N = 44), all from the same manufacturer. The biographic variables evaluated were age at implantation, level of education, and years of hearing loss. The audiometric factors explored were preoperative and postoperative pure-tone average residual hearing and preoperative speech perception score. The electrode position factors analyzed, as measured from images obtained with the ultrahigh-resolution computed tomography scan, were the scalar location, angular insertion depth of the basal and apical electrode contacts, and the wrapping factor (i.e., electrode-to-modiolus distance), as well as the type of electrode used. These 11 variables were tested for their effect on three speech perception outcomes: consonant-vowel-consonant words in quiet tests at 50 dB SPL (CVC50) and 65 dB SPL (CVC65), and the digits-in-noise test. Results: A lower age at implantation was correlated with a higher CVC50 phoneme score in the straight electrode group. Other biographic variables did not correlate with speech perception. Furthermore, participants implanted with a precurved electrode and who had poor preoperative hearing thresholds performed better in all speech perception outcomes than the participants implanted with a straight electrode and relatively better preoperative hearing thresholds. After correcting for biographic factors, audiometric variables, and scalar location, we showed that the precurved electrode led to an 11.8 percentage points (95% confidence interval: 1.4-20.4%; p = 0.03) higher perception score for the CVC50 phonemes compared with the straight electrode. Furthermore, contrary to our initial expectations, the preservation of residual hearing with the straight electrode was poor, as the median preoperative and the postoperative residual hearing thresholds for the straight electrode were 88 and 122 dB, respectively. Conclusions: Cochlear implantation with a precurved electrode results in a significantly higher speech perception outcome, independent of biographic factors, audiometric factors, and scalar location. Show less
Objectives:The ability to perceive soft speech by cochlear implant (CI) users is restricted in part by the inherent system noise produced by the speech processor, and in particular by the... Show moreObjectives:The ability to perceive soft speech by cochlear implant (CI) users is restricted in part by the inherent system noise produced by the speech processor, and in particular by the microphone(s). The algorithm "SoftVoice" (SV) was developed by Advanced Bionics to enhance the perception of soft speech by reducing the system noise in speech processors. The aim of this study was to examine the effects of SV on speech recognition and listening effort.Design:Seventeen adult Advanced Bionics CI recipients were recruited and tested in two sessions. The effect of SV on speech recognition was tested by determining the SRT in quiet using the Matrix test. Based on the individual subjects' SRTs, we investigated speech-recognition scores at fixed speech levels, namely SRT -5 dB, SRT +0 dB, SRT +5 dB, and SRT +10 dB, again in quiet and using the Matrix test. Listening effort was measured at each of these speech levels subjectively by using a rating scale, and objectively by determining pupil dilation with pupillometry. To verify whether SoftVoice had any negative effects on speech perception in noise, we determined the SRT in steady state, speech-weighted noise of 60 dBA.Results:Our results revealed a significant improvement of 2.0 dB on the SRT in quiet with SoftVoice. The average SRT in quiet without SoftVoice was 38 dBA. SoftVoice did not affect the SRT in steady state, speech-weighted noise of 60 dB. At an average speech level of 33 dBA (SRT -5 dB) and 38 dBA (SRT +0 dB) in quiet, significant improvements of 17% and 9% on speech-recognition scores were found with SoftVoice, respectively. At higher speech levels, SoftVoice did not significantly affect speech recognition. Pupillometry did not show significant effects of SoftVoice at any speech level. However, subjective ratings of listening effort indicated a decrease of listening effort with SoftVoice at a speech level of 33 dBA.Conclusions:We conclude that SoftVoice substantially improves recognition of soft speech and lowers subjective listening effort at low speech levels in quiet. However, no significant effect of SoftVoice was found on pupil dilation. As SRTs in noise were not statistically significantly affected by SoftVoice, we conclude that SoftVoice can be used in noisy listening conditions with little negative impact on speech recognition, if any. The increased power demands of the algorithm are considered to be negligible. It is expected that SoftVoice will reduce power consumption at low ambient sound levels. These results support the use of SoftVoice as a standard feature of Advanced Bionics CI fittings for everyday use. Show less
Objectives: The impact of the newly introduced cochlear implantation criteria of the United Kingdom and Flanders (Dutch speaking part of Belgium) was examined in the patient population of a... Show moreObjectives: The impact of the newly introduced cochlear implantation criteria of the United Kingdom and Flanders (Dutch speaking part of Belgium) was examined in the patient population of a tertiary referral center in the Netherlands. We compared the patients who would be included/excluded under the new versus old criteria in relation to the actual improvement in speech understanding after implantation in our center. We also performed a sensitivity analysis to examine the effectiveness of the different preoperative assessment approaches used in the United Kingdom and Flanders. Design: The selection criteria were based on preoperative pure-tone audiometry at 0.5, 1, 2, and 4 kHz and a speech perception test (SPT) with and without best-aided hearing aids. Postoperatively, the same SPT was conducted to assess the benefit in speech understanding. Results: The newly introduced criteria in Flanders and the United Kingdom were less restrictive, resulting in greater percentages of patients implanted with CI (increase of 30%), and sensitivity increase of 31%. The preoperative best-aided SPT, used by both countries, had the highest diagnostic ability to indicate a postoperative improvement of speech understanding. We observed that patient selection was previously dominated by the pure-tone audiometry criteria in both countries, whereas speech understanding became more important in their new criteria. Among patients excluded by the new criteria, seven of eight (the United Kingdom and Flanders) did exhibit improved postoperative speech understanding. Conclusions: The new selection criteria of the United Kingdom and Flanders led to increased numbers of postlingually deafened adults benefitting from CI. The new British and Flemish criteria depended on the best-aided SPT with the highest diagnostic ability. Notably, the new criteria still led to the rejection of candidates who would be expected to gain considerably in speech understanding after implantation. Show less
Objectives: Phantom electrode stimulation was developed for cochlear implant (CI) systems to provide a lower pitch percept by stimulating more apical regions of the cochlea, without inserting the... Show moreObjectives: Phantom electrode stimulation was developed for cochlear implant (CI) systems to provide a lower pitch percept by stimulating more apical regions of the cochlea, without inserting the electrode array deeper into the cochlea. Phantom stimulation involves simultaneously stimulating a primary and a compensating electrode with opposite polarity, thereby shifting the electrical field toward the apex and eliciting a lower pitch percept. The current study compared the effect sizes (in shifts of place of excitation) of multiple phantom configurations by matching the perceived pitch with phantom stimulation to that perceived with monopolar stimulation. Additionally, the effects of electrode location, type of electrode array, and stimulus level on the perceived pitch were investigated. Design: Fifteen adult advanced bionics CI users participated in this study, which included four experiments to eventually measure the shifts in place of excitation with five different phantom configurations. The proportions of current delivered to the compensating electrode, expressed as sigma, were 0.5, 0.6, 0.7, and 0.8 for the symmetrical biphasic pulses (SBC0.5, SBC0.6, SBC0.7, and SBC0.8) and 0.75 for the pseudomonophasic pulse shape (PSA(0.75)). A pitch discrimination experiment was first completed to determine which basal and apical electrode contacts should be used for the subsequent experiments. An extensive loudness balancing experiment followed where both the threshold level (T-level) and most comfortable level (M-level) were determined to enable testing at multiple levels of the dynamic range. A pitch matching experiment was then performed to estimate the shift in place of excitation at the chosen electrode contacts. These rough shifts were then used in the subsequent experiment, where the shifts in place of excitation were determined more accurately. Results: Reliable data were obtained from 20 electrode contacts. The average shifts were 0.39, 0.53, 0.64, 0.76, and 0.53 electrode contacts toward the apex for SBC0.5, SBC0.6, SBC0.7, SBC0.8, and PSA(0.75), respectively. When only the best configurations per electrode contact were included, the average shift in place of excitation was 0.92 electrode contacts (range: 0.25 to 2.0). While PSA(0.75)leads to equal results as the SBC configurations in the apex, it did not result in a significant shift at the base. The shift in place of excitation was significantly larger at the apex and with lateral wall electrode contacts. The stimulus level did not affect the shift. Conclusions: Phantom stimulation results in significant shifts in place of excitation, especially at the apical part of the electrode array. The phantom configuration that leads to the largest shift in place of excitation differs between subjects. Therefore, the settings of the phantom electrode should be individualized so that the phantom stimulation is optimized for each CI user. The real added value to the sound quality needs to be established in a take-home trial. Show less
Objective: The reliability of the electrically evoked compound action potential (eCAP) threshold depends on its precision and accuracy. The precision of the eCAP threshold reflects its variability,... Show moreObjective: The reliability of the electrically evoked compound action potential (eCAP) threshold depends on its precision and accuracy. The precision of the eCAP threshold reflects its variability, while the accuracy of the threshold shows how close it is to the actual value. The objective of this study was to determine the test/retest variability of the eCAP threshold in Advanced Bionics cochlear implant users, which has never been reported before. We hypothesized that the test/retest variability is dependent on the presence of random noise in the recorded eCAP waveforms. If this holds true, the recorded error should be reduced by approximately the square-root of the number of averages. As secondary objectives, we assessed the effects of the slope of the amplitude growth function (AGF), cochlear location, and eCAP threshold on eCAP threshold precision. We hypothesized that steeper slopes should result in better precision of the linearly extrapolated eCAP threshold. As other studies have shown that apical regions have steeper slopes and larger eCAPs, we recorded eCAPs in three different cochlear locations. The difference of the precision between two commonly applied stimulus-artifact reduction paradigms on eCAP threshold precision was compared, namely averaging of alternating stimulus polarities (AP averaging) and forward masking (FM). FM requires the addition of more waveforms than AP averaging, and hence we expected FM to have lower precision than AP.Design: This was an unmasked, descriptive, and observational study with a cross-over (repeated measures) design that included 13 subjects. We recorded eCAPs on three electrode contacts: in the base, middle, and apex of the cochlea at 10 stimulus intensities. Per stimulus level, 256 eCAP waveforms were recorded. eCAP thresholds were determined by constructing AGFs and linear extrapolation to zero-amplitude. The precision of the eCAP threshold was calculated as the SD using a Monte Carlo simulation, as a function of the number of waveform averages.Results: The SD of the eCAP threshold was reduced by approximately the square root of two when the number of averages in the eCAP waveforms was doubled. The precision was significantly better when the slope of the AGF was steeper and was more favorable in the cochlear base than in the apex. Precision was better when AP averaging was used. Absolute eCAP threshold did not significantly affect precision. At the default number of 32 waveform averages in the Advanced Bionics system, we report a median SD of the eCAP threshold of 2 to 3 mu A, with a range of 1 to 11 mu A across the cochlea. Previous studies have shown that the total error, based on the 95% confidence bounds of the linear extrapolation, can be as high as -260 to +120 mu A.Conclusions: The median variability in the eCAP threshold proved to be small compared with the total variability introduced by the linear extrapolation method. Yet there was substantial intersubject variability. Therefore, we recommend monitoring the SD during eCAP recording to facilitate informed decisions when to terminate waveform collection. From a precision perspective, AP averaging is preferable over FM as it has better precision, while fewer recordings are needed, making it the more time-efficient method of the two. Show less
Objectives: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear... Show moreObjectives: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear current spread. For example, tripolar stimulation administers current to a central electrode and uses the two flanking electrodes as the return pathway, creating a narrower intracochlear electrical field and hence increases spectral resolution when compared with monopolar (MP) stimulation. However, more current is required, and in some patients, specifically the ones with high electrode impedances, full loudness growth cannot be supported because of compliance limits. The present study describes and analyses a new loudness encoding approach that uses tripolar stimulation near threshold and gradually broadens the excitation (by decreasing compensation coefficient sigma) to increase loudness without the need to increase overall current. It is hypothesized that this dynamic current focusing (DCF) strategy increases spatial selectivity, especially at lower loudness levels, while maintaining maximum selectivity at higher loudness levels, without reaching compliance limits.Design: Eleven adult cochlear implant recipients with postlingual hearing loss, with at least 9 months of experience with their HiRes90K implant, were selected to participate in this study. Baseline performance regarding speech intelligibility in noise (Dutch matrix sentence test), spectral ripple discrimination at 45 and 65 dB, and temporal modulation detection thresholds were assessed using their own clinical program, fitted on a Harmony processor. Subsequently, the DCF strategy was fitted on a research Harmony processor. Threshold levels were determined with sigma = 0.8, which means 80% of current is returned to the flanking electrodes and the remaining 20% to the extracochlear ground electrode. Instead of increasing overall pulse magnitude, sigma was decreased to determine most comfortable loudness. After 2 to 3hr of adaptation to the research strategy, the same psychophysical measures were taken.Results: At 45 dB, average spectral ripple scores improved significantly from 2.4 ripples per octave with their clinical program to 3.74 ripples per octave with the DCF strategy (p = 0.016). Eight out of 11 participants had an improved spectral resolution at 65 dB. Nevertheless, no significant difference between DCF and MP was observed at higher presentation levels. Both speech-in-noise and temporal modulation detection thresholds were equal for MP and DCF strategies. Subjectively, 2 participants preferred the DCF strategy over their own clinical program, 2 preferred their own strategy, while the majority of the participants had no preference. Battery life was decreased and ranged from 1.5 to 4hr.Conclusions: The DCF strategy gives better spectral resolution, at lower loudness levels, but equal performance on speech tests. These outcomes warrant for a longer adaptation period to study long-term outcomes and evaluate if the outcomes in the ripple tests transfer to the speech scores. Further research, for example, with respect to fitting rules and reduction of power consumption, is necessary to make the DCF strategy suitable for routine clinical application. Show less
Objectives: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear... Show moreObjectives: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear current spread.For example, tripolar stimulation administers current to a central electrode and uses the two flanking electrodes as the return pathway, creating a narrower intracochlear electrical field and hence increases spectral resolution when compared with monopolar (MP) stimulation. However, more current is required, and in some patients, specifically the ones with high electrode impedances, full loudness growth cannot be supported because of compliance limits. The present study describes and analyses a new loudness encoding approach that uses tripolar stimulation near threshold and gradually broadens the excitation (by decreasing compensation coefficient σ) to increase loudness without the need to increase overall current. It is hypothesized that this dynamic current focusing (DCF) strategy increases spatial selectivity, especially at lower loudness levels, while maintaining maximum selectivity at higher loudness levels, without reaching compliance limits. Design: Eleven adult cochlear implant recipients with postlingual hearing loss, with at least 9 months of experience with their HiRes90K implant, were selected to participate in this study. Baseline performance regarding speech intelligibility in noise (Dutch matrix sentence test), spectral ripple discrimination at 45 and 65 dB, and temporal modulation detection thresholds were assessed using their own clinical program, fittedon a Harmony processor. Subsequently, the DCF strategy was fitted on a research Harmony processor. Threshold levels were determined with σ = 0.8, which means 80% of current is returned to the flanking electrodes and the remaining 20% to the extracochlear ground electrode. Instead of increasing overall pulse magnitude, σ was decreased to determine most comfortable loudness. After 2 to 3 hr of adaptation to the research strategy, the same psychophysical measures were taken. Results: At 45 dB, average spectral ripple scores improved significantly from 2.4 ripples per octave with their clinical program to 3.74 ripples peroctave with the DCF strategy (p = 0.016). Eight out of 11 participants had an improved spectral resolution at 65 dB. Nevertheless, no significant difference between DCF and MP was observed at higher presentationlevels. Both speech-in-noise and temporal modulation detection thresholds were equal for MP and DCF strategies. Subjectively, 2 participants preferred the DCF strategy over their own clinical program, 2 preferred their own strategy, while the majority of the participants had no preference. Battery life was decreased and ranged from 1.5 to 4 hr. Conclusions: The DCF strategy gives better spectral resolution, at lower loudness levels, but equal performance on speech tests. These outcomes warrant for a longer adaptation period to study long-term outcomes and evaluate if the outcomes in the ripple tests transfer to the speech scores. Further research, for example, with respect to fitting rules and reduction of power consumption, is necessary to make the DCF strategy suitable for routine clinical application. Show less
