Evaluation of the American English Matrix Test with Cochlear Implant Recipients

OBJECTIVE

Currently, the variety of speech recognition tests used to evaluate cochlear implant (CI) recipients makes it difficult to compare results, especially across languages. The Matrix Test limits contextual cues and is available in multiple languages, including American English. The current study investigated test format and noise type for the American English Matrix Test (AMT) and compared results to AzBio sentence scores in adult CI recipients.

DESIGN

Fifteen experienced CI recipients were administered the AMT in fixed- and adaptive-level formats and AzBio sentences in a fixed-level format. Testing in noise used the AMT-specific noise and 4-talker babble.

RESULTS

Ceiling effects were present for all AMT fixed-level conditions and AzBio sentences in quiet. Group mean AzBio scores were poorer than AMT scores. Noise type affected performance regardless of format; 4-talker babble was more challenging.

CONCLUSIONS

The limited number of word choices in each category likely aided listeners performance for the AMT compared to AzBio sentences. The use of the AMT in the designed adaptive-level format would allow effective evaluation and comparison of CI performance internationally. A test battery with the AMT may also benefit from including AzBio sentences in 4-talker babble to reflect performance during listening challenges.

Asymmetric Hearing Loss in Adult Cochlear Implant Recipients: Results and Recommendations From a Multisite Prospective Clinical Trial

OBJECTIVE

A multisite clinical trial was conducted to obtain cochlear implant (CI) efficacy data in adults with asymmetric hearing loss (AHL) and establish an evidence-based framework for clinical decision-making regarding CI candidacy, counseling, and assessment tools. Study hypotheses were threefold: (1) 6-month postimplant performance in the poor ear (PE) with a CI will be significantly better than preimplant performance with a hearing aid (HA), (2) 6-month postimplant performance with a CI and HA (bimodal) will be significantly better than preimplant performance with bilateral HAs (Bil HAs), and (3) 6-month postimplant bimodal performance will be significantly better than aided, better ear (BE) performance.

DESIGN

Forty adults with AHL from four, metropolitan CI centers participated. Hearing criteria for the ear to be implanted included (1) pure-tone average (PTA, 0.5, 1, 2 kHz) of >70 dB HL, (2) aided, monosyllabic word score of ≤30%, (3) duration of severe-to-profound hearing loss of ≥6 months, and (4) onset of hearing loss ≥6 years of age. Hearing criteria for the BE included (1) PTA (0.5, 1, 2, 4 kHz) of 40 to 70 dB HL, (2) currently using a HA, (3) aided, word score of >40%, and (4) stable hearing for the previous 1-year period. Speech perception and localization measures, in quiet and in noise, were administered preimplant and at 3-, 6-, 9-, and 12-months postimplant. Preimplant testing was performed in three listening conditions, PE HA, BE HA, and Bil HAs. Postimplant testing was performed in three conditions, CI, BE HA, and bimodal. Outcome factors included age at implantation and length of deafness (LOD) in the PE.

RESULTS

A hierarchical nonlinear analysis predicted significant improvement in the PE by 3 months postimplant versus preimplant for audibility and speech perception with a plateau in performance at approximately 6 months. The model predicted significant improvement in postimplant, bimodal outcomes versus preimplant outcomes (Bil HAs) for all speech perception measures by 3 months. Both age and LOD were predicted to moderate some CI and bimodal outcomes. In contrast with speech perception, localization in quiet and noise was not predicted to improve by 6 months when comparing Bil HAs (preimplant) to bimodal (postimplant) outcomes. However, when participants' preimplant everyday listening condition (BE HA or Bil HAs) was compared with bimodal performance, the model predicted significant improvement by 3 months for localization in quiet and noise. Lastly, BE HA results were stable over time; a generalized linear model analysis revealed bimodal performance was significantly better than performance with a BE HA at all postimplant intervals for most speech perception measures and localization.

CONCLUSIONS

Results revealed significant CI and bimodal benefit for AHL participants by 3-months postimplant, with a plateau in CI and bimodal performance at approximately 6-months postimplant. Results can be used to inform AHL CI candidates and to monitor postimplant performance. On the basis of this and other AHL research, clinicians should consider a CI for individuals with AHL if the PE has a PTA (0.5, 1, 2 kHz) >70 dB HL and a Consonant-Vowel Nucleus-Consonant word score ≤40%. LOD >10 years should not be a contraindication.

Relationship between electrode position and temporal modulation sensitivity in cochlear implant users: Are close electrodes always better?

Temporal modulation sensitivity has been studied extensively for cochlear implant (CI) users due to its strong correlation to speech recognition outcomes. Previous studies reported that temporal modulation detection thresholds (MDTs) vary across the tonotopic axis and attributed this variation to patchy neural survival. However, correlates of neural health identified in animal models depend on electrode position in humans. Nonetheless, the relationship between MDT and electrode location has not been explored. We tested 13 ears for the effect of distance on modulation sensitivity, specifically targeting the question of whether electrodes closer to the modiolus are universally beneficial. Participants in this study were postlingually deafened and users of Cochlear Nucleus CIs. The distance of each electrode from the medial wall (MW) of the cochlea and mid-modiolar axis (MMA) was measured from scans obtained using computerized tomography (CT) imaging. The distance measures were correlated with slopes of spatial tuning curves measured on selected electrodes to investigate if electrode position accounts, at least in part, for the width of neural excitation. In accordance with previous findings, electrode position explained 24% of the variance in slopes of the spatial tuning curves. All functioning electrodes were also measured for MDTs. Five ears showed a positive correlation between MDTs and at least one distance measure across the array; 6 ears showed negative correlations and the remaining two ears showed no relationship. The ears showing positive MDT-distance correlations, thus benefiting from electrodes being close to the neural elements, were those who performed better on the two speech recognition measures, i.e., speech reception thresholds (SRTs) and recognition of the AzBio sentences. These results could suggest that ears able to take advantage of the proximal placement of electrodes are likely to have better speech recognition outcomes. Previous histological studies of humans demonstrated that speech recognition is correlated with spiral ganglion cell counts. Alternatively, ears with good speech recognition outcomes may have good overall neural health, which is a precondition for close electrodes to produce spatially confined neural excitation patterns that facilitate modulation sensitivity. These findings suggest that the methods to reduce channel interaction, e.g., perimodiolar electrode array or current focusing, may only be beneficial for a subgroup of CI users. Additionally, it suggests that estimating neural survival preoperatively is important for choosing the most appropriate electrode array type (perimodiolar vs. lateral wall) for optimal implant function.

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.

The Core Rehabilitation Outcome Set for Single-Sided Deafness (CROSSSD) study: International consensus on outcome measures for trials of interventions for adults with single-sided deafness

Background

Single-sided deafness (SSD) has functional, psychological, and social consequences. Interventions for adults with SSD include hearing aids and auditory implants. Benefits and harms (outcome domains) of these interventions are until now reported inconsistently in clinical trials. Inconsistency in reporting outcome measures prevents meaningful comparisons or syntheses of trial results. The Core Rehabilitation Outcome Set for Single-Sided Deafness (CROSSSD) international initiative used structured communication techniques to achieve consensus among healthcare users and professionals working in the field of SSD. The novel contribution is a set of core outcome domains that experts agree are critically important to assess in all clinical trials of SSD interventions.

Methods

A long list of candidate outcome domains compiled from a systematic review and published qualitative data, informed the content of a two-round online Delphi survey. Overall, 308 participants from 29 countries were enrolled. Of those, 233 participants completed both rounds of the survey and scored each outcome domain on a 9-point scale. The set of core outcome domains was finalised via a web-based consensus meeting with 12 participants. Votes involved all stakeholder groups, with an approximate 2:1 ratio of professionals to healthcare users participating in the Delphi survey, and a 1:1 ratio participating in the consensus meeting.

Results

The first round of the survey listed 44 potential outcome domains, organised thematically. A further five outcome domains were included in Round 2 based on participant feedback. The structured voting at round 2 identified 17 candidate outcome domains which were voted on at the consensus meeting. Consensus was reached for a core outcome domain set including three outcome domains: spatial orientation, group conversations in noisy social situations, and impact on social situations. Seventy-seven percent of the remaining Delphi participants agreed with this core outcome domain set.

Conclusions

Adoption of the internationally agreed core outcome domain set would promote consistent assessment and reporting of outcomes that are meaningful and important to all relevant stakeholders. This consistency will in turn enable comparison of outcomes reported across clinical trials comparing SSD interventions in adults and reduce research waste. Further research will determine how those outcome domains should best be measured.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06702-1.

Prefrontal cortex supports speech perception in listeners with cochlear implants

Cochlear implants are neuroprosthetic devices that can restore hearing in people with severe to profound hearing loss by electrically stimulating the auditory nerve. Because of physical limitations on the precision of this stimulation, the acoustic information delivered by a cochlear implant does not convey the same level of acoustic detail as that conveyed by normal hearing. As a result, speech understanding in listeners with cochlear implants is typically poorer and more effortful than in listeners with normal hearing. The brain networks supporting speech understanding in listeners with cochlear implants are not well understood, partly due to difficulties obtaining functional neuroimaging data in this population. In the current study, we assessed the brain regions supporting spoken word understanding in adult listeners with right unilateral cochlear implants (n=20) and matched controls (n=18) using high-density diffuse optical tomography (HD-DOT), a quiet and non-invasive imaging modality with spatial resolution comparable to that of functional MRI. We found that while listening to spoken words in quiet, listeners with cochlear implants showed greater activity in the left prefrontal cortex than listeners with normal hearing, specifically in a region engaged in a separate spatial working memory task. These results suggest that listeners with cochlear implants require greater cognitive processing during speech understanding than listeners with normal hearing, supported by compensatory recruitment of the left prefrontal cortex.

Hearing and Quality-of-Life Outcomes After Cochlear Implantation in Adult Hearing Aid Users 65 Years or Older: A Secondary Analysis of a Nonrandomized Clinical Trial

Importance

Hearing loss, especially moderate to severe forms, has the potential to negatively affect an individual's physical, social, emotional, and cognitive well-being. Moreover, having ineffective binaural hearing increases difficulty understanding speech in noise and leads to a greater degree of social isolation and loneliness and a reduced quality of life (QoL).

Objective

To explore the audiometric and holistic effects of cochlear implantation in a group of adults 65 years or older compared with an optimized bilateral hearing aid condition.

Design, Setting, and Participants

This ad hoc secondary analysis of a prospective, single-subject, repeated-measures nonrandomized clinical trial included 13 cochlear implantation centers across the United States. Participants 65 years or older with postlingual bilateral moderate-to-profound sensorineural hearing loss with aided Consonant-Vowel Nucleus-Consonant (CNC) word scores in quiet of 40% or less in the ear to undergo implantation and 50% or less in the contralateral ear were included in the analysis. Baseline QoL testing was performed after 1 month of optimized bilateral hearing aid use. Participants were enrolled from February 20, 2017, to May 3, 2018, and follow-up was completed December 21, 2018. Data were analyzed from March 25, 2019, to March 31, 2020.

Interventions

Unilateral implantation with a slim, modiolar cochlear implant device. Hearing aid use in the contralateral ear was required through the 6-month primary end-point interval.

Main Outcomes and Measures

The primary objective was to evaluate speech perception before and 6 months after activation of a new cochlear implant. Secondary objectives were QoL metrics in the everyday listening condition before and 6 months after implantation.

Results

Seventy participants (51 men [73%]) with a median age of 74 (range, 65-91) years were included in the analysis. No major adverse events occurred. Mixed-model analysis with estimated marginal means and 95% CIs compared preimplantation baseline performance with 6-month postimplantation performance. A clinically important improvement in CNC words was shown in the bimodal condition, with a mean difference of 37.2% (95% CI, 32.0%-42.4%), and in the unilateral (cochlear implant only) condition, with a mean difference of 44.1% (95% CI, 39.0%-49.2%). A clinically important improvement in noise (AzBio sentences signal-to-noise ratio of +10 dB) was also shown, with a mean difference of 21.6% (95% CI, 15.7%-27.5%) in the bimodal condition and 24.5% (95% CI, 18.3%-30.7%) in the unilateral condition. The Health Utilities Index Mark 3 multiple-attribute score improved by 0.186 (95% CI, 0.136-0.234); the Speech, Spatial, and Qualities of Hearing Scale total score improved by 2.58 (95% CI, 2.18-2.99); and a novel Device Use Questionnaire reported 94% of participants were satisfied with overall hearing in the everyday listening condition.

Conclusions and Relevance

This subgroup analysis of patients 65 years or older enrolled in a within-subject clinical trial of cochlear implantation demonstrated clinically meaningful audiometric and QoL benefit with an acceptable risk profile. These findings suggest that cochlear implantation in older adults may facilitate the concept of healthy aging.

Trial Registration

ClinicalTrials.gov Identifier: NCT03007472.

Cortical Regions Activated by Spectrally Degraded Speech in Adults With Single Sided Deafness or Bilateral Normal Hearing

Those with profound sensorineural hearing loss from single sided deafness (SSD) generally experience greater cognitive effort and fatigue in adverse sound environments. We studied cases with right ear, SSD compared to normal hearing (NH) individuals. SSD cases were significantly less correct in naming last words in spectrally degraded 8- and 16-band vocoded sentences, despite high semantic predictability. Group differences were not significant for less intelligible 4-band sentences, irrespective of predictability. SSD also had diminished BOLD percent signal changes to these same sentences in left hemisphere (LH) cortical regions of early auditory, association auditory, inferior frontal, premotor, inferior parietal, dorsolateral prefrontal, posterior cingulate, temporal-parietal-occipital junction, and posterior opercular. Cortical regions with lower amplitude responses in SSD than NH were mostly components of a LH language network, previously noted as concerned with speech recognition. Recorded BOLD signal magnitudes were averages from all vertices within predefined parcels from these cortex regions. Parcels from different regions in SSD showed significantly larger signal magnitudes to sentences of greater intelligibility (e.g., 8- or 16- vs. 4-band) in all except early auditory and posterior cingulate cortex. Significantly lower response magnitudes occurred in SSD than NH in regions prior studies found responsible for phonetics and phonology of speech, cognitive extraction of meaning, controlled retrieval of word meaning, and semantics. The findings suggested reduced activation of a LH fronto-temporo-parietal network in SSD contributed to difficulty processing speech for word meaning and sentence semantics. Effortful listening experienced by SSD might reflect diminished activation to degraded speech in the affected LH language network parcels. SSD showed no compensatory activity in matched right hemisphere parcels.

Assessment of Speech Understanding After Cochlear Implantation in Adult Hearing Aid Users: A Nonrandomized Controlled Trial

Importance

Cochlear implants were approved for use in adults in the 1980s, but use remains low owing to a lack of awareness regarding cochlear implantation candidacy criteria and expected outcomes. There have been limited, small series examining the safety and effectiveness of cochlear implantation in adult hearing aid (HA) users with and without mild cognitive impairment (MCI).

Objective

To investigate the safety and effectiveness of a single-ear cochlear implant in a group of optimized adult HA users with and without MCI across a variety of domains.

Design, Setting, and Participants

In this nonrandomized controlled trial, a multicenter, prospective, repeated-measures investigation was conducted at 13 US institutions. The setting was academic and community-based cochlear implant programs. Eligible participants were 100 adults (aged >18 years) with postlinguistic onset of bilateral moderate sloping to profound or worse sensorineural hearing loss (≤20 years' duration). Fluent English speakers underwent an optimized bilateral HA trial for at least 30 days. Individuals with aided Consonant-Vowel Nucleus-Consonant (CNC) word score in quiet of 40% or less correct in the ear to be implanted and 50% or less correct in the contralateral ear were offered cochlear implants. The first participant was enrolled on February 20, 2017, and the last participant was enrolled on May 3, 2018. The final follow-up was on December 21, 2018.

Interventions

Participants received the same cochlear implant system and contralateral HA.

Main Outcomes and Measures

The primary outcome measure was speech understanding in quiet (CNC word score) using both the cochlear implant and opposite ear HA. Secondary outcome measures included the following: adverse events; speech understanding in noise (AzBio signal-to-noise ratio of +10 db [+10 SNR]) Health Utilities Index Mark 3 (HUI3); Speech, Spatial, and Qualities of Hearing Questionnaire 49 (SSQ49); and Montreal Cognitive Assessment (MoCA).

Results

The median age at cochlear implantation of the 96 patients included in the trial was 71 years (range, 23-91 years), and 62 patients (65%) were male. Three serious adverse events requiring revision surgery occurred, and all resolved without sequelae. By 6 months after activation, the absolute marginal mean change in CNC word score and AzBio +10 SNR was 40.5% (95% CI, 35.9%-45.0%) and 24.1% (95% CI, 18.9%-29.4%), respectively. Ninety-one percent (87 of 96) of participants had a clinically important improvement (>15%) in the CNC word score in the implant ear. Mild cognitive impairment (MoCA total score ≤25) was observed in 48 of 81 study participants (59%) at baseline. Speech perception marginal mean improvements were similar between individuals with and without baseline MCI, with values of 40.9% (95% CI, 35.2%-46.6%) and 39.6% (95% CI, 31.8%-47.4%), respectively, for CNC word score and 27.5% (95% CI, 21.0%-33.9%) and 17.8% (95% CI, 9.0%-26.6%), respectively, for AzBio +10 SNR. Statistically significant and clinically important improvements in the HUI3 and SSQ49 were evident at 6 months.

Conclusions and Relevance

The findings of this nonrandomized controlled trial seem to indicate that cochlear implants are safe and effective in restoring speech understanding in both quiet and noise and improve quality of life in individuals with and without MCI.

Trial Registration

ClinicalTrials.gov Identifier: NCT03007472.

Assessment of Cochlear Implants for Adult Medicare Beneficiaries Aged 65 Years or Older Who Meet Expanded Indications of Open-Set Sentence Recognition: A Multicenter Nonrandomized Clinical Trial

Importance

Current indications for Medicare beneficiaries to receive a cochlear implant are outdated. Multichannel cochlear implant systems may be effective when provided to Medicare beneficiaries using expanded indications.

Objective

To examine the effectiveness of cochlear implants, as measured by improvement on the AzBio Sentence Test, for newly implanted Medicare beneficiaries who meet the expanded indications of an AzBio Sentence Test score of 41% to 60% in their best-aided condition.

Design, Setting, and Participants

A multicenter nonrandomized trial examined preoperative and postoperative speech recognition, telephone communication, hearing device benefit, health utility, and quality of life for 34 participants enrolled at 8 different centers who received a cochlear implant between September 17, 2014, and July 10, 2018. All participants were 65 years or older, had bilateral moderate to profound hearing loss, and had a best-aided preoperative AzBio Sentence Test score in quiet of 41% to 60%. Analysis was performed on an intention-to-treat basis. Statistical analysis of final results took place from July 29 to October 1, 2019.

Intervention

Multichannel cochlear implants.

Main Outcomes and Measures

The study examined the a priori hypothesis that the cochlear implant would improve the AzBio Sentence Test score in the best-aided condition by 25% or more and in the implanted ear-alone condition by 30% or more. The study additionally examined word and telephone recognition and examined device benefit, health utility, and quality of life.

Results

A total of 34 participants received a cochlear implant; 31 (23 men [74%]; median age, 73.6 years [range, 65.7-85.1 years]) completed testing through the 6-month evaluation, and 29 completed testing through the 12-month evaluation. Median preoperative AzBio Sentence Test scores were 53% (range, 26%-60%) for the best-aided condition and 24% (range, 0%-53%) for the cochlear implant-alone condition; median scores 12 months after implantation improved to 89% (range, 36%-100%) for the best-aided condition and 77% (range, 13%-100%) for the cochlear implant-alone condition. This outcome represents a median change of 36% (range, -22% to 75%) for the best-aided condition (lower bound of 1-sided 95% CI, 31%) and a median change of 53% (range, -15% to 93%) for the cochlear implant-alone condition (lower bound of 1-sided 95% CI, 45%).

Conclusions and Relevance

Intervention with a cochlear implant was associated with improved sentence, word, and telephone recognition in adult Medicare beneficiaries whose preoperative AzBio Sentence Test scores were between 41% and 60%. These findings support expansion of the Center for Medicare & Medicaid current indications for cochlear implants.

Trial Registration

ClinicalTrials.gov Identifier: NCT02075229.

Speech Recognition in Quiet and Noise in Borderline Cochlear Implant Candidates

The present study 1) examined speech recognition at three intensity levels and in noise for adults with bilateral hearing loss who wore amplification and were referred for cochlear implant evaluation but did not meet current audiological criteria, and 2) compared their performance to cochlear implant recipients using current implant technology. When tested at 70 dB SPL, hearing aid subjects' word and sentence recognition scores were similar to or greater than the scores of cochlear implant recipients. Compared to their implanted peers, however, subjects' scores were significantly poorer at normal (60 dB SPL) and soft (50 dB SPL) presentation levels for words and at soft levels for sentences; detection thresholds were also significantly poorer at 1000 Hz and above. The assessment of candidates at louder-than-normal levels (i.e., 70 dB SPL) may not correctly portray their day-to-day communication struggles. El presente estudio examina, (1) el reconocimiento del lenguaje a tres niveles de intensidad en adultos con hipoacusia bilateral que usaban amplificación y que fueron referidos para una evaluación de implante coclear, pero que no cumplieron con los criterios audiológicos actuales, y (2) compara el desempeño de sujetos implantados utilizando la tecnología actual de implantes. Cuando se evaluaron a 70 dB SPL, los puntajes de los sujetos con audífonos para reconocimiento de palabras y frases fueron similares o mejores que los puntajes de los sujetos con implante coclear. Comparado con los implantados, sin embargo, los puntajes de los sujetos amplificados fueron significativamente peores a niveles de presentación normales (60 dB SPL) y suaves (50 dB SPL), y a niveles bajos para frases; los umbrales de detección fueron también significativamente bajos a 1000 Hz y en frecuencias mayores. La evaluación de candidatos a niveles por encima del normal (p.e., 70 dB SPL) puede no representar correctamente las dificultades de comunicación cotidianas.

Effects of Electrode Location on Estimates of Neural Health in Humans with Cochlear Implants

There are a number of psychophysical and electrophysiological measures that are correlated with SGN density in animal models, and these same measures can be performed in humans with cochlear implants (CIs). Thus, these measures are potentially applicable in humans for estimating the condition of the neural population (so called "neural health" or "cochlear health") at individual sites along the electrode array and possibly adjusting the stimulation strategy in the CI sound processor accordingly. Some measures used to estimate neural health in animals have included the electrically evoked compound potential (ECAP), psychophysical detection thresholds, and multipulse integration (MPI). With regard to ECAP measures, it has been shown that the change in the ECAP response as a function of increasing the stimulus interphase gap ("IPG Effect") also reflects neural density in implanted animals. These animal studies have typically been conducted using preparations in which the electrode was in a fixed position with respect to the neural population, whereas in human cochlear implant users, the position of individual electrodes varies widely within an electrode array and also across subjects. The current study evaluated the effects of electrode location in the implanted cochlea (specifically medial-lateral location) on various electrophysiological and psychophysical measures in eleven human subjects. The results demonstrated that some measures of interest, specifically ECAP thresholds, psychophysical detection thresholds, and ECAP amplitude-growth function (AGF) linear slope, were significantly related to the distances between the electrode and mid-modiolar axis (MMA). These same measures were less strongly related or not significantly related to the electrode to medial wall (MW) distance. In contrast, neither the IPG Effect for the ECAP AGF slope or threshold, nor the MPI slopes were significantly related to MMA or MW distance from the electrodes. These results suggest that "within-channel" estimates of neural health such as the IPG Effect and MPI slope might be more suitable for estimating nerve condition in humans for clinical application since they appear to be relatively independent of electrode position.

Correction to: Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study: protocol for an international consensus on outcome measures for single sided deafness interventions using a modified Delphi survey

Following the publication of our article [1], the authors have notified us of a typo in the third bullet point of the Consensus Criteria section.

Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study: protocol for an international consensus on outcome measures for single sided deafness interventions using a modified Delphi survey

BACKGROUND

Single-sided deafness (SSD) describes the presence of a unilateral severe to profound sensorineural hearing loss. SSD disrupts spatial hearing and understanding speech in background noise. It has functional, psychological and social consequences. Potential options for rehabilitation include hearing aids and auditory implants. Benefits and harms of these interventions are documented inconsistently in the literature, using a variety of outcomes ranging from tests of speech perception to quality of life questionnaires. It is therefore difficult to compare interventions when rehabilitating SSD. The Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study is an international initiative that aims to develop a minimum set of core outcomes for use in future trials of SSD interventions.

METHODS/DESIGN

The CROSSSD study adopts an international two-round online modified Delphi survey followed by a stakeholder consensus meeting to identify a patient-centred core outcome domain set for SSD based on what is considered critical and important for assessing whether an intervention for SSD has worked.

DISCUSSION

The resulting core outcome domain set will act as a minimum standard for reporting in future clinical trials and could have further applications in guiding the use of outcome measures in clinical practice. Standardisation will facilitate comparison of research findings.

Effects of Early Acoustic Hearing on Speech Perception and Language for Pediatric Cochlear Implant Recipients

Purpose The overall goal of the current study was to identify an optimal level and duration of acoustic experience that facilitates language development for pediatric cochlear implant (CI) recipients-specifically, to determine whether there is an optimal duration of hearing aid (HA) use and unaided threshold levels that should be considered before proceeding to bilateral CIs. Method A total of 117 pediatric CI recipients (ages 5-9 years) were given speech perception and standardized tests of receptive vocabulary and language. The speech perception battery included tests of segmental perception (e.g., word recognition in quiet and noise, and vowels and consonants in quiet) and of suprasegmental perception (e.g., talker and stress discrimination, and emotion identification). Hierarchical regression analyses were used to determine the effects of speech perception on language scores, and the effects of residual hearing level (unaided pure-tone average [PTA]) and duration of HA use on speech perception. Results A continuum of residual hearing levels and the length of HA use were represented by calculating the unaided PTA of the ear with the longest duration of HA use for each child. All children wore 2 devices: Some wore bimodal devices, while others received their 2nd CI either simultaneously or sequentially, representing a wide range of HA use (0.03-9.05 years). Regression analyses indicate that suprasegmental perception contributes unique variance to receptive language scores and that both segmental and suprasegmental skills each contribute independently to receptive vocabulary scores. Also, analyses revealed an optimal duration of HA use for each of 3 ranges of hearing loss severity (with mean PTAs of 73, 92, and 111 dB HL) that maximizes suprasegmental perception. Conclusions For children with the most profound losses, early bilateral CIs provide the greatest opportunity for developing good spoken language skills. For those with moderate-to-severe losses, however, a prescribed period of bimodal use may be more advantageous for developing good spoken language skills.

Unilateral Hearing Loss: Understanding Speech Recognition and Localization Variability-Implications for Cochlear Implant Candidacy

OBJECTIVES

At a minimum, unilateral hearing loss (UHL) impairs sound localization ability and understanding speech in noisy environments, particularly if the loss is severe to profound. Accompanying the numerous negative consequences of UHL is considerable unexplained individual variability in the magnitude of its effects. Identification of covariables that affect outcome and contribute to variability in UHLs could augment counseling, treatment options, and rehabilitation. Cochlear implantation as a treatment for UHL is on the rise yet little is known about factors that could impact performance or whether there is a group at risk for poor cochlear implant outcomes when hearing is near-normal in one ear. The overall goal of our research is to investigate the range and source of variability in speech recognition in noise and localization among individuals with severe to profound UHL and thereby help determine factors relevant to decisions regarding cochlear implantation in this population.

DESIGN

The present study evaluated adults with severe to profound UHL and adults with bilateral normal hearing. Measures included adaptive sentence understanding in diffuse restaurant noise, localization, roving-source speech recognition (words from 1 of 15 speakers in a 140° arc), and an adaptive speech-reception threshold psychoacoustic task with varied noise types and noise-source locations. There were three age-sex-matched groups: UHL (severe to profound hearing loss in one ear and normal hearing in the contralateral ear), normal hearing listening bilaterally, and normal hearing listening unilaterally.

RESULTS

Although the normal-hearing-bilateral group scored significantly better and had less performance variability than UHLs on all measures, some UHL participants scored within the range of the normal-hearing-bilateral group on all measures. The normal-hearing participants listening unilaterally had better monosyllabic word understanding than UHLs for words presented on the blocked/deaf side but not the open/hearing side. In contrast, UHLs localized better than the normal-hearing unilateral listeners for stimuli on the open/hearing side but not the blocked/deaf side. This suggests that UHLs had learned strategies for improved localization on the side of the intact ear. The UHL and unilateral normal-hearing participant groups were not significantly different for speech in noise measures. UHL participants with childhood rather than recent hearing loss onset localized significantly better; however, these two groups did not differ for speech recognition in noise. Age at onset in UHL adults appears to affect localization ability differently than understanding speech in noise. Hearing thresholds were significantly correlated with speech recognition for UHL participants but not the other two groups.

CONCLUSIONS

Auditory abilities of UHLs varied widely and could be explained only in part by hearing threshold levels. Age at onset and length of hearing loss influenced performance on some, but not all measures. Results support the need for a revised and diverse set of clinical measures, including sound localization, understanding speech in varied environments, and careful consideration of functional abilities as individuals with severe to profound UHL are being considered potential cochlear implant candidates.

Evaluation of hearing aid frequency response fittings in pediatric and young adult bimodal recipients

BACKGROUND

A coordinated fitting of a cochlear implant (CI) and contralateral hearing aid (HA) for bimodal device use should emphasize balanced audibility and loudness across devices. However, guidelines for allocating frequency information to the CI and HA are not well established for the growing population of bimodal recipients.

PURPOSE

The study aim was to compare the effects of three different HA frequency responses, when fitting a CI and an HA for bimodal use, on speech recognition and localization in children/young adults. Specifically, the three frequency responses were wideband, restricted high frequency, and nonlinear frequency compression (NLFC), which were compared with measures of word recognition in quiet, sentence recognition in noise, talker discrimination, and sound localization.

RESEARCH DESIGN

The HA frequency responses were evaluated using an A B₁ A B₂ test design: wideband frequency response (baseline-A), restricted high-frequency response (experimental-B₁), and NLFC-activated (experimental-B2). All participants were allowed 3-4 weeks between each test session for acclimatization to each new HA setting. Bimodal benefit was determined by comparing the bimodal score to the CI-alone score.

STUDY SAMPLE

Participants were 14 children and young adults (ages 7-21 yr) who were experienced users of bimodal devices. All had been unilaterally implanted with a Nucleus CI24 internal system and used either a Freedom or CP810 speech processor. All received a Phonak Naida IX UP behind-the-ear HA at the beginning of the study.

DATA COLLECTION AND ANALYSIS

Group results for the three bimodal conditions (HA frequency response with wideband, restricted high frequency, and NLFC) on each outcome measure were analyzed using a repeated measures analysis of variance. Group results using the individual "best bimodal" score were analyzed and confirmed using a resampling procedure. Correlation analyses examined the effects of audibility (aided and unaided hearing) in each bimodal condition for each outcome measure. Individual data were analyzed for word recognition in quiet, sentence recognition in noise, and localization. Individual preference for the three bimodal conditions was also assessed.

RESULTS

Group data revealed no significant difference between the three bimodal conditions for word recognition in quiet, sentence recognition in noise, and talker discrimination. However, group data for the localization measure revealed that both wideband and NLFC resulted in significantly improved bimodal performance. The condition that yielded the "best bimodal" score varied across participants. Because of this individual variability, the "best bimodal" score was chosen for each participant to reassess group data within word recognition in quiet, sentence recognition in noise, and talker discrimination. This method revealed a bimodal benefit for word recognition in quiet after a randomization test was used to confirm significance. The majority of the participants preferred NLFC at the conclusion of the study, although a few preferred a restricted high-frequency response or reported no preference.

CONCLUSIONS

These results support consideration of restricted high-frequency and NLFC HA responses in addition to traditional wideband response for bimodal device users.

A Longitudinal Study in Children With Sequential Bilateral Cochlear Implants: Time Course for the Second Implanted Ear and Bilateral Performance

PURPOSE

Whether, and if so when, a second-ear cochlear implant should be provided to older, unilaterally implanted children is an ongoing clinical question. This study evaluated rate of speech recognition progress for the second implanted ear and with bilateral cochlear implants in older sequentially implanted children and evaluated localization abilities.

METHOD

A prospective longitudinal study included 24 bilaterally implanted children (mean ear surgeries at 5.11 and 14.25 years). Test intervals were every 3-6 months through 24 months postbilateral. Test conditions were each ear and bilaterally for speech recognition and localization.

RESULTS

Overall, the rate of progress for the second implanted ear was gradual. Improvements in quiet continued through the second year of bilateral use. Improvements in noise were more modest and leveled off during the second year. On all measures, results from the second ear were poorer than the first. Bilateral scores were better than either ear alone for all measures except sentences in quiet and localization.

CONCLUSIONS

Older sequentially implanted children with several years between surgeries may obtain speech understanding in the second implanted ear; however, performance may be limited and rate of progress gradual. Continued contralateral ear hearing aid use and reduced time between surgeries may enhance outcomes.

Identification and evaluation of cochlear implant candidates with asymmetrical hearing loss

OBJECTIVE

Recommendation for cochlear implant (CI) treatment for individuals with severe to profound single-sided deafness (SSD) and asymmetrical hearing loss (AHL) is on the rise. This raises the need for greater consistency in the definition of CI candidacy for these cases and in the assessment methods of patient-related benefits to permit effective comparison and interpretation of the outcomes with both conventional and implantable options across studies.

METHOD

During a dedicated seminar on implant treatment in AHL patients, the panellists of the closing round table reviewed the clinical experience presented with the aim to define clear audiometric characteristics for both AHL and SSD cases, as well as a common data set enabling consistent evaluation of hearing benefits in this population.

CONCLUSIONS

The panellists agreed on a clear differentiation between AHL and SSD CI candidates, defining average pure-tone thresholds up to 4 kHz for better and poorer ears. Agreement was reached on a minimum set of assessment procedures, and included the necessity of trials with conventional CROS/BICROS hearing aids and bone conduction devices before considering CI treatment. Objective assessment of sound localisation abilities was identified as the most relevant criterion to quantify performance before and after treatment. In parallel, subjective assessment of overall hearing ability was recommended via the Speech, Spatial and Qualities of hearing questionnaire. Longitudinal follow-up of these parameters and the hours of daily use were considered essential to reflect the potential treatment benefits for this population. The consistency in the data collection and its report will further support health authorities in their decision on acceptable gains from available hearing loss treatment options.

Quantification of speech-in-noise and sound localisation abilities in children with unilateral hearing loss and comparison to normal hearing peers

The study objective was to quantify abilities of children with unilateral hearing loss (UHL) on measures that address known deficits for this population, i.e. speech understanding in quiet and noise, and sound localisation. Noise conditions varied by noise type and source location. Parent reports of real-world abilities were also obtained. Performance was compared to gender- and age-matched normal hearing (NH) peers. UHL performance was poorer and more varied compared to NH peers. Among the findings, age correlated with localisation ability for UHL but not NH participants. Low-frequency hearing in the better ear of UHL children was associated with performance in noise; however, there was no relation for NH children. Considerable variability was evident in the outcomes of children with UHL and needs to be understood as future treatment options are considered.

Localization training results in individuals with unilateral severe to profound hearing loss

Adults with unilateral hearing loss often demonstrate decreased sound localization ability and report that situations requiring spatial hearing are especially challenging. Few studies have evaluated localization abilities combined with training in this population. The present pilot study examined whether localization of two sound types would improve after training, and explored the relation between localization ability or training benefit and demographic factors. Eleven participants with unilateral severe to profound hearing loss attended five training sessions; localization cues gradually decreased across sessions. Localization ability was assessed pre- and post-training. Assessment stimuli were monosyllabic words and spectral and temporal random spectrogram sounds. Root mean square errors for each participant and stimulus type were used in group and correlation analyses; individual data were examined with ordinary least squares regression. Mean pre-to post-training test results were significantly different for all stimulus types. Among the participants, eight significantly improved following training on at least one localization measure, whereas three did not. Participants with the poorest localization ability improved the most and likewise, those with the best pre-training ability showed the least training benefit. Correlation results suggested that test age, age at onset of severe to profound hearing loss and better ear high frequency audibility may contribute to localization ability. Results support the need for continued investigation of localization training efficacy and consideration of localization training within rehabilitation protocols for individuals with unilateral severe to profound hearing loss.

Effects of unilateral input and mode of hearing in the better ear: self-reported performance using the speech, spatial and qualities of hearing scale

OBJECTIVE

To evaluate effects of hearing mode (normal hearing, cochlear implant, or hearing aid) on everyday communication among adult unilateral listeners using the Speech, Spatial and Qualities of Hearing Scale (SSQ). Individuals with one good, naturally hearing ear were expected to have higher overall ratings than unilateral listeners dependent on a cochlear implant or hearing aid. The authors anticipated that listening environments reliant on binaural processing for successful communication would be rated most disabling by all unilateral listeners. Regardless of hearing mode, all hearing-impaired participants were expected to have lower ratings than individuals with normal hearing bilaterally. A secondary objective was to compare post-treatment SSQ results of participants who subsequently obtained a cochlear implant for the poorer hearing ear with those of participants with a single normal-hearing ear.

DESIGN

Participants were 87 adults recruited as part of ongoing research investigating asymmetric hearing effects. Sixty-six participants were unilateral listeners who had one unaided/nonimplanted severe to profound hearing-loss ear and were grouped based on hearing mode of the better ear: 30 had one normal-hearing ear (i.e., unilateral hearing-loss participants); 20 had a unilateral cochlear implant; and 16 had a unilateral hearing aid. Data were also collected from 21 normal-hearing individuals, as well as a subset of participants who subsequently received a cochlear implant in the poorer ear and thus became bilateral listeners. Data analysis was completed at the domain and subscale levels.

RESULTS

A significant mode-of-hearing group effect for the hearing-impaired participants (i.e., with unilateral hearing loss, unilateral cochlear implant, or unilateral hearing aid) was identified for two domains (Speech and Qualities) and six subscales (Speech in Quiet, Speech in Noise, Speech in Speech Contexts, Multiple Speech Stream Processing and Switching, Identification of Sound and Objects, and Sound Quality and Naturalness). There was no significant mode-of-hearing group effect for the Spatial domain or the other four subscales (Localization, Distance and Movement, Segregation of Sounds, and Listening Effort). Follow-up analysis indicated the unilateral normal-hearing ear group had significantly higher ratings than the unilateral cochlear implant or hearing aid groups for the Speech domain and four of the ten subscales; neither the cochlear implant nor hearing aid group had subscale ratings significantly higher than each other or the unilateral hearing loss group. Audibility and sound quality imparted by hearing mode were identified as factors related to subjective listening experience. After cochlear implantation to restore bilateral hearing, SSQ ratings for bilateral cochlear implant or cochlear implant plus hearing aid participants were significantly higher than those of the unilateral hearing-loss group for Speech in Quiet, Speech in Noise, Localization, Distance and Movement, Listening Effort, and the Spatial domain. Hearing-impaired individuals had significantly poorer ratings in all areas compared with those with bilateral normal hearing.

CONCLUSIONS

Adults reliant on a single ear, irrespective of better ear hearing mode, including those with one normal hearing ear, are at a disadvantage in all aspects of everyday listening and communication. Audibility and hearing mode were shown to differentially contribute to listening experience.

A longitudinal study in adults with sequential bilateral cochlear implants: time course for individual ear and bilateral performance

PURPOSE

The purpose of this study was to examine the rate of progress in the 2nd implanted ear as it relates to the 1st implanted ear and to bilateral performance in adult sequential cochlear implant recipients. In addition, this study aimed to identify factors that contribute to patient outcomes.

METHOD

The authors performed a prospective longitudinal study in 21 adults who received bilateral sequential cochlear implants. Testing occurred at 6 intervals: prebilateral through 12 months postbilateral implantation. Measures evaluated speech recognition in quiet and noise, localization, and perceived benefit.

RESULTS

Second ear performance was similar to 1st ear performance by 6 months postbilateral implantation. Bilateral performance was generally superior to either ear alone; however, participants with shorter 2nd ear length of deafness (<20 years) had more rapid early improvement and better overall outcomes than those with longer 2nd ear length of deafness (>30 years). All participants reported bilateral benefit.

CONCLUSIONS

Adult cochlear implant recipients demonstrated benefit from 2nd ear implantation for speech recognition, localization, and perceived communication function. Because performance outcomes were related to length of deafness, shorter time between surgeries may be warranted to reduce negative length-of-deafness effects. Future study may clarify the impact of other variables, such as preimplant hearing aid use, particularly for individuals with longer periods of deafness.

Changes in auditory perceptions and cortex resulting from hearing recovery after extended congenital unilateral hearing loss

Monaural hearing induces auditory system reorganization. Imbalanced input also degrades time-intensity cues for sound localization and signal segregation for listening in noise. While there have been studies of bilateral auditory deprivation and later hearing restoration (e.g., cochlear implants), less is known about unilateral auditory deprivation and subsequent hearing improvement. We investigated effects of long-term congenital unilateral hearing loss on localization, speech understanding, and cortical organization following hearing recovery. Hearing in the congenitally affected ear of a 41 year old female improved significantly after stapedotomy and reconstruction. Pre-operative hearing threshold levels showed unilateral, mixed, moderately-severe to profound hearing loss. The contralateral ear had hearing threshold levels within normal limits. Testing was completed prior to, and 3 and 9 months after surgery. Measurements were of sound localization with intensity-roved stimuli and speech recognition in various noise conditions. We also evoked magnetic resonance signals with monaural stimulation to the unaffected ear. Activation magnitudes were determined in core, belt, and parabelt auditory cortex regions via an interrupted single event design. Hearing improvement following 40 years of congenital unilateral hearing loss resulted in substantially improved sound localization and speech recognition in noise. Auditory cortex also reorganized. Contralateral auditory cortex responses were increased after hearing recovery and the extent of activated cortex was bilateral, including a greater portion of the posterior superior temporal plane. Thus, prolonged predominant monaural stimulation did not prevent auditory system changes consequent to restored binaural hearing. Results support future research of unilateral auditory deprivation effects and plasticity, with consideration for length of deprivation, age at hearing correction and degree and type of hearing loss.

Hearing thresholds and FMRI of auditory cortex following eighth cranial nerve surgery

OBJECTIVE

Determine whether auditory cortex (AC) organization changed following eighth cranial nerve surgery in adults with vestibular-cochlear nerve pathologies. We examined whether hearing thresholds before and after surgery correlated with increased ipsilateral activation of AC from the intact ear.

STUDY DESIGN

During magnetic resonance imaging sessions before and 3 and 6 months after surgery, subjects listened with the intact ear to noise-like random spectrogram sounds.

SETTING

Departments of Radiology and Otolaryngology of Washington University School of Medicine.

SUBJECTS AND METHODS

Three patients with acoustic neuromas received Gamma Knife radiosurgery (GK); 1 patient with Meniere's disease and 5 with acoustic neuromas had surgical resections (SR); 2 of the latter also had GK. Hearing thresholds in each ear were for pure tone stimuli from 250 to 8000 Hz before and after surgery (3 and 6 months). At the same intervals, we imaged blood oxygen level-dependent responses to auditory stimulation of the intact ear using an interrupted single-event design.

RESULTS

Hearing thresholds in 2 of 3 individuals treated with GK did not change. Five of 6 individuals became unilaterally deaf after SRs. Ipsilateral AC activity was present before surgery in 6 of 9 individuals with ipsilateral spatial extents greater than contralateral in 3 of 9. Greater contralateral predominance was significant especially in left compared to right ear affected individuals, including those treated by GK.

CONCLUSION

Lateralization of auditory-evoked responses in AC did not change significantly after surgery possibly due to preexisting sensory loss before surgery, indicating that less than profound loss may prompt cortical reorganization.

Postlingual adult performance in noise with HiRes 120 and ClearVoice Low, Medium, and High

OBJECTIVES

The study's objectives were to evaluate speech recognition in multiple listening conditions using several noise types with HiRes 120 and ClearVoice (Low, Medium, High) and to determine which ClearVoice program was most beneficial for everyday use.

METHODS

Fifteen postlingual adults attended four sessions; speech recognition was assessed at sessions 1 and 3 with HiRes 120 and at sessions 2 and 4 with all ClearVoice programs. Test measures included sentences presented in restaurant noise (R-SPACE), in speech-spectrum noise, in four- and eight-talker babble, and connected discourse presented in 12-talker babble. Participants completed a questionnaire comparing ClearVoice programs.

RESULTS

Significant group differences in performance between HiRes 120 and ClearVoice were present only in the R-SPACE; performance was better with ClearVoice High than HiRes 120. Among ClearVoice programs, no significant group differences were present for any measure. Individual results revealed most participants performed better in the R-SPACE with ClearVoice than HiRes 120. For other measures, significant individual differences between HiRes 120 and ClearVoice were not prevalent. Individual results among ClearVoice programs differed and overall preferences varied. Questionnaire data indicated increased understanding with High and Medium in certain environments.

DISCUSSION

R-SPACE and questionnaire results indicated an advantage for ClearVoice High and Medium. Individual test and preference data showed mixed results between ClearVoice programs making global recommendations difficult; however, results suggest providing ClearVoice High and Medium and HiRes 120 as processor options for adults willing to change settings. For adults unwilling or unable to change settings, ClearVoice Medium is a practical choice for daily listening.

Evaluation of TIMIT sentence list equivalency with adult cochlear implant recipients

BACKGROUND

Current measures used to determine sentence recognition abilities in cochlear implant recipients often include tests with one talker and one rate of speech. Performance with these measures may not accurately represent the speech recognition abilities of the listeners. Evaluation of cochlear implant performance should include measures that reflect realistic listening conditions. For example, the use of multiple talkers who vary in gender, rate of speech, and regional dialects represent varied communication interactions that people encounter daily. The TIMIT sentences, which use multiple talkers and incorporate these variations, provide additional test material for evaluating speech recognition. Dorman and colleagues created 34 lists of TIMIT sentences that were normalized for equal intelligibility using simulations of cochlear implant processing with normal-hearing listeners. Adults with sensorineural hearing loss who listen with cochlear implants represent a different population. Further study is needed to determine if these lists are equivalent for adult cochlear implant recipients and, if not, to identify a subset of lists that may be used with this population.

PURPOSE

To evaluate the speech recognition equivalence of 34 TIMIT sentence lists with adult cochlear implant recipients.

RESEARCH DESIGN

A prospective study comparing test-retest results within the same group of listeners.

STUDY SAMPLE

Twenty-two adult cochlear implant recipients who met the inclusion criteria of at least 3 mo device use and a monosyllabic word score of 30% or greater participated in the study.

DATA COLLECTION AND ANALYSIS

Participants were administered 34 TIMIT sentence lists (20 sentences per list) at each of two test sessions several months apart. List order was randomized and results scored as percent of words correct. Test-retest correlations and 95% confidence intervals for the means were used to identify equivalent lists with high test-retest reliability.

RESULTS

Mean list scores across participants ranged from 66 to 81% with an overall mean of 73%. Twenty-nine lists had high test-retest reliability. Using the overall mean as a benchmark, the 95% confidence intervals indicated that 25 of the remaining 29 lists were equivalent (e.g., the benchmark of 73% fell within the 95% confidence interval for both test and retest).

CONCLUSIONS

Twenty-five of the TIMIT lists evaluated are equivalent when used with adult cochlear implant recipients who have open-set word recognition abilities. These lists may prove valuable for monitoring progress, comparing listening conditions or treatments, and developing aural rehabilitation plans for cochlear implant recipients.

Optimization of programming parameters in children with the advanced bionics cochlear implant

BACKGROUND

Cochlear implants provide access to soft intensity sounds and therefore improved audibility for children with severe-to-profound hearing loss. Speech processor programming parameters, such as threshold (or T-level), input dynamic range (IDR), and microphone sensitivity, contribute to the recipient's program and influence audibility. When soundfield thresholds obtained through the speech processor are elevated, programming parameters can be modified to improve soft sound detection. Adult recipients show improved detection for low-level sounds when T-levels are set at raised levels and show better speech understanding in quiet when wider IDRs are used. Little is known about the effects of parameter settings on detection and speech recognition in children using today's cochlear implant technology.

PURPOSE

The overall study aim was to assess optimal T-level, IDR, and sensitivity settings in pediatric recipients of the Advanced Bionics cochlear implant.

RESEARCH DESIGN

Two experiments were conducted. Experiment 1 examined the effects of two T-level settings on soundfield thresholds and detection of the Ling 6 sounds. One program set T-levels at 10% of most comfortable levels (M-levels) and another at 10 current units (CUs) below the level judged as "soft." Experiment 2 examined the effects of IDR and sensitivity settings on speech recognition in quiet and noise.

STUDY SAMPLE

Participants were 11 children 7-17 yr of age (mean 11.3) implanted with the Advanced Bionics High Resolution 90K or CII cochlear implant system who had speech recognition scores of 20% or greater on a monosyllabic word test.

DATA COLLECTION AND ANALYSIS

Two T-level programs were compared for detection of the Ling sounds and frequency modulated (FM) tones. Differing IDR/sensitivity programs (50/0, 50/10, 70/0, 70/10) were compared using Ling and FM tone detection thresholds, CNC (consonant-vowel nucleus-consonant) words at 50 dB SPL, and Hearing in Noise Test for Children (HINT-C) sentences at 65 dB SPL in the presence of four-talker babble (+8 signal-to-noise ratio). Outcomes were analyzed using a paired t-test and a mixed-model repeated measures analysis of variance (ANOVA).

RESULTS

T-levels set 10 CUs below "soft" resulted in significantly lower detection thresholds for all six Ling sounds and FM tones at 250, 1000, 3000, 4000, and 6000 Hz. When comparing programs differing by IDR and sensitivity, a 50 dB IDR with a 0 sensitivity setting showed significantly poorer thresholds for low frequency FM tones and voiced Ling sounds. Analysis of group mean scores for CNC words in quiet or HINT-C sentences in noise indicated no significant differences across IDR/sensitivity settings. Individual data, however, showed significant differences between IDR/sensitivity programs in noise; the optimal program differed across participants.

CONCLUSIONS

In pediatric recipients of the Advanced Bionics cochlear implant device, manually setting T-levels with ascending loudness judgments should be considered when possible or when low-level sounds are inaudible. Study findings confirm the need to determine program settings on an individual basis as well as the importance of speech recognition verification measures in both quiet and noise. Clinical guidelines are suggested for selection of programming parameters in both young and older children.

Sequential bilateral cochlear implantation in a patient with bilateral Ménière's disease

This case study describes a 45-yr-old female with bilateral, profound sensorineural hearing loss due to Ménière's disease. She received her first cochlear implant in the right ear in 2008 and the second cochlear implant in the left ear in 2010. The case study examines the enhancement to speech recognition, particularly in noise, provided by bilateral cochlear implants. Speech recognition tests were administered prior to obtaining the second implant and at a number of test intervals following activation of the second device. Speech recognition in quiet and noise as well as localization abilities were assessed in several conditions to determine bilateral benefit and performance differences between ears. The results of the speech recognition testing indicated a substantial improvement in the patient's ability to understand speech in noise and her ability to localize sound when using bilateral cochlear implants compared to using a unilateral implant or an implant and a hearing aid. In addition, the patient reported considerable improvement in her ability to communicate in daily life when using bilateral implants versus a unilateral implant. This case suggests that cochlear implantation is a viable option for patients who have lost their hearing to Ménière's disease even when a number of medical treatments and surgical interventions have been performed to control vertigo. In the case presented, bilateral cochlear implantation was necessary for this patient to communicate successfully at home and at work.

Activation lateralization in human core, belt, and parabelt auditory fields with unilateral deafness compared to normal hearing

We studied activation magnitudes in core, belt, and parabelt auditory cortex in adults with normal hearing (NH) and unilateral hearing loss (UHL) using an interrupted, single-event design and monaural stimulation with random spectrographic sounds. NH patients had one ear blocked and received stimulation on the side matching the intact ear in UHL. The objective was to determine whether the side of deafness affected lateralization and magnitude of evoked blood oxygen level-dependent responses across different auditory cortical fields (ACFs). Regardless of ear of stimulation, NH showed larger contralateral responses in several ACFs. With right ear stimulation in UHL, ipsilateral responses were larger compared to NH in core and belt ACFs, indicating neuroplasticity in the right hemisphere. With left ear stimulation in UHL, only posterior core ACFs showed larger ipsilateral responses, suggesting that most ACFs in the left hemisphere had greater resilience against reduced crossed inputs from a deafferented right ear. Parabelt regions located posterolateral to core and belt auditory cortex showed reduced activation in UHL compared to NH irrespective of RE/LE stimulation and lateralization of inputs. Thus, the effect in UHL compared to NH differed by ACF and ear of deafness.

Optimizing the perception of soft speech and speech in noise with the Advanced Bionics cochlear implant system

OBJECTIVE

This study aimed to provide guidelines to optimize perception of soft speech and speech in noise for Advanced Bionics cochlear implant (CI) users.

DESIGN

Three programs differing in T-levels were created for ten subjects. Using the T-level setting that provided the lowest FM-tone, sound-field threshold levels for each subject, three additional programs were created with input dynamic range (IDR) settings of 50, 65 and 80 dB.

STUDY SAMPLE

Subjects were postlinguistically deaf adults implanted with either the Clarion CII or 90K CI devices.

RESULTS

Sound-field threshold levels were lowest with T-levels set higher than 10% of M-levels and with the two widest IDRs. Group data revealed significantly higher scores for CNC words presented at a soft level with an IDR of 80 dB and 65 dB compared to 50 dB. Although no significant group differences were seen between the three IDRs for sentences in noise, significant individual differences were present.

CONCLUSIONS

Setting Ts higher than the manufacturer's recommendation of 10% of M-levels and providing IDR options can improve overall speech perception; however, for some users, higher Ts and wider IDRs may not be appropriate. Based on the results of the study, clinical programming recommendations are provided.

Interregional brain interactions in children with unilateral hearing loss

OBJECTIVE

To determine whether patterns of functional connectivity of cortical regions responsible for auditory processing and executive functions differ in children with unilateral hearing loss (UHL) versus their normal-hearing (NH) siblings.

STUDY DESIGN

Prospective observational study.

SETTING

Academic medical center.

SUBJECTS AND METHODS

Children with severe-to-profound UHL (9 right UHL, 7 left UHL) and 10 NH sibling controls were imaged using resting state functional connectivity magnetic resonance imaging (rs-fcMRI). All MRI images were transformed to a single common atlas; regions of interest (ROI) were chosen based on previous literature and unpublished results. Mean regionwise correlations and conjunction analyses were performed across 34 seed ROIs to identify temporally synchronized, low-frequency spontaneous fluctuations in the resting state blood oxygenation level-dependent signal that reveal functionally related regions.

RESULTS

Mean regionwise Student t tests found a left posterior opercular region with more correlated resting state activity with the inferior parietal lobule seed in the children with both left and right UHL than NH. In conjunction analysis, 4 regions showed different resting-state functional interactions between the NH and both UHL groups. These differences were in left medial globus pallidus, left middle temporal gyrus, right parahippocampal gyrus, and mid-cingulate cortex. These regions include areas associated with auditory processing, executive function, and memory formation.

CONCLUSIONS

Resting state fcMRI identified differences in brain network interconnections between children with UHL and NH and may inform further investigation into the educational and behavioral difficulties experienced by children with UHL.

Current Steering Creates Additional Pitch Percepts in Adult Cochlear Implant Recipients

OBJECTIVE

The number of spectral channels is the number of discriminable pitches heard as current is delivered to distinct locations along the cochlea. This study aimed to determine whether cochlear implant users could hear additional spectral channels using current "steering." Current steering involves the simultaneous delivery of current to adjacent electrodes, where stimulation can be steered to sites between the contacts by varying the proportion of current delivered to each electrode in an electrode pair. Current steering may increase the number of spectral channels beyond the number of fixed electrode contacts.

STUDY DESIGN

Prospective clinical study.

SETTING

Twelve tertiary care centers in North America.

PATIENTS

The subjects were 106 adults with postlingual onset of severe-to-profound hearing loss.

INTERVENTIONS

Subjects received the Advanced Bionics CII or HiResolution 90K device (Advanced Bionics Corporation, Valencia, CA, USA).

MAIN OUTCOME MEASURES

After loudness balancing and pitch ranking the 3 electrode pairs (2 and 3, 8 and 9, and 13 and 14), the subjects identified the electrode with the higher pitch while current was varied proportionally between the electrodes in each pair. The smallest change in proportion yielding a discriminable change in pitch was defined as the spectral resolution.

RESULTS

The data from 115 ears indicate that the number of spectral channels averaged 3.8 for the basal pair, 6.0 for the midarray pair, and 5.3 for the apical pair. Assuming that the number of channels on these 3 electrode pairs represents the entire array, the total potential number of spectral channels was calculated and ranged from 8 to 451, with an average of 63.

CONCLUSION

These results indicate that additional pitch percepts can be created using current steering.

More Challenging Speech-Perception Tasks Demonstrate Binaural Benefit in Bilateral Cochlear Implant Users

OBJECTIVE

Preliminary studies show that bilateral cochlear implantation improves speech-recognition ability in many subjects; however, the magnitude of this improvement has been variable. The objective of our research was to explore means to better differentiate the binaural benefit that many patients who receive bilateral cochlear implants (CIs) describe.

HYPOTHESIS

Binaural improvements in speech-perception performance will be consistently evident across patients when they are tested in more challenging listening situations.

DESIGN

This was a prospective clinical study. Speech-perception performance was compared between the unilateral and bilateral cochlear implant conditions. Because the purpose was to investigate testing parameters that would demonstrate binaural benefit, word- and sentence-recognition tests were administered under several stimulation conditions: with and without noise and at three presentation levels. In addition, all subjects completed the Abbreviated Profile of Hearing Aid Benefit as a measure of subjective benefit. Subjects were adult cochlear implant recipients. Three device manufacturers were represented (Advanced Bionics Corporation, Cochlear Americas, and the Med-El Corporation); three patients received simultaneous implantation, and the other four patients received sequential CIs. The setting was a comprehensive cochlear implant program/tertiary referral center. The main outcomes measures were speech-recognition scores in percent correct, mean score difference for unilateral versus bilateral conditions, and subjective benefit scores.

RESULTS

The most significant improvements in binaural cochlear implant use were found when subjects were tested with sentence material presented at 60 dB SPL with a +8 dB signal-to-noise ratio. Six of seven subjects showed significant binaural improvement, with a mean improvement score of 12.43% (SD = 5.32). All subjects preferred the binaural listening condition. Measured improvements in quality of life were seen.

CONCLUSIONS

Preliminary study findings suggest that significant cochlear implant binaural benefit in speech perception may be observed when testing in more difficult listening situations (i.e., lower presentation levels and in noise). According to the outcome of our study, testing the binaural benefit of CIs requires consideration of suitable test materials and stimulation parameters.

Differential representation of speech sounds in the human cerebral hemispheres

Various methods in auditory neuroscience have been used to gain knowledge about the structure and function of the human auditory cortical system. Regardless of method, hemispheric differences are evident in the normal processing of speech sounds. This review article, augmented by the authors' own work, provides evidence that asymmetries exist in both cortical and subcortical structures of the human auditory system. Asymmetries are affected by stimulus type, for example, hemispheric activation patterns have been shown to change from right to left cortex as stimuli change from speech to nonspeech. In addition, the presence of noise has differential effects on the contribution of the two hemispheres. Modifications of typical asymmetric cortical patterns occur when pathology is present, as in hearing loss or tinnitus. We show that in response to speech sounds, individuals with unilateral hearing loss lose the normal asymmetric pattern due to both a decrease in contralateral hemispheric activity and an increase in the ipsilateral hemisphere. These studies demonstrate the utility of modern neuroimaging techniques in functional investigations of the human auditory system. Neuroimaging techniques may provide additional insight as to how the cortical auditory pathways change with experience, including sound deprivation (e.g., hearing loss) and sound experience (e.g., training). Such investigations may explain why some populations appear to be more vulnerable to changes in hemispheric symmetry such as children with learning problems and the elderly.

Biomechanical Strength of Reconstruction Plates when Used for Medial Support of Med-El Cochlear Implants: Implications for Diagnostic MRI

PURPOSE

It is hypothesized that a mesh reconstruction plate designed to fit a cochlear implant (CI) internal device will provide immediate structural support to the site of the implant and that this strength far exceeds the forces induced by a 1.5-tesla MRI.

PROCEDURES

Human calvarial specimens were drilled and plated with reconstruction mesh. Force was applied until failure was reached.

RESULTS

Mean maximum force, mean force to first failure and mean displacement measures for group 1 (resorbable mesh, n = 10) were 302.9 N, 283.0 N and 3.05 mm, respectively. The mean maximum force for group 2 (0.4-mm titanium mesh, n = 10) and group 3 (0.6-mm titanium mesh, n = 8), were 121.3 and 234.0 N, respectively. Mean force of first failure was 92.0 N for group 2 and 164.8 N for group 3.

CONCLUSIONS

The force required for failure of the mesh is significantly greater than the 0.17 N exerted on a CI magnet by a 1.5-tesla MRI scan.

Electrosurgery after Cochlear Implantation: Eighth Nerve Electrophysiology

HYPOTHESIS

Monopolar electrosurgery below the neck in cochlear implant recipients can be performed without damage to the internal cochlear stimulator, electrode array, and the cochlear nerve.

STUDY DESIGN

Prospective pre- and postintervention electrically evoked compound action potential (ECAP) study of cochlear nerve function and behavioral sound perception assessment.

METHODS

Neural response telemetry (NRT) was used to measure ECAPs before and after the use of monopolar electrosurgery during coronary artery bypass surgery to assess prosthetic device function and electrophysiologic function of the cochlear nerve. In addition, electrode voltage impedances and behavioral sound perception was measured at the same time intervals.

RESULTS

ECAPs, behavioral sound perception, and electrode voltage impedances were within the normal range, within compliance, and similar preoperatively and on postoperative day 6.

CONCLUSION

The studies reported herein were a series of measurements designed to test neural integrity and prosthetic device function before and after the use of monopolar electrosurgery. With appropriate precautions, use of monopolar electrosurgery below the neck in cochlear implant recipients can be performed safely.

Gamma Knife Radiosurgery for Acoustic Neuromas Performed by a Neurotologist: Early Experiences and Outcomes

OBJECTIVE

To assess early outcomes after Gamma knife radiosurgery of acoustic neuromas and other skull base tumors.

BACKGROUND

Gamma knife radiosurgery is one of the available methods to treat acoustic neuromas, in addition to micro-surgical resection. Neuro-otologists have long been associated with microsurgical resection of these tumors; however, the application of Gamma knife radiosurgery to the treatment of these tumors by neuro-otologists has not been previously described.

SETTING

Acoustic Neuroma and Skull Base Surgery Program / Tertiary Referral Center. STUDY DESIGN/PATIENTS/INTERVENTION: Prospective clinical study of all patients treated by the senior author and our gamma knife team beginning in June 2000.

MAIN OUTCOME MEASURES

Preoperative MRI, audiometry, vestibular testing and facial nerve electromyography were completed. At six-month intervals postoperatively, audiometry, caloric testing and MRI were performed to determine thresholds and speech discrimination ability, vestibular function, and the size of the tumor.

RESULTS

From June 2000 until March 2004, 38 patients were treated, and these included 33 acoustic neuromas, two meningiomas, one glomus jugulare tumor, and two facial neuromas. Greater than 36 month follow-up was available in 7 patients, > 24 months in 24, > 12 months in 31, and > 6 months in 34 patients. Statistically significant reduction in tumor size was seen over time, and tumor control was achieved in all but two patients. Various patterns of changes in auditory function, both in threshold and speech discrimination were observed in either positive or negative directions.

CONCLUSIONS

Preliminary experience with Gamma knife radiosurgery indicates that this treatment method represents another option for neuro-otologists to use in managing patients with skull base tumors.

Effect of magnetic resonance imaging on internal magnet strength in Med-El Combi 40+ cochlear implants

OBJECTIVE

Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med-El Combi 40+ cochlear implant internal magnets after MRI studies.

STUDY DESIGN/METHODS

Two fresh cadavers were used to study demagnetization using a repeated measures design and a magnetometer. Pre- and postMRI measurement of magnetic field strength was completed. Five sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 0.2 Tesla in the device-up and device-down positions. In the other cadaver, 15 sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 1.5 Tesla were conducted, 5 each with the head oriented at 80, 90, and 100 degrees rotated around the yaw plane (rotated around the z-axis). Subsequently, three cochlear implant patients completed 0.2 Tesla MRIs. For these patients, subjective and objective assessment of cochlear implant performance was performed.

SETTING

Academic medical center.

RESULTS

In the cadaver studies, analysis of variance showed no significant difference in the magnetic field strength after the 0.2 or 1.5 Tesla scans. There was no significant difference in the magnetic field strength for the three patients undergoing 0.2 Tesla MRIs and no adverse consequences, including no changes in telemetry, auditory sensations, nonauditory sensations, and sound quality.

CONCLUSIONS

No significant demagnetization of the internal magnet occurred during repeated 1.5 Tesla MRI scans with the head orientations used in this study. In the cochlear implant patients, no significant demagnetization of the internal magnet occurred after a 0.2 Tesla MRI.

Recognition of Speech Presented at Soft to Loud Levels by Adult Cochlear Implant Recipients of Three Cochlear Implant Systems

OBJECTIVE

The purpose of this study was to conduct a large-scale investigation with adult recipients of the Clarion, Med-El, and Nucleus cochlear implant systems to (1) determine average scores and ranges of performance for word and sentence stimuli presented at three intensity levels (70, 60, and 50 dB SPL); (2) provide information on the variability of scores for each subject by obtaining test-retest measures for all test conditions; and (3) further evaluate the potential use of lower speech presentation levels (i.e., 60 and/or 50 dB SPL) in cochlear implant candidacy assessment.

DESIGN

Seventy-eight adult cochlear implant recipients, 26 with each of the three cochlear implant systems, participated in the study. To ensure that the data collected reflect the range of performance of adult recipients using recent technology for the three implant systems (Clarion HiFocus I or II, Med-El Combi 40+, Nucleus 24M or 24R), a composite range and distribution of consonant-nucleus-consonant (CNC) monosyllabic word scores was determined. Subjects using each device were selected to closely represent this range and distribution of CNC performance. During test sessions, subjects were administered the Hearing in Noise Test (HINT) sentence test and the CNC word test at three presentation levels (70, 60, and 50 dB SPL). HINT sentences also were administered at 60 dB SPL with a signal-to-noise ratio (SNR) of +8 dB. Warble tones were used to determine sound-field threshold levels from 250 to 4000 Hz. Test-retest measures were obtained for each of the speech recognition tests as well as for warble-tone sound-field thresholds.

RESULTS

Cochlear implant recipients using the Clarion, Med-El, or Nucleus devices performed on average equally as well at 60 compared with 70 dB SPL when listening for words and sentences. Additionally, subjects had substantial open-set speech perception performance at the softer level of 50 dB SPL for the same stimuli; however, subjects' ability to understand speech was poorer when listening in noise to signals of greater intensity (60 dB SPL + 8 SNR) than when listening to signals presented at a soft presentation level (50 dB SPL) in quiet. A significant correlation was found between sound-field thresholds and speech recognition scores for presentation levels below 70 dB SPL. The results demonstrated a high test-retest reliability with cochlear implant users for these presentation levels and stimuli. Average sound-field thresholds were between 24 and 29 dB HL for frequencies of 250 to 4000 Hz, and results across sessions were essentially the same.

CONCLUSIONS

Speech perception measures used with cochlear implant candidates and recipients should reflect the listening challenges that individuals encounter in natural communication situations. These data provide the basis for recommending new candidacy criteria based on speech recognition tests presented at 60 and/or 50 dB SPL, intensity levels that reflect real-life listening, rather than 70 dB SPL.

Fungal biofilm formation on cochlear implant hardware after antibiotic-induced fungal overgrowth within the middle ear

Cochlear implantation in patients with chronic suppurative otitis media is managed with perioperative antibiotics; however, fungal overgrowth can occur. We present a child who received oral cefdinir and topical ofloxacin (Floxin). After 6 weeks, a fungal (Candida) biofilm was demonstrated on the implant surface. In this clinical setting, an antimicrobial strategy using an oral antifungal to prevent fungal overgrowth is a possibility.

Auditory Sensitivity in Children Using the Auditory Steady-State Response

OBJECTIVE

To determine the effectiveness of auditory steady-state response (ASSR) as a measure of hearing sensitivity in young children suspect for significant hearing loss.

DESIGN

Within-subject comparisons of click auditory brainstem response (ABR) thresholds and ASSR thresholds.

SUBJECTS

The study population comprised 42 children suspect for hearing loss and subsequently referred for hearing assessment using electrophysiologic techniques.

MAIN OUTCOME MEASURES

Electrophysiologic threshold responses for click ABR and ASSR stimuli (0.5, 1, 2, and 4 kHz) for right and left ears.

RESULTS

Based on ABR and ASSR thresholds, 50% of the subjects demonstrated significant hearing loss in the severe to profound range. In some subjects, ASSRs were present at higher stimulus levels when click ABRs were absent. Significant correlations (P<.05) were found between high-frequency ASSR and click ABR thresholds for this study sample. For some subjects, ASSR findings suggested differences between ears that were not observable from the no-response click ABR results.

CONCLUSIONS

Auditory steady-state response testing may provide additional information for children who demonstrate hearing levels in the severe to profound range. This information may be helpful when selecting the ear for cochlear implantation for a young hearing-impaired child. Multiple objective methods, such as ABR and ASSR testing, may be needed to determine accurate hearing sensitivity for young children being considered for sensory devices, and in particular, cochlear implants.

Electrophysiologic Effects of Placing Cochlear Implant Electrodes in a Perimodiolar Position in Young Children

OBJECTIVE

The purpose of this study was to intraoperatively record the electrically evoked auditory brainstem response (EABR) before and after placement of the electrode positioning system (EPS) (CII Bionic Ear with HiFocus I cochlear implant electrode array) as well as before and after stylet removal (Nucleus Contour cochlear implant electrode array). It was hypothesized that physiologic changes would occur after perimodiolar positioning of the electrode array and these changes would be evident from the EABR recordings.

STUDY DESIGN

Consecutive young (11-36 month old) pediatric cochlear implant recipients (n = 17) had intraoperative EABRs recorded from three intracochlear electrodes that represented apical, medial, and basal locations. Wave V amplitudes and thresholds were studied relative to electrode location and pre- versus postperimodiolar positioning. These evoked potential measures were analyzed for statistical significance.

SETTING

Tertiary referral children's hospital/medical college.

RESULTS

Wave V thresholds of the EABR were lower, and amplitudes were larger after perimodiolar positioning, although the changes were dependent on electrode location and implant design. Statistically significant decreases in EABR wave V threshold and increases in suprathreshold wave V amplitude were found for the basal electrode for the CII Bionic Ear HiFocus I and for the apical electrode for the Nucleus Contour.

CONCLUSIONS

Placement of either the CII Bionic Ear HiFocus I or Nucleus Contour cochlear implant electrode array in the perimodiolar position in young children resulted in less electrical current necessary to stimulate the auditory system. Changes in electrophysiologic thresholds and amplitudes, measured with EABR, indicate that the electrode array is placed closer to the modiolus with both electrode designs.

Electrically evoked auditory brain stem responses for lateral and medial placement of the Clarion HiFocus electrode

OBJECTIVE

The purpose of this study was to compare the electrically evoked auditory brain stem response (EABR) for lateral and medial placement of the Clarion HiFocus cochlear implant electrode array via the electrode positioning system (EPS).

DESIGN

Twenty-five adult and pediatric cochlear implant recipients participated in the study. Intraoperatively recorded EABRs were evoked by stimuli via three intracochlear electrodes representing apical, medial, and basal locations, and responses were elicited before and after positioner insertion. Evoked potential measures of wave V amplitude and threshold were examined for statistical significance using ANOVA for repeated measures and Chi-Square methods.

RESULTS

For a given supra-threshold stimulus level, the increase in EABR wave V amplitude was significantly larger after EPS placement compared to before EPS placement for electrodes 1 (apical) and 13 (basal). Likewise, when the stimulus was decreased to obtain a minimal amplitude, the wave V threshold was significantly lower after EPS placement for electrodes 7 (medial) and 13. The number of measurements that showed decreased wave V threshold after EPS insertion was significantly dependent on intracochlear electrode location.

CONCLUSIONS

Placement of the Clarion Electrode Positioning System following HiFocus electrode insertion resulted in a reduction in the electrical current required to activate the auditory system. The effect of the EPS was greatest for the basal location, demonstrated by lower wave V thresholds and a larger percentage increase in wave V amplitude. The EABR reflected electrophysiologic changes relative to lateral-to-medial changes in intracochlear electrode position due to the EPS.

Intensity-dependent activation of the primary auditory cortex in functional magnetic resonance imaging

PURPOSE

The purpose of this study was to investigate the activation patterns of the primary auditory cortex in response to varying intensities of pure tone stimuli.

METHOD

A 1,000-Hz pure tone stimulus was delivered monaurally to the right ear of 12 normal-hearing right-handed volunteers in 20-second on-off cycles. Stimuli were applied at 20 and 50 dB hearing level (HL) above threshold in 12 subjects and at 0, 20, 40, and 50 dB HL above threshold in 6 subjects. Functional magnetic resonance imaging (fMRI) data were obtained using a 1.5-T scanner and echoplanar imaging. Activated pixels were identified in the transverse temporal gyrus (TTG) of both hemispheres in response to pure tone stimuli at each intensity level using cross-correlation analysis (0.6; P < 0.0001).

RESULTS

Of the 24 right and left TTGs imaged (n = 12), activation to pure tone stimuli at 20 and 50 dB HL above threshold was seen in 46% and 79% of TTGs, respectively, with bilateral hemispheric activation in 27% and 64% of subjects, respectively. The mean numbers of activated voxels were 4.0 and 13.0, respectively. Of the 12 right and left TTGs imaged at 0, 20, 40, and 50 dB HL above threshold, activation was seen in 33%, 42%, 58%, and 75% of TTGs, respectively. The mean numbers of activated voxels were 5.8, 3.2, 9.8, and 15.3, respectively. There was a nonsignificant trend toward contralateral (left) dominant TTG activation with increased tone intensity.

CONCLUSION

Our results show an increased likelihood of TTG activation, increased TTG activation volume, and increased bilateral hemisphere TTG activation with increasing pure tone intensity. Our results suggest that the primary auditory cortex reflects or is directly involved in the central processing of sound intensity and that varying the intensity of even simple stimuli can alter the patterns of fMRI activation in auditory cortex.

Neurophysiology of cochlear implant users I: effects of stimulus current level and electrode site on the electrical ABR, MLR, and N1-P2 response

OBJECTIVE

As the need for objective measures with cochlear implant users increases, it is critical to understand how electrical potentials behave when stimulus parameters are systematically varied. The purpose of this study was to record and evaluate the effects of implanted electrode site and stimulus current level on latency, amplitude, and threshold measures of electrically evoked auditory potentials, representing brainstem and cortical levels of the auditory system.

DESIGN

The electrical auditory brainstem response (EABR), electrical auditory middle latency response (EAMLR), and the electrical late auditory response (ELAR) were recorded from the same experimental subjects, 11 adult Clarion cochlear implant users. The Waves II, III, and V of the EABR, the Na-Pa complex of the EAMLR and the N1-P2 complex of the ELAR were investigated relative to electrode site (along the intra-cochlear electrode array) and stimulus current level. Evoked potential measures were examined for statistical significance using analysis of variance (ANOVA) for repeated measures.

RESULTS

For the EABR, Wave V latency was significantly longer for the basal electrode (7) compared with the mid (4) and apical (1) electrodes. For the EAMLR and ELAR, there were no significant differences in latency by electrode site. For all subjects and each of the evoked potentials, the apical electrodes tended to have the largest amplitude and the basal electrodes the smallest amplitude, although amplitude differences did not reach statistical significance. In general, decreases in stimulus current level resulted in statistically significant decreases in the amplitude of Wave V, Na-Pa and N1-P2. The evoked potential thresholds for Wave V, Na-Pa, and N1-P2 were significantly higher for the basal Electrode 7 than for Electrodes 4 and 1.

CONCLUSIONS

Electrophysiologic responses of Waves II, III, and V of the EABR, Na-Pa of the EAMLR, and N1-P2 of the ELAR were characterized as functions of current level and electrode site. Data from this study may serve as a normative reference for expected latency, amplitude and threshold values for the recording of electrically evoked auditory brainstem and cortical potentials. Responses recorded from cochlear implant users show many similar patterns, yet important distinctions, compared with auditory potentials elicited with acoustic signals.