Speech Perception in Noise for Children with Auditory Neuropathy/Dys-Synchrony Type Hearing Loss

Predictors of cochlear implant outcomes in pediatric auditory neuropathy: A matched case-control study

OBJECTIVES

Current evidence supports the benefits of cochlear implants (CIs) in children with hearing loss, including those with auditory neuropathy spectrum disorder (ANSD). However, there is limited evidence regarding factors that hold predictive value for intervention outcomes.

DESIGN

This retrospective case-control study consisted of 66 children with CIs, including 22 with ANSD and 44 with sensorineural hearing loss (SNHL) matched on sex, age, age at CI activation, and the length of follow-up with CIs (1:2 ratio). The case and control groups were compared in the results of five open-set speech perception tests, and a Forward Linear Regression Model was used to identify factors that can predict the post-CI outcomes.

RESULTS

There was no significant difference in average scores between the two groups across five outcome measures, ranging from 88.40% to 95.65%. The correlation matrix revealed that younger ages at hearing aid fitting and CI activation positively influenced improvements in speech perception test scores. Furthermore, among the variables incorporated in the regression model, the duration of follow-up with CIs, age at CI activation, and the utilization of two CIs demonstrated prognostic significance for improved post-CI speech perception outcomes.

CONCLUSIONS

Children with ANSD can achieve similar open-set speech perception outcomes as children with SNHL. A longer CI follow-up, a lower age at CI activation, and the use of two CIs are predictive for optimal CI outcome.

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Intracochlear electrocochleography findings in cochlear implant recipients with auditory neuropathy spectrum disorder

OBJECTIVES

This study aimed to compare intracochlear electrocochleography (ECochG) findings in a group of cochlear implant (CI) recipients with auditory neuropathy spectrum disorder (ANSD) with a group of CI recipients with sensorineural hearing loss (SNHL). Auditory outcome and spectral resolution findings were also compared among CI recipients with and without cochlear microphonic (CM) responses.

METHODS

This single-center, prospective cohort study was undertaken at a tertiary referral center. CM responses by the intracochlear ECochG test were recorded in CI recipients at 0.25-2 kHz. Speech, spatial, and hearing quality (SSQ) outcomes and spectral resolution measured with the spectral-temporally modulated ripple test were obtained for each recipient. The study included 62 implanted ears in 46 recipients, of which 59% (n = 27) were male and 41% (n = 19) were female. Twenty-nine ears with ANSD and 33 ears with SNHL were included. The mean age of the participants was 11 years. The results compared the intracochlear ECochG findings of the ANSD group with those of the SNHL group.

RESULTS

Participants were divided into two groups with and without obtainable CM responses. CM responses were obtained in 13 of 29 ears in the ANSD group and 14 of 33 ears in the SNHL group. CM thresholds obtained were better according to behavioral audiometric responses in some frequencies in the ANSD group. No significant difference was found in the auditory outcome and spectral resolution among CI recipients with and without CM responses.

CONCLUSIONS

Intracochlear ECochG has a limited potential clinical value for monitoring ANSD. CM thresholds obtained using ECochG may not reflect behavioral hearing thresholds.

Auditory and Speech Outcomes of Cochlear Implantation in Children With Auditory Neuropathy Spectrum Disorder: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of this meta-analysis was to critically assess the effect of cochlear implantation on auditory and speech performance outcomes of children with auditory neuropathy spectrum disorder (ANSD).

MATERIAL AND METHODS

A systematic literature search was conducted on PubMed, EMbase, and Web of Science. The outcomes included speech recognition score, Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR) score, and open-set speech perception. Results were expressed as standardized mean difference (SMD) or risk ratio (RR) with a 95% confidence interval (95% CI).

RESULTS

A total of 15 studies was included in this meta-analysis. Pooled data showed that, there were no significant differences between ANSD and sensorineural hearing loss (SNHL) groups in terms of speech recognition score (SMD = 0.01, 95% CI: -0.45, 0.47; P = .959),CAP (SMD = 0.71, 95% CI: -0.13, 1.54; P = .098), SIR score (SMD = -0.09, 95% CI: -0.49, 0.32; P = .667), and open-set speech perception (RR = 0.85, 95% CI: 0.69, 1.05; P = .142). Sensitivity analysis by removing individual studies one at a time showed that the overall estimate and level of heterogeneity did not change substantially.

CONCLUSION

The current evidence suggested that children with ANSD who underwent cochlear implants achieved comparable effects in auditory and speech performance as children with non-ANSD SNHL.

Impact of Noise on Sound Processing at Lower Auditory System: An Electrophysiological Study

The importance of signal-to-noise ratio (SNR) is well documented in behavioral speech perception experiments and psychophysical measurements. Studies on ABR related to the encoding of signals in ipsilateral noise are very limited. The present study aimed to systematically investigate the effect of various SNRs on the latency and amplitude of ABR to a range of stimuli & to compare the latency and amplitude of ABR recorded in various ipsilateral SNRs in children and adults. We recorded auditory brain stem responses (ABR) in children and young adults for clicks, a speech token /da/ of 40 ms duration, and for a 1000 Hz tone burst in the presence of a broad band noise and quiet. There were four SNR conditions (+ 10 dB SNR, 0 dB SNR and -10 dB SNR), and the level of noise was varied, while the stimulus level was fixed at 60 dB HL. The results showed that SNR affects the latency and amplitude of the wave V peak differentially for the different stimuli. A difference in the performance of children and adults was also observed. SNR measurements using ABR provide an objective index of brainstem ability to process sound in the presence of background noise. This measure is important and can be used to assess the sound-in-noise processing ability in the difficult-to-test population such as infants and children where measures of signal-to-noise tests cannot be administered.

[Auditory neuropathy and prematurity: modern view of the issue (literature review)]

Auditory neuropathy spectrum disorder (ANSD) is a specific auditory disorder caused by dysfunction of periphery part of the auditory system, in which the function of the outer hair cells is preserved, but the afferent input at the cochlear level suffers due to the pathology of the inner hair cells, neurons of the spiral ganglion and/or the auditory nerve, as well as synaptic contact between them. As a result, a specific condition is formed, in which a patient's otoacoustic emissions and/or cochlear microphonics are present, auditory brainstem responses are abnormal or absent, the discrepancy between the hearing level and the electrophysiological data, poor speech perception which may not correlate with the hearing thresholds. ANSD is a multifactorial disease. One of the main risk factors is perinatal pathology and, in particular, prematurity. The possible factors associated with prematurity that provoke the onset of the disease, features of the pathogenesis, clinical and audiological peculiarities of ANSD in premature infants, contemporary approaches to the habilitation of such patients are discussed in the article. The necessity of an individual, patient-oriented approach to the treatment of premature infants with ANSD is substantiated; such an approach should be based both on the genesis of the disorder, taking into account possible points of lesion in the auditory system, and the developmental peculiarities of a premature baby considering the presence of concomitant diseases associated with prematurity. In the article attention is focused on the main directions of habilitation work with such children, including a multidisciplinary approach, regular careful monitoring of the auditory, speech and language skills, intensive psychological and speech therapist support, the choice of an adequate way of intervention and its improvement as necessary.

Prevalence, risk factors, and audiological characteristics of auditory neuropathy

OBJECTIVE

The objective of this study was to determine the prevalence, risk factors, and audiological characteristics of auditory neuropathy spectrum disorder (ANSD) in the pediatric population.

DESIGN

A retrospective review of medical charts was conducted for children visiting two hospitals in Saudi Arabia.

STUDY SAMPLE

Medical records of 1025 patients with sensorineural hearing loss (SNHL) were reviewed. We analyzed the databases for results of audiological examinations, risk factors, and outcomes of intervention including hearing aid (HA) and cochlear implantation (CI).

RESULTS

Out of 1025 children with SNHL, 101 patients (9.85%) were identified to have ANSD. Audiological characteristics of the ANSD group revealed a severe-to-profound degree of hearing loss, all showed type A tympanogram and absent reflexes, absent auditory brainstem response (ABR) findings with present cochlear microphonic while otoacoustic emissions were absent in 54.5% of patients. The most prevalent risk factors for ANSD in this group were family history of hearing loss, consanguinity, hyperbilirubinemia, and low birth weight. Pure tone and speech detection thresholds improved significantly with CI compared to HA use in this sample of patients with ANSD.

CONCLUSION

This study shows that ANSD is not extremely rare among Saudi children with severe to profound hearing loss, with a prevalence of 9.85%.

Multiple Cases of Auditory Neuropathy Illuminate the Importance of Subcortical Neural Synchrony for Speech-in-noise Recognition and the Frequency-following Response

OBJECTIVES

The role of subcortical synchrony in speech-in-noise (SIN) recognition and the frequency-following response (FFR) was examined in multiple listeners with auditory neuropathy. Although an absent FFR has been documented in one listener with idiopathic neuropathy who has severe difficulty recognizing SIN, several etiologies cause the neuropathy phenotype. Consequently, it is necessary to replicate absent FFRs and concomitant SIN difficulties in patients with multiple sources and clinical presentations of neuropathy to elucidate fully the importance of subcortical neural synchrony for the FFR and SIN recognition.

DESIGN

Case series. Three children with auditory neuropathy (two males with neuropathy attributed to hyperbilirubinemia, one female with a rare missense mutation in the OPA1 gene) were compared to age-matched controls with normal hearing (52 for electrophysiology and 48 for speech recognition testing). Tests included standard audiological evaluations, FFRs, and sentence recognition in noise. The three children with neuropathy had a range of clinical presentations, including moderate sensorineural hearing loss, use of a cochlear implant, and a rapid progressive hearing loss.

RESULTS

Children with neuropathy generally had good speech recognition in quiet but substantial difficulties in noise. These SIN difficulties were somewhat mitigated by a clear speaking style and presenting words in a high semantic context. In the children with neuropathy, FFRs were absent from all tested stimuli. In contrast, age-matched controls had reliable FFRs.

CONCLUSION

Subcortical synchrony is subject to multiple forms of disruption but results in a consistent phenotype of an absent FFR and substantial difficulties recognizing SIN. These results support the hypothesis that subcortical synchrony is necessary for the FFR. Thus, in healthy listeners, the FFR may reflect subcortical neural processes important for SIN recognition.

Auditory Neuropathy/Auditory Synaptopathy

Patients with auditory neuropathy (AN)/auditory synaptopathy (AS) present unique evaluation and management challenges. Communication ability using auditory stimuli varies among patients, with particular difficulty understanding speech in noise. Auditory physiologic responses are key to accurate identification and monitoring of patients with AN/AS. Management approaches should consider individual variation and the possibility of change over time. Many patients with accurately characterized AN/AS demonstrate success with cochlear implants. Areas of discovery, including understanding of synaptic and neural mechanisms, genotype/phenotype relationships, and use of cochlear and cortical evoked potentials, will promote accurate clinical evaluation and management of infants, children, and adults with AN/AS.

Cortical Auditory Event-Related Potentials and Categorical Perception of Voice Onset Time in Children With an Auditory Neuropathy Spectrum Disorder

Objective: This study evaluated cortical encoding of voice onset time (VOT) in quiet and noise, and their potential associations with the behavioral categorical perception of VOT in children with auditory neuropathy spectrum disorder (ANSD). Design: Subjects were 11 children with ANSD ranging in age between 6.4 and 16.2 years. The stimulus was an /aba/-/apa/ vowel-consonant-vowel continuum comprising eight tokens with VOTs ranging from 0 ms (voiced endpoint) to 88 ms (voiceless endpoint). For speech in noise, speech tokens were mixed with the speech-shaped noise from the Hearing In Noise Test at a signal-to-noise ratio (SNR) of +5 dB. Speech-evoked auditory event-related potentials (ERPs) and behavioral categorization perception of VOT were measured in quiet in all subjects, and at an SNR of +5 dB in seven subjects. The stimuli were presented at 35 dB SL (re: pure tone average) or 115 dB SPL if this limit was less than 35 dB SL. In addition to the onset response, the auditory change complex (ACC) elicited by VOT was recorded in eight subjects. Results: Speech evoked ERPs recorded in all subjects consisted of a vertex positive peak (i.e., P1), followed by a trough occurring approximately 100 ms later (i.e., N2). For results measured in quiet, there was no significant difference in categorical boundaries estimated using ERP measures and behavioral procedures. Categorical boundaries estimated in quiet using both ERP and behavioral measures closely correlated with the most-recently measured Phonetically Balanced Kindergarten (PBK) scores. Adding a competing background noise did not affect categorical boundaries estimated using either behavioral or ERP procedures in three subjects. For the other four subjects, categorical boundaries estimated in noise using behavioral measures were prolonged. However, adding background noise only increased categorical boundaries measured using ERPs in three out of these four subjects. Conclusions: VCV continuum can be used to evaluate behavioral identification and the neural encoding of VOT in children with ANSD. In quiet, categorical boundaries of VOT estimated using behavioral measures and ERP recordings are closely associated with speech recognition performance in children with ANSD. Underlying mechanisms for excessive speech perception deficits in noise may vary for individual patients with ANSD.

Long-term treatment outcomes in children with auditory neuropathy spectrum disorder (ANSD)

INTRODUCTION

The present article shows long-term results in the hearing and speech development of children with auditory neuropathy spectrum disorder (ANSD). Some children were followed up for nearly 20 years, monitoring their progress through childhood into adulthood.

METHODS

This retrospective study examined data from 10 children who were diagnosed and treated at our tertiary referral center. All children were provided with hearing aids and/or cochlear implants. The children's hearing and speech development and their social and educational development were evaluated.

RESULTS

Seven children were provided with cochlear implants on both sides; three children, one of which had single-sided deafness, received hearing aids. All children with cochlear implants on both sides used their devices full-time. Speech perception ranged between 100% and 0% on one side. Five children attended a school for the hearing impaired; four children attended a regular school. Four children attended vocational training.

CONCLUSIONS

At present, there is a lack of literature on the long-term outcomes of treatment in children with ANSD. The data presented show that the hearing and speech development in children with ANSD are significantly heterogeneous. Regular school education and social integration of children with ANSD can be achieved with intensive and supportive rehabilitative methods.

Outcomes of audiometric testing in children with auditory neuropathy spectrum disorder

INTRODUCTION

Auditory Neuropathy Spectrum Disorder (ANSD) is characterized by hearing loss ranging from normal to profound. Additionally, results are confounded by commonly fluctuating hearing thresholds in ANSD. As such, we sought to evaluate results of audiometric testing on children with ANSD and the impact of age and time on testing results.

METHODS

Retrospective chart review on children <18 years of age diagnosed with ANSD at two tertiary care academic institutions. Data analyzed included initial audiogram with speech detection thresholds (SDT) and pure tone averages (PTA) as well as most recent unaided audiogram SDT and PTA.

RESULTS

75 ANSD patients were analyzed, of which 32 (42.7%) were female. Bilateral and unilateral ANSD was seen in 55 (73.3%) and 20 (26.7%), respectively. A total of 130 ears with ANSD were assessed with 80 (61.5%) meeting inclusion criteria. Of these patients, the median age in years at first audiogram and most recent audiogram were 1.94 (0.45-13.68) and 4.22 (0.97-14.61), respectively. The median ages at which an SDT and PTA could first be acquired on the audiogram in ANSD patients were 1.94 (0.50-13.68) and 2.86 (0.45-13.68), respectively. The average SDT/PTA at the initial and most recent audiogram were 47.5/45.7 and 49.4/53.0 dB, respectively. SDT to PTA within the same audiogram exhibited strong correlation (r = 0.82, p < 0.001). Similarly, comparison of initial SDT to SDT at a later time interval showed strong correlation (r = 0.73, p < 0.001). SDT and PTA at initial audiogram and PTA at later time demonstrated lower correlation but was still statistically significant (r = 0.49, p < 0.009 and r = 0.51, p < 0.044, respectively). Individual PTA was associated with age (r = -0.56, p < 0.001).

CONCLUSIONS

SDT and PTA within the same audiogram and initial SDT to SDT acquired at a later time correlate strongly in audiometric testing in children with ANSD. Although not as strong, initial SDT and PTA still correlate with PTA at a later time interval. These findings suggest that audiometric results yielding a reliable SDT and frequency specific information necessary to calculate the PTA is not typically obtained until 2-3 years old. However, once this information is obtained, the child's hearing is fairly stable but may fluctuate over time.

Evaluation and therapy outcome in children with auditory neuropathy spectrum disorder (ANSD)

OBJECTIVES

The aims of the present study are to: describe diagnostic findings in patients with auditory neuropathy spectrum disorder (ANSD); and demonstrate the outcomes of different therapies like hearing aids (HAs) or cochlear implantation.

METHODS

32 children were diagnosed and treated at our tertiary referral center and provided with HAs or cochlear implants (CIs). All of them underwent free-field or pure-tone audiometry. Additionally, otoacoustic emissions (OAEs), impedance measurements, auditory brainstem responses (ABRs), auditory steady-state responses (ASSR), electrocochleography, and cranial magnetic resonance imaging (cMRI) were all performed. Some patients also underwent genetic evaluation. Following suitable provision pediatric audiological tests, psychological developmental diagnostic and speech and language assessments were carried out at regular intervals in all the children.

RESULTS

OAEs could initially be recorded in most of the children; 17 had no ABRs. The other eight children had a poor ABR morphology. Most of the children had typical, long-oscillating cochlear microphonics (CMs) in their ABRs, which was also observed in all of those who underwent electrocochleography. Eight children were provided with a HA and 17 received a CI. The functional gain was between 32 and 65 decibel (dB) with HAs and between 32 and 50 dB with CI. A speech discrimination level between 35 and 100% was achieved during open-set monosyllabic word tests in quiet with HA or CI. With the Hochmair-Schulz-Moser (HSM) sentence test at 65 dB SPL (sound pressure level), 75% of the children with a CI achieved a speech discrimination in noise score of at least 60% at a signal to noise ratio (SNR) of 5, and four scored 80% or higher. Most of the children (72%) were full-time users of their devices. All the children with a CI used it on a regular basis.

CONCLUSION

Only a few case reports are available in the literature regarding the long-term outcomes of ANSD therapy. The present study reveals satisfactory outcomes with respect to hearing and speech discrimination in children with CIs or HAs. The nearly permanent use of the devices reflects a subjective benefit for the children. Provision with a suitable hearing device depends on audiological results, the speech and language development of an individual child, and any accompanying disorders. Repeated audiological evaluations, interdisciplinary diagnostics, and intensive hearing and speech therapy are essential for adequate rehabilitation of this group of children.

The Effects of Stimulus Rate on ABR Morphology and its Relationship to P1 CAEP Responses and Auditory Speech Perception Outcomes in Children with Auditory Neuropathy Spectrum Disorder: Evidence from Case Reports

OBJECTIVE

Auditory Neuropathy Spectrum Disorder (ANSD) affects approximately 5-15% of children with sensorineural hearing loss. ANSD is characterized by the presence of otoacoustic emissions (OAE) and an absent or abnormal auditory brainstem response (ABR). The purpose of this study was to investigate the prognostic value of slow-rate ABR in predicting the auditory cortical development and auditory speech perception outcomes in case studies of children with ANSD.

DESIGN

ABR waveform characteristics were collected at slow stimulation rates (5.1 clicks/second) and a fast stimulation rates (>11-31.1 clicks/second, rates typically used in a clinical setting) in 3 case reports of children with ANSD. P1 CAEP responses and measures of auditory speech perception using the Infant Toddler Meaningful Auditory Integration Scale (IT-MAIS) were also collected in these children. Retrospective analysis was performed to evaluate the prognostic value of slow- versus fast-rate ABR in predicting P1 CAEP responses and auditory speech perception outcomes in these children.

STUDY SAMPLE

Participants included case reports of 3 pediatric participants with a clinical diagnosis of ANSD.

RESULTS

Slow-rate ABR did not elicit significant improvements in waveform morphology compared to fast-rate ABR. P1 CAEP results were present in 2 out of 3 cases and were consistent with auditory speech perception outcomes.

CONCLUSIONS

Even when ABR stimulation rates were slowed, ABR responses in these children with ANSD did not display any characteristic or replicable pattern, and ABR responses were not predictive of cortical auditory maturation or behavioral performance. In contrast, P1 CAEP responses provided valuable information regarding the maturational status of the auditory cortex and P1 CAEP responses were consistent with behavioral measures of auditory speech perception. Overall, results highlight the high prognostic value of P1 CAEP testing when used in conjunction with behavioral measures of auditory speech perception in children with ANSD.

Auditory neuropathy in Brown-Vialetto-Van Laere syndrome due to riboflavin transporter RFVT2 deficiency

AIM

Mutations in the genes encoding the riboflavin transporters RFVT2 and RFVT3 have been identified in Brown-Vialetto-Van Laere syndrome, a neurodegenerative disorder characterized by hearing loss and pontobulbar palsy. Treatment with riboflavin has been shown to benefit individuals with the phenotype of RFVT2 deficiency. Understanding the characteristics of hearing loss in riboflavin transporter deficiency would enable early diagnosis and therapy.

METHOD

We performed hearing assessments in seven children (from four families) with RFVT2 deficiency and reviewed results from previous assessments. Assessments were repeated after 12 months and 24 months of riboflavin therapy and after cochlear implantation in one individual.

RESULTS

Hearing loss in these individuals was due to auditory neuropathy spectrum disorder (ANSD). Hearing loss was identified between 3 years and 8 years of age and progressed rapidly. Hearing aids were not beneficial. Riboflavin therapy resulted in improvement of hearing thresholds during the first year of treatment in those with recent-onset hearing loss. Cochlear implantation resulted in a significant improvement in speech perception in one individual.

INTERPRETATION

Riboflavin transporter deficiency should be considered in all children presenting with an auditory neuropathy. Speech perception in children with ANSD due to RFVT2 deficiency may be significantly improved by cochlear implantation.

Acoustically evoked auditory change complex in children with auditory neuropathy spectrum disorder: a potential objective tool for identifying cochlear implant candidates

OBJECTIVES

The overall aim of the study was to evaluate the feasibility of using electrophysiological measures of the auditory change complex (ACC) to identify candidates for cochlear implantation in children with auditory neuropathy spectrum disorder (ANSD). To achieve this overall aim, this study (1) assessed the feasibility of measuring the ACC evoked by temporal gaps in a group of children with ANSD across a wide age range and (2) investigated the association between gap detection thresholds (GDTs) measured by the ACC recordings and open-set speech-perception performance in these subjects.

DESIGN

Nineteen children with bilateral ANSD ranging in age between 1.9 and 14.9 years (mean: 7.8 years) participated in this study. Electrophysiological recordings of the auditory event-related potential (ERP), including the onset ERP response and the ACC, were completed in all subjects and open-set speech perception was evaluated for a subgroup of 16 subjects. For the ERP recordings, the stimulus was a Gaussian noise presented through ER-3A insert earphones to the test ear. Two stimulation conditions were used. In the "control condition," the stimulus was an 800-msec Gaussian noise. In the "gapped condition," the stimuli were two noise segments, each being 400 msec in duration, separated by one of five gaps (i.e., 5, 10, 20, 50, or 100 msec). The interstimulation interval was 1200 msec. The aided open-set speech perception ability was assessed using the Phonetically Balanced Kindergarten (PBK) word lists presented at 60 dB SPL using recorded testing material in a sound booth. For speech perception tests, subjects wore their hearing aids at the settings recommended by their clinical audiologists. For a subgroup of five subjects, psychophysical GDTs for the Gaussian noise were also assessed using a three-interval, three-alternative forced-choice procedure.

RESULTS

Responses evoked by the onset of the Gaussian noise (i.e., onset responses) were recorded in all stimulation conditions from all subjects tested in this study. The presence/absence, peak latency and amplitude, and response width of the onset response did not correlate with aided PBK word scores. The objective GDTs measured with the ACC recordings from 17 subjects ranged from 10 to 100 msec. The ACC was not recorded from two subjects for any gap durations tested in this study. There was a robust negative correlation between objective GDTs and aided PBK word scores. In general, subjects with prolonged objective GDTs showed low-aided PBK word scores. GDTs measured using electrophysiological recordings of the ACC correlated well with those measured using psychophysical procedures in four of five subjects who were evaluated using both procedures.

CONCLUSIONS

The clinical application of the onset response in predicting open-set speech-perception ability is relatively limited in children with ANSD. The ACC recordings can be used to objectively evaluate temporal resolution abilities in children with ANSD having no severe comorbidities, and who are older than 1.9 years. The ACC can potentially be used as an objective tool to identify poor performers among children with ANSD using properly fit amplification, and who are thus, cochlear implant candidates.

Pathophysiological mechanisms and functional hearing consequences of auditory neuropathy

The effects of inner ear abnormality on audibility have been explored since the early 20th century when sound detection measures were first used to define and quantify 'hearing loss'. The development in the 1970s of objective measures of cochlear hair cell function (cochlear microphonics, otoacoustic emissions, summating potentials) and auditory nerve/brainstem activity (auditory brainstem responses) have made it possible to distinguish both synaptic and auditory nerve disorders from sensory receptor loss. This distinction is critically important when considering aetiology and management. In this review we address the clinical and pathophysiological features of auditory neuropathy that distinguish site(s) of dysfunction. We describe the diagnostic criteria for: (i) presynaptic disorders affecting inner hair cells and ribbon synapses; (ii) postsynaptic disorders affecting unmyelinated auditory nerve dendrites; (iii) postsynaptic disorders affecting auditory ganglion cells and their myelinated axons and dendrites; and (iv) central neural pathway disorders affecting the auditory brainstem. We review data and principles to identify treatment options for affected patients and explore their benefits as a function of site of lesion.

Auditory Neuropathy/Dys-Synchrony Disorder: Diagnosis and Management

Auditory neuropathy/dys-synchrony disorder affects neural responses, either directly or indirectly. Patients may demonstrate good ability to detect sound, but have significant difficulty listening in noise. Clinical auditory physiologic measures are used to characterize cochlear, eighth nerve, and brainstem function, and are needed to accurately identify this disorder. Cochlear implants provide benefit to many patients, and some patients derive benefit from amplification. This disorder can be identified and managed in infants, may have later onset, may be a part of a syndrome, and may include fluctuation in hearing ability.

Objective measurement of high-level auditory cortical function in children

OBJECTIVE

This study examined whether the N2 latency of the cortical auditory evoked potential (CAEP) could be used as an objective indicator of temporal processing ability in normally hearing children.

METHODS

The N2 latency was evoked using three temporal processing paradigms: (1) differences in voice-onset-times (VOTs); (2) speech-in-noise using the CV/da/embedded in broadband noise (BBN) with varying signal-to-noise ratios (SNRs); and (3) 16Hz amplitude-modulated (AM) BBN presented (i) alone and (ii) following an unmodulated BBN, using four modulation depths. Thirty-four school-aged children with normal hearing, speech, language and reading were stratified into two groups: 5-7 years (n=13) and 8-12 years (n=21).

RESULTS

The N2 latency shifted significantly and systematically with differences in VOT and SNR, and was significantly different in the two AM-BBN conditions.

CONCLUSIONS

For children without an N1 peak in the cortical waveform, the N2 peak can be used as a sensitive measure of temporal processing for these stimuli.

SIGNIFICANCE

N2 latency of the CAEP can be used as an objective measure of temporal processing ability in a paediatric population with temporal processing disorder who are difficult to assess via behavioural response.

Cortical development and neuroplasticity in Auditory Neuropathy Spectrum Disorder

Cortical development is dependent to a large extent on stimulus-driven input. Auditory Neuropathy Spectrum Disorder (ANSD) is a recently described form of hearing impairment where neural dys-synchrony is the predominant characteristic. Children with ANSD provide a unique platform to examine the effects of asynchronous and degraded afferent stimulation on cortical auditory neuroplasticity and behavioral processing of sound. In this review, we describe patterns of auditory cortical maturation in children with ANSD. The disruption of cortical maturation that leads to these various patterns includes high levels of intra-individual cortical variability and deficits in cortical phase synchronization of oscillatory neural responses. These neurodevelopmental changes, which are constrained by sensitive periods for central auditory maturation, are correlated with behavioral outcomes for children with ANSD. Overall, we hypothesize that patterns of cortical development in children with ANSD appear to be markers of the severity of the underlying neural dys-synchrony, providing prognostic indicators of success of clinical intervention with amplification and/or electrical stimulation. This article is part of a Special Issue entitled <Auditory Synaptology>.

Auditory neural myelination is associated with early childhood language development in premature infants

BACKGROUND

Auditory neural myelination (ANM) as evaluated by auditory brainstem evoked response (ABR) during the neonatal period has been used as a surrogate outcome for long-term neurodevelopment. The validity of ANM as a surrogate outcome for long-term neurodevelopment has not been well studied.

AIM

Evaluate the association of ABR I-V interpeak latency (IPL), an index of ANM, at 35 week postmenstrual age (PMA) with language outcome at 3 years of age.

DESIGN

Prospective study.

SUBJECTS

24-33 week gestational age (GA) infants were eligible if they did not meet exclusion criteria: craniofacial malformation, chromosomal disorders, deafness, auditory dys-synchrony, TORCH infection, or non-English speaking parents. Infants with malignancy, head injury, encephalopathy, meningitis, blindness, or who died or relocated were also excluded.

OUTCOME MEASURES

ABRs were performed at 35 week PMA using 80 dB nHL and I-V IPL (ms) measured. Auditory Comprehension (AC) and Expressive Communication (EC) were evaluated by a speech-language pathologist at 3 years of age using Preschool Language Scale.

RESULTS

Eighty infants were studied. The mean GA and birth weight of infants were 29.2 weeks and 1336 g, respectively. There was association of worse ear I-V IPL and better ear I-V IPL with AC (Coefficient-5.4, 95% CI: -9.8 to -0.9 and Coefficient-5.5, 95% CI: -10 to-0.9, respectively) and EC (Coefficient-5.6, 95% CI: -9.5 to-1.8 and Coefficient-6.7, 95% CI: -10.6 to-2.7, respectively) after controlling for confounders.

CONCLUSION

The neonatal I-V IPL is a predictor of language development at 3 years of age in preterms.

Auditory neuropathy spectrum disorder: a review

PURPOSE

Auditory neuropathy spectrum disorder, or ANSD, can be a confusing diagnosis to physicians, clinicians, those diagnosed, and parents of children diagnosed with the condition. The purpose of this review is to provide the reader with an understanding of the disorder, the limitations in current tools to determine site(s) of lesion, and management techniques.

METHOD

This article is a review of what is known about ANSD. It includes descriptions of assessment tools, causes of ANSD, and patient management techniques.

CONCLUSIONS

This review is a guide to audiologists, speech-language pathologists, and early interventionists who work with individuals diagnosed with ANSD and/or their families. It highlights the need for more precise tools to describe the disorder in order to facilitate decisions about interventions and lead to better predictions of outcome.

Influence of hearing loss on children's identification of spondee words in a speech-shaped noise or a two-talker masker

OBJECTIVE

This study evaluated the influence of hearing loss on children's speech-perception abilities in a speech-shaped noise or a two-talker masker. For both masker conditions, it was predicted that children with hearing loss would require a more advantageous signal to noise ratio (SNR) than children with normal hearing to achieve the same criterion level of performance. However, it was hypothesized that the performance gap between children with hearing loss and children with normal hearing would be larger in the two-talker than in the speech-shaped noise masker.

DESIGN

A repeated-measures design compared the spondee identification performance of two age groups of children with hearing loss (9-11 and 13-17 years of age) and a group of children with normal hearing (9-11 years of age) in continuous speech-shaped noise or a two-talker masker. Estimates of the SNR required for 70.7% correct spondee identification were obtained using an adaptive, four-alternative, forced-choice procedure. Children were tested in the sound field. Children with hearing loss wore their personal hearing aids at their regular settings during testing.

RESULTS

Both groups of children with hearing loss performed more poorly than children with normal hearing in the speech-shaped noise masker. Younger children required an additional 2.7 dB SNR and older children required an additional 4.7 dB SNR to achieve the same level of performance as children with normal hearing. This disadvantage decreased to 8.1 dB for both age groups of children with hearing loss in the two-talker masker. For children with hearing loss, degree of hearing loss was significantly correlated with performance in the speech-shaped noise masker, but not in the two-talker masker.

CONCLUSIONS

A larger performance gap was observed between children with hearing loss and children with normal hearing in competing speech than in steady state noise. These results are consistent with the hypothesis that hearing loss influenced children's perceptual processing abilities.

Relationship between electrically evoked auditory brainstem response and auditory performance after cochlear implant in patients with auditory neuropathy spectrum disorder

OBJECTIVE

To analyze the pattern of electrically evoked auditory brainstem response (EABR) in auditory neuropathy spectrum disorder (ANSD) patients and to compare their performances with controls.

STUDY DESIGN

Retrospective analysis.

SETTING

Tertiary referral center.

PATIENTS

Eleven patients with ANSD and 9 control subjects with sensorineural hearing loss who did not have neural pathology.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

Patients and control subjects each received a cochlear implant (CI) and underwent EABR. EABR threshold, wave V latency, and amplitude were measured as EABR parameters. The results of EABR were categorized as good response, variable response, or no response. Speech perception ability was assessed by the categories of auditory performance (CAP) score.

RESULTS

All controls responded to EABR, whereas 6 of the 11 ANSD patients did not respond to EABR. The EABR threshold of the ANSD patients was measured almost within the value of disease controls. However, the Wave V latency displayed variable lengths, and the amplitude showed a wider distribution compared with the value of the disease control. The EABR response group among the ANSD patients showed relatively good performance after CI. In contrast, the nonresponse group demonstrated variable outcomes, although all of them still benefited from CI.

CONCLUSION

The data suggested that all ANSD patients require CI and that EABR results can help establish realistic expectations about future performance. Even if electrical stimulation fails to generate sufficiently synchronized signal for eliciting EABR, CI provides at least partial, measurable auditory benefit in ANSD.

Language Outcomes Using Hearing Aids in Children with Auditory Dys-Synchrony

There is a considerable debate on the use of hearing aid in children with auditory dys-synchrony (AD). To current date there are no similar Studies which show the effect of acoustic amplification on outcomes on speech and language development in children with AD are found in the literature. Thus, in the present study three children diagnosed to have AD were recruited and subjected to hearing aid trial and fitting based on the late latency response thresholds. Ranging from 7 months to 41 months of intervention period, each child's language age was reassessed and compared with that of their pre-therapy language age. The comparison showed a good improvement in receptive age, though the children had moderate to severe degree of hearing loss. But their expressive age was significantly delayed irrespective of their age of identification and duration of intervention. Thus the delay in expression with a good amount of improvement in reception can be a characteristic of an AD child with amplification.

Temporal processing and speech perception in noise by listeners with auditory neuropathy

Aim

The present study evaluated the relation between speech perception in the presence of background noise and temporal processing ability in listeners with Auditory Neuropathy (AN).

Method

The study included two experiments. In the first experiment, temporal resolution of listeners with normal hearing and those with AN was evaluated using measures of temporal modulation transfer function and frequency modulation detection at modulation rates of 2 and 10 Hz. In the second experiment, speech perception in quiet and noise was evaluated at three signal to noise ratios (SNR) (0, 5, and 10 dB).

Results

Results demonstrated that listeners with AN performed significantly poorer than normal hearing listeners in both amplitude modulation and frequency modulation detection, indicating significant impairment in extracting envelope as well as fine structure cues from the signal. Furthermore, there was significant correlation seen between measures of temporal resolution and speech perception in noise.

Conclusion

Results suggested that an impaired ability to efficiently process envelope and fine structure cues of the speech signal may be the cause of the extreme difficulties faced during speech perception in noise by listeners with AN.

Auditory processing deficits in children with Friedreich ataxia

Friedreich ataxia is a neurodegenerative disease with an average age of onset of 10 years. The authors sought to investigate the presence and functional consequences of auditory neuropathy in a group of affected children and to evaluate the ability of personal FM-listening systems to improve perception. Nineteen school-aged individuals with Friedreich ataxia and a cohort of matched control subjects underwent a battery of auditory function tests. Sound detection was relatively normal, but auditory temporal processing and speech understanding in noise were severely impaired, with children with Friedreich ataxia typically able to access less than 40% of the information available to controls. Use of FM-listening devices did, however, improve the speech perception performance of those with Friedreich ataxia to the level of their unaffected peers in conditions designed to replicate the listening environment of the average school classroom.

Assessing speech perception in children with language difficulties: effects of background noise and phonetic contrast

Deficits in speech perception are reported for some children with language impairments. This deficit is more marked when listening against background noise. This study investigated the speech perception skills of young children with and without language difficulties. A speech discrimination task, using non-word minimal pairs in an XAB paradigm, was presented to 20 5-7-year-old children with language difficulties and 33 typically-developing (TD) children aged between 4- to 7-years. Stimuli were presented in quiet and in background noise (babble), and stimuli varied in phonetic contrasts, differing in either place of articulation or presence/absence of voicing. Children with language difficulties performed less well than TD children in all conditions. There was an interaction between group and noise condition, such that children with language difficulties were more affected by the presence of noise. Both groups of children made more errors with one voicing contrast /s z/ and there was some indication that children with language difficulties had proportionately greater difficulty with this contrast. Speech discrimination scores were significantly correlated with language scores for children with language difficulties. Issues in developing material for assessment of speech discrimination in children with LI are discussed.

[Auditory synaptopathy/neuropathy: clinical findings and diagnosis]

Auditory synaptopathy/neuropathy (AS/AN) is a special subtype of sensorineural hearing disorders with heterogeneous phenotypes and underestimated incidence. AS/AN generally develops in infancy, occasionally in adulthood. Symptoms include fluctuating, mostly bilateral hearing loss and abnormally reduced speech comprehension, especially in noisy environments. Within audiological assessments, patients with AS/AN present otoacoustic emissions (TEOAE; DPOAE) and cochlear microphonics (CM), absence of stapedius reflexes (SR) as well as absent or pathologically altered auditory evoked brainstem potentials (ABR). Children with AS/AN cannot be identified within OAE-based newborn hearing screening programs. Clinical findings, transtympanic electrocochleography (ECoG) and further diagnostic tools permit further identification of individual characteristics. In individual cases conventional amplification and the use of FM systems may improve hearing and communication skills. If these interventions, accompanied by intensive hearing, speech and language therapy are unsuccessful, cochlear implants (CI) or alternative forms of communication may be useful options for rehabilitation.

Audiologic management of auditory neuropathy spectrum disorder in children: a systematic review of the literature

PURPOSE

This review summarizes current evidence related to the audiologic management of children with auditory neuropathy spectrum disorder (ANSD).

METHOD

A systematic search of the literature was conducted in 25 electronic databases (e.g., PubMed, CINAHL, and ERIC) using key words such as auditory neuropathy, auditory neuropathy spectrum disorder, auditory neuropathy/dyssynchrony, and hearing loss. Eighteen studies met the inclusion criteria by addressing 1 or more of 8 clinical questions. Studies were evaluated for methodological quality, and data regarding participant, intervention, and outcome variables are reported.

RESULTS

Fifteen of the 18 studies addressed the use of cochlear implantation, and 4 addressed conventional acoustic amplification. All participants demonstrated improved auditory performance; however, all 18 studies were considered exploratory, and many had methodological limitations.

CONCLUSION

The clinical evidence related to intervention for ANSD is at a very preliminary stage. Additional research is needed to address the efficacy of acoustic amplification and cochlear implantation in children with ANSD and the impact of this disorder on developmental outcomes.

Cortical maturation and behavioral outcomes in children with auditory neuropathy spectrum disorder

OBJECTIVE. Auditory neuropathy spectrum disorder (ANSD) affects approximately 10% of patients with sensorineural hearing loss. While many studies report abnormalities at the level of the cochlea, auditory nerve, and brainstem in children with ANSD, much less is known about their cortical development. We examined central auditory maturation in 21 children with ANSD. DESIGN. Morphology, latency and amplitude of the P1 cortical auditory evoked potential (CAEP) were used to assess auditory cortical maturation. Children's scores on a measure of auditory skill development (IT-MAIS) were correlated with CAEPs. Study Sample. Participants were 21 children with ANSD. All were hearing aid users.

RESULT

Children with ANSD exhibited differences in central auditory maturation. Overall, two-thirds of children revealed present P1 CAEP responses. Of these, just over one third (38%) showed normal P1 response morphology, latency and amplitude, while another third (33%) showed delayed P1 response latencies and significantly smaller amplitudes. The remaining children (29%) revealed abnormal or absent P1 responses. Overall, P1 responses were significantly correlated with auditory skill development.

CONCLUSION

Our results suggest that P1 CAEP responses may be: (i) A useful indicator of the extent to which neural dys-synchrony disrupts cortical development, (ii) A good predictor of behavioral outcome in children with ANSD.

Risk factors for auditory neuropathy spectrum disorder in NICU infants compared to normal-hearing NICU controls

OBJECTIVES

To evaluate independent etiologic factors associated with auditory neuropathy spectrum disorder (ANSD) in infants who have been admitted to the neonatal intensive care unit (NICU) compared to normal-hearing controls.

STUDY DESIGN

Case-control study.

METHODS

We included all infants (n = 9) with the ANSD profile admitted to the NICU of Sophia Children's Hospital between 2004 and 2009. Each patient was matched with four normal-hearing controls of the same gender and postconceptional age. The following possible risk factors were studied: birth weight, dysmorphic features, APGAR scores (at 1, 5, and 10 minutes), respiratory distress (IRDS), cytomegalovirus (CMV) infection, sepsis, meningitis, cerebral bleeding, hyperbilirubinemia requiring phototherapy, peak total bilirubin level, furosemide, dexamethason, vancomycin, gentamycin, and tobramycin administration.

RESULTS

Nine infants met the ANSD criteria in one or both ears. IRDS (P = .02), meningitis (P = .04), and vancomycin administration (P = .009) were significantly increased in infants with ANSD compared to controls.

CONCLUSIONS

In high-risk NICU infants IRDS, meningitis and vancomycin administration are associated with auditory neuropathy spectrum disorder.

Rate of neural recovery in implanted children with auditory neuropathy spectrum disorder

OBJECTIVES

The study objectives were to compare the rate of neural recovery and speech perception performance in children with auditory neuropathy spectrum disorder (ANSD) and children with sensorineural hearing loss (SNHL) from other etiologies.

STUDY DESIGN

Cohort study.

SETTING

Academic hospital and cochlear implant center.

SUBJECTS AND METHODS

Ten children with ANSD were matched based on type of implant and age at implantation with peers diagnosed with SNHL. Electrically evoked compound action potential (ECAP) recovery functions were obtained to measure neural refractory behaviors in response to stimulation from the cochlear implant. Speech perception performance was measured using speech recognition thresholds (SRTs) for monosyllable and spondee word stimuli. These outcome measures were compared between groups.

RESULTS

There was no difference in average recovery function exponent in children with ANSD compared to children with SNHL. Similarly, there were no differences in average SRTs in quiet and in noise in children with ANSD compared to children with SNHL. Relationships between SRT and recovery rate were not present within groups or for all subjects for SRT in quiet, but a significant relationship was found for all subjects for SRT in noise (P = .04).

CONCLUSIONS

Dyssynchronous neural activity in ANSD may affect temporal encoding of electrical stimulation from a cochlear implant. As a group, children with ANSD did not demonstrate slower neural recovery compared to those with SNHL, but there was slower neural recovery observed for some subjects. The utility of ECAP recovery functions on optimizing the stimulation rate for individual patients with ANSD requires further investigation.

Risk factors for sensorineural hearing loss in NICU infants compared to normal hearing NICU controls

OBJECTIVES

To evaluate independent etiologic factors associated with sensorineural hearing loss in infants who have been admitted to the neonatal intensive care unit compared to normal hearing controls.

METHOD

Between 2004 and 2009, 3366 infants were admitted to the neonatal intensive care unit of Sophia Children's Hospital, of which 3316 were screened with AABR. A total of 103 infants were referred for auditory brainstem response analysis after failure on neonatal hearing screening. We included all infants diagnosed with sensorineural hearing loss. Each patient was matched with two normal hearing controls from the neonatal intensive care unit of the same gender and postconceptional age. The following risk factors were studied: birth weight, dysmorphic features, APGAR scores (at 1, 5 and 10 min), respiratory distress (IRDS), CMV infection, sepsis, meningitis, cerebral bleeding, cerebral infarction, hyperbilirubinemia requiring phototherapy, peak total bilirubin level, furosemide, dexamethason, vancomycin, gentamycin and tobramycin administration.

RESULTS

Fifty-eight infants were diagnosed with sensorineural hearing loss: 26 girls and 32 boys. The incidence of dysmorphic features (P=0.000), low APGAR score (1 min) (P=0.01), sepsis (P=0.003), meningitis (P=0.013), cerebral bleeding (P=0.016) and cerebral infarction (P=0.000) were significantly increased in infants with sensorineural hearing loss compared to normal hearing controls (n=116).

CONCLUSION

Dysmorphic features, low APGAR scores at 1 min, sepsis, meningitis, cerebral bleeding and cerebral infarction are associated with sensorineural hearing loss independent of neonatal intensive care unit admittance.

Chronic bilirubin encephalopathy: diagnosis and outcome

Chronic bilirubin encephalopathy (kernicterus) can be diagnosed using semi-objective criteria based on history, physical and neurological examination and laboratory findings including auditory brainstem responses and magnetic resonance imaging. Classical kernicterus is a well-described clinical tetrad of (i) abnormal motor control, movements and muscle tone, (ii) an auditory processing disturbance with or without hearing loss, (iii) oculomotor impairments, especially impairment of upward vertical gaze, and (iv) dysplasia of the enamel of deciduous teeth. Subtle kernicterus or bilirubin-induced neurologic dysfunction (BIND) refers to individuals with subtle neurodevelopmental disabilities without classical findings of kernicterus that, after careful evaluation and consideration, appear to be due to bilirubin neurotoxicity. Kernicterus can be further classified as auditory predominant or motor predominant and characterized based on the severity of clinical sequelae. Proposed research definitions for kernicterus diagnosis in infants from 3 to 18 months are reviewed, as are treatments of auditory and motor deficits and other complications of bilirubin encephalopathy.

Bilateral paediatric cochlear implants: a critical review

A recent trend has been the implantation of bilateral cochlear implants (CIs) for children with severe to profound hearing loss. A review of available research on bilateral CIs was conducted to determine the support for this trend. A replicable review was undertaken to evaluate published research studies that examined the effectiveness of bilateral paediatric cochlear implantation. Databases, reference lists, and journals were searched for relevant documents using a pre-determined search protocol. Twenty-nine articles met the review's inclusion criteria and were retrieved and reviewed. This review adds to the previously published reviews on the topic by identifying additional paediatric studies. Sound localization and speech recognition in noise appear to be improved with bilateral compared to unilateral cochlear implants. Similarly, evoked potential measures suggest improved morphology when the second CI is implanted early. Well-designed and controlled studies that explore a variety of outcomes including cost-effectiveness, quality of life, speech, language, and psycho-educational measures should be further explored in order to provide additional support for parents and clinicians confronted with the bilateral cochlear implant decision.

N100 cortical potentials accompanying disrupted auditory nerve activity in auditory neuropathy (AN): effects of signal intensity and continuous noise

OBJECTIVE

Auditory temporal processes in quiet are impaired in auditory neuropathy (AN) similar to normal hearing subjects tested in noise. N100 latencies were measured from AN subjects at several tone intensities in quiet and noise for comparison with a group of normal hearing individuals.

METHODS

Subjects were tested with brief 100 ms tones (1.0 kHz, 100-40 dB SPL) in quiet and in continuous noise (90 dB SPL). N100 latency and amplitude were analyzed as a function of signal intensity and audibility.

RESULTS

N100 latency in AN in quiet was delayed and amplitude was reduced compared to the normal group; the extent of latency delay was related to psychoacoustic measures of gap detection threshold and speech recognition scores, but not to audibility. Noise in normal hearing subjects was accompanied by N100 latency delays and amplitude reductions paralleling those found in AN tested in quiet. Additional N100 latency delays and amplitude reductions occurred in AN with noise.

CONCLUSIONS

N100 latency to tones and performance on auditory temporal tasks were related in AN subjects. Noise masking in normal hearing subjects affected N100 latency to resemble AN in quiet.

SIGNIFICANCE

N100 latency to tones may serve as an objective measure of the efficiency of auditory temporal processes.

Perception of envelope-enhanced speech in the presence of noise by individuals with auditory neuropathy

OBJECTIVE

To investigate the effect of background noise on perception of unprocessed and envelope-enhanced speech in individuals with auditory neuropathy (AN).

DESIGN

Open-set speech identification abilities were assessed for unprocessed and envelope-enhanced speech in quiet and at three signal to noise ratios (10, 5, and 0 dB signal to noise ratio) in 15 individuals with AN.

RESULTS

Results revealed that speech identification ability was affected more in the presence of noise than in quiet. The participants were classified into two groups, Good Performers and Poor Performers, based on their speech identification scores in quiet. It was observed that the reduction in mean speech identification scores in noise was less for Good Performers when compared with that of Poor Performers. Envelope enhancement of the signal improved speech identification scores in both the groups. The analysis of results also showed that Good Performers showed a significant improvement in all the conditions, whereas Poor Performers showed improvement only in quiet and +10 dB signal to noise ratio.

CONCLUSIONS

For individuals with AN, listening in background noise is more difficult than in quiet condition. Envelope enhancement of speech signal improves speech identification scores in quiet and in background noise for individuals with AN. However, the benefit obtained varies depending on the speech identification ability in quiet.

Auditory neuropathy: endocochlear lesion or temporal processing impairment? Implications for diagnosis and management

BACKGROUND/OBJECTIVE

Auditory neuropathy/dys-synchrony, characterized by absent auditory brainstem responses, normal otoacoustic emissions or cochlear microphonics, and word discrimination disproportional to the pure-tone audiogram, may be accompanied by perceptual consequences that could jeopardize language acquisition in affected children. However, the related evidence is constantly changing leading to a serious debate. The aim of the present paper is to review the current knowledge on auditory neuropathy/dys-synchrony, and to present the therapeutic strategies that can be employed in its management, taking into account the potentially underlying pathophysiology.

MATERIALS/METHODS

Literature review from Medline and database sources. Related books were also included.

STUDY SELECTION

Controlled clinical trials, prospective and retrospective cohort studies, nested-based case-control and analytical family studies, laboratory and electrophysiological studies, animal models, case-reports, joint statements and review articles.

DATA SYNTHESIS

Auditory neuropathy/dys-synchrony, in contrast to what is widely believed, is a very frequent disease, responsible for approximately 8% of newly diagnosed cases of hearing loss in children per year. Hyperbilirubinemia and hypoxia represent major risk factors, whereas generalized neuropathic disorders, or a genetic substrate involving the otoferlin gene, are responsible for the phenotype of auditory neuropathy/dys-synchrony in certain cases. Auditory nerve myelinopathy and/or desynchrony of neural discharges are the most probable underlying pathophysiologic mechanisms. Genetic testing may be helpful in cases of non-syndromic prelingual children. Auditory neuropathy/dys-synchrony management aims at restoring the compromised processing of auditory information, either through conventional amplification and/or alternative forms of communication, or by cochlear implantation (combined with intensive speech and language therapy).

CONCLUSION

Auditory neuropathy/dys-synchrony is more frequent than considered in the past, especially amongst hearing-impaired children. Accurate diagnosis, based on subjective and objective hearing assessment techniques (including the various electrophysiological assessment measures), and timely treatment of the affected children is of paramount importance, with hearing aids, intensive speech and language therapy (and sign language when indicated) providing the mainstay of habilitation, and cochlear implantation representing a valid therapeutic alternative.

Speech perception ability in individuals with Friedreich ataxia

The aim of this study was to investigate auditory pathway function and speech perception ability in individuals with Friedreich ataxia (FRDA). Ten subjects confirmed by genetic testing as being homozygous for a GAA expansion in intron 1 of the FXN gene were included. While each of the subjects demonstrated normal, or near normal sound detection, 3 of the 10 showed electrophysiological evidence of auditory pathway disorder [presenting with the auditory neuropathy/dyssynchrony (AN/AD) result pattern], and 9 of the 10 showed abnormal speech understanding when tested with levels of background noise typical of everyday listening conditions. Information transmission analyses of the speech perception findings for the three FRDA subjects with AN/AD type hearing loss when compared with those of a cohort of individuals with peripheral [sensorineural (SN)] hearing loss, showed a distinct pattern of perceptual disruption. Where the listeners with SN loss confused sounds on the basis of frequency (pitch) differences, the FRDA subjects with AN/AD made errors that reflected an inability to perceive temporal (timing) cues in the speech sounds.