Speech and language outcomes in children with auditory neuropathy/dys-synchrony managed with either cochlear implants or hearing aids

An Umbrella Review of Cochlear Implant Outcomes in Children With Auditory Neuropathy

PURPOSE

The objective of this overview of systematic reviews (SRs; umbrella review) was to systematically summarize and critically appraise current evidence of cochlear implant (CI) outcomes in children with auditory neuropathy spectrum disorder (ANSD).

METHOD

This study was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement. The methodological quality and the risk of bias in the included SRs were assessed using A MeaSurement Tool to Assess systematic Reviews 2 checklist and the Risk of Bias in Systematic Reviews tool, respectively.

RESULTS

According to eight included SRs, children with ANSD achieve CI outcomes (speech perception performance) similar to their peers with sensorineural hearing loss. In children with postsynaptic ANSD (cochlear nerve deficiency), cochlear nerve hypoplasia is associated with better speech recognition outcomes compared with cochlear nerve aplasia, especially in the absence of additional disabilities. Except for one study, the overall quality of the included SRs was critically low, and except for three studies, evidence of a high risk of bias was identified in other included SRs.

CONCLUSIONS

Current evidence supports CI benefits for children with ANSD. To improve the quality of evidence, well-designed, prospective studies with appropriate sample sizes, using valid outcome measures, clarifying matching criteria, and taking into account the role of confounding factors are essential.

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.

Improvement in quality of life comparing noninvasive versus invasive hearing rehabilitation in children

Objectives

The young population requires early rehabilitation of their hearing loss for normal cognitive, auditive hence social development. All of which, in turn, may have an impact on quality of life (QoL). This study aims to evaluate QoL between two different bone conduction (BC) hearing devices: a noninvasive adhesive hearing aid (Adhear [ADH]) vs. an active transcutaneous implant (Bonebridge [BB]).

Methods

This study composed of 12 BB and 15 ADH users. Pure tone as well as speech in noise and quiet measurements were evaluated and compared to the Assessment in QoL questionnaire (AQoL-6d).

Results

Freefield results showed significant improvements for both devices compared to the unaided condition (p < .0001). Emphasis needs to be drawn on the different unaided level of conductive hearing loss as well as the indication range for both evaluated device groups: the ADH subjects exhibited a mean BC value of 9.50 ± 7.96 dB HL (the indication range up to 25 dB) and the BB subjects a mean of 23.33 ± 25.66 dB HL (the indication range up to 45 dB). Speech perception in quiet and in noise was significantly improved (p < .05; p < .001, respectively). QoL was significantly improved for both treatments (p < .05) but was not different among the devices, and the values were similar to their normal hearing, age, and sex-matched control group. High correlations were found between QoL utility scores and improved PTA4 in the aided condition (r ² = .8839 and .7810 for BB and ADH, respectively).

Conclusion

Our results show that both devices offer significant beneficial audiological rehabilitations with significantly increased QoL. However, the underlying condition and the unaided degree of hearing loss, hence the required higher stimulation must be the deciding factor when opting for a hearing device, and this should be independent of age.

Level of evidence

2c.

Mitochondrial Disease and Hearing Loss in Children: A Systematic Review

OBJECTIVES

Hearing loss is a clinical symptom, frequently mentioned in the context of mitochondrial disease. With no cure available for mitochondrial disease, supportive treatment of clinical symptoms like hearing loss is of the utmost importance. The aim of this study was to summarize current knowledge on hearing loss in genetically proven mitochondrial disease in children and deduce possible and necessary consequences in patient care.

METHODS

Systematic literature review, including Medline, Embase, and Cochrane library. Review protocol was established and registered prior to conduction (International prospective register of systematic reviews-PROSPERO: CRD42020165356). Conduction of this review was done in accordance with MOOSE criteria.

RESULTS

A total of 23 articles, meeting predefined criteria and providing sufficient information on 75 individuals with childhood onset hearing loss was included for analysis. Both cochlear and retro-cochlear origin of hearing loss can be identified among different types of mitochondrial disease. Analysis was hindered by inhomogeneous reporting and methodical limitations.

CONCLUSION

Overall, the findings do not allow for a general statement on hearing loss in children with mitochondrial disease. Retro-cochlear hearing loss seems to be found more often than expected. A common feature appears to be progression of hearing loss over time. However, hearing loss in these patients shows manifold characteristics. Therefore, awareness of mitochondrial disease as a possible causative background is important for otolaryngologists. Future attempts rely on standardized reporting and long-term follow-up.

LEVEL OF EVIDENCE

NA Laryngoscope, 132:2459-2472, 2022.

Case report: Clinical and genetic analysis of a family with nonsyndromic auditory neuropathy

BACKGROUND

Auditory neuropathy (AN) is a hearing disorder caused by the failure of inner hair cells, auditory nerve synapses and/or auditory nerves. With the development of high-throughput sequencing technology, the genetic factors of AN have been revealed, and genetic testing has become an important tool for identifying different types of AN.

CASE DESCRIPTION

To study the genetic cause of nonsyndromic auditory neuropathy in a Chinese family. The family was from Henan Province with three affected individuals. The audiological examinations were performed on the affected individuals, and whole-exome sequencing was carried out on the proband. The suspected pathogenic variants screened by the bioinformatic analysis were validated using Sanger sequencing in the family members. We identified three novel variants c.3277G > A (p.Glu1093Lys), c.4024-4G > T, and c.898-2A > G of the OTOF gene in the three children with AN. The first two variants were inherited from their father, and the third variant was inherited from their mother. A minigene assay was designed to test the effect of c.4024-4G > T on splicing. The variants c.3277G > A, c.4024-4G > T, and c.898-2A > G could be classified as likely pathogenic/pathogenic following the ACMG guidelines, and they are considered as the genetic causes for the patients in the family.

CONCLUSION

New pathogenic/likely pathogenic variants of the OTOF gene were identified in a family with AN, enriching the mutational spectrum of the OTOF gene.

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%.

Perception of temporally enhanced and hearing aid processed speech in children with late-onset Auditory Neuropathy Spectrum Disorder

OBJECTIVE

To investigate phrase perception and subjective quality preference of temporal enhancement-based speech processing strategies: Deep-band modulation and Stretching, and hearing aid processed speech in adolescents with late-onset Auditory Neuropathy.

METHODS

15 participants with Auditory Neuropathy Spectrum Disorder were involved. Speech perception was assessed using unprocessed, deep-band modulated, stretched, and hearing aid processed conditions. Subjective preference was also assessed using the pair-wise comparison technique. Gap detection test was done using broadband noise to investigate the possible correlation with benefit from processing strategies.

RESULTS

As a group, no significant benefits were found with processed speech. Clinically relevant trends emerged on subdividing the group into good and poor performers. Deep-band modulation processing was significantly better than unprocessed speech in those with poorer speech recognition abilities. There was a trend for those with poorer temporal processing abilities to benefit more with deep-band modulation processing. In those with relatively better speech recognition abilities, processing showed no benefit, and hearing aid processed speech was inferior to unprocessed speech. Quality-wise, the unprocessed speech was preferred by all the participants. Among the processed conditions, deep-band modulation was preferred by most, followed by stretching and hearing aid processed speech.

CONCLUSION

Results indicate that temporal enhancement strategies may be beneficial for a subset of individuals with ANSD with poorer temporal processing and speech perception abilities. However, processing strategies need to take into account the quality aspect and not just intelligibility.

OTOF mutation analysis with massively parallel DNA sequencing in 2,265 Japanese sensorineural hearing loss patients

The OTOF gene (Locus: DFNB9), encoding otoferlin, is reported to be one of the major causes of non-syndromic recessive sensorineural hearing loss, and is also reported to be the most common cause of non-syndromic recessive auditory neuropathy spectrum disorder (ANSD). In the present study, we performed OTOF mutation analysis using massively parallel DNA sequencing (MPS). The purpose of this study was to reveal the frequency and precise genetic and clinical background of OTOF-related hearing loss in a large hearing loss population. A total of 2,265 Japanese sensorineural hearing loss (SNHL) patients compatible with autosomal recessive inheritance (including sporadic cases) from 53 otorhinolaryngology departments nationwide participated in this study. The mutation analysis of 68 genes, including the OTOF gene, reported to cause non-syndromic hearing loss was performed using MPS. Thirty-nine out of the 2,265 patients (1.72%) carried homozygous or compound heterozygous mutations in the OTOF gene. It is assumed that the frequency of hearing loss associated with OTOF mutations is about 1.72% of autosomal recessive or sporadic SNHL cases. Hearing level information was available for 32 of 39 patients with biallelic OTOF mutations; 24 of them (75.0%) showed profound hearing loss, 7 (21.9%) showed severe hearing loss and 1 (3.1%) showed mild hearing loss. The hearing level of patients with biallelic OTOF mutations in this study was mostly severe to profound, which is consistent with the results of past reports. Eleven of the 39 patients with biallelic OTOF mutations had been diagnosed with ANSD. The genetic diagnosis of OTOF mutations has significant benefits in terms of clinical decision-making. Patients with OTOF mutations would be good candidates for cochlear implantation; therefore, the detection of OTOF mutations is quite beneficial for patients, especially for those with ANSD.

International consensus (ICON) on audiological assessment of hearing loss in children

The prevalence of hearing loss in newborns and infants is estimated between 1 to 3.47 cases per 1000 live births. Early diagnosis and rehabilitation of congenital hearing loss are mandatory in order to achieve a satisfactory linguistic and cognitive development. Without appropriate opportunities to learn language, these children will fall behind their normal hearing peers in communication, cognition, reading and socio-emotional development. After promising results, neonatal screening for hearing loss and audiological evaluation are becoming more extensively carried out. In planning universal neonatal hearing screening programs, transient evoked otoacoustic emissions and auditory brainstem responses are the gold standard for the screening and diagnosis program. However, there is no consensus regarding the use of audiometry and other electrophysiological tests (such as auditory steady-state responses) in current practices. Several screening and audiological assessment procedures have been described and advocated all around the world. But, a systematic scheme of performing diagnosis in the pediatric audiology population is lacking. A consensus conference was held at the International Federation of Oto-rhino-laryngological Societies Congress, in June 2017, to discuss the different current practices and to identify the best neonatal hearing screening and audiological assessment management. This article is intended to provide professionals with recommendations about the "best practice" based on consensus opinion of the session's speakers, and a review of the literature on the efficacy of various assessment options for children with hearing loss.

Temporal Response Properties of the Auditory Nerve in Implanted Children with Auditory Neuropathy Spectrum Disorder and Implanted Children with Sensorineural Hearing Loss

OBJECTIVE

This study aimed to (1) characterize temporal response properties of the auditory nerve in implanted children with auditory neuropathy spectrum disorder (ANSD), and (2) compare results recorded in implanted children with ANSD with those measured in implanted children with sensorineural hearing loss (SNHL).

DESIGN

Participants included 28 children with ANSD and 29 children with SNHL. All subjects used cochlear nucleus devices in their test ears. Both ears were tested in 6 children with ANSD and 3 children with SNHL. For all other subjects, only one ear was tested. The electrically evoked compound action potential (ECAP) was measured in response to each of the 33 pulses in a pulse train (excluding the second pulse) for one apical, one middle-array, and one basal electrode. The pulse train was presented in a monopolar-coupled stimulation mode at 4 pulse rates: 500, 900, 1800, and 2400 pulses per second. Response metrics included the averaged amplitude, latencies of response components and response width, the alternating depth and the amount of neural adaptation. These dependent variables were quantified based on the last six ECAPs or the six ECAPs occurring within a time window centered around 11 to 12 msec. A generalized linear mixed model was used to compare these dependent variables between the 2 subject groups. The slope of the linear fit of the normalized ECAP amplitudes (re. amplitude of the first ECAP response) over the duration of the pulse train was used to quantify the amount of ECAP increment over time for a subgroup of 9 subjects.

RESULTS

Pulse train-evoked ECAPs were measured in all but 8 subjects (5 with ANSD and 3 with SNHL). ECAPs measured in children with ANSD had smaller amplitude, longer averaged P2 latency and greater response width than children with SNHL. However, differences in these two groups were only observed for some electrodes. No differences in averaged N1 latency or in the alternating depth were observed between children with ANSD and children with SNHL. Neural adaptation measured in these 2 subject groups was comparable for relatively short durations of stimulation (i.e., 11 to 12 msec). Children with ANSD showed greater neural adaptation than children with SNHL for a longer duration of stimulation. Amplitudes of ECAP responses rapidly declined within the first few milliseconds of stimulation, followed by a gradual decline up to 64 msec after stimulus onset in the majority of subjects. This decline exhibited an alternating pattern at some pulse rates. Further increases in pulse rate diminished this alternating pattern. In contrast, ECAPs recorded from at least one stimulating electrode in six ears with ANSD and three ears with SNHL showed a clear increase in amplitude over the time course of stimulation. The slope of linear regression functions measured in these subjects was significantly greater than zero.

CONCLUSIONS

Some but not all aspects of temporal response properties of the auditory nerve measured in this study differ between implanted children with ANSD and implanted children with SNHL. These differences are observed for some but not all electrodes. A new neural response pattern is identified. Further studies investigating its underlying mechanism and clinical relevance are warranted.

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.

Clinical role of electrocochleography in children with auditory neuropathy spectrum disorder

OBJECTIVES

To assess electrocochleography (ECochG) to tones as an instrument to account for CI speech perception outcomes in children with auditory neuropathy spectrum disorder (ANSD).

MATERIALS & METHODS

Children (<18 years) receiving CIs for ANSD (n = 30) and non-ANSD (n = 74) etiologies of hearing loss were evaluated with ECochG using tone bursts (0.25-4 kHz). The total response (TR) is the sum of spectral peaks of responses across frequencies. The compound action potential (CAP) and the auditory nerve neurophonic (ANN) in ECochG waveforms were used to estimate nerve activity and calculate nerve score. Performance on open-set monosyllabic word tests was the outcome measure. Standard statistical methods were applied.

RESULTS

On average, TR was larger in ANSD than in non-ANSD subjects. Most ANSD (73.3%) and non-ANSD (87.8%) subjects achieved open-set speech perception; TR accounted for 33% and 20% of variability in the outcomes, respectively. In the ANSD group, the PTA accounted for 69.3% of the variability, but there was no relationship with outcomes in the non-ANSD group. In both populations, nerve score was sensitive in identifying subjects at risk for not acquiring open-set speech perception, while the CAP and the ANN were more specific.

CONCLUSION

In both subject groups, the TRs correlated with outcomes but these measures were notably larger in the ANSD group. There was also strong correlation between PTA and speech perception outcome in ANSD group. In both subject populations, weaker evidence of neural activity was related to failure to achieve open-set speech perception.

Current trends in outcome studies for children with hearing loss and the need to establish a comprehensive framework of measuring outcomes in children with hearing loss in China

Since the 1970s, outcome studies for children with hearing loss expanded from focusing on assessing auditory awareness and speech perception skills to evaluating language and speech development. Since the early 2000s, the multi-center large scale research systematically studied outcomes in the areas of auditory awareness, speech-perception, language development, speech development, educational achievements, cognitive development, and psychosocial development. These studies advocated the establishment of baseline and regular follow-up evaluations with a comprehensive framework centered on language development. Recent research interests also include understanding the vast differences in outcomes for children with hearing loss, understanding the relationships between neurocognitive development and language acquisition in children with hearing loss, and using outcome studies to guide evidence-based clinical practice. After the establishment of standardized Mandarin language assessments, outcomes research in Mainland China has the potential to expand beyond auditory awareness and speech perception studies.

Auditory neuropathy--neural and synaptic mechanisms

Sensorineural hearing impairment is the most common form of hearing loss, and encompasses pathologies of the cochlea and the auditory nerve. Hearing impairment caused by abnormal neural encoding of sound stimuli despite preservation of sensory transduction and amplification by outer hair cells is known as 'auditory neuropathy'. This term was originally coined for a specific type of hearing impairment affecting speech comprehension beyond changes in audibility: patients with this condition report that they "can hear but cannot understand". This type of hearing impairment can be caused by damage to the sensory inner hair cells (IHCs), IHC ribbon synapses or spiral ganglion neurons. Human genetic and physiological studies, as well as research on animal models, have recently shown that disrupted IHC ribbon synapse function--resulting from genetic alterations that affect presynaptic glutamate loading of synaptic vesicles, Ca(2+) influx, or synaptic vesicle exocytosis--leads to hearing impairment termed 'auditory synaptopathy'. Moreover, animal studies have demonstrated that sound overexposure causes excitotoxic loss of IHC ribbon synapses. This mechanism probably contributes to hearing disorders caused by noise exposure or age-related hearing loss. This Review provides an update on recently elucidated sensory, synaptic and neural mechanisms of hearing impairment, their corresponding clinical findings, and discusses current rehabilitation strategies as well as future therapies.

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.

Auditory neuropathy spectrum disorder (ANSD) and cochlear implantation

We discuss issues related to cochlear implantation in children with auditory neuropathy spectrum disorder (ANSD). We describe the varied nature of this disease category including the numerous potential causes of auditory neuropathy. The most prevalent etiology for infants with ANSD is associated with prolonged neonatal intensive care unit (NICU) stay. We discuss the potential contribution of cochlear hypoxia to this etiology. The second part of this review describes in detail our own experience at the Hospital for Sick Children in Toronto, with cochlear implantation of children diagnosed with ANSD. We outline the detection, diagnosis, and referral routes for our patients. We provide an overview of our "standard operation procedures" regarding candidacy, and discuss some of the special considerations that need to be applied to children with ANSD. This includes decisions to implant children with better audiometric thresholds that are standard in non-ANSD patients, concerns about the possibility of spontaneous remission and the appropriate timing of implantation. Finally we review an extensive published literature in outcomes after cochlear implantation (CI) in ANSD. This is not a systematic review but rather an exercise to distill out some important reoccurring themes and the general consensus of opinion to date. Our conclusion is that the hearing loss category ANSD, together with its numerous co-morbidities, is far too heterogeneous to make definitive statements about prognosis with CI.

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.

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>.

Parents' perspectives on the dilemmas with intervention for infants with auditory neuropathy spectrum disorder: A qualitative study

OBJECTIVE

This paper explores parental experiences of choices surrounding auditory management and language and communication development for infants and children with auditory neuropathy spectrum disorder (ANSD) in the light of the heterogeneity of condition, a poor evidence base for best outcomes in relation to management options, and the scarcity of data rooted in parent and family experience.

DESIGN

Qualitative narrative study.

STUDY SAMPLE

Twenty-five parents of 21 children (aged four months to six years) identified with ANSD through the newborn hearing screening programme.

RESULTS

Families identify barriers to early management due to conflicting expert opinions and ANSD-specific challenges with diagnosis and prognosis in infants, and share their accounts on their own evaluations of intervention benefit in their children.

CONCLUSIONS

The results are of relevance to the clinicians and other professionals involved in early intervention, management, and support of infants with ANSD.

Objective measures of electrode discrimination with electrically evoked auditory change complex and speech-perception abilities in children with auditory neuropathy spectrum disorder

OBJECTIVES

This study aimed to (1) determine the sensitivity of the electrically evoked auditory change complex (eACC) to changes in stimulating electrode position; and (2) investigate the association between results of eACC measures and behavioral electrode discrimination and their association with speech-perception performance in pediatric cochlear implant (CI) users who have auditory neuropathy spectrum disorder (ANSD).

DESIGN

Fifteen children with ANSD ranging in age between 5.4 and 18.6 years participated in this study. All subjects used Cochlear Nucleus devices. For each subject, open-set speech-perception ability was assessed using the Phonetically Balanced Kindergarten word lists presented at 60 dB SPL, using monitored live voice in a sound booth. Behavioral and objective measures of electrode discrimination were assessed in a nonclinical test environment. The stimuli used to elicit these measures were 800 msec biphasic pulse trains delivered by a direct interface to the CI. Data were collected from two basic stimulation conditions. In the standard condition, the entire pulse train was delivered to a mid-array electrode (electrode 11 or 12) at the maximum comfortable level (C level). In the change condition, the stimulus was split into two 400 msec pulse train segments presented sequentially on two different electrodes. The stimulation level of the second 400 msec pulse train was loudness balanced to the C level of the mid-array electrode used in the standard condition. The separation between the pair of stimulating electrodes was systematically varied. For behavioral electrode-discrimination measures, each subject was required to determine whether he or she heard one or two sounds for stimuli presented in different stimulation conditions. For the eACC measures, two replicates of 100 artifact-free sweeps were recorded for each stimulation condition.

RESULTS

The eACC in response to changes in stimulating electrode position was recorded from all subjects with ANSD using direct electrical stimulation. Electrode-discrimination thresholds determined with the eACC and behavioral measures were consistent. Children with ANSD using CIs who showed poorer speech performance also required larger separations between the stimulating electrode pair to reliably elicit the eACC than subjects with better speech-perception performance. There was a robust correlation between electrode-discrimination capacities and speech-perception performances in subjects tested in this study. The effect of electrode separation on eACC amplitudes was not monotonic.

CONCLUSIONS

These results demonstrate the feasibility of using eACC to evaluate electrode-discrimination capacities in children with ANSD. These results suggest that the eACC elicited by changes in stimulating electrode position holds great promise as an objective tool for evaluating spectral-pattern detection in such subjects, which may be predictive of their potential speech-perception performance.

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.

Principles and guidelines for early intervention after confirmation that a child is deaf or hard of hearing

This document is a supplement to the year 2007 position statement of the Joint Committee on Infant Hearing and provides comprehensive guidelines for establishing strong early intervention (EI) systems with appropriate expertise to meet the needs of children who are deaf or hard of hearing (D/HH). Optimal outcomes can only be achieved when there is high quality to the universal newborn hearing screening programs, the audiologic diagnostic process of confirmation that a child is D/HH and fitting of amplification, and the provision of appropriate, individualized, targeted, and high-quality EI services. There are 12 best practice guidelines for EI programs that include the provision of timely referral to EI services with providers who have knowledge and skills in early childhood deafness and hearing loss, infusion within the system of partnerships with parents as well as professionals who are D/HH, longitudinal developmental assessments for monitoring the child's development, data management systems that include developmental outcomes, a process to monitor the fidelity of the intervention, and appropriate services for children with additional disabilities, those from non-English speaking families, and those from special populations, including unilateral hearing loss and auditory neuropathy/dyssynchrony.

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.

Impact of the presence of auditory neuropathy spectrum disorder (ANSD) on outcomes of children at three years of age

OBJECTIVE

To determine the influence of the presence of auditory neuropathy spectrum disorder (ANSD) on speech, language, and psycho-social development of children at three years of age.

DESIGN

A population-based, longitudinal study was performed on outcomes of children with hearing impairment (LOCHI) in Australia. The demographic characteristics of the children were described, and their developmental outcomes were evaluated at three years of age. Performance of children with ANSD was compared with that of children without ANSD in the LOCHI study.

STUDY SAMPLE

There were 47 children with ANSD in the study sample.

RESULTS

Sixty-four percent of children with ANSD have hearing sensitivity loss ranging from mild to severe degree, and the remaining have profound hearing loss. At three years, 27 children used hearing aids, 19 used cochlear implants, and one child did not use any hearing device. Thirty percent of children have disabilities in addition to hearing loss. On average, there were no significant differences in performance level between children with and without ANSD. Also, the variability of scores was not significantly different between the two groups.

CONCLUSIONS

There was no significant difference in performance levels or variability between children with and without ANSD, both for children who use hearing aids, and children who use cochlear implants.

Central auditory maturation and behavioral outcome in children with auditory neuropathy spectrum disorder who use cochlear implants

OBJECTIVE

We examined cortical auditory development and behavioral outcomes in children with ANSD fitted with cochlear implants (CI).

DESIGN

Cortical maturation, measured by P1 cortical auditory evoked potential (CAEP) latency, was regressed against scores on the infant toddler meaningful auditory integration scale (IT-MAIS). Implantation age was also considered in relation to CAEP findings.

STUDY SAMPLE

Cross-sectional and longitudinal samples of 24 and 11 children, respectively, with ANSD fitted with CIs.

RESULTS

P1 CAEP responses were present in all children after implantation, though previous findings suggest that only 50-75% of ANSD children with hearing aids show CAEP responses. P1 CAEP latency was significantly correlated with participants' IT-MAIS scores. Furthermore, more children implanted before age two years showed normal P1 latencies, while those implanted later mainly showed delayed latencies. Longitudinal analysis revealed that most children showed normal or improved cortical maturation after implantation.

CONCLUSION

Cochlear implantation resulted in measureable cortical auditory development for all children with ANSD. Children fitted with CIs under age two years were more likely to show age-appropriate CAEP responses within six months after implantation, suggesting a possible sensitive period for cortical auditory development in ANSD. That CAEP responses were correlated with behavioral outcome highlights their clinical decision-making utility.

Cochlear implantation in unique pediatric populations

PURPOSE OF REVIEW

Over the last decade, the selection criteria for cochlear implantation have expanded to include children with special auditory, otologic, and medical problems. Included within this expanded group of candidates are those children with auditory neuropathy spectrum disorder, cochleovestibular malformations, cochlear nerve deficiency, associated syndromes, as well as multiple medical and developmental disorders. Definitive indications for cochlear implantation in these unique pediatric populations are in evolution. This review will provide an overview of managing and habilitating hearing loss within these populations with specific focus on cochlear implantation as a treatment option.

RECENT FINDINGS

Cochlear implants have been successfully implanted in children within unique populations with variable results. Evaluation for cochlear implant candidacy includes the core components of a full medical, audiologic, and speech and language evaluations. When considering candidacy in these children, additional aspects to consider include disorder-specific surgical considerations and child/caregiver counseling regarding reasonable postimplantation outcome expectations.

SUMMARY

Cochlear implants are accepted as the standard of care for improving hearing and speech development in children with severe-to-profound hearing loss. However, children with sensorineural hearing loss who meet established audiologic criteria for cochlear implantation may have unique audiologic, medical, and anatomic characteristics that necessitate special consideration regarding cochlear implantation candidacy and outcome. Individualized preoperative candidacy and counseling, surgical evaluation, and reasonable postoperative outcome expectations should be taken into account in the management of these children.

Bilateral cochlear implantation in Friedreich's ataxia: a case study

With an incidence of 1:29 000 among Caucasians, Friedreich's ataxia (FRDA) is the most common inherited ataxia, leading to both sensory and motor degeneration. Despite many FRDA patients exhibiting normal or near normal sound detection thresholds, many individuals show abnormal neural conduction along their central auditory pathways. Electrophysiological testing can show abnormal or absent cochlear nerve and auditory brainstem recordings in the presence of normal pre-neural cochlear function (otoacoustic emissions or cochlear microphonics). This pattern of normal pre-neural cochlear function and disrupted neural conduction has been termed auditory neuropathy spectrum disorder (ANSD). Studies of FRDA patients with ANSD have shown that they exhibit severe deficits in temporal processing, impaired frequency discrimination, and deficits in speech perception. Rehabilitation of these auditory percept deficits remains difficult, as hearing aids may amplify sounds without adding clarity to the temporally disrupted or distorted signal that FRDA patients with ANSD may receive. There is limited data on the best intervention for patients with FRDA with ANSD, although personal radio aids (FM systems) have been shown to be beneficial. We report a case, where cochlear implantation has led to a dramatic improvement in speech perception in an individual with FRDA and ANSD. The majority of the literature on ANSD treatment has focused on paediatric patients with the 'dyssynchrony' type of ANSD, rather than the true neuropathy type underlying the hearing loss in FRDA patients.

Plasticity in the developing auditory cortex: evidence from children with sensorineural hearing loss and auditory neuropathy spectrum disorder

The developing auditory cortex is highly plastic. As such, the cortex is both primed to mature normally and at risk for reorganizing abnormally, depending upon numerous factors that determine central maturation. From a clinical perspective, at least two major components of development can be manipulated: (1) input to the cortex and (2) the timing of cortical input. Children with sensorineural hearing loss (SNHL) and auditory neuropathy spectrum disorder (ANSD) have provided a model of early deprivation of sensory input to the cortex and demonstrated the resulting plasticity and development that can occur upon introduction of stimulation. In this article, we review several fundamental principles of cortical development and plasticity and discuss the clinical applications in children with SNHL and ANSD who receive intervention with hearing aids and/or cochlear implants.

Auditory neuropathies: understanding their pathogenesis to illuminate intervention strategies

PURPOSE OF REVIEW

For lack of therapy targeting sensorineural hearing loss, hearing-impaired patients must be fitted with sound-amplifying hearing aids or cochlear implants, successfully in a majority of cases. Yet failures are often found among auditory neuropathies.

RECENT FINDINGS

Auditory neuropathies are a class of conditions characterized by disrupted spike synchrony in auditory pathways despite reasonably preserved hearing sensitivity: amplification by hearing aids is inadequate and electrical stimulation of the auditory nerve may not improve discharge synchrony.

SUMMARY

Among the already partially understood pathogenetic frameworks, this article reviews physiological reasons why some rehabilitation procedures can restore neural synchrony, whereas others either fail or might even increase the damage, and what tests could help predict the outcome of intervention.

Outcomes in cochlear implantation: variables affecting performance in adults and children

This article highlights variables that affect cochlear implant performance, emerging factors warranting consideration, and variables shown not to affect performance. Research on the outcomes following cochlear implantation has identified a wide spectrum of variables known to affect pos0timplantation performance. These variables relate to the device itself as well as individual patient characteristics. Factors believed to affect spiral ganglion cell survival and function have been shown to influence postoperative performance. Binaural hearing affects performance. Social and educational factors also affect postoperative performance. Novel variables capable of affecting performance continue to emerge with increased understanding of auditory pathway development and neural plasticity.

Nerve maintenance and regeneration in the damaged cochlea

Following the onset of sensorineural hearing loss, degeneration of mechanosensitive hair cells and spiral ganglion cells (SGCs) in humans and animals occurs to variable degrees, with a trend for greater neural degeneration with greater duration of deafness. Emergence of the cochlear implant prosthesis has provided much needed aid to many hearing impaired patients and has become a well-recognized therapy worldwide. However, ongoing peripheral nerve fiber regression and subsequent degeneration of SGC bodies can reduce the neural targets of cochlear implant stimulation and diminish its function. There is increasing interest in bio-engineering approaches that aim to enhance cochlear implant efficacy by preventing SGC body degeneration and/or regenerating peripheral nerve fibers into the deaf sensory epithelium. We review the advancements in maintaining and regenerating nerves in damaged animal cochleae, with an emphasis on the therapeutic capacity of neurotrophic factors delivered to the inner ear after an insult. Additionally, we summarize the histological process of neuronal degeneration in the inner ear and describe different animal models that have been employed to study this mechanism. Research on enhancing the biological infrastructure of the deafened cochlea in order to improve cochlear implant efficacy is of immediate clinical importance.

Cochlear implants: current status and future potential

This article reviews the current status of cochlear implantation in both adults and children, including expanding candidacy groups, bilateral implantation, advances in speech processing software, internal and external device hardware, surgical techniques and outcomes. Promising advances, novel therapies and evolving concepts are also highlighted in terms of their future impact on clinical outcomes.

Auditory impairment in infants at risk for bilirubin-induced neurologic dysfunction

Classical and subtypes of kernicterus associated with bilirubin toxicity can be differentiated in part with physiological auditory measures that include auditory-evoked potentials and measures of cochlear integrity. The combination of these auditory measures suggests that bilirubin exposure results in auditory system damage initially at the level of the brainstem, progressing to the level of the VIII cranial nerve and then to greater neural centers. There is no evidence of neural damage at the level of the cochlea. Auditory neural damage from bilirubin toxicity ranges from neural timing deficits, including neural firing delays and dyssynchrony, to neural response reduction and even elimination of auditory neural responses. This condition is comprehensively described as auditory neuropathy spectrum disorder. Independent measures of cochlear function and auditory neural function up to the level of the brainstem can effectively diagnose auditory neural damage resulting from bilirubin neurotoxicity. Intervention, including cochlear implants can be effective.

Cochlear implantation in the very young child: issues unique to the under-1 population

Since the advent of cochlear implantation, candidacy criteria have slowly broadened to include increasingly younger patients. Spurred by evidence demonstrating both perioperative safety and significantly increased speech and language benefit with early auditory intervention, children younger than 12 months of age are now being successfully implanted at many centers. This review highlights the unique challenges involved in cochlear implantation in the very young child, specifically diagnosis and certainty of testing, anesthetic risk, surgical technique, intraoperative testing and postoperative programming, long-term safety, development of receptive and expressive language, and outcomes of speech perception. Overall, the current body of literature indicates that cochlear implantation prior to 1 year of age is both safe and efficacious.