Prevalence of auditory neuropathy (AN) among infants and young children with severe to profound hearing loss

Prevalence and Auditory Characteristics of Auditory Neuropathy Spectrum Disorder in Adult Population with Sensory Neural Hearing Loss: A Hospital Based Study in South India

Auditory neuropathy spectrum disorder (ANSD) is a heterogenous group of disorder characterized by abnormalities in auditory brainstem responses (ABR) with preserved otoacoustic emissions and/or cochlear microphonics. The aim of the study is to estimate the prevalence and evaluate the audiological characteristics of ANSD in adult population with sensory neural hearing loss. A prospective study was conducted on the adult population (≥ 18 years) attending ENT outpatients clinic at Rajiv Gandhi Government General Hospital, Chennai. All patients reported to the department with auditory and vestibular symptoms underwent case history, otoscopic examination, and routine audiological evaluation (pure tone audiometry, speech audiometry and immittance audiometry). Patients with indications of ANSD in case history and routine audiological evaluation were further evaluated using distortion product otoacoustic emissions and ABR. A total of 8682 adult population was evaluated during the period of 2017 to 2018. Out of 8682 patients, 1343 (15.46%) of them had sensory neural hearing loss of varying degrees. Out of 1343 adults with sensory neural hearing loss, 24 (1.78%) adults were diagnosed as ANSD. The prevalence of ANSD in adult population with sensory neural hearing loss in our study is 1.32% per 1000 adults. The clinical characteristics of ANSD shows impairment in speech perception irrespective of degree of hearing loss, preserved cochlear functions and abnormal ABR. Hence ANSD is not a rare clinical finding in adults with sensory neural hearing loss, but its prevalence was estimated to be lower in Indian population. Often young females are affected causing significant impairment in speech perception and disability.

Newborn hearing screening methodology impacts the timing of diagnosis for auditory neuropathy spectrum disorder

INTRODUCTION

Auditory Neuropathy Spectrum Disorder (ANSD) accounts for 10 % to 15 % of pediatric hearing loss. In most cases, otoacoustic emissions (OAE) are present as the outer hair cell function is normal, and the auditory brainstem response (ABR) is abnormal. Newborn hearing screen (NBHS) is completed using OAE or ABR depending on the institution. Because OAEs are often present in ANSD, NBHS done solely with OAE can miss and delay diagnosis of patients with ANSD.

OBJECTIVES

To assess whether NBHS methodology impacts the age of diagnosis of ANSD.

METHODS

This is a retrospective study of patients, 0-18 years of age, diagnosed with ANSD at two tertiary pediatric hospitals from 1/01/2010 to 12/31/2018 after referral from NBHS performed in the community. Data recorded included patient demographics, method of NBHS, NICU stay, and age at ANSD diagnosis.

RESULTS

264 patients were diagnosed with ANSD. Of those, 123 (46.6 %) were female, and 141 (53.4 %) were male. Ninety-seven (36.8 %) were admitted to NICU and the mean stay was 6.98 weeks (STD = 10.7; CI = 4.8-9.1). The majority (244, 92.4 %) of patients had NBHS with ABR, and 20 (7.5 %) had NBHS with OAE. Patients screened with ABR were diagnosed with ANSD earlier than those who screened with OAE, with a mean age of 14.1 versus 27.3 weeks (p = 0.0397, CI = 15.2-39.3). Among those screened with ABR, median age at diagnosis was 4 months for NICU infants and 2.5 months for infants with no history of NICU stay over 5 days. In comparison, median diagnosis age was 8 months for non-NICU infants screened with OAEs.

CONCLUSION

Patients with ANSD who had NBHS with ABR were diagnosed earlier than those with OAE. Our data suggest that universal screening with ABR may facilitate earlier diagnosis of ANSD and earlier evaluation for aural rehabilitation, especially in high-risk cohorts such as NICU patients. Further research is needed into factors that contribute to earlier diagnosis among patients screened with ABR.

Identification of a novel AIFM1 variant from a Chinese family with auditory neuropathy

Background: Auditory neuropathy (AN) is a specific type of hearing loss characterized by impaired language comprehension. Apoptosis inducing factor mitochondrion associated 1 (AIFM1) is the most common gene associated with late-onset AN. In this study, we aimed to screen the pathogenic variant of AIFM1 in a Chinese family with AN and to explore the molecular mechanism underlying the function of such variant in the development of AN.

Methods: One patient with AN and eight unaffected individuals from a Chinese family were enrolled in this study. A comprehensive clinical evaluation was performed on all participants. A targeted next-generation sequencing (NGS) analysis of a total of 406 known deafness genes was performed to screen the potential pathogenic variants in the proband. Sanger sequencing was used to confirm the variants identified in all participants. The pathogenicity of variant was predicted by bioinformatics analysis. Immunofluorescence and Western blot analyses were performed to evaluate the subcellular distribution and expression of the wild type (WT) and mutant AIFM1 proteins. Cell apoptosis was evaluated based on the TUNEL analyses.

Results: Based on the clinical evaluations, the proband in this family was diagnosed with AN. The results of NGS and Sanger sequencing showed that a novel missense mutation of AIFM1, i.e., c.1367A > G (p. D456G), was identified in this family. Bioinformatics analysis indicated that this variant was pathogenic. Functional analysis showed that in comparison with the WT, the mutation c.1367A > G of AIFM1 showed no effect on its subcellular localization and the ability to induce apoptosis, but changed its protein expression level.

Conclusion: A novel variant of AIFM1 was identified for the first time, which was probably the genetic cause of AN in a Chinese family with AN.

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%.

Familial Temperature-Sensitive Auditory Neuropathy: Distinctive Clinical Courses Caused by Variants of the OTOF Gene

Objective: To investigate the clinical course and genetic etiology of familial temperature-sensitive auditory neuropathy (TSAN), which is a very rare subtype of auditory neuropathy (AN) that involves an elevation of hearing thresholds due to an increase in the core body temperature, and to evaluate the genotype-phenotype correlations in a family with TSAN. Methods: Six members of a non-consanguineous Chinese family, including four siblings complaining of communication difficulties when febrile, were enrolled in this study. The clinical and audiological profiles of the four siblings were fully evaluated during both febrile and afebrile episodes, and the genetic etiology of hearing loss (HL) was explored using next-generation sequencing (NGS) technology. Their parents, who had no complaints of fluctuating HL due to body temperature variation, were enrolled for the genetics portion only. Results: Audiological tests during the patients' febrile episodes met the classical diagnostic criteria for AN, including mild HL, poor speech discrimination, preserved cochlear microphonics (CMs), and absent auditory brainstem responses (ABRs). Importantly, unlike the pattern observed in previously reported cases of TSAN, the ABRs and electrocochleography (ECochG) signals of our patients improved to normal during afebrile periods. Genetic analysis identified a compound heterozygous variant of the OTOF gene (which encodes the otoferlin protein), including one previously reported pathogenic variant, c.5098G > C (p.Glu1700Gln), and one novel variant, c.4882C > A (p.Pro1628Thr). Neither of the identified variants affected the C2 domains related to the main function of otoferlin. Both variants faithfully cosegregated with TSAN within the pedigree, suggesting that OTOF is the causative gene of the autosomal recessive trait segregation in this family. Conclusion: The presence of CMs with absent (or markedly abnormal) ABRs is a reliable criterion for diagnosing AN. The severity of the phenotype caused by dysfunctional neurotransmitter release in TSAN may reflect variants that alter the C2 domains of otoferlin. The observations from this study enrich the current understanding of the phenotype and genotype of TSAN and may lay a foundation for further research on its pathogenesis.

Novel Mutation in AIFM1 Gene Associated with X-Linked Deafness in a Moroccan Family

INTRODUCTION

Auditory neuropathy is a hearing disorder where outer hair cell function within the cochlea is normal, but inner hair cell and/or the auditory nerve function is disrupted. It is a heterogeneous disorder, which can have either congenital or acquired causes.

METHODS

We found a disease-segregating mutation in the X-linked AIFM1 gene through whole-exome sequencing, encoding the apoptosis-inducing factor mitochondrion-associated 1.

RESULTS

The impact of the c.1045A>G; p.(Ser349Gly) mutation on the AIFM1 protein was predicted using different bioinformatics tools. The pedigree analysis in the examined family was consistent with X-linked dominant inheritance.

DISCUSSION/CONCLUSION

To our knowledge, this is the first study that identifies a mutation in the AIFM1 gene in Moroccan patients suffering from X-linked auditory neuropathy.

Auditory Neuropathy: Bridging the Gap Between Hearing Aids and Cochlear Implants

Auditory neuropathy spectrum disorder (ANSD) is a complex and heterogeneous disorder associated with altered neural synchrony with respect to auditory stimuli. Patients have characteristic auditory findings including normal otoacoustic emissions in the setting of abnormal auditory brainstem response. Patients with ANSD have a high incidence of comorbid developmental delay that may impact speech outcomes. Treatment options for ANSD include hearing amplification and cochlear implantation. The article highlights issues and controversies with the diagnosis and treatment of this complex disorder.

Unilateral congenital hearing loss in children: Challenges and potentials

The estimated incidence of sensorineural hearing impairment (>40 dB HL) at birth is 1.86 per 1000 newborns in developed countries and 30-40% of these are unilateral. Profound sensorineural unilateral hearing impairment or single sided deafness (SSD) can be treated with a cochlear implant. However, this treatment is costly and invasive and unnecessary in the eyes of many. Very young children with SSD often do not exhibit language and cognitive delays and it is hard to imagine that neurocognitive skills will present difficulties with one good ear. In the current paper we review the most recent evidence on the consequences of unilateral hearing impairment for auditory and neurocognitive factors. While data of both adults and children are discussed, we focus on developmental factors, congenital deafness and a window of opportunity for intervention. We discuss which etiologies qualify for a cochlear implant and present our multi-center prospective study on cochlear implants in infants with one deaf ear. The large, state-of-the art body of research allows for evidence-based decisions regarding management of unilateral hearing loss in children.

Evaluation of saccular and inferior vestibular nerve function in children with auditory neuropathy spectrum disorder

PURPOSE

The aim of the current work was to evaluate the function of the saccule and inferior vestibular nerve in children with auditory neuropathy spectrum disorder (ANSD) by recording the cervical-evoked myogenic potentials (C-VEMP) on those children and to compare C-VEMP results in ANSD children of pre-lingual onset to those in ANSD children of post-lingual onset.

METHODS

The study included 38 ANSD children of pre-lingual onset, 16 ANSD children of post-lingual onset, and 20 control children. All participant children were subjected to C-VEMP testing using 500 Hz tone burst stimuli.

RESULTS

The vast majority of ANSD children of pre-lingual onset (35 out of 38; 92.1%) had bilateral intact C-VEMP response with C-VEMP parameters (amplitude, asymmetric ratio, latency, and inter-aural latency difference) that were not statistically different than those in the control children. Only three children had bilateral absent C-VEMP response. On the other hand, the majority of ANSD children of post-lingual onset (11 out of 16; 68.75%) had bilateral absent C-VEMP response. The remaining five children had bilateral intact C-VEMP response with C-VEMP parameters that were not statistically different than those in the control children.

CONCLUSIONS

The pathology of ANSD spares the saccule and inferior vestibular nerve in the vast majority of ANSD children of pre-lingual onset, while it involves them in the majority of ANSD of post-lingual onset reflecting different site(s) of lesion between the two ANSD categories. Such results have important clinical implications as regards to the management of ANSD in children.

Cochlear implantation in children with auditory neuropathy spectrum disorder: A multicenter study on auditory performance and speech production outcomes

OBJECTIVES

To evaluate the auditory performance and speech production outcome in children with auditory neuropathy spectrum disorder (ANSD). The effect of age on the outcomes of the surgery at the time of implantation was also evaluated.

METHODS

Cochlear implantation was performed in 136 children with bilateral severe-to- profound hearing loss due to ANSD, at four tertiary academic centers. The patients were divided into two groups based on the age at the time of implantation; Group I: Children ≤24 months, and Group II: subjects >24 months. The categories of auditory performance (CAP) and speech intelligibility rating (SIR) scores were evaluated after the first and second years of implantation. The differences between the CAP and SIR scores in the two groups were assessed.

RESULTS

The median CAP scores improved significantly after the cochlear implantation in all the patients (p value < 0.001). The improvement in the CAP scores during the first year in Group II was greater than Group I (p value: 0.007), but the improvement in CAP scores tended to be significantly higher in patients who were implanted at ≤24 months (p value < 0.001). There was no significant difference between two groups in SIR scores at first-year and second-year follow-ups. The evaluation of the SIR improvement revealed significantly higher values for Group I during the second-year follow-up (p value: 0.003).

CONCLUSION

The auditory performance and speech production skills of the children with ANSD improved significantly after cochlear implantation, and this improvement was affected by age at the time of implantation.

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.

ATP1A3 mutations can cause progressive auditory neuropathy: a new gene of auditory synaptopathy

The etiologies and prevalence of sporadic, postlingual-onset, progressive auditory neuropathy spectrum disorder (ANSD) have rarely been documented. Thus, we aimed to evaluate the prevalence and molecular etiologies of these cases. Three out of 106 sporadic progressive hearing losses turned out to manifest ANSD. Through whole exome sequencing and subsequent bioinformatics analysis, two out of the three were found to share a de novo variant, p.E818K of ATP1A3, which had been reported to cause exclusively CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) syndrome. However, hearing loss induced by CAPOS has never been characterized to date. Interestingly, the first proband did not manifest any features of CAPOS, except subclinical areflexia; however, the phenotypes of second proband was compatible with that of CAPOS, making this the first reported CAPOS allele in Koreans. This ANSD phenotype was compatible with known expression of ATP1A3 mainly in the synapse between afferent nerve and inner hair cells. Based on this, cochlear implantation (CI) was performed in the first proband, leading to remarkable benefits. Collectively, the de novo ATP1A3 variant can cause postlingual-onset auditory synaptopathy, making this gene a significant contributor to sporadic progressive ANSD and a biomarker ensuring favorable short-term CI outcomes.

Relationship Between Patients with Clinical Auditory Neuropathy Spectrum Disorder and Mutations in Gjb2 Gene

The auditory neuropathy is a condition which there is a dyssynchrony in the nerve conduction of the auditory nerve fibers. There is no evidence about the relationship between patients with clinical auditory neuropathy spectrum disorder and mutations in GJB2 gene. There are only two studies about this topic in the medical literature. Connexin 26 (GJB2 gene) mutations are common causes of genetic deafness in many populations and we also being reported in subjects with auditory neuropathy.

Study of cochlear microphonic potentials in auditory neuropathy

Introduction

Auditory Neuropathy/Dyssynchrony is a disorder characterized by the presence of Otoacoustic Emissions and Cochlear Microphonic Potentials, an absence or severe alteration of Brainstem Evoked Auditory Potential, auditory thresholds incompatible with speech thresholds and altered acoustic reflexes. The study of the Cochlear Microphonic Potential appears to be the most important tool for an accurate diagnosis of this pathology.

Objective

Determine the characteristics of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony using an integrative review.

Methods

Bibliographic survey of Pubmed and Bireme platforms and MedLine, LILACS and SciELO data banks, with standardized searches up to July 2014, using keywords. Criteria were established for the selection and assessment of the scientific studies surveyed, considering the following aspects: author, year/place, degree of recommendation/level of scientific evidence, objective, sample, age range, mean age, tests, results and conclusion.

Results

Of the 1959 articles found, 1914 were excluded for the title, 20 for the abstract, 9 for the text of the article, 2 for being repeated and 14 were selected for the study.

Conclusion

The presence of the Cochlear Microphonic is a determining finding in the differential diagnosis of Auditory Neuropathy/Dyssynchrony. The protocol for the determination of Cochlear Microphonic must include the use of insert earphones, reverse polarity and blocking the stimulus tube to eliminate electrical artifact interference. The amplitude of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony shows no significant difference from that of normal individuals. The duration of the Cochlear Microphonic is longer in individuals with Auditory Neuropathy/Dyssynchrony.

Detection Rates of Cortical Auditory Evoked Potentials at Different Sensation Levels in Infants with Sensory/Neural Hearing Loss and Auditory Neuropathy Spectrum Disorder

With the introduction of newborn hearing screening, infants are being diagnosed with hearing loss during the first few months of life. For infants with a sensory/neural hearing loss (SNHL), the audiogram can be estimated objectively using auditory brainstem response (ABR) testing and hearing aids prescribed accordingly. However, for infants with auditory neuropathy spectrum disorder (ANSD) due to the abnormal/absent ABR waveforms, alternative measures of auditory function are needed to assess the need for amplification and evaluate whether aided benefit has been achieved. Cortical auditory evoked potentials (CAEPs) are used to assess aided benefit in infants with hearing loss; however, there is insufficient information regarding the relationship between stimulus audibility and CAEP detection rates. It is also not clear whether CAEP detection rates differ between infants with SNHL and infants with ANSD. This study involved retrospective collection of CAEP, hearing threshold, and hearing aid gain data to investigate the relationship between stimulus audibility and CAEP detection rates. The results demonstrate that increases in stimulus audibility result in an increase in detection rate. For the same range of sensation levels, there was no difference in the detection rates between infants with SNHL and 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.

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>.

Determination of benefits of cochlear implantation in children with auditory neuropathy

Background

Auditory neuropathy (AN) is a recently recognized hearing disorder characterized by intact outer hair cell function, disrupted auditory nerve synchronization and poor speech perception and recognition. Cochlear implants (CIs) are currently the most promising intervention for improving hearing and speech in individuals with AN. Although previous studies have shown optimistic results, there was large variability concerning benefits of CIs among individuals with AN. The data indicate that different criteria are needed to evaluate the benefit of CIs in these children compared to those with sensorineural hearing loss. We hypothesized that a hierarchic assessment would be more appropriate to evaluate the benefits of cochlear implantation in AN individuals.

Methods

Eight prelingual children with AN who received unilateral CIs were included in this study. Hearing sensitivity and speech recognition were evaluated pre- and postoperatively within each subject. The efficacy of cochlear implantation was assessed using a stepwise hierarchic evaluation for achieving: (1) effective audibility, (2) improved speech recognition, (3) effective speech, and (4) effective communication.

Results

The postoperative hearing and speech performance varied among the subjects. According to the hierarchic assessment, all eight subjects approached the primary level of effective audibility, with an average implanted hearing threshold of 43.8 ± 10.2 dB HL. Five subjects (62.5%) attained the level of improved speech recognition, one (12.5%) reached the level of effective speech, and none of the subjects (0.0%) achieved effective communication.

Conclusion

CIs benefit prelingual children with AN to varying extents. A hierarchic evaluation provides a more suitable method to determine the benefits that AN individuals will likely receive from cochlear implantation.

Mutations in apoptosis-inducing factor cause X-linked recessive auditory neuropathy spectrum disorder

Background

Auditory neuropathy spectrum disorder (ANSD) is a form of hearing loss in which auditory signal transmission from the inner ear to the auditory nerve and brain stem is distorted, giving rise to speech perception difficulties beyond that expected for the observed degree of hearing loss. For many cases of ANSD, the underlying molecular pathology and the site of lesion remain unclear. The X-linked form of the condition, AUNX1, has been mapped to Xq23-q27.3, although the causative gene has yet to be identified.

Methods

We performed whole-exome sequencing on DNA samples from the AUNX1 family and another small phenotypically similar but unrelated ANSD family.

Results

We identified two missense mutations in AIFM1 in these families: c.1352G>A (p.R451Q) in the AUNX1 family and c.1030C>T (p.L344F) in the second ANSD family. Mutation screening in a large cohort of 3 additional unrelated families and 93 sporadic cases with ANSD identified 9 more missense mutations in AIFM1. Bioinformatics analysis and expression studies support this gene as being causative of ANSD.

Conclusions

Variants in AIFM1 gene are a common cause of familial and sporadic ANSD and provide insight into the expanded spectrum of AIFM1-associated diseases. The finding of cochlear nerve hypoplasia in some patients was AIFM1-related ANSD implies that MRI may be of value in localising the site of lesion and suggests that cochlea implantation in these patients may have limited success.

Profound childhood hearing loss in a South Africa cohort: risk profile, diagnosis and age of intervention

OBJECTIVE

To describe profound childhood hearing loss in a South African population of pediatric cochlear implant recipients in terms of risk profile, and age of diagnosis and intervention.

METHODS

A retrospective review of patient files for 264 pediatric cochlear implant recipients from five cochlear implant programs was conducted. Data was captured from 264 eligible subjects, of which all were implanted between 1996 and 2013 and PCEHL was confirmed under the age of 5 years old. Data collected included demographical information, risk factors from case histories, diagnostic test procedures conducted, diagnosis (type, onset and degree of hearing loss) and documented ages of caregiver suspicion, initial diagnosis and intervention.

RESULTS

Risk factors for permanent childhood hearing loss were present in 51.1% of cases, with the most prevalent risks being NICU admittance (28.1%), family history of childhood hearing loss (19.6%) and prematurity (15.1%). An associated syndrome was diagnosed in 10% of children and 23.5% presented with at least one additional developmental condition. Hearing loss for most (77.6%) children was confirmed as congenital/early onset, while 20.3% presented with postnatal onset of hearing loss. ANSD was diagnosed in 5% of children, with admittance to NICU (80%) and hyperbilirubinemia (50%) being the most prevalent risk factors for these cases. Hearing loss was typically diagnosed late (15.3 months), resulting in delayed initial hearing aid fitting (18.8 months), enrollment in early intervention services (19.5 months) and eventual cochlear implantation (43.6 months).

CONCLUSION

Most prevalent risk factors in profound childhood hearing loss were admittance to NICU, family history and prematurity. Diagnosis and intervention was typically delayed predisposing this population to poorer outcomes.

Prevalence and Audiological Characteristics of Auditory Neuropathy Spectrum Disorder in Pediatric Population: A Retrospective Study

Auditory neuropathy spectrum disorder (ANSD) is a type of hearing disorder which is challenging for assessment and rehabilitation. This disorder has been studied over a decade and prevalence of the disorder is variable. The study aimed at estimating the prevalence and audiological characteristics of ANSD in children. A retrospective study was conducted from the medical records of pediatric patients evaluated at Rajiv Gandhi Government General Hospital and Madras Medical College, Chennai to estimate the prevalence of ANSD. Medical records of 2,624 children evaluated during the period of November 2010 to October 2012 within the age range of 6 months to 12 years were analyzed. Out of 2,624 pediatric population assessed 217 (8.26 %) of them had unilateral or bilateral sensory neural hearing loss with varying degrees. Out of 217 children with sensory neural hearing loss 5.06 % (N = 11) had ANSD. Audiological characteristics varied among the group. Children with ANSD had varied degree of hearing thresholds from normal to profound hearing impairment. All of them had 'A' type tympanogram with absent stapedial reflexes. DPOAEs or TEOAEs were observed in 54 % of population with ANSD. All of them had abnormal auditory brainstem responses (ABR). Replicable cochlear microphonics was observed in 46 % of children with ANSD. These results indicate that ANSD is not a rare condition among children and we emphasize the use of objective tests like tympanometry, Stapedial Reflex test, otoacoustic emissions and ABR in routine hearing assessment procedure for all children to identify ANSD.

Preliminary performance of cochlear implants in post-lingual patients with auditory neuropathy

CONCLUSIONS

Auditory restoration can be obtained by using cochlear implants (CIs) in post-lingual patients with auditory neuropathy (AN). However, improvements in postoperative speech recognition for these patients varied.

OBJECTIVES

The primary purpose of this study was to assess the postoperative performances of two post-lingual AN patients after receiving CIs.

METHODS

Two post-lingual AN patients received unilateral CIs and the efficacy of the implants was then evaluated. One patient was female with bilateral mid-severe hearing loss and received an implant at age 28 years. The second patient was male with severe hearing loss and he received an implant at age 15 years. The postoperative performance for both patients was evaluated.

RESULTS

After using the CI for 6 months, the hearing ability of both subjects was improved by the CI with an average post-implant threshold of 35 dB and 44 dB, respectively. The woman made significant progress in speech recognition with an open-set spondee recognition score of 55% and sentence recognition in quiet score of 90%. Sentence recognition in noise scores were 94% (SNR = +10 dB), 88% (SNR = +5 dB), and 80% (SNR = 0 dB). The boy achieved improved recognition scores for monosyllables (40%) and disyllables (26%), but poor sentence recognition both in quiet (0%) and in noise (0%).

Auditory dyssynchrony or auditory neuropathy: understanding the pathophysiology and exploring methods of treatment

OBJECTIVE

To review the literature on auditory dyssynchrony (AD) or neuropathy which is characterized by absent auditory brainstem responses, normal otoacoustic emissions, and word discrimination disproportional to the pure tone audiogram.

RESULTS

Several papers attempt to estimate the prevalence of AD that seems to range between 0.23 and 2% in infants "at risk" for hearing impairment and it is considered to be responsible for approximately 8% of newly diagnosed cases of hearing loss in children per year. The prevalence gets even higher, reaching 10% in children with permanent hearing loss. It seems that AD is not a single disease but a spectrum of pathologies that affect the auditory pathway at the level of the inner hair cells, the synapses, or the auditory nerve. Many predisposing or contribution factors have been reported, including prematurity, hyperbilirubinemia, hypoxia, low-birth weight, immunological conditions, infectious diseases, etc. Before proposing any method of management, parents should be informed about the variation among patients and the changes that may appear in some children's audition over time. Sigh language, speech and language therapy, hearing-aids, and cochlear implantation have been used in the treatment of AD. In general, AD is rather refractory to conventional amplification and cochlear implantation has been found an effective method of management in young implanted children with severe/profound deafness and AD. However, the situation is more complicated and challenging in milder hearing losses.

CONCLUSION

The selected and proposed 30 related articles published in the International Journal of Pediatric Otorhinolaryngology aim to stimulate the related research in order to further explore the etiology, pathophysiology, and management of AD.

Prevalence of auditory neuropathy spectrum disorder in an auditory health care service

Auditory neuropathy spectrum disorder (ANSD) is characterized by impairment of the auditory nerve associated with preservation of outer hair cell function.

Objective

To establish the prevalence of ANSD in subjects with sensorineural hearing loss (SNHL).

Method

This retrospective study was carried out between 2010 and 2012 and included the charts of 2,292 individuals with SNHL. Data from otolaryngological and audiological examinations based on pure-tone and speech audiometry, impedance tests, otoacoustic emissions (OAEs), and brainstem auditory evoked potentials (BAEPs) were collected. Inclusion criteria: presence of OAEs and/or cochlear microphonic (CM); absent or altered BAEPs, and normal MRI scans of the brain.

Results

Twenty-seven (1.2%) of the 2,292 subjects with SNHL had ANSD (37% males; 63% females). Mild SNHL was seen in 29.6% of the individuals with ANSD; 55.5% had moderate SNHL; 7.4% had severe SNHL; and 7.5% had profound SNHL. In terms of age, 14.8% were aged between zero and 20 years, 44.1% were 41 to 60 years old, and 7.4% were above the age of 60.

Conclusion

ANSD was seen in 1.2% of the individuals with SNHL included in this study.

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.

Targeted versus Universal Neonatal Hearing Screening in a Single Egyptian Center

Aim. To compare targeted neonatal hearing screening (TNHS) and universal neonatal hearing screening (UNHS) since many developing countries, including Egypt, implement selective screening for high-risk neonates. Methods. 150 neonates were assessed; 50 full terms consecutively admitted to the well-baby nursery and 100 neonates consecutively admitted to neonatal intensive care unit (NICU), Ain Shams University. Patients were further subdivided into high-risk group which included 50 neonates with multiple risk factors for hearing loss and low risk group which included 50 neonates with only one risk factor. Transient evoked otoacoustic emissions (TEOAEs) were used for hearing screening. Auditory brain response (ABR) was performed 3 months later for failed TEOAEs. Results. The most frequent risk factor was consanguinity (46%). In the well-baby population, 16% failed TEOAEs. In the NICU, 30% of the low risk and 38% of the high risk groups failed TEOAEs. Regarding ABR, failed results were 12%, 10%, and 8% in the high-risk, low-risk, and healthy groups, respectively. Conclusion. The use of TNHS would have missed 8% of neonates from the well-baby group who actually had PCHL (permanent congenital hearing loss). The use of UNHS would identify all cases with PCHL, allowing for early intervention and follow-up.

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.

Prevalence and risk factors for auditory neuropathy spectrum disorder in a screened newborn population at risk for hearing loss

OBJECTIVE

To determine the prevalence of Auditory Neuropathy Spectrum Disorder (ANSD) among infants with sensorineural hearing loss (SNHL) and discuss the risk factors.

METHODS

The study group was comprised of children diagnosed with ANSD. Criteria for inclusion in the study group were as follows: permanent sensorineural hearing loss (SNHL); normal transient evoked or distortion product OAEs; absent or elevated middle-ear muscle reflexes (MEMR); severely abnormal or absent ABR waveform. All newborns were screened via a two-stage protocol, involving OAEs and ABR for the repeatedly referred cases and all neonates with one or more risk factors.

RESULTS

From 2002 to 2011, 9419 infants whose hearing ability was uncertain or who had risk factors for hearing loss were investigated. From this population, 352 were diagnosed with SNHL. Of these 352 children, 18 (5.1%) were diagnosed with ANSD. In the ANSD group, prematurity and low birth weight (<1500 g) were observed in 5 cases; ototoxical medication in 8 cases; mechanical ventilation in excess of 5 days in 5 cases. Hyperbilirubinemia was observed in 7 cases, but severe hyperbilirubinemia requiring an exchange transfusion was not observed; 4 patients had no risk factors, 6 patients had only one risk factor, and the 8 remaining had two or more risk factors.

CONCLUSION

Auditory Neuropathy Spectrum Disorder is not an extremely rare hearing disorder. Screening for hearing loss via OAEs, MEMR and ABR examinations concurrently are essential for the accurate diagnosis of ANSD.

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.

The performance of distortion product otoacoustic emissions and automated auditory brainstem response in the same ear of the babies in neonatal unit

OBJECTIVE

To identify the outcomes of hearing screening using different protocols of both Distortion Product Otoacoustic Emissions (DPOAE) and Automated Auditory Brainstem Response (AABR) tests in the same ear of the babies in a neonatal unit population.

METHODS

A cross-sectional study was carried out on babies who were admitted into a neonatal unit. By using a formula of single proportion and considering 20% drop out, the number of sample required was 114. The subjects were chosen by using a systematic random sampling. The infants selected were subjected to DPOAE followed by AABR tests screening at the same setting before discharge.

RESULTS

There were 73 newborns (61.6% male and 38.4% female) participated in this study with a total of 146 ears screened. Ototoxic medication was the most common risk factor followed by hyperbilirubinaemia and low birth weight. AABR had higher passing rate (82.9%) as compared to DPOAE (77.4%). The highest passing rate was achieved if the protocol of either passed DPOAE or AABR was used (90.4%). The rate was lower when auditory neuropathy spectrum disorder (ANSD) has been considered (82.9%). Hyperbilirubinaemia, prematurity, craniofacial malformation and ototoxic drugs seem to be the high risk factors for auditory neuropathy.

CONCLUSION

AABR has a higher passing rate as compared to DPOAE. However, the use of both instruments in the screening process especially in NICU will be useful to determine the infants with ANSD who may need different approach to management. Therefore, a protocol in which newborns are tested with AABR first and then followed by DPOAE on those who fail the AABR is recommended.

Validity of cochlear microphonics at high sound pressure levels as an important clinical aspect

INTRODUCTION

Cochlear microphonics are electrical stimulus responses of the inner ear, generated by mechanical displacement of the hair cells caused by acoustic stimulation. As cochlear microphonics are often used in the diagnosis of hearing impairment and deafness, in preliminary investigations it was seen that obliteration or ossification have no effect on the extent to which cochlear microphonics can be recorded at high sound pressure levels. As artifacts at high sound pressure levels suggested, measurements were subsequently conducted using temporal bone specimens.

METHODS

In a test setup equivalent to that for electrocochleography, a needle electrode was placed on the cochlear promontory and used to record potentials following application of an acoustic stimulus.

RESULTS

Curves comparable to cochlear microphonics were registrable down to a threshold of 80 dB HL. Additional measurements conducted on damp cloths yielded comparable findings.

CONCLUSIONS

Registration of cochlear microphonics at high sound pressure levels does not serve as an indicator of hair cell function, but should instead be regarded as artifacts. The possible sources are discussed.

Neuropatia auditiva: alerta aos pediatras

OBJETIVO: Alertar os pediatras sobre a neuropatia auditiva, doença descrita recentemente e ainda desconhecida por muitos médicos. Descrever seus fatores de risco, características clínicas e diagnósticas, com a finalidade de possibilitar uma intervenção terapêutica precoce e eficaz. FONTES DE DADOS: Realizada pesquisa nas bases de dados PubMed, Lilacs e SciELO utilizando os descritores "neuropatia auditiva" e "auditory neuropathy", entre os anos de 1996 e 2010. SÍNTESE DOS DADOS: A neuropatia auditiva, também conhecida como dessincronia auditiva, descrita em 1996, caracteriza-se clinicamente pela dificuldade na compreensão das palavras, mesmo em casos de perdas auditivas leves ou moderadas. Foi relacionada a diversas neuropatias generalizadas e fatores de risco neonatais, como internação em terapia intensiva, hiperbilirrubinemia, sepse e hipóxia. Após suspeita clínica, o diagnóstico é confirmado pela presença das emissões otoacústicas associada a um potencial evocado auditivo de tronco encefálico ausente ou alterado. Sua terapêutica permanece controversa, tendo como opções a protetização auditiva, o acompanhamento fonoterápico para habilitação ou reabilitação da linguagem e, em casos de insucesso, há relatos de resultados satisfatórios com o implante coclear. CONCLUSÕES: Enfatiza-se a importância do reconhecimento pelo pediatra da neuropatia auditiva, entidade ainda pouco citada na literatura latino-americana da especialidade.

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.

Cortical Auditory Evoked Potentials in Auditory Neuropathy Spectrum Disorder: Clinical Implications

Standard clinical audiologic assessments have proven useful in the detection and diagnosis of auditory neuropathy spectrum disorder (ANSD). However, beyond initial diagnosis, clinicians have fewer tools to appropriately manage infants and young children with ANSD. While cortical auditory evoked potentials (CAEP) are not currently used routinely in the management of children with ANSD, mounting evidence suggests that they are not only recordable in this population, but that they may provide useful information regarding treatment and behavioral outcomes in children with ANSD. The report discusses the potential clinical utility of CAEPs in children with ANSD, using a case illustration.

The genetic basis of auditory neuropathy spectrum disorder (ANSD)

OBJECTIVE

Auditory neuropathy is a hearing disorder where outer hair cell function within the cochlea is normal, but inner hair cell and/or the auditory nerve function is disrupted. It is a heterogeneous disorder which can have either congenital or acquired causes. Furthermore, the aetiology of auditory neuropathy is vast, which may include prematurity, hyperbilirubinaemia, anoxia, hypoxia, congenital brain anomalies, ototoxic drug exposure, and genetic factors. It is estimated that approximately 40% of cases have an underlying genetic basis, which can be inherited in both syndromic and non syndromic conditions. This review paper provides an overview of the genetic conditions associated with auditory neuropathy spectrum disorders (ANSDs) and highlights some of the defective genes that have been found to be linked to the pathological auditory changes.

METHOD

Literature search was conducted using a number of resources including textbooks, professional journals and the relevant websites.

RESULTS

The largest proportion of auditory neuropathy spectrum disorders (ANSDs) is due to genetic factors which can be syndromic, non-syndromic or mitochondrial related. The inheritance pattern can include all the four main types of inheritances such as autosomal dominant, autosomal recessive, X-linked and mitochondrial.

CONCLUSION

This paper has provided an overview of mutation with some of the genes and/or loci discovered to be the cause for auditory neuropathy spectrum disorders (ANSDs). It has been noted that different gene mutations may trigger different pathological changes in patients with this disorder. These discoveries have provided us with vital information as to the sites of pathology in auditory neuropathy spectrum disorders (ANSDs), and the results highlight the heterogeneity of the disorder.