Cortical development and neuroplasticity in Auditory Neuropathy Spectrum Disorder

The neural characteristics influencing literacy outcome in children with cochlear implants

Early hearing intervention in children with congenital hearing loss is critical for improving auditory development, speech recognition and both expressive and receptive language, which translates into better educational outcomes and quality of life. In children receiving hearing aids or cochlear implants, both adaptive and potentially maladaptive neural reorganization can mitigate higher-level functions that impact reading. The focus of the present study was to dissect the neural underpinnings of the reading networks in children with cochlear implants and assess how these networks mediate the reading ability in children with cochlear implants. Cortical activity was obtained using naturalistic stimuli from 75 children (50 cochlear implant recipients, aged 7-17, and 25 age-matched children with typical hearing) using functional near-infrared spectroscopy. Assessment of basic reading skill was completed using the Reading Inventory and Scholastic Evaluation. We computed directed functional connectivity of the haemodynamic activity in reading-associated anterior and posterior brain regions using the time-frequency causality estimation method known as temporal partial directed coherence. The influence of the cochlear implant-related clinical measures on reading outcome and the extent to which neural connectivity mediated these effects were examined using structural equation modelling. Our findings reveal that the timing of intervention (e.g. age of first cochlear implants, age of first hearing aid) in children with cochlear implants significantly influenced their reading ability. Furthermore, reading-related processes (word recognition and decoding, vocabulary, morphology and sentence processing) were substantially mediated by the directed functional connectivity within reading-related neural circuits. Notably, the impact of these effects differed across various reading skills. Hearing age, defined as the age at which a participant received adequate access to sound, and age of initial implantation emerged as robust predictors of reading proficiency. The current study is one of the first to identify the influence of neural characteristics on reading outcomes for children with cochlear implants. The findings emphasize the importance of the duration of deafness and early intervention for enhancing outcomes and strengthening neural network connections. However, the neural evidence further suggested that such positive influences cannot fully offset the detrimental impact of early auditory deprivation. Consequently, additional, perhaps more specialized, interventions might be necessary to maximize the benefits of early prosthetic hearing intervention.

Brazilian Society of Otology task force - cochlear implant ‒ recommendations based on strength of evidence

OBJECTIVE

To make evidence-based recommendations for the indications and complications of Cochlear Implant (CI) surgery in adults and children.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on cochlear implantation were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Evaluation of candidate patients and indications for CI surgery; (2) CI surgery - techniques and complications.

CONCLUSIONS

CI is a safe device for auditory rehabilitation of patients with severe-to-profound hearing loss. In recent years, indications for unilateral hearing loss and vestibular schwannoma have been expanded, with encouraging results. However, for a successful surgery, commitment of family members and patients in the hearing rehabilitation process is essential.

Task force Guideline of Brazilian Society of Otology - hearing loss in children - Part II - Treatment

OBJECTIVES

To provide an overview of the main evidence-based recommendations for the diagnosis of hearing loss in children and adolescents aged 0-18 years.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on childhood hearing loss were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) treatment of sensorineural hearing loss: individual hearing aids, bilateral cochlear implants, cochlear implants in young children, unilateral hearing loss, and auditory neuropathy spectrum disorder; and (2) treatment of conductive/mixed hearing loss: external/middle ear malformations, ventilation tube insertion, and tympanoplasty in children.

CONCLUSIONS

In children with hearing loss, in addition to speech therapy, Hearing AIDS (HAs) or implantable systems may be indicated. Even in children with profound hearing loss, both the use of HAs and behavioral assessments while using the device are important.

Precision Medicine Approach to Cochlear Implantation

In the early days of cochlear implantation (CI) surgery, when the types of electrodes were limited and the etiology of sensorineural hearing loss (SNHL) was not well understood, the one-size-fits-all approach to CI held true, as in all other fields. However, in the era of personalized medicine, there have been attempts to associate CI performance with the etiology of SNHL and to establish customized surgical techniques that can maximize performance according to individual cochlear dimensions. Personalized genomic-driven assessments of CI candidates and a better understanding of genotype-phenotype correlations could provide clinically applicable diagnostic and prognostic information about questions such as who, how, and when to implant. Rigorous and strategic imaging assessments also provide better insights into the anatomic etiology of SNHL and cochlear dimensions, leading to individualized surgical techniques to augment CI outcomes. Furthermore, the precision medicine approach to CI is not necessarily limited to preoperative planning, but can be extended to either intraoperative electrode positioning or even the timing of the initial switch-on. In this review, we discuss the implications of personalized diagnoses (both genetic and nongenetic) on the planning and performance of CI in patients with prelingual and postlingual SNHL.

Acoustic Change Complex and Visually Reinforced Infant Speech Discrimination Measures of Vowel Contrast Detection

OBJECTIVES

To measure the effect of stimulus rate and vowel change direction on the acoustic change complex (ACC) latencies and amplitudes and compare ACC metrics to behavioral measures of vowel contrast detection for infants tested under the age of 1 year. We tested the hypothesis that the direction of spectral energy shift from a vowel change would result in differences in the ACC, owing to the sensitivity of cortical neurons to the direction of frequency change. We evaluated the effect of the stimulus rate (1/s versus 2/s) on the infants' ACC. We evaluated the ACC amplitude ratio's sensitivity (proportion of ACCs present for each change trial) and compared it to perceptual responses obtained using a visually reinforced infant speech discrimination paradigm (VRISD). This report provides normative data from infants for the ACC toward the ultimate goal of developing a clinically useful index of neural capacity for vowel discrimination.

DESIGN

Twenty-nine infants, nine females, 4.0 to 11.8 months of age, participated. All participants were born at full term and passed their newborn hearing screens. None had risk factors for hearing or neurologic impairment. Cortical auditory evoked potentials were obtained in response to synthesized vowel tokens /a/, /i/, /o/, and /u/ presented at a rate of 1- or 2/s in an oddball stimulus paradigm with a 25% probability of the deviant stimulus. All combinations of vowel tokens were tested at the two rates. The ACC was obtained in response to the deviant stimulus. The infants were also tested for vowel contrast detection using a VRISD paradigm with the same combinations of vowel tokens used for the ACC. The mean age at the time of the ACC test was 5.4 months, while the mean age at the behavioral test was 6.8 months.

RESULTS

Variations in ACC amplitude and latency occurred as a function of the initial vowel token and the contrast token. However, the hypothesis that the direction of vowel (spectral) change would result in significantly larger change responses for high-to-low spectral changes was not supported. The contrasts with /a/ as the leading vowel of the contrast pair resulted in the largest ACC amplitudes than other conditions. Significant differences in the ACC presence and amplitude were observed as a function of rate, with 2/s resulting in ACCs with the largest amplitude ratios. Latency effects of vowel contrast and rate were present, but not systematic. The ACC amplitude ratio's sensitivity for detecting a vowel contrast was greater for the 2/s rate than the 1/s rate. For an amplitude ratio criterion of ≥1.5, the sensitivity was 93% for ACC component P2-N2 at 2/s, whereas at 1/s sensitivity was 70%. VRISD tests of vowel-contrast detection had a 71% hit and a 21% false-positive rate. Many infants who could not reach performance criteria for VRISD had ACC amplitude ratios of ≥2.0.

CONCLUSIONS

The ACC for vowel contrasts presented at a rate of 2/s is a robust index of vowel-contrast detection when obtained in typically developing infants under the age of 1 year. The ACC is present in over 90% of infants tested at this rate when an amplitude ratio criterion of ≥1.5 is used to define a response. The amplitude ratio appears to be a sensitive metric for the difference between a control and contrast condition. The ACC can be obtained in infants who do not yet exhibit valid behavioral responses for vowel change contrasts and may be useful for estimating neural capacity for discriminating these sounds.

[The issue of auditory neuropathy: from origins to the present]

The issue of auditory neuropathy spectrum disorders (ANSD) has been in a focus of specialists attention for a relatively short time, but during this time a huge amount of scientific and practical knowledge about this hearing disorder has been accumulated. ANSD is a specific auditory deficit caused by dysfunction of periphery part of the auditory system, which may affect the inner hair cells, the spiral ganglion neurons and the auditory nerve, as well as the area of synaptic contact between them, while the outer hair cells, as a rule, remain intact. As a result, a specific condition is formed, in which a patient's otoacoustic emissions and/or cochlear microphonics are present, auditory brainstem responses are abnormal or absent, electrophysiological data may not correlate with hearing level, the discrepancy between pure tone audiometry and speech discrimination is observed. ANSD prevalence, epidemiology, contemporary views on its etiology, including detailed information on hereditary forms of the disorder and its risk factors are considered in the review. The data on the basic rungs of the ANSD pathogenesis, which underlie the development of various forms of the disorder and mainly determine the rehabilitation approach, are presented. The detailed clinical and audiological characteristics of ANSD are presented; contemporary approach to ANSD diagnosis and rehabilitation, including indications for surgical treatment, are considered.

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

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

Cortical Auditory Plasticity Following Cochlear Implantation in Children With Auditory Neuropathy Spectrum Disorder: A Prospective Study

OBJECTIVES

The cortical auditory evoked potential (CAEP) can provide an insight into the maturation of the central auditory nervous system by recording the auditory cortex responses to speech stimuli. This study aimed to explore the central auditory system development in children with auditory neuropathy spectrum disorder (ANSD) using cochlear implants (CIs) and to find the correlation of CAEP biomarkers with speech perception.

METHODS

This study was performed on 23 children with prelingual deafness, diagnosed with ANSD, as well as 23 children with prelingual deafness, without ANSD as the control group. All children underwent unilateral CI before the age of 3 years. Children with ANSD were classified into two groups, based on their CAEP results prior to implantation: children with a clear CAEP response (ANSD-I) and children without an identifiable CAEP (ANSD-II). The P1 component of CAEPs and speech intelligibility rating (SIR) were recorded before the initial device activation (baseline) and at 6, 12, and 24 months postimplantation.

RESULTS

The P1 CAEP responses were present in all children in the control group, while they were recorded in only 52% of ANSD children before the CI surgery. The longitudinal analysis revealed a significant reduction in the P1 latency and a significant improvement in the P1 amplitude across different time points in all study groups. However, the P1 latency and P1 amplitude were significantly shorter and larger in the control group than the ANSD group, respectively. Also, children in the ANSD-I group exhibited a slightly shorter P1 latency, a larger P1 amplitude, and a higher SIR score than the ANSD-II group after 2 years of follow-up. The P1 CAEP latency was significantly correlated with the SIR score.

CONCLUSION

The CAEP can be used as an objective indicator of auditory cortical maturation and a predictor of speech perception performance in implanted children with ANSD.

Central auditory maturation and behavioral outcomes after cochlear implantation in prelingual auditory neuropathy spectrum disorder related to OTOF variants (DFNB9): Lessons from pilot study

The cortical auditory evoked potential (CAEP)-based P1 component acts as a biomarker for cochlear implantation (CI) outcomes in children with auditory neuropathy spectrum disorder (ANSD). To date, early intervention primarily before the age of two years and six months of CI usage is necessary and sufficient to achieve age-appropriate cortical maturation and good prognosis. However, varying degrees of neural dyssynchrony, resulting from the etiological heterogeneity of ANSD, may preclude uniform application of this hypothesis to ensure auditory cortical maturation. Thus, a focused evaluation of those carrying OTOF variants, which may be the salient molecular etiology of prelingual ANSD, would circumvent the issue of heterogeneity. Here, we sought to provide a much better understanding of the brain perspectives (i.e., P1 maturation) in OTOF-associated ANSD subjects and set the stage for an optimal strategy to enhance language development. We conducted a preliminary study comprising 10 subjects diagnosed with OTOF-related ANSD who underwent CI by a single surgeon and subsequently underwent measurements of the P1 component. We observed that DFNB9 subjects who received CI after 2 years of age exhibited “absent” or “anomalous” P1 components that correspond to delayed language development. However, timely implantation, as early as 12 months of age per se, might be insufficient to achieve age-appropriate cortical maturation of DFNB9 in cases with six to seven months of device use. This suggests the importance of sustained rehabilitation in DFNB9 than in other etiologies. Indeed, an additional follow-up study showed that a reduction in P1 latency was linked to an improvement in auditory performance. Collectively, our results suggest that central auditory maturation and successful outcome of CI in DFNB9 may have more demanding requirements, that is, earlier implantation and more sustained rehabilitation. We believe that the current study opens a new path toward genome-based neuroimaging in the field of hearing research.

A Novel Bone Conduction Hearing System May Improve Memory Function in Children with Single Side Hearing loss: A Case-Control Study

OBJECTIVES

To evaluate the effects of an adhesive adapter prosthesis (AAP) on memory function in pediatric subjects with single side hearing loss (SSHL).

MATERIALS AND METHODS

Case-control study. 19 pediatric subjects with mild to moderate SSHL treated with AAP and 15 subjects with normal hearing (control group) were included in this study. Working and short-term memory functions were tested in all subjects, in silence and noise conditions. In SSHL subjects, tests were performed before the AAP was applied (T0) and at 1-month (T1) follow-up. The control group was tested once.

RESULTS

AAP significantly improved working memory function in noise as measured at T1 (p<0.01) compared with T0, but T1 scores in children with SSHL remained significantly different from the ones of the control group (p<0.01). AAP also significantly improved short- term memory function test scores at T1 compared with T0 (p<0.01), but despite being in the normal range for the subjects' age, the scores remained significantly different from those of the control group (p<0.01).

CONCLUSION

In pediatric subjects with mild, moderate, and moderate-severe SSHL, restoration of bilateral hearing through AAP improved short-term memory function and working memory function in noise, as measured at 1 month follow-up; however, AAP did not seem to lead to a full restoration of such functions as measured by a comparison with healthy controls. Further studies with longer follow-ups might help elucidate whether AAP can elicit further improvements in memory functions.

Cortical Neurophysiologic Correlates of Auditory Threshold in Adults and Children With Normal Hearing and Auditory Neuropathy Spectrum Disorder

Purpose Auditory threshold estimation using the auditory brainstem response or auditory steady state response is limited in some populations (e.g., individuals with auditory neuropathy spectrum disorder [ANSD] or those who have difficulty remaining still during testing and cannot tolerate general anesthetic). However, cortical auditory evoked potentials (CAEPs) can be recorded in many such patients and have been employed in threshold approximation. Thus, we studied CAEP estimates of auditory thresholds in participants with normal hearing, sensorineural hearing loss, and ANSD. Method We recorded CAEPs at varying intensity levels to speech (i.e., /ba/) and tones (i.e., 1 kHz) to estimate auditory thresholds in normal-hearing adults (n = 10) and children (n = 10) and case studies of children with sensorineural hearing loss and ANSD. Results Results showed a pattern of CAEP amplitude decrease and latency increase as stimulus intensities declined until waveform components disappeared near auditory threshold levels. Overall, CAEP thresholds were within 10 dB HL of behavioral thresholds for both stimuli. Conclusions The above findings suggest that CAEPs may be clinically useful in estimating auditory threshold in populations for whom such a method does not currently exist. Physiologic threshold estimation in difficult-to-test clinical populations could lead to earlier intervention and improved outcomes.

An integrative approach for pediatric auditory neuropathy spectrum disorders: revisiting etiologies and exploring the prognostic utility of auditory steady-state response

Auditory neuropathy is an important entity in childhood sensorineural hearing loss. Due to diverse etiologies and clinical features, the management is often challenging. This study used an integrative patient-history, audiologic, genetic, and imaging-based approach to investigate the etiologies and audiologic features of 101 children with auditory neuropathy. Etiologically, 48 (47.5%), 16 (15.8%), 11 (10.9%), and 26 (25.7%) children were categorized as having acquired, genetic, cochlear nerve deficiency-related, and indefinite auditory neuropathy, respectively. The most common causes of acquired and genetic auditory neuropathy were prematurity and OTOF mutations, respectively. Patients with acquired auditory neuropathy presented hearing loss earlier (odds ratio, 10.2; 95% confidence interval, 2.2–47.4), whereas patients with genetic auditory neuropathy had higher presence rate of distortion product otoacoustic emissions (odds ratio, 10.7; 95% confidence interval, 1.3–85.4). In patients with different etiologies or pathological sites, moderate to strong correlations (Pearson’s r = 0.51–0.83) were observed between behavioral thresholds and auditory steady-state response thresholds. In conclusion, comprehensive assessments can provide etiological clues in ~75% of the children with auditory neuropathy. Different etiologies are associated with different audiologic features, and auditory steady-state responses might serve as an objective measure for estimating behavioral thresholds.

Cochlear Implantation Outcomes in Patients With OTOF Mutations

Auditory neuropathy is a special type of hearing loss caused by dysfunction of the synapse of the inner hair cells, the auditory nerve, and/or the auditory nerve itself. For patients with auditory neuropathy who have severe to profound hearing loss or failed auditory skills development with hearing-aids, cochlear implantation (CI) serves as the only possible effective treatment. It is accepted that the exact sites of lesion causing auditory neuropathy determine the CI performance. Mutations in the OTOF gene were the first identified and the most common cause of congenital auditory neuropathy. The site of lesion in patients with auditory neuropathy caused by biallelic OTOF mutations (OTOF-related auditory neuropathy) is presumed to be presynaptic, leaving auditory nerve function intact. Thus, OTOF-related auditory neuropathy is expected to have good CI performances. In this review, we describe the CI outcomes in patients with OTOF mutations. We will focus on whether biallelic OTOF mutations are ideal indications for CI in patients with auditory neuropathy. Also, the factors that may still influence the CI outcomes in patients with OTOF mutations are discussed.

Music and psychoacoustic perception abilities in cochlear implant users with auditory neuropathy spectrum disorder

OBJECTIVE

Auditory neuropathy spectrum disorder (ANSD) is a condition wherein the pre-neural or cochlear outer hair cell activity is intact, but the neural activity in the auditory nerve is disrupted. Cochlear implant (CI) can be beneficial for subjects with ANSD; however, little is known about the music perception and psychoacoustic abilities of CI users with ANSD. Music perception in CI users is a multidimensional and complex ability requiring the contribution of both auditory and nonauditory abilities. Even though auditory abilities lay the foundation, the contribution of patient-related variables such as ANSD may affect the music perception. This study aimed to evaluate the psychoacoustic and music perception abilities of CI recipients with ANSD.

STUDY DESIGN

Twelve CI users with ANSD and twelve age- and gendermatched CI users with sensorineural hearing loss (SNHL) were evaluated. Music perception abilities were measured using the Turkish version of the Clinical Assessment of Music Perception (T-CAMP) test. Psychoacoustic abilities were measured using the spectral ripple discrimination (SRD) and temporal modulation transfer function (TMTF) tests. In addition, the age of diagnosis and implantation was recorded.

RESULTS

Pitch direction discrimination (PDD), timbre recognition, SRD, and TMTF performance of CI users with ANSD were concordant with those reported in previous studies, and differences between ANSD and SNHL groups were not statistically significant. However, the ANSD group performed poorly compared with SNHL group in melody recognition subtest of T-CAMP, and the difference was statistically significant.

CONCLUSION

CI can prove beneficial for patients with ANSD with respect to their music and psychoacoustic abilities, similar to patients with SNHL, except for melody recognition. Recognition of melodies requires both auditory and non-auditory abilities, and ANSD may have an extensive but subtle effect in the life of CI users.

Cochlear Implantation in a Case of Auditory Neuropathy Spectrum Disorder with CAPOS Syndrome

Auditory neuropathy spectrum disorder (ANSD) is a hearing disorder which characterized with normal outer hair cell function but disrupted neural synchrony in the afferent auditory pathway. CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) syndrome can manifest itself with ANSD and this rare situation and audiological rehabilitation outcomes have not well documented in the literature. We aim to present a cochlear implant user subject with CAPOS syndrome and ANSD. A 14-year-old girl diagnosed with ANSD and CAPOS syndrome. She received unilateral cochlear implant (CI). Her hearing sensitivity and speech perception abilities have been improved with CI. Also, she has a good music perception ability measured with the Turkish version of Clinical Assessment of Music Perception Test. After detailed audiological evaluations, CI could be a good option for patients who have ANSD and CAPOS syndrome.

Mutational and phenotypic spectrum of OTOF-related auditory neuropathy in Koreans: eliciting reciprocal interaction between bench and clinics

BACKGROUND

While auditory neuropathy spectrum disorder (ANSD) is a heterogeneous disorder and its management quite varies depending upon the etiology, even including self-resolution, OTOF is an important molecular etiology of prelingual ANSD and has emerged as an attractive target for implementation of precision medicine in terms of timing and prognosis prediction of auditory rehabilitation. However, to date, the literature is lacking in the genotype-phenotype relationship of this gene as well as efficient molecular testing strategy in the clinic in many populations and to make things more complicated in Koreans, the most prevalent variant p.Arg1939Gln among Korean ANSD children frequently evaded detection by next generation sequencing (NGS), resulting in delayed genetic diagnosis and late cochlear implantation (CI). The aims of this study are to document the mutational and phenotypic spectrum of OTOF-related ANSD (DFNB9) in the Korean population, further establishing genotype-phenotype correlation and proposing a set of the most commonly found OTOF variants to be screened first.

METHODS

Genetic diagnosis through the NGS-based sequencing was made on patients with ANSD in two tertiary hospitals. Genotype and phenotypes of eleven DFNB9 patients were reviewed. For data analysis, Mann-Whitney test and Fisher's exact test were applied.

RESULTS

This study disclosed four prevalent variants in Koreans: p.Arg1939Gln with an allele frequency of 40.9%, p.Glu841Lys (13.6%), p.Leu1011Pro and p.Arg1856Trp (9.1%). Three novel variants (c.4227 + 5G > C, p.Gly1845Glu, and p.Pro1931Thr) were identified. Interestingly, a significant association of p.Arg1939Gln with worse ASSR thresholds was observed despite consistently no ABR response. Ten of 11 DFNB9 patients received CI for auditory rehabilitation, showing favorable outcomes with more rapid improvement on early-CI group (age at CI ≤ 18 mo.) than late-CI group.

CONCLUSIONS

This study included the largest Korean DFNB9 cohort to date and proposed a set of the most frequent four OTOF variants, allowing the potential prioritization of exons during Sanger sequencing. Further, a significant association of p.Arg1939Gln homozygotes with poor residual hearing was observed. We may have to suspect p.Arg1939Gln homozygosity in cases of poor auditory thresholds in ANSD children with putative negative OTOF variants solely screened by NGS. Reciprocal feedback between bench and clinics regarding DFNB9 would complement each other.

Cortical Auditory Evoked Potentials in Children with Auditory Neuropathy/Dys-Synchrony

Auditory neuropathy/spectrum disorder (ANSD), also referred to as auditory neuropathy/dys-synchrony (AN/AD) is a recently described form of hearing impairment. Many studies have shown that changing the pattern of afferent input to the cortex significantly affects cortical organization and there is little studies about cortical neuromaturation and plasticity in children with ANSD. Study of P1 component of cortical auditory evoked potentials (CAEPs) in children with ANSD. This survey was descriptive cross-sectional. During that 97 hearing impairment children were under hearing screening tests. Of these, 14 selected subjects (ear = 28) diagnosed with ANSD (an average age of 8.5 years) and evaluated by P1 component of CAEPs. Based on latency results of p1 wave, the ears of the subjects fell into two seperate groups: Control (normal: n = 10) and case {total: n = 18 (delayed: n = 12) + (absent: n = 6)}. The averages of mean latency of P1 components of the case group in the right and the left ears compared to the control group had significant differences (p < 0.05). Abnormal latency of p1 component in ANSD children shows the possibility of different scales of disturbances in cortical auditory maturation and grow.

Outcome of Cochlear Implantation in Prelingually Deafened Children According to Molecular Genetic Etiology

OBJECTIVES

About 60% of Korean pediatric cochlear implantees could be genetically diagnosed (GD) and we previously reported that a substantial portion of undiagnosed cases by deafness gene panel sequencing were predicted to have a nongenetic or complex etiology. We aimed to compare the outcomes of cochlear implantation (CI) in GD and genetically undiagnosed (GUD) patients and attempted to determine CI outcomes according to etiology.

DESIGN

Ninety-three pediatric cochlear implantees underwent molecular genetic testing. Fifty-seven patients carried pathogenic variants and 36 patients remained GUD after panel sequencing of 204 known or potential deafness genes (TRS-204). Among them, 55 cochlear implantees with reliable speech evaluation results with a follow-up of longer than 24 months were recruited. Longitudinal changes in the audiologic performance were compared between the GD (n = 31) and GUD (n = 24) groups. The GD group was subdivided into cochlear implantee with SLC26A4 mutations (group 1) and cochlear implantee with other genetic etiology (group 2), and the GUD group was subdivided into groups 3 and 4, that is, patients with or without inner ear anomaly, respectively.

RESULTS

Group 1 related to SLC26A4 mutations had the highest categories of auditory perception scores among all groups pre- and postoperatively. Group 4 with inner ear anomaly had the lowest categories of auditory perception scores. At 24 months post-CI, the group 2 with another genetic etiology had significantly better outcomes than molecularly undiagnosed group 3, which had with the same condition as group 2 except that the candidate gene was not detected. This finding was recapitulated when we limited cases to those that underwent CI before 24 months of age to minimize age-related bias at implantation. Furthermore, on extending the follow-up to 36 months postoperatively, this tendency became more prominent. Additionally, our preliminary clinical data suggest a narrower sensitive window period for good CI outcomes for implantees with OTOF mutation rather than the GJB2 and other genes.

CONCLUSIONS

Current molecular genetic testing including deafness panel sequencing helps to predict the 2-year follow-up outcomes after CI in prelingually deafened children. GD cochlear implantees show better functional outcomes after CI than undiagnosed cochlear implantees as determined by deafness panel sequencing, suggesting a genotype-functional outcome correlation. The genetic testing may provide a customized optimal window period in terms of CI timing for favorable outcome according to genetic etiology.

Outcomes of Cochlear Implantation in Auditory Neuropathy Spectrum Disorder and the Role of Cortical Auditory Evoked Potentials in Benefit Evaluation

Objective

To compare the outcomes of cochlear implantation (CI) in children with auditory neuropathy spectrum disorder (ANSD) and age-matched controls with profound sensorineural hearing loss, using categories of auditory performance (CAP), speech intelligibility rate (SIR), meaningful auditory integration scale (MAIS), and meaningful use of speech scale (MUSS), and to determine the role of Cortical Auditory Evoked Potentials (CAEP) in benefit evaluation after CI.

Methods

Ten patients (8 males and two females) with ANSD who underwent CI were included in the study. Auditory and speech scores were compared between baseline and after 12 months of habilitation in children with ANSD. Post CI speech scores in children with ANSD were compared with the control group (age-matched children with profound sensorineural hearing loss) at 12 months of habilitation. P1 latency of CAEP has a good correlation with auditory and speech scores in children with ANSD in the study group.

Results

Significant benefits were seen in children with ANSD who underwent CI compared to the baseline CAP and SIR scores and one year after habilitation. There is no statistically significant difference in outcomes between the two groups with CI (ANSD and profound sensorineural hearing loss) (p-value: CAP=1.00, SIR=0.84, MAIS=0.33, MUSS=0.08). Speech perception in noise test (SPIN) scores in children with ANSD were 63% and 80% with 0 dB signal noise ratio (SNR) and +10dB SNR, respectively. P1 wave of CAEP has a good correlation with the subjective outcomes.

Conclusion

CI in children with ANSD has showed benefits comparable to children with profound sensorineural hearing loss. CAEP is a useful tool in objectively assessing cortical maturity in children with ANSD following CI.

Neural Correlates of Sensory Abnormalities Across Developmental Disabilities

Abnormalities in sensory processing are a common feature of many developmental disabilities (DDs). Sensory dysfunction can contribute to deficits in brain maturation, as well as many vital functions. Unfortunately, while some patients with DD benefit from the currently available treatments for sensory dysfunction, many do not. Deficiencies in clinical practice surrounding sensory dysfunction may be related to lack of understanding of the neural mechanisms that underlie sensory abnormalities. Evidence of overlap in sensory symptoms between diagnoses suggests that there may be common neural mechanisms that mediate many aspects of sensory dysfunction. Thus, the current manuscript aims to review the extant literature regarding the neural correlates of sensory dysfunction across DD in order to identify patterns of abnormality that span diagnostic categories. Such anomalies in brain structure, function, and connectivity may eventually serve as targets for treatment.

[Auditory evoked potentials in children with auditory neuropathy spectrum disorder]

The objective of the present study was to estimate peculiarities of the auditory brainstem evoked potentials (ABR), auditory steady-state responses (ASSR) and cortical auditory evoked potentials (CAEP) in the children presenting with bilateral auditory neuropathy spectrum disorder (ANSD). The study included 100 patients with bilateral ANSD diagnosed based on the positive response of otoacoustic emissions (OAEs) and/or cochlear microphonic (CM) detection, while no synchronous neural activity was detected in the ABR test. Cochlear microphonic was the main clue for the ANSD diagnosing, because OAE was absent in both ears of 49 children. ABR testing revealed no response bilaterally in 72 cases (out of 100). In contrast to ABR, the ASSR thresholds were detectable at all the four main frequencies in both ears in 73 % of the cases (47 out of the 64 tested ones). Both ABR and ASSR in most cases were incomparable with the behavioral audiometric thresholds. 28 children underwent CAEP testing. In 7 cases out of 8 with mild hearing loss detectable CAEP were recorded. CAEP registration in l7 children making use of the hearing aids and in 3 children after cochlear implantation revealed, in the majority of the cases, the concordance between CAEP detectability with behavioral thresholds and rehabilitation outcomes with fairly good speech intelligibility. It is concluded that the ABR registration with CM evaluation is the most informative test for ANSD diagnosis. However, ABR as well as ASSR is useless for the estimation of the behavioral thresholds. The results of this study suggest that the presence or absence of CAEPs can provide some indication of the audibility of a speech sound in the children with ANSD; however this method requires further investigation.

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.

AUNA2: A Novel Type of Non-Syndromic Slowly Progressive Auditory Synaptopathy/Auditory Neuropathy with Autosomal-Dominant Inheritance

BACKGROUND

Auditory synaptopathy/neuropathy (AS/AN) is a heterogeneous disorder, which may be caused by environmental factors like postnatal hyperbilirubinemia or by genetic factors. The genetic forms are subdivided into syndromic and non-syndromic types, and show different inheritance patterns with a strong preponderance of autosomal-recessive forms. To date, only a single locus for non-syndromic autosomal-dominant AS/AN (AUNA1) has been reported in a single family, in which a non-coding DIAPH3 mutation was subsequently described as causative.

MATERIALS AND METHODS

Here, we report detailed clinical data on a large German AS/AN family with slowly progressive postlingual hearing loss. Affected family members developed their first symptoms in their second decade. Moderate hearing loss in the fourth decade then progressed to profound hearing impairment in older family members. Comprehensive audiological and neurological tests were performed in the affected family members. Genetic testing comprised linkage analyses with polymorphic markers and a genome-wide linkage analysis using the Affymetrix GeneChip® Human Mapping 250K.

RESULTS AND CONCLUSION

We identified a large family with autosomal-dominant AS/AN. By means of linkage analyses, the AUNA1 locus was excluded, and putatively linked regions on chromosomal bands 12q24 and 13q34 were identified as likely carrying the second locus for autosomal-dominant AS/AN (AUNA2). AUNA2 is associated with a slowly progressive postlingual hearing loss without any evidence for additional symptoms in other organ systems.

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.

The P1 biomarker for assessing cortical maturation in pediatric hearing loss: a review

We review evidence for a high degree of neuroplasticity of the central auditory pathways in early childhood, citing evidence of studies of the P1 and N1 cortical auditory evoked potentials in congenitally deaf children receiving cochlear implants at different ages during childhood, children with auditory neuropathy spectrum disorder and children with hearing loss and comorbid multiple disabilities. We discuss neuroplasticity, including cortico-cortical de-coupling and cross-modal re-organization that occurs in deafness. We provide evidence for the clinical utility of the P1 cortical auditory evoked potential (CAEP) as a non-invasive biomarker that can be used to objectively assess maturation of auditory cortex in clinical cases of cochlear implant patients and candidates. Finally, we present clinical case studies in which the P1 CAEP biomarker proved useful in clinical decision-making regarding intervention in cases of single-sided deafness, auditory neuropathy spectrum disorder, mild hearing loss and hypoplastic auditory nerve.