Clinical characteristics and hearing loss etiology of cochlear implantees undergoing surgery in their teens, 20s, and 30s

PURPOSE

This study aimed to investigate the etiology of hearing loss, including genetic variants, in individuals who underwent cochlear implantation (CI) in their teens to thirties. It also sought to analyze post-CI speech performance and identify prognostic factors affecting CI outcomes in this age group.

METHODS

We conducted a retrospective review of 421 cochlear implant patients at Seoul National University Bundang Hospital, focusing on 63 subjects aged 10-39 years who underwent their first CI by a single surgeon between July 2018 and June 2022. The study included audiologic evaluation, molecular genetic testing, and analysis of speech performance post-CI. Statistical analyses were performed using SPSS 25 and GraphPad Prism 7.

RESULTS

Among 63 participants (M:F, 24:39), nine underwent CI in their teens, 24 in their 20 s, and 30 in their 30 s. Most of them (40, 63.5%) had postlingual deafness. The study found that 65.2% (40/63) of subjects received a genetic diagnosis, with DFNB4 being the most common etiology (37.5%, 15/40). Post-CI speech evaluation showed an average sentence score of 80% across all subjects. Factors such as the onset of hearing loss, duration of deafness (DoD), and preoperative Speech Intelligibility Rating (SIR) significantly influenced CI outcomes. Notably, longer DoD was associated with poorer CI outcomes, but this did not affect individuals with postlingual hearing loss as much.

CONCLUSION

The study concludes that in individuals aged 10-39 undergoing CI, the onset of hearing loss and preoperative SIR are critical predictors of postoperative outcomes. CI is recommended for those with postlingual hearing loss in this age group, irrespective of the DoD. The study highlights the importance of genetic factors especially DFNB4 in hearing loss etiology and underscores the value of the relatively easy-to-evaluate factor, preoperative SIR in predicting CI outcomes.

Low-Frequency Air-Bone Gap and Pulsatile Tinnitus Due to a Dural Arteriovenous Fistula: Considerations upon Possible Pathomechanisms and Literature Review

Low-frequency air-bone gap (ABG) associated with pulsatile tinnitus (PT) and normal impedance audiometry represents a common finding in patients with third window syndromes. Other inner disorders, including Meniere's disease (MD), perilymphatic fistula and intralabyrinthine schwannoma, might sometimes result in a similar scenario. On the other hand, PT is frequently associated with dural arteriovenous fistula (DAVF), while conductive hearing loss (CHL) is extremely rare in this clinical setting. A 47-year-old patient was referred to our center with progressive left-sided PT alongside ipsilateral fullness and hearing loss. She also experienced headache and dizziness. Otoscopy and video-oculographic examination were unremarkable. Conversely, a detailed instrumental audio-vestibular assessment revealed low-frequency CHL with normal impedance audiometry, slight left-sided caloric weakness, slightly impaired vestibular-evoked myogenic potentials on the left and normal results on the video-head impulse test, consistent with an MD-like instrumental profile. Gadolinium-enhanced brain MRI revealed an early enhancement of the left transverse sinus, consistent with a left DAVF between the left occipital artery and the transverse sinus, which was then confirmed by angiography. A trans-arterial embolization with Onyx glue was performed, resulting in a complete recession of the symptoms. Post-operatively, the low-frequency ABG disappeared, supporting the possible role of venous intracranial hypertension and abnormal pressure of inner ear fluids in the onset of symptoms and offering new insights into the pathomechanism of inner ear CHL.

A Large Vestibular Aqueduct With Conductive Hearing Loss as the Only Manifestation

Conductive hearing loss is a common clinical condition caused by disorders of the middle and external ear. Here, we report a case of conductive hearing loss with complete tympanic membranes. Clinical examinations revealed no external and middle ear lesions, but high-resolution temporal bone computed tomography revealed enlarged vestibular aqueducts. Detailed audiological tests and follow-up results indicate that the exclusive air-bone gap is the outcome of inner ear malformation but not middle ear lesions, preventing the need for tympanic assessment.

Insight into the Natural History of Pathogenic Variant c.919-2A>G in the SLC26A4 Gene Involved in Hearing Loss: The Evidence for Its Common Origin in Southern Siberia (Russia)

Pathogenic variants in the SLC26A4 gene leading to nonsyndromic recessive deafness (DFNB4), or Pendred syndrome, are some of the most common causes of hearing loss worldwide. Earlier, we found a high proportion of SLC26A4-related hearing loss with prevailing pathogenic variant c.919-2A>G (69.3% among all mutated SLC26A4 alleles that have been identified) in Tuvinian patients belonging to the indigenous Turkic-speaking Siberian people living in the Tyva Republic (Southern Siberia, Russia), which implies a founder effect in the accumulation of c.919-2A>G in Tuvinians. To evaluate a possible common origin of c.919-2A>G, we genotyped polymorphic STR and SNP markers, intragenic and flanking SLC26A4, in patients homozygous for c.919-2A>G and in healthy controls. The common STR and SNP haplotypes carrying c.919-2A>G were revealed, which convincingly indicates the origin of c.919-2A>G from a single ancestor, supporting a crucial role of the founder effect in the c.919-2A>G prevalence in Tuvinians. Comparison analysis with previously published data revealed the identity of the small SNP haplotype (~4.5 kb) in Tuvinian and Han Chinese carriers of c.919-2A>G, which suggests their common origin from founder chromosomes. We assume that c.919-2A>G could have originated in the geographically close territories of China or Tuva and subsequently spread to other regions of Asia. In addition, the time intervals of the c.919-2A>G occurrence in Tuvinians were roughly estimated.

The Genetic Background of Hearing Loss in Patients with EVA and Cochlear Malformation

The most frequently observed congenital inner ear malformation is enlarged vestibular aqueduct (EVA). It is often accompanied with incomplete partition type 2 (IP2) of the cochlea and a dilated vestibule, which together constitute Mondini malformation. Pathogenic SLC26A4 variants are considered the major cause of inner ear malformation but the genetics still needs clarification. The aim of this study was to identify the cause of EVA in patients with hearing loss (HL). Genomic DNA was isolated from HL patients with radiologically confirmed bilateral EVA (n = 23) and analyzed by next generation sequencing using a custom HL gene panel encompassing 237 HL-related genes or a clinical exome. The presence and segregation of selected variants and the CEVA haplotype (in the 5' region of SLC26A4) was verified by Sanger sequencing. Minigene assay was used to evaluate the impact of novel synonymous variant on splicing. Genetic testing identified the cause of EVA in 17/23 individuals (74%). Two pathogenic variants in the SLC26A4 gene were identified as the cause of EVA in 8 of them (35%), and a CEVA haplotype was regarded as the cause of EVA in 6 of 7 patients (86%) who carried only one SLC26A4 genetic variant. In two individuals with a phenotype matching branchio-oto-renal (BOR) spectrum disorder, cochlear hypoplasia resulted from EYA1 pathogenic variants. In one patient, a novel variant in CHD7 was detected. Our study shows that SLC26A4, together with the CEVA haplotype, accounts for more than half of EVA cases. Syndromic forms of HL should also be considered in patients with EVA. We conclude that to better understand inner ear development and the pathogenesis of its malformations, there is a need to look for pathogenic variants in noncoding regions of known HL genes or to link them with novel candidate HL genes.

Hearing loss patterns in enlarged vestibular aqueduct syndrome: Do fluctuations have clinical significance?

OBJECTIVES

To reveal hearing loss patterns in patients with enlarged vestibular aqueduct (EVA) syndrome according to demographic and clinical characteristics.

METHODS

A retrospective, longitudinal study design was utilized to identify patients with EVA. Ears of patients were categorized into one of four cohorts: progressive fluctuating, progressive non-fluctuating, stable fluctuating, and stable non-fluctuating patterns. Pairwise and group comparisons were performed with non-parametric tests to assess vestibular aqueduct (VA) morphology, clinical, and demographic variables between hearing loss pattern cohorts. Rates of hearing loss in the subgroups were determined utilizing a mixed linear effects model.

RESULTS

44 patients (25 female, 19 male, median diagnosis age: 8.06 years) met inclusion criteria. 16 individuals demonstrated unilateral EVA and 29 had bilateral EVA, resulting in 74 total ears with EVA. Amongst the four cohorts, differences in operculum widths amongst groups were statistically significant (p = 0.049) while VA midpoint widths were not (p = 0.522). Progressive hearing loss ears without fluctuations demonstrated a 3.20 dB per year (p < 0.001) progression while progressive hearing loss ears with fluctuations reported a rate of 3.52 dB loss per year (p < 0.001).

CONCLUSION

Hearing fluctuations occur similarly in EVA patients with stable and progressive hearing loss. With the exception of increased rates of hearing loss progression for fluctuating progressive hearing loss patients, vestibular aqueduct morphology, demographic, and clinical characteristics commonly reported are likely not strong predictors for whether patients will or will not experience fluctuating patterns of hearing loss.

Rapid Genetic Diagnosis for Okinawan Patients with Enlarged Vestibular Aqueduct Using Single-Stranded Tag Hybridization Chromatographic Printed-Array Strip

Both Pendred syndrome (PS) and nonsyndromic hearing loss with an enlarged vestibular aqueduct (EVA) are autosomal recessive disorders caused by SLC26A4 pathogenic variants. The spectrum of SLC26A4 pathogenic variants varies with the ethnic background. Among the patients with EVA in Okinawa, 94% had some combination of NM_000441.2(SLC26A4):c.1707+5G>A and NM_000441.2(SLC26A4):c.2168A>G(p.His723Arg), the two SLC26A4 pathogenic variants that are the most common in this population. We identified these two pathogenic variants using a novel genotyping method that employed an allele-specific polymerase chain reaction (PCR) from a gDNA and single-stranded tag hybridization chromatographic printed-array strip (STH-PAS) in DNA samples obtained from 48 samples in Okinawa, including 34 patients with EVA and 14 carriers of c.1707+5G>A or c.2168A>G. In addition, whole blood and saliva samples were used for analysis in this genotyping method with direct PCR. The results of STH-PAS genotyping were consistent with those obtained using standard Sanger sequencing for all samples. The accuracy of the STH-PAS method is 100% under the optimized conditions. STH-PAS genotyping provided a diagnosis in 30 out of 34 patients (88%) in Okinawan patients with EVA in under 3 h. The turn-around time for STH-PAS genotyping used with direct PCR was 2 h as a result of the omission of the DNA extraction and purification steps. Using information about the ethnic distribution of pathogenic variants in the SLC26A4 gene, STH-PAS genotyping performs a rapid genetic diagnosis that is simple and has a considerably improved efficiency.

Different Rates of the SLC26A4-Related Hearing Loss in Two Indigenous Peoples of Southern Siberia (Russia)

Hereditary hearing loss (HL) is known to be highly locus/allelic heterogeneous, and the prevalence of different HL forms significantly varies among populations worldwide. Investigation of region-specific landscapes of hereditary HL is important for local healthcare and medical genetic services. Mutations in the SLC26A4 gene leading to nonsyndromic recessive deafness (DFNB4) and Pendred syndrome are common genetic causes of hereditary HL, at least in some Asian populations. We present for the first time the results of a thorough analysis of the SLC26A4 gene by Sanger sequencing in the large cohorts of patients with HL of unknown etiology belonging to two neighboring indigenous Turkic-speaking Siberian peoples (Tuvinians and Altaians). A definite genetic diagnosis based on the presence of biallelic SLC26A4 mutations was established for 28.2% (62/220) of all enrolled Tuvinian patients vs. 4.3% (4/93) of Altaian patients. The rate of the SLC26A4-related HL in Tuvinian patients appeared to be one of the highest among populations worldwide. The SLC26A4 mutational spectrum was characterized by the presence of Asian-specific mutations c.919-2A>G and c.2027T>A (p.Leu676Gln), predominantly found in Tuvinian patients, and c.2168A>G (p.His723Arg), which was only detected in Altaian patients. In addition, a novel pathogenic variant c.1545T>G (p.Phe515Leu) was found with high frequency in Tuvinian patients. Overall, based on the findings of this study and our previous research, we were able to uncover the genetic causes of HL in 50.5% of Tuvinian patients and 34.5% of Altaian patients.

Predictive Modeling and Risk Stratification of Patients With Enlarged Vestibular Aqueduct

OBJECTIVES/HYPOTHESIS

To investigate patient-specific characteristics that independently predict for progressive hearing loss in patients with enlarged vestibular aqueduct (EVA). Utilize multivariable predictive models to identify subgroups of patients with significantly different progression risks.

STUDY DESIGN

Retrospective analysis of patients evaluated at an academic tertiary care center. Cohort included 74 ears of patients with a diagnosis of EVA as defined by the Cincinnati criteria.

METHODS

Hearing trajectories were characterized, and a Kaplan-Meier estimator was utilized to determine progressive phenotype probabilities across the first 10 years after diagnosis. Cox proportional hazard regression was used to identify patient characteristics that independently altered this probability. Stratified risk groups were delineated from generated nomogram scores.

RESULTS

Male gender was associated with a 4.53 hazard ratio for progressive hearing loss (95% confidence interval [CI], 2.53 to 12.59). Each millimeter increase in operculum size was independently associated with an 80.40% increase in expected hazard (95% CI, 40.18 to 120.62). Each dB increase in air pure tone average at time of diagnosis decreased expected hazard by 1.59% (95% CI, -3.02 to -0.17). The presence of incomplete partition type II was associated with a 2.44 hazard ratio (95% CI, 1.04 to 5.72). Risk groups stratified by median nomogram score evidenced the discriminative ability of our model with the progression probability in the high-risk group being six times higher at 1 year, nearly five times greater at 3 years, and three times greater at 9 years.

CONCLUSIONS

EVA patient characteristics can be used to predict hearing loss probability with a high degree of accuracy (C-index of 0.79). This can help clinicians make more proactive management decisions by identifying patients at high risk for hearing loss.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Genetics of Inner Ear Malformations: A Review

Inner ear malformations are present in 20% of patients with sensorineural hearing loss. Although the first descriptions date to the 18th century, in recent years the knowledge about these conditions has experienced terrific improvement. Currently, most of these conditions have a rehabilitative option. Much less is known about the etiology of these anomalies. In particular, the evolution of genetics has provided new data about the possible relationship between inner ear malformations and genetic anomalies. In addition, in syndromic condition, the well-known presence of sensorineural hearing loss can now be attributed to the presence of an inner ear anomaly. In some cases, the presence of these abnormalities should be considered as a characteristic feature of the syndrome. The present paper aims to summarize the available knowledge about the possible relationships between inner ear malformations and genetic mutations.

Genetic Determinants of Non-Syndromic Enlarged Vestibular Aqueduct: A Review

Hearing loss is the most common sensorial deficit in humans and one of the most common birth defects. In developed countries, at least 60% of cases of hearing loss are of genetic origin and may arise from pathogenic sequence alterations in one of more than 300 genes known to be involved in the hearing function. Hearing loss of genetic origin is frequently associated with inner ear malformations; of these, the most commonly detected is the enlarged vestibular aqueduct (EVA). EVA may be associated to other cochleovestibular malformations, such as cochlear incomplete partitions, and can be found in syndromic as well as non-syndromic forms of hearing loss. Genes that have been linked to non-syndromic EVA are SLC26A4, GJB2, FOXI1, KCNJ10, and POU3F4. SLC26A4 and FOXI1 are also involved in determining syndromic forms of hearing loss with EVA, which are Pendred syndrome and distal renal tubular acidosis with deafness, respectively. In Caucasian cohorts, approximately 50% of cases of non-syndromic EVA are linked to SLC26A4 and a large fraction of patients remain undiagnosed, thus providing a strong imperative to further explore the etiology of this condition.

Exploring the missing heritability in subjects with hearing loss, enlarged vestibular aqueducts, and a single or no pathogenic SLC26A4 variant

Pathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype–phenotype correlation, a significant part of cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, we first determined the presence of the previously described EVA-associated haplotype (Caucasian EVA (CEVA)), characterized by 12 single nucleotide variants located upstream of SLC26A4. We found this haplotype and a delimited V1-CEVA haplotype to be significantly enriched in our M1 patient cohort (10/16 cases). The CEVA haplotype was also present in two M0 cases (2/12). Short- and long-read whole genome sequencing and optical genome mapping could not prioritize any of the variants present within the CEVA haplotype as the likely pathogenic defect. Short-read whole-genome sequencing of the six M1 cases without this haplotype and the two M0/CEVA cases only revealed previously overlooked or misinterpreted splice-altering SLC26A4 variants in two cases, who are now genetically explained. No deep-intronic or structural variants were identified in any of the M1 subjects. With this study, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases. For pinpointing the pathogenic effect of the CEVA haplotype, additional analyses are required addressing defect(s) at the RNA, protein, or epigenetic level.

Genetic architecture and phenotypic landscape of SLC26A4-related hearing loss

Mutations of coding regions and splice sites of SLC26A4 cause Pendred syndrome and nonsyndromic recessive hearing loss DFNB4. SLC26A4 encodes pendrin, a transmembrane exchanger of anions and bases. The mutant SLC26A4 phenotype is characterized by inner ear malformations, including an enlarged vestibular aqueduct (EVA), incomplete cochlear partition type II and modiolar hypoplasia, progressive and fluctuating hearing loss, and vestibular dysfunction. A thyroid iodine organification defect can lead to multinodular goiter and distinguishes Pendred syndrome from DFNB4. Pendred syndrome and DFNB4 are each inherited as an autosomal recessive trait caused by biallelic mutations of SLC26A4 (M2). However, there are some EVA patients with only one detectable mutant allele (M1) of SLC26A4. In most European-Caucasian M1 patients, there is a haplotype that consists of 12 variants upstream of SLC26A4, called CEVA (Caucasian EVA), which acts as a pathogenic recessive allele in trans to mutations affecting the coding regions or splice sites of SLC26A4. This combination of an M1 genotype with the CEVA haplotype is associated with a less severe phenotype than the M2 genotype. The phenotype in EVA patients with no mutant alleles of SLC26A4 (M0) has a very low recurrence probability and is likely to be caused by other factors.

Toward the Pathogenicity of the SLC26A4 p.C565Y Variant Using a Genetically Driven Mouse Model

Recessive variants of the SLC26A4 gene are globally a common cause of hearing impairment. In the past, cell lines and transgenic mice were widely used to investigate the pathogenicity associated with SLC26A4 variants. However, discrepancies in pathogenicity between humans and cell lines or transgenic mice were documented for some SLC26A4 variants. For instance, the p.C565Y variant, which was reported to be pathogenic in humans, did not exhibit functional pathogenic consequences in cell lines. To address the pathogenicity of p.C565Y, we used a genotype-based approach in which we generated knock-in mice that were heterozygous (Slc26a4+/C565Y), homozygous (Slc26a4C565Y/C565Y), and compound heterozygous (Slc26a4919-2A>G/C565Y) for this variant. Subsequent phenotypic characterization revealed that mice with these genotypes demonstrated normal auditory and vestibular functions, and normal inner-ear morphology and pendrin expression. These findings indicate that the p.C565Y variant is nonpathogenic for mice, and that a single p.C565Y allele is sufficient to maintain normal inner-ear physiology in mice. Our results highlight the differences in pathogenicity associated with certain SLC26A4 variants between transgenic mice and humans, which should be considered when interpreting the results of animal studies for SLC26A4-related deafness.

Natural Course of Residual Hearing with Reference to GJB2 and SLC26A4 Genotypes: Clinical Implications for Hearing Rehabilitation

BACKGROUND

Understanding the characteristics of residual hearing at low frequencies and its natural course in relation to molecular genetic etiology may be important in developing rehabilitation strategies. Thus, we aimed to explore the characteristics and natural course of residual hearing at low frequencies associated with the two most frequent deafness genes: GJB2 and SLC26A4.

METHODS

Initially, 53 GJB2 and 65 SLC26A4 subjects were enrolled, respectively. Only those whose audiograms exhibited hearing thresholds ≤70 dB at 250 and 500 Hz, and who had at least 1-year follow-up period between the first and last audiograms, were included. Collectively, the clinical characteristics of 14 ears from eight subjects with GJB2 variants, and 31 ears from 22 subjects with SLC26A4 variants fulfilled the strict criteria. In this study, a dropout rate refers to an incidence of dropping out of the cohort by cochlear implant surgery due to severe hearing deterioration.

RESULTS

Among the ears with complete serial audiogram data set, significant residual hearing at low frequencies at the time of inclusion was observed in 18.8% of those with GJB2 variants (15 out of 80 ears) and 42.6% of those with SLC26A4 variants (46 out of 108 ears), revealing a difference between two deafness genes. Subsequently, ears with SLC26A4 variants (11 of 46 ears, 23.9%) turned out to have a higher dropout rate for cochlear implantation due to hearing deterioration within the first year than those with GJB2 variants (1 of 15, 6.7%), albeit with no statistical significance. Throughout the follow-up period (mean: 37.2 ± 6.8, range: 12 to 80 months), deterioration of residual hearing at low frequencies at 250 Hz (dB HL/y) and 500 Hz (dB HL/y) of those with GJB2 variants exhibited 3.1 ± 1.3 (range: 0 to 15) and 5.2 ± 1.6 (range: 0 to 20), respectively, suggesting the deterioration of residual hearing in GJB2 variants was rather slow and gradual. Specifically, GJB2 p.Leu79Cysfs*3 show less remarkable residual hearing at low frequencies, but then a relatively stable nature. In contrast, SLC26A4 variants demonstrated a significantly higher dropout rate due to severe hearing deterioration requiring cochlear implantation compared with the GJB2 variants. This trend was observed not only in the first-year follow-up period but also in the follow-up periods thereafter. The p.His723Arg;c.919-2A>G genotype of SLC26A4, in particular, was associated with a high propensity for sudden hearing deterioration, as indicated by the dropout rate, which was as high as 46.2% for cochlear implantation due to hearing deterioration during the first year follow-up period. Furthermore, the dropout rate for cochlear implantation was observed in 7.1% of those with GJB2 variants (one out of 14 ears) and 30.3% of those with SLC26A4 variants (10 out of 33 ears) throughout the entire follow-up period.

CONCLUSIONS

Our results suggest that there is a difference with respect to the progressive nature of residual hearing at low frequencies between the two most common genes responsible for hearing loss, which may provide clinical implications of having individualized rehabilitation and timely intervention.

Hearing Loss in Enlarged Vestibular Aqueduct: A Prognostic Factor Systematic Review of the Literature

OBJECTIVE

There is a need to highlight individual prognostic factors determining hearing loss in enlarged (wide) vestibular aqueduct, as currently clinicians cannot counsel parents about the expected clinical course, nor provide individualized hearing rehabilitation plans following identification at newborn screening. We apply a novel methodology to specifically outline and assess the accuracy of prognostic factors reporting for hearing loss in enlarged vestibular aqueduct.

DATA SOURCES

A preferred reporting items for systematic reviews and meta-analyses compliant systematic review (Prospero ID: CRD42019151199), with searches applied to Medline, EMBASE, and Cochrane. Studies with longitudinal design were included between 1995 and 2019.

STUDY SELECTION

The CHARMS-PF tool was used to assess robustness of prognostic factor study designs.

DATA EXTRACTION

The QUIPS tool was used to assess for individual study risk of bias.

DATA SYNTHESIS & RESULTS

Seventy papers were suitable for data extraction. In the six studies with low risk of bias, the domains of enlarged vestibular aqueduct (EVA) morphology, age, hearing thresholds, sex, head trauma, and genotype provided exploratory prognostic factors for hearing loss associated with enlarged vestibular aqueduct. Overall, study heterogeneity and risk of bias precluded reporting by forest plots and meta-analysis.

CONCLUSIONS

The majority of exploratory prognostic factor studies for hearing loss associated with enlarged vestibular aqueduct are hampered by risk of bias. However, this systematic review identifies potential independent prognostic factors which should be measured, and adjusted for, in subsequent confirmatory studies utilizing multivariate analysis. This would determine the true independent prognostic effects associated with hearing loss in enlarged vestibular aqueduct, while facilitating prognostic model development and the ability to predict individual hearing loss trajectory.

Effect of Cochlear Implantation on Hearing Fluctuation in Patients with Biallelic SLC26A4 Variants

INTRODUCTION

Fluctuating hearing loss is a distinctive feature caused by SLC26A4 variants. We investigated whether cochlear implantation had protective or deleterious effect on hearing fluctuation in patients with biallelic SLC26A4 variants.

METHODS

Patients with biallelic SLC26A4 variants (N = 16; age = 10.24 ± 9.20 years) who had unilateral cochlear implantation and consecutive postsurgical, bilateral pure-tone audiograms more than 3 times were selected. We retrospectively reviewed the patients' medical records from 2008 to 2019 obtained from a tertiary medical center and used the auditory threshold change (Shift) over time as a marker of hearing fluctuation. Fluctuation events were counted, and the Shift of the implanted and contralateral ears was compared using logistic regression with a generalized estimating equation and linear mixed model. A total of 178 values were included.

RESULTS

The odds of fluctuating hearing frequency were 11.185-fold higher in the unimplanted ears than in the implanted ears postoperatively (p = 0.001). The extent of fluctuation at 250 and 500 Hz was also significantly lower in the implanted ears than in the unimplanted ears after adjusting for every other effect (p = 0.003 and p < 0.001, respectively). Notably, higher residual hearing was rather associated with lesser fluctuation in frequency and the extent of fluctuation at 500 Hz, indicating residual hearing function is not the positive predictor for hearing fluctuation.

CONCLUSION

In patients with biallelic SLC26A4 variants, cochlear implantation may reduce the frequency and extent of hearing fluctuations.

Bimodal strategy for excellent audiological rehabilitation in a subject with a novel nonsense mutation of the SLC26A4 gene: A case report

Sensorineural hearing loss is a heterogeneous disease caused by mutations in many genes. However, in the presence of enlarged vestibular aqueduct, it is frequently associated with mutations in the solute carrier family 26 member 4 (SLC26A4), a gene causative of a syndromic form (Pendred) as well as a non-syndromic form of hearing loss (DFNB4). We describe a clinical case presenting bilateral sensorineural hearing loss and enlarged vestibular aqueduct in which a novel homozygous SLC26A4 mutation was identified. Despite a late diagnosis of hearing loss, a peculiar rehabilitation therapy strategy was identified that provided excellent results.

Inner-Ear Disorders Presenting with Air-Bone Gaps: A Review

Air-bone gaps (ABGs) are commonly found in patients with conductive or mixed hearing loss generally due to outer- and/or middle-ear diseases such as otitis externa, tympanic membrane perforation, interruption or fixation of the ossicular chain, and chronic suppurative otitis media. ABGs can also be found in correlation with inner-ear disorders, such as endolymphatic hydrops, enlarged vestibular aqueduct syndrome, semicircular canal dehiscence, gusher syndrome, cochlear dehiscence, and Paget disease's as well cerebral vascular anomalies including dural arteriovenous fistula. The typical clinical presentation of inner-ear conditions or cerebral vascular anomalies causing ABGs includes audiological and vestibular symptoms like vertigo, oscillopsia, dizziness, imbalance, spinning sensation, pulsatile or continuous tinnitus, hyperacusis, autophony, auricular fullness, Tullio's phenomenon, and Hennebert's sign. Establishing a definitive diagnosis of the underlying condition in patients presenting with an ABG is often challenging to do and, in many patients, the condition may remain undefined. Results from an accurate clinical, audiological, and vestibular evaluation can be suggestive for the underlying condition; however, radiological assessment by computed tomography and/or magnetic resonance imaging is mandatory to confirm any diagnostic suspicion. In this review, we describe and discuss the most recent updates available regarding the clinical presentation and diagnostic workup of inner-ear conditions that may present together with ABGs.

The Natural History of Hearing Loss in Pendred Syndrome and Non-Syndromic Enlarged Vestibular Aqueduct

INTRODUCTION

The aim was to investigate the progress of hearing loss over time in a cohort of pendred syndrome and non-syndromic enlarged vestibular aqueduct (PS/NSEVA) with one or two confirmed pathogenic variations in SLC26A4.

STUDY DESIGN

Retrospective cohort study.

SUBJECTS AND METHODS

At our tertiary referral center, a retrospective search of all patients with enlarged vestibular aqueduct, hearing loss and SLC26A4 mutations yielded 103 individuals by March 2017, 96 of whom had records of hearing levels; both an early audiometry and the latest between 3 and 668 months follow-up. Pure-tone average (PTA; average of thresholds at 0.5, 1, 2 and 4 kHz) was calculated for both ears at time 1 and time 2. Neonatal screening results were retrieved.

RESULTS

Eighty-seven (87) individuals had biallelic (M2) and 16 had monoallelic alterations (M1) in their SLC26A4. On average, the PTA progressed to 80 dB HL by the age of 6 years for the entire cohort, and 3.2 years for the biallelic (M2) affected individuals. 25% of the cohort was screened in the neonatal screening program; of these 42% had "passed" at least monaurally. Audiometric profiles related to age show faster deterioration in high frequencies than in low frequencies.

CONCLUSION

In patients with PS/NSEVA and SLC26A4 mutations, the average hearing loss progresses to 80 dB HL by the age of 6 years. For biallelic (M2) affected individuals it was 3.2 years. Although hearing levels reached severe to profound during childhood, almost 1/2 had passed neonatal hearing screening, at least monaurally, emphasizing the need for close follow-up.

Mutation analysis of the SLC26A4 gene in three Chinese families

In order to investigate the genetic causes of hearing loss in a Chinese proband (in Family A) with enlarged vestibular aqueduct (EVA) and to investigate the genotype of two Chinese probands with SLC26A4 singe-allelic mutation and normal hearing (in Families B and C, respectively), the three probands and their parents were clinically and genetically evaluated. Twenty exons and flanking splice sites of the SLC26A4 gene were screened for pathogenic mutations via amplification with PCR and bidirectional sequencing. As controls, a group of 400 healthy newborns from the same ethnic background underwent SLC26A4 gene screening using the same method. The three probands all harbored two mutations in the SLC26A4 gene in the form of compound heterozygosity. The genotypes of mutations in Families A, B, and C are c.1211C>A/c.919-2A>G, c.1729G>A/c.919-2A>G, and c.1286C>A/c.919-2A>G, respectively. The missense mutations c.1211C>A (p.T430Q) in exon 10 and c.1729G>A (p.V577I) in exon 16 are both reported for the first time and were absent in 400 healthy newborns. c.1211C>A has Glutamine (Gln) at amino acid 430 instead of Threonine (Thr), and c.1729G>A has Isoleucine (Ile) at amino acid 577 instead of Valine (Val). c.1286C>A, a mutation previously reported in DVD and HGMD, was associated with Mondini deformity, but a proband with the c.1286C>A mutation in this study was normal. This study has demonstrated that the novel missense mutation c.1211C>A in compound heterozygosity with c.919-2A>G in the SLC26A4 gene is likely to be the cause of deafness in Family A. A novel variant, c.1729G>A, was identified and is likely benign. The pathogenicity of the c.1286C>A mutation warrants more in-depth study. These findings will broaden the spectrum of known SLC26A4 mutations in the Chinese population, providing more information for genetic counseling and diagnosis of hearing loss with EVA.

Association of SLC26A4 mutations, morphology, and hearing in pendred syndrome and NSEVA

OBJECTIVE

To investigate the relations of monoallelic (M1), biallelic (M2), or the absence of mutations (M0) in SLC26A4 to inner ear morphology and hearing levels in individuals with Pendred syndrome (PS) or nonsyndromic enlarged vestibular aqueduct (NSEVA) associated with hearing loss.

METHODS

In a cohort of 139 PS/NSEVA individuals, 115 persons from 95 unrelated families had full genetic sequencing of SLC26A4, and 113 had retrievable images for re-assessment of inner ear morphology. The association between the number of mutant alleles in SLC26A4, inner ear morphology (including endolymphatic sac size and protein content on magnetic resonance imaging), and hearing level (pure tone average) was explored.

RESULTS

Biallelic SLC26A4 mutations (M2) occurred in three-quarters of the cohort and was invariably associated with poor hearing; in 87%, it was associated with incomplete partition type II of the cochlea as well as enlarged endolymphatic sac and vestibular aqueduct. M1 or M0 individuals exhibited a greater variability in inner ear morphology. Endolymphatic sac size and presence of "high-protein" sac contents were significantly higher in M2 individuals compared to M1 and M0 individuals.

CONCLUSION

The number of SLC26A4 mutations is associated with severity and variability of inner ear morphology and hearing level in individuals with PS or NSEVA. M2 individuals have poorer hearing and present largely incomplete partition type II of the cochleas with enlarged endolymphatic sacs, whereas individuals with M1 and no detectable SLC26A4 mutations have less severe hearing loss and more diverse inner ear morphology.

LEVEL OF EVIDENCE

4. Laryngoscope, 129:2574-2579, 2019.

Analysis of mutations in the FOXI1 and KCNJ10 genes in infants with a single-allele SLC26A4 mutation

The current study investigated how the FOXI1 and KCNJ10 genes were affected in infants with a single-allele mutation in the SLC26A4 gene, and it determined the audiological phenotypes of infants with double heterozygous mutations (DHMs) in the three genes. Subjects were 562 infants with a single-allele SLC26A4 mutation detected during neonatal deafness genetic screening; the infants were seen as outpatients by Otology at Beijing Tongren Hospital. All subjects underwent SLC26A4 sequencing. Twenty infants had a second-allele variant while the remaining 542 had an SLC26A4 single-allele mutation. Infants also underwent FOXI1 and KCNJ10 sequencing. All patients with double heterozygous mutations in the aforementioned genes underwent an audiological evaluation and a limited imaging study; variants and audiological phenotypes were analyzed. Of 562 patients, 20 had SLC26A4 bi-allelic mutations; 8 carried single mutations in both SLC26A4 and KCNJ10. No pathogenic mutations in the FOXI1 gene were found. Four missense mutations in KCNJ10 were detected, including c.812G>A, c.800A>G, c.53G>A, and c.1042C>T. Eight individuals with a DHMs all passed universal newborn hearing screening, and all were found to have normal hearing. These data suggest that individuals with an SLC26A4 single-allele mutation, combined with FOXI1 or KCNJ10 gene mutations, do not suffer hearing loss during infancy, though this finding is worthy of further follow-up and in-depth discussion.

SLC26A4-linked CEVA haplotype correlates with phenotype in patients with enlargement of the vestibular aqueduct

Background

Recessive mutations of coding regions and splice sites of the SLC26A4 gene cause hearing loss with enlargement of the vestibular aqueduct (EVA). Some patients also have a thyroid iodination defect that can lead to multinodular goiter as part of Pendred syndrome. A haplotype of variants upstream of SLC26A4, called CEVA, acts as a pathogenic recessive allele in trans to mutations affecting the coding regions or splice sites of SLC26A4. Our first hypothesis is that CEVA, acting as a pathogenic recessive allele, is correlated with a less severe phenotype than mutations affecting the coding regions and splice sites of SLC26A4. Our second hypothesis is that CEVA acts as a modifier of the phenotype in patients with EVA caused by mutations affecting the coding regions or splice sites of both alleles of SLC26A4 or EVA caused by other factors.

Methods

This was a prospective cohort study of 114 individuals and 202 ears with EVA. To test our first hypothesis, we compared the thyroid and auditory phenotypes of subjects with mutations affecting coding regions of both alleles of SLC26A4 with those of subjects carrying CEVA in trans to mutations affecting the coding regions. To test our second hypothesis, we compared the phenotypes associated with the presence versus absence of CEVA among subjects with no coding region mutations, as well as among subjects with mutations affecting coding regions of both alleles.

Results

Subjects carrying CEVA in trans to a mutation of SLC26A4 have a normal thyroid phenotype and less severe hearing loss in comparison to individuals with mutations affecting coding regions of both alleles of SLC26A4. In subjects with no mutant alleles of SLC26A4, hearing loss was more severe in subjects who carry the CEVA haplotype in comparison to non-carriers. There was no correlation of CEVA with the phenotype of subjects with mutations affecting coding regions of both alleles.

Conclusions

CEVA, acting as a likely pathogenic recessive allele, is associated with a less severe phenotype than alleles with a mutation affecting the coding regions or splice sites of SLC26A4. CEVA may act as a genetic modifier in patients with EVA caused by other factors.

Hearing loss in unilateral and bilateral enlarged vestibular aqueduct syndrome

OBJECTIVE

To investigate any meaningful differences in hearing between patients with unilateral and bilateral enlarged vestibular aqueduct (EVA). EVA is a common radiological finding in children presenting with hearing loss. We hope to provide insight into the pathogenesis of EVA and provide further guidelines for unilateral EVA management. We hypothesized that hearing loss in unilateral EVA would be similar to that seen in bilateral EVA.

METHODS

A longitudinal retrospective study design was used. Three measures of hearing, pure tone average (PTA) word recognition score (WRS) and speech awareness threshold (SAT) and radiologic morphologies were tested for difference across unilateral versus bilateral ear EVA status. Linear mixed effects models were used to identify differences while accounting for time and multiple measurements per ear.

RESULTS

Using Cincinnati criteria, 89 ears fit inclusion criteria, 75 of which were from patients with bilateral EVA compared to 14 ears from patients with unilateral EVA. No significant differences across bilateral status were observed in audiological measurements. Models showed that speech recognition threshold (SRT) (p = 0.925), word recognition score (WRS)(p = 0.521) and pure tone average (PTA) of air and bone conduction from 250 to 4000 Hz (p = 0.281-0.933) were not statistically different with respect to bilateral status. Wilcoxon rank-sum tests showed no statistical difference in vestibular aqueduct width or operculum size (VA)(p = 0.234, p = 0.623). Each year after the first audiogram was associated with significantly greater SRT (p = 0.003) decreased WRS (0.014) and increased PTA (0.003.). Greater midpoint width was associated with significantly lower SRT (p = 0.004) WRS (<0.001) and PTA (<0.001.) CONCLUSION: Our results indicate no statistically significant difference in hearing ability with respect to bilateral EVA status, suggesting that unilateral EVA patients require close follow-up. Our results also demonstrate the progressive nature of EVA and a relationship between VA midpoint width and hearing loss severity.

Genotyping and audiological characteristics of infants with a single-allele SLC26A4 mutation

OBJECTIVES

To identify second-allele variant in infants with a known single-allele mutation of the SLC26A4 gene and to determine the frequency of their occurrence; and to investigate the clinical audiological characteristics of infants with bi-allelic mutations in SLC26A4.

METHODS

The study subjects were 371 patients with a single-allele SLC26A4 mutation detected by neonatal deafness gene screening (4 genes and 9 pathogenic variants) who were treated at the otology outpatient department of Beijing Tongren Hospital. The exonic and flanking splice site regions of the SLC26A4 gene were sequenced for all patients. All patients with bi-allelic SLC26A4 mutations underwent audiological evaluation, and some also underwent temporal bone computed tomography and/or inner ear magnetic resonance imaging.

RESULTS

Of the 371 patients, 314 (84.64%) had an c.919-2A > G heterozygous mutation and 57 (15.36%) had a c.2168A > G (p.H723R) heterozygous mutation. 13 patients (3.50%) had a second-allele variant, including 11 (2.96%) with pathogenic mutations and 1 (0.27%) with a likely benign variant. Of the 13 patients with bi-allelic mutations, 11 had hearing loss and 2 had normal hearing, the latter of whom had c.919-2A > G/c.1766A > G and c.919-2A > G/c.757A > G compound heterozygous mutations, respectively. Four of the 13 patients with bi-allelic mutations had passed the universal newborn hearing screening, including 2 cases (15.38%) with hearing loss. The most prevalent degree of hearing loss was profound (40.91%), followed by severe (36.36%). The most prevalent audiometric configuration was sloping hearing loss (50.00%), followed by flat-type hearing loss (40.91%).

CONCLUSIONS

This is the first report in China of the frequency of occurrence of second-allele variant in infants with a known single-allele mutation of the SLC26A4 gene; the frequency was 3.50% for any type of variant and 2.96% for pathogenic mutations. A novel variant, c.1766A > G (p.Q589R), which is likely benign, was identified. The pathogenicity of c.757A > G (p.I253V) mutation deserves more in-depth research. For infants with bi-allelic SLC26A4 mutations, the degree of hearing loss was mainly severe-to-profound and the audiometric configuration was mainly sloping.

Genetic mutations in non-syndromic deafness patients in Hainan Province have a different mutational spectrum compared to patients from Mainland China

OBJECTIVES

To provide appropriate genetic testing and counseling for non-syndromic hearing impairment patients in Hainan Province, an island in the South China Sea.

METHODS

299 unrelated students with non-syndromic hearing loss who attended a special education school in Hainan Province were enrolled in this study. Three prominent deafness-related genes (GJB2, SLC26A4, and mtDNA 12S rRNA) were analyzed using Sanger sequencing.

RESULTS

GJB2 mutations were detected in 32.78% (98/299) of the entire cohort; however, only 5.69% (17/299) had two confirmed pathogenic mutations. The most common mutation observed in this population was c.109G > A in the GJB2 gene, with an allelic frequency of 15.05% (90/598), which is significantly higher than that reported in previous cohorts. A total of 16 patients had two confirmed pathogenic SLC26A4 gene mutations, and 16 patients had one. The IVS7-2A > G mutation was the most commonly observed, with an allelic frequency of 3.51% (21/598). Three patients had a m.1555A > G mutation in the mtDNA 12S rRNA gene.

CONCLUSIONS

These results reveal that genetic etiology occurred in 11.71% (35/299) of patients, suggesting that Hainan province have a different mutational spectrum compare to Mainland China in non-syndromic deafness patients, which provide useful information to genetic counseling in Hainan province.

Functional Testing of SLC26A4 Variants-Clinical and Molecular Analysis of a Cohort with Enlarged Vestibular Aqueduct from Austria

The prevalence and spectrum of sequence alterations in the SLC26A4 gene, which codes for the anion exchanger pendrin, are population-specific and account for at least 50% of cases of non-syndromic hearing loss associated with an enlarged vestibular aqueduct. A cohort of nineteen patients from Austria with hearing loss and a radiological alteration of the vestibular aqueduct underwent Sanger sequencing of SLC26A4 and GJB2, coding for connexin 26. The pathogenicity of sequence alterations detected was assessed by determining ion transport and molecular features of the corresponding SLC26A4 protein variants. In this group, four uncharacterized sequence alterations within the SLC26A4 coding region were found. Three of these lead to protein variants with abnormal functional and molecular features, while one should be considered with no pathogenic potential. Pathogenic SLC26A4 sequence alterations were only found in 12% of patients. SLC26A4 sequence alterations commonly found in other Caucasian populations were not detected. This survey represents the first study on the prevalence and spectrum of SLC26A4 sequence alterations in an Austrian cohort and further suggests that genetic testing should always be integrated with functional characterization and determination of the molecular features of protein variants in order to unequivocally identify or exclude a causal link between genotype and phenotype.

Etiologic and Audiologic Characteristics of Patients With Pediatric-Onset Unilateral and Asymmetric Sensorineural Hearing Loss

Importance

Pediatric-onset unilateral and asymmetric sensorineural hearing loss (SNHL) is a common condition, but in most patients, the cause remains unclear; thus, determination of the hearing outlook is difficult.

Objective

To analyze the etiologic and audiologic characteristics of pediatric-onset unilateral and asymmetric SNHL.

Design, Setting, and Participants

In this retrospective cohort study performed from January 1, 2008, through December 31, 2016, patients at a tertiary referral center who were diagnosed with pediatric-onset unilateral or asymmetric SNHL were divided into 3 groups according to their hearing levels: unilateral hearing loss with scaled-out levels (UHL-SO), unilateral hearing loss with residual hearing (UHL-RH), and asymmetric hearing loss (AHL).

Main Outcomes and Measures

Basic demographic data, family and medical histories, audiologic results, imaging findings, and genetic results were ascertained and compared among patients of the 3 groups.

Results

A total of 133 patients (mean [SD] age, 9.1 [10.9] years; 63 [47.4%] male and 70 [52.6%] female), including 50 with UHL-SO, 42 with UHL-RH, and 41 with AHL, were enrolled for analyses. Of 50 patients with UHL-SO, 49 (98.0%) had stable hearing levels with time, whereas 10 of 42 patients with UHL-RH (23.8%) and 18 of 41 patients with AHL (43.9%) revealed progressive or fluctuating hearing loss. Inner ear malformations detected with temporal bone high-resolution computed tomography, particularly cochlear aperture stenosis, were detected at higher rates in patients with UHL-SO (9 of 31 [29.0%]) and UHL-RH (6 of 24 [25.0%]) than in those with AHL (1 of 30 [3.3%]). In contrast, screening for mutations in 3 common deafness genes-GJB2, SLC26A4, and MTRNR1-achieved definite diagnosis in a higher percentage of patients with AHL (10 of 37 [27.0%]) than patients with UHL-SO (0 of 33) and UHL-RH (1 of 25 [4.0%]).

Conclusions and Relevance

The UHL-SO and UHL-RH conditions share a common or similar etiopathogenesis different from that of AHL. Imaging studies and genetic testing might be prioritized during the respective general etiologic workups for patients with UHL and AHL. Regular hearing checkups are warranted for patients with UHL and AHL because a certain proportion of patients might sustain progression in SNHL.

Unilateral Enlarged Vestibular Aqueduct Syndrome and Bilateral Endolymphatic Hydrops

Enlarged vestibular aqueduct (EVA) syndrome is a common congenital inner ear malformation characterized by a vestibular aqueduct with a diameter larger than 1.5 mm, mixed or sensorineural hearing loss that ranges from mild to profound, and vestibular disorders that may be present with a range from mild imbalance to episodic objective vertigo. In our study, we present the case of a patient with unilateral enlarged vestibular aqueduct and bilateral endolymphatic hydrops (EH). EH was confirmed through anamnestic history and audiological exams; EVA was diagnosed using high-resolution CT scans and MRI images. Therapy included intratympanic infusion of corticosteroids with a significant hearing improvement, more evident in the ear contralateral to EVA. Although most probably unrelated, EVA and EH may present with similar symptoms and therefore the diagnostic workup should always include the proper steps to perform a correct diagnosis. Association between progression of hearing loss and head trauma in patients with a diagnosis of EVA syndrome is still uncertain; however, these individuals should be advised to avoid activities that increase intracranial pressure to prevent further hearing deterioration. Intratympanic treatment with steroids is a safe and well-tolerated procedure that has demonstrated its efficacy in hearing, tinnitus, and vertigo control in EH.

Hearing loss associated with enlarged vestibular aqueduct and zero or one mutant allele of SLC26A4

OBJECTIVES/HYPOTHESIS

To characterize the severity and natural history of hearing loss, and the prevalence of having a cochlear implant in a maturing cohort of individuals with enlarged vestibular aqueduct (EVA) and zero or one mutant allele of SLC26A4.

STUDY DESIGN

Prospective cohort study of subjects ascertained between 1998 and 2015 at the National Institutes of Health Clinical Center.

METHODS

Study subjects were 127 individuals (median age, 8 years; range, 0-59 years) with EVA in at least one ear.

RESULTS

Ears with EVA and zero or one mutant allele of SLC26A4 had mean 0.5/1/2/4-kHz pure-tone averages of 62.6 and 52.9 dB HL, respectively, in contrast to EVA ears with two mutant alleles of SLC26A4 (88.1 dB HL; P < .01). This association was independent of age, sex, or side of EVA (P < .001). Natural history of hearing loss was not associated with number of mutant alleles (P = .94). The prevalence of having a cochlear implant was nine (12%) of 76, two (13%) of 15, and 12 (38%) of 32 subjects with zero, one, and two mutant alleles, respectively (P = .00833). This association was not independent (P = .534) but reflected underlying correlations with age at time of first audiogram (P = .003) or severity of hearing loss (P = .000).

CONCLUSIONS

Ears with EVA and zero or one mutant allele of SLC26A4 have less severe hearing loss, no difference in prevalence of fluctuation, and a lower prevalence of cochlear implantation in comparison to ears with two mutant alleles of SLC26A4.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E238-E243, 2017.

Establishment of a Flexible Real-Time Polymerase Chain Reaction-Based Platform for Detecting Prevalent Deafness Mutations Associated with Variable Degree of Sensorineural Hearing Loss in Koreans

Many cutting-edge technologies based on next-generation sequencing (NGS) have been employed to identify candidate variants responsible for sensorineural hearing loss (SNHL). However, these methods have limitations preventing their wide clinical use for primary screening, in that they remain costly and it is not always suitable to analyze massive amounts of data. Several different DNA chips have been developed for screening prevalent mutations at a lower cost. However, most of these platforms do not offer the flexibility to add or remove target mutations, thereby limiting their wider use in a field that requires frequent updates. Therefore, we aimed to establish a simpler and more flexible molecular diagnostic platform based on ethnicity-specific mutation spectrums of SNHL, which would enable bypassing unnecessary filtering steps in a substantial portion of cases. In addition, we expanded the screening platform to cover varying degrees of SNHL. With this aim, we selected 11 variants of 5 genes (GJB2, SLC26A4, MTRNR1, TMPRSS3, and CDH23) showing high prevalence with varying degrees in Koreans and developed the U-TOP™ HL Genotyping Kit, a real-time PCR-based method using the MeltingArray technique and peptide nucleic acid probes. The results of 271 DNA samples with wild type sequences or mutations in homo- or heterozygote form were compared between the U-TOP™ HL Genotyping Kit and Sanger sequencing. The positive and negative predictive values were 100%, and this method showed perfect agreement with Sanger sequencing, with a Kappa value of 1.00. The U-TOP™ HL Genotyping Kit showed excellent performance in detecting varying degrees and phenotypes of SNHL mutations in both homozygote and heterozygote forms, which are highly prevalent in the Korean population. This platform will serve as a useful and cost-effective first-line screening tool for varying degrees of genetic SNHL and facilitate genome-based personalized hearing rehabilitation for the Korean population.

Diagnostic Value of SLC26A4 Mutation Status in Hereditary Hearing Loss With EVA: A PRISMA-Compliant Meta-Analysis

Many SLC26A4 mutations have been identified in patients with nonsyndromic enlarged vestibular aqueduct (EVA). However, the roles of SLC26A4 genotypes and phenotypes in hereditary deafness remain unexplained. This study aims to perform a meta-analysis based on the PRISMA statement to evaluate the diagnostic value of SLC26A4 mutant alleles and their correlations with multiethnic hearing phenotypes in EVA patients. The systematic literature search of the PubMed, Wiley Online Library, EMBASE, Web of Science, and Science Direct databases was conducted in English for articles published before July 15, 2015. Two investigators independently reviewed retrieved literature and evaluated eligibility. Discrepancy was resolved by discussion and a third investigator. Quality of included studies was evaluated using Newcastle-Ottawa Quality Assessment Scale. Data were synthesized using random-effect or fixed-effect models. The effect sizes were estimated by measuring odds ratios (ORs) with 95% confidence interval (CI). Twenty-five eligible studies involved 2294 cases with EVA data. A total of 272 SLC26A4 variations were found in deafness with EVA and 26 mutations of SCL26A4 had higher frequency. The overall OR was 646.71 (95% CI: 383.30-1091.15, P = 0.000). A total of 22 mutants were considered statistically significant in all ethnicities (ORs >1, P < 0.05). In particular, 8 mutants were specificity of EVA phenotypes in mutations of SLC26A4 for Asia deafness populations (ORs >1, P < 0.05), 4 mutants for Europe and North America (ORs >1, P < 0.05), and the IVS7-2A>G mutations in SLC26A4 were found to have the highest frequency in deafness individuals with EVA phenotype (62.42%). Moreover, subgroups for studies limited to cases with EVA phenotype, 11 mutants relevant risks (RRs) were P < 0.05, especially for IVS7-2A>G bi-allelic mutants assayed in a deafness population (RR = 0.880, P = 0.000). Diagnostic accuracy of SLC26A4 mutation results also identified the significant association of IVS7-2A>G (AUC = 0.99, 95% CI: 0.97-0.99) and p.H723R (AUC = 0.99, 95% CI: 0.98-1.00) detecting deafness with EVA. To conclude, the IVS7-2A>G and H723R in SLC26A4 present a significant predicting value and discriminatory ability for clinical use on diagnosis of EVA within a deafness population.