A novel intronic variant causing aberrant splicing identified in two deaf Chinese siblings with enlarged vestibular aqueducts

OBJECTIVE

We aimed to evaluate the genotype-phenotype relationship in two Chinese family members with enlarged vestibular aqueduct (EVA).

METHODS

We collected blood samples and clinical data from each pedigree family member. Genomic DNA was isolated from peripheral leukocytes using standard methods. Targeted next-generation sequencing and Sanger sequencing were performed to find the pathogenic mutation in this family. Minigene assays were used to verify whether the novel intronic mutation SLC26A4c.765+4A>G influenced mRNA splicing.

RESULTS

Hearing loss in the patients with EVA was diagnosed using auditory tests and imaging examinations. Two pathogenic mutations, c.765+4A>G and c.919-2A>G were detected in SLC26A4. In vitro minigene analysis confirmed that c.765+4A>G variant could cause aberrant splicing, resulting in skipping over exon 6.

CONCLUSIONS

The SLC26A4c.765+4A>G mutation is the causative variant in the Chinese family with EVA. Particular attention should be paid to intronic variants.

Study of the factors related to air-bone gap in enlarged vestibular aqueduct

BACKGROUND

Over half of patients with enlarged vestibular aqueducts (EVA) will have an air-bonr gap (ABG), however, current research on audiology has focused on the influencing factors of air-conducted.

OBJECTIVE

To retrospectively analyse the influencing factors and clinical manifestations of the bone-conduction threshold and ABG in patients with EVA.

MATERIALS AND METHODS

We included 286 patients with EVA; among them, 126 had full SLC26A4 gene sequence results. We performed a descriptive analysis of the bone-conduction threshold and explored the effect of age. Finally, we analyzed the relationship of ABG and SLC26A4 genes with the degree of vestibular aqueduct (VA) enlargement.

RESULTS

Among 555 ears, 312 (57.8%) ears had ABG; approximately 94% of the patients' bone-conduction hearing is almost completely lost at frequencies of 2 and 4 kHz. There was no linear correlation between age and bone-conduction threshold (p > 0.05). ABG did not significantly differ according to the degree of VA enlargement and number of SLC26A4 allele mutations (p > 0.05).

CONCLUSIONS AND SIGNIFICANCE

Among patients with EVA, ABG is mainly produced at low frequencies and is not significantly correlated with age, size of the VA opening or SLC26A4 genes, which could be attributed to the biomechanical effects.

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.

Classifying the Large Vestibular Aqueduct: Morphometry to Audiometry

OBJECTIVE

Large vestibular aqueduct (LVA) is the most common inner ear dysplasia identified in patients with hearing loss. Our objective was to systematically quantify LVA morphologies and correlate imaging findings with established audiometric outcomes.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

PATIENTS

Patients with large vestibular aqueduct identified radiographically, with or without hearing loss.

INTERVENTIONS

Diagnostic only.

MAIN OUTCOME MEASURES

Vestibular aqueduct (VA) width at midpoint, width at external aperture, and length were measured on cross-sectional imaging. Morphology was classified as type I (borderline), type II (tubular), or type III (funneled). Audiometric endpoints included air/bone conduction, pure tone averages, and air-bone gaps at 250 and 500 Hz. Statistical associations were evaluated using linear regression models, adjusted for age at first audiogram and sex.

RESULTS

One hundred seventeen patients (197 ears) were included, with mean age at first audiogram of 22.2 years (standard deviation, 21.7 yr). Imaging features associated with poor audiometric outcomes were increasing VA width at midpoint and external aperture, decreasing VA length, dilated extraosseous endolymphatic sac, cochleovestibular malformations, and increasing VA type (III > II > I).

CONCLUSIONS

Quantitative LVA measurements and a standardized morphologic classification system aid in prediction of early audiometric endpoints.

[Relationship between imaging features and intraoperative perilymph gusher in patients with Mondini inner ear malformation]

Objective:To investigate the relationship between imaging characteristics and intraoperative perilymph gusher in patients with Mondini inner ear malformation in cochlear implantation, in order to provide basis and clinical guidance for predicting of intraoperative perilymph gusher before cochlear implantation. Methods:According to Sennaroglu's classification method, children with severe sensorineural hearing loss screened from January 2020 to December 2021 were divided into Mondini group, simple enlarged vestibular aqueduct group and normal inner ear group according to inclusion criteria strictly. The images of temporal bone HRCT and inner ear MRI were post-processed, some relative indicators were measured, including cochlear height and width of vestibular aqueduct, etc., and the gusher situation during cochlear implantation was recorded. The mean value of each indicator among the three groups were compared respectively, and the differences of each indicator between the gusher group and the non-gusher group were analyzed. Results:There were statistically significant differences in cochlear height, length of cochlear bottom turn, width of cochlear aperture, vestibular length and vestibular width among the Mondini group（24 cases）, simple EVA group（15 cases） and normal inner ear group（28 cases）. The incidence of gusher of Mondini group in cochlear implantation was 30.77%（8/26）. The outer diameter of the VA（[3.10±0.74]mm） and the middle width of the VA（[1.90±0.68] mm） in the gusher group were wider than those in the non-gusher group, and the difference was statistically significant. The incidence of intraoperative gusher in patients with EVA was 20.00%（3/15）, and there was statistically significant difference in the length of endolymph sac between gusher group and non-gusher group（P<0.05）. Conclusion:The causes of intraoperative perilymph gusher in patients with Mondini inner ear malformation are complex. The enlarged vestibular aqueduct may be one of the anatomical basis. Whether it can be used to guide the preoperative assessment of the risk of intraoperative perilymph gusher need to be further confirmed by a large sample of clinical research from multiple centers in the future.

[Diagnosis of a Chinese pedigree affected with autosomal recessive deafness 4 with enlarged vestibular aqueduct due to compound heterozygous variants of FOXI1 gene]

OBJECTIVE

To explore the genetic basis for a Chinese pedigree affected with congenital deafness pedigree in conjunct with enlarged vestibular aqueduct.

METHODS

Whole-exome sequencing was carried out for the proband to analyze the genes associated with hereditary deafness. Candidate variant was verified by Sanger sequencing of the proband's parents and her younger brother.

RESULTS

The proband was found to harbor compound heterozygous variants including c.748dupG (p.Asp250Glyfs*30Asn) (pathogenic, PVS1+PM2+PP4) and c.879C>A (p.Ser293Arg) (likely pathogenic, PM2+PM3+PP1+PP4) of the FOXI1 gene, which has been associated with enlarged vestibular aqueduct (OMIM 600791). Both variants were unreported previously. The variants were respectively inherited from proband's parents whom had normal hearing. Her younger brother was heterozygous for the c.748dupG variant but also had normal hearing.

CONCLUSION

The compound heterozygous variants of the FOXI1 gene probably underlay the pathogenicity of congenital deafness and enlarged vestibular aqueduct in the proband. The co-segregation of the two variants with the hearing loss has facilitated genetic counseling and prenatal diagnosis for this pedigree.

[Correlation of temporal bone HRCT, SLC26A4 gene and hearing loss in enlarged vestibular aqueduct]

Objective:To explore the correlation between high-resolution computed tomography（HRCT） of temporal bones, SLC26A4 gene mutation and hearing loss in patients with enlarged vestibular aqueduct（EVA）. Methods:The medical records of 257 subjects hospitalized for moderate to severe sensorineural hearing loss in the Department of Otolaryngology Head and Neck Surgery, Hainan General Hospital between May 2018 to 2021 were retrospectively reviewed. All included cases received audiological examination, HRCT scanning of temporal bones and SLC26A4 gene sequencing. According to the Valvassori standard, cases with the diameter from the common peduncle of the semicircular canal to the midpoint of the outer orifice of the vestibular aqueduct（MP） over 1.5 mm, or the diameter of the outer orifice of the vestibular aqueduct（OP） more than 2.0 mm were diagnosed as EVA. There were 22 cases（44 ears） of EVA in the study, aged between 6 months to 17 years old. Based on the hearing changes at birth and during growth, 18 ears of which were classified into the stable hearing group, while the other 26 ears in the unstable group. Moreover, all involved cases were grouped by MP（1.5 to <3.0 mm and ≥3.0 mm） and OP（2.0 to <4.0 mm and ≥4.0 mm）. SPSS 25.0 software was applied in the study. The correlation between hearing loss and MP and OP was analyzed. The results of HRCT of temporal bones and SLC26A4 gene sequencing were compared as well. Results:Though the size of MP and OP was not statistically different between the stable and hearing groups in EVA ears（P>0.05）, it was significantly correlated with the severity of hearing loss（P<0.05）. Of the 22 EVA patients diagnosed by HRCT, 21 were positive for SLC26A4 gene mutation. The positive rate of EVA by SLC26A4 gene sequencing was highly consistent with HRCT（Kappa=0.975）. Conclusion:The size of MP and OP in EVA patients was related to the degree of hearing loss, but not to the stable nature of hearing loss. Temporal bone HRCT scanning and SLC26A4 gene sequencing are highly consistent in the diagnosis of EVA. The latter has no radiation and can be combined with hearing screening for early diagnosis of EVA.

Clinical and genetic analysis of children with hearing loss and bilateral enlarged vestibular aqueducts

OBJECTIVES

To evaluate the clinical and genetic features of children with hearing loss associated with one of the most common malformations of the inner ear: bilateral enlargement of vestibular aqueducts (EVA).

METHODS

Clinical and genetic features were investigated in 28 children with hearing loss diagnosed with bilateral EVA by computed tomography from January 2008 to September 2019.

RESULTS

Fourteen subjects had undergone newborn hearing screening (NHS). Nine subjects (64.3%) were referred in both ears, 4 subjects (28.6%) were referred in one ear, and one subject (7.1%) passed in both ears. Nineteen of 26 subjects (73.1%) who were followed for more than 3 years had hearing fluctuations, while 17 (65.4%) had hearing loss progression. Eleven of 28 subjects (39.2%) had vertigo attacks. Pathogenic variants were identified in two alleles of the SLC26A4 gene in 24 of 27 subjects (88.9%) by sequencing of all exons and flanking introns, leading to genetic diagnosis of Pendred syndrome/DFNB4. Our results indicate that genetic screening for specific SLC26A4 variants using a commercial clinical laboratory test in Japan would have achieved genetic diagnoses in 13 of the 27 subjects (54.2%). Although there was no statistically significance in the frequency of hearing fluctuation or progression depending on the presence or absence of the gene variant, mean hearing level was severe in subjects with two pathogenic variants in SLC26A4 gene. The most common variant detected in our subjects was p.His723Arg (13 alleles, 27.1%), followed by c. 919-2A > G (four alleles, 8.3%). Two novel variants were detected in this study: c.1544+1G > T and c.1614+5G > A.

CONCLUSIONS

Our data suggest that some subjects may present with bilateral EVA that cannot be detected by NHS. We estimated that genetic diagnosis for SLC264 gene would not have been made in almost half subjects with the commercial genetic screening approach used in the present study in Japan. Although there were some limitations in this study, the subjects with pathogenic variants in two alleles of the SLC26A4 gene could have more severe hearing loss.

Retrospective Review of Midpoint Vestibular Aqueduct Size in the 45° Oblique (Pöschl) Plane and Correlation with Hearing Loss in Patients with Enlarged Vestibular Aqueduct

BACKGROUND AND PURPOSE

Vestibular aqueduct measurements in the 45° oblique (Pöschl) plane provide a reliable depiction of the vestibular aqueduct; however, adoption among clinicians attempting to counsel patients has been limited due to the lack of correlation with audiologic measures. This study aimed to determine the correlation between midpoint vestibular aqueduct measurements in the Pöschl plane in patients with an enlarged vestibular aqueduct with repeat audiologic measures.

MATERIALS AND METHODS

Two radiologists independently measured the midpoint vestibular aqueduct diameter in the Pöschl plane reformatted from CT images in 54 pediatric patients (77 ears; mean age at first audiogram, 5 years) with an enlarged vestibular aqueduct. Four hundred nineteen audiograms were reviewed, with a median of 6 audiograms per patient (range, 3-17; mean time between first and last audiograms, 97.4 months). The correlation between midpoint vestibular aqueduct size and repeat audiologic measures (pure tone average, speech-reception threshold, and word recognition score) using a linear mixed-effects model was determined.

RESULTS

The mean midpoint vestibular aqueduct size was 1.78 mm (range, 0.81-3.46 mm). There was excellent interobserver reliability with intraclass correlation coefficients for the 2 readers measuring 0.92 (P < .001). Each millimeter increase in vestibular aqueduct size was associated with an increase of 10.5 dB (P = .006) in the pure tone average, an increase of 14.0 dB (P = .002) in the speech-reception threshold, and a decrease in the word recognition score by 10.5% (P = .05).

CONCLUSIONS

Midpoint vestibular aqueduct measurements in the Pöschl plane are highly reproducible and demonstrate a significant correlation with audiologic data in this longitudinal study with repeat measures. These data may be helpful for clinicians who are counseling patients with an enlarged vestibular aqueduct using measurements obtained in the Pöschl plane.

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.

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.

Large Vestibular Aqueduct Syndrome: A Case Study

A 23-month-old female was referred for hearing aid fitting after failing newborn hearing screening and being diagnosed with significant hearing loss through subsequent diagnostic testing. Auditory brainstem response (ABR) and behavioral testing revealed a moderate-to-severe bilateral mixed hearing loss. Prior to the hearing aid evaluation, tympanostomy tubes had been placed bilaterally with little or no apparent change in hearing sensitivity. Initial testing during the hearing aid fitting confirmed earlier findings, but abnormal middle ear results were observed, requiring referral for additional otologic management. Following medical clearance, binaural digital programmable hearing aids were fit using Desired Sensation Level parameters. Behavioral testing and probe microphone measures showed significant improvements in audibility. Decrease in hearing sensitivity was observed six months following hearing aid fitting. Radiological studies, ordered due to the mixed component and decreased hearing sensitivity, revealed large vestibular aqueduct syndrome (LVAS). Based on the diagnosis of LVAS, a cochlear implant was placed on the right ear; almost immediate speech-language gains were observed.

A phase I/IIa double blind single institute trial of low dose sirolimus for Pendred syndrome/DFNB4

INTRODUCTION

Pendred syndrome (PDS)/DFNB 4 is a disorder with fluctuating and progressive hearing loss, vertigo, and thyroid goiter. We identified pathophysiology of a neurodegenerative disorder in PDS patient derived cochlear cells that were induced via induced pluripotent stem cells and found sirolimus, an mTOR inhibitor, as an inhibitor of cell death with the minimum effective concentration less than 1/10 of the approved dose for other diseases. Given that there is no rational standard therapy for PDS, we planned a study to examine effects of low dose oral administration of sirolimus for the fluctuating and progressive hearing loss, and the balance disorder of PDS by daily monitor of their audio-vestibular symptoms.

METHODS AND ANALYSIS

This is a phase I/IIa double blind parallel-group single institute trial in patient with PDS/DFNB4. Sixteen of outpatients with fluctuating hearing diagnosed as PDS in SLC26A4 genetic testing aged in between 7 and 50 years old at the time of consent are given either placebo or sirolimus tablet (NPC-12T). In NPC-12T placebo arm, placebo will be given for 36 weeks; in active substance arm, placebo will be given for 12 weeks and the NPC-12T for 24 weeks. Primary endpoints are safety and tolerability. The number of occurrences and types of adverse events and of side effects will be sorted by clinical symptoms and by abnormal change of clinical test results. A 2-sided 95% confidence interval of the incidence rate by respective dosing arms will be calculated using the Clopper-Pearson method. Clinical effects on audio-vestibular tests performed daily and precise physiological test at each visit will also be examined as secondary and expiratory endpoints.

TRIAL REGISTRATION NUMBER

JMA-IIA00361; Pre-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.

Morphology and cochlear implantation in enlarged vestibular aqueduct

PURPOSE

The purpose of this work is to explore audiometry following cochlear implantation (CI) in patients with enlarged vestibular aqueduct (EVA) and to investigate the effects of inner ear morphological variation on post CI audiometry.

METHODS

This was a retrospective review of both natural and cochlear-implant-aided audiometry results, using all available measurements in a mixed-effects model accounting for longitudinal change and the grouping structure of ears. Patients who visited our tertiary academic medical center between 2000 and 2016 were identified as having EVA according to Cincinnati criteria on radiological examination; patients eligible for CI were then selected for analysis.

RESULTS

Multivariable modeling showed a statistically significant hearing improvement in ears with EVA undergoing CI with regards to pure tone average (-64.0 dB, p < 0.0001), speech reception threshold (-57.90 dB, p < 0.0001), and word score (34.8%, p > 0.0001). Vestibular aqueduct midpoint size and the presence of incomplete partition type II (IP II) did not have significant independent associations with audiometric findings. However, multivariable modeling revealed a statistically significant interaction between IP II and CI such that IP II ears demonstrated a decrease in WS improvement of 30.2% (p = 0.0059) compared to non-IP II ears receiving CI.

CONCLUSION

There is a statistically significant audiometric benefit to ears with EVA receiving CI. Morphology, specifically the presence of IP II, may hinder CI benefit in terms of word score however this finding needs clinical validation. This data improves personalization of surgical counseling and planning for patients with EVA considering CI.

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.

Molecular characterization of autosomal recessive non syndromic hearing loss in selected families from District Mardan, Pakistan

Deafness is the most common sensory disorder, which affects 1/1000 neonates globally. Genetic factors are major contributors for hearing impairment. This study was conducted to explore the linkage of DFNB loci and their mutations with NSHL in selected Pakistani families. We included 10 families with history of deafness from district Mardan, Pakistan. Blood sample (5ml) along with personal and clinical information was collected from the available family members including both diseased and un-affected individuals. Genomic DNA was amplified using loci specific STR markers to investigate the linkage of DFNB loci. Family found linked with DFNB4 locus was screened for SLC26A4 mutations. One out of the ten explored families was found linked with DFNB4 locus which was further investigated for SLC26A4 gene mutation through direct DNA sequencing. Two novel mutations were observed in the studied family, one at splice donor site (164+2T>G) and the other at position 164+5C>G only in the affected members of the linked family. DFNB4 locus was found linked in the present study which harbors SLC26A4 gene. The novel mutation of SLC26A4 gene at the splice donor site results in skipping of the first coding exon and thus can lead to loss of expression of SLC26A4 product in the inner ear.

[Enlarged vestibular aqueduct in a ten-year-old girl]

Enlarged vestibular aqueduct (EVA) is a malformation in the inner ear and occurs in approximately 1-12% of the hearing-impaired individuals. A ten-year-old girl was seen at the emergency room (ER) because of sudden hearing loss on the right ear. The patient was known with sudden deafness on the left ear. In the ER she appeared completely deaf. A head CT-scan showed EVA, and she was treated with cochlear implant. This case report illustrates the importance of performing MR- or CT-scan, especially when diagnosing children with sudden hearing loss after a head injury.

[Identification of a novel SLC26A4 mutation in a child with enlarge vestibular aqueduct syndrome]

OBJECTIVE

To analyze mutations of SLC26A4 gene and explore their origins for a patient with enlarge vestibuar aqueduct syndrome.

METHODS

Clinical data and peripheral venous blood samples were collected from the patient and her parents. Genome DNA was extracted from the peripheral blood. All of the 21 exons of the SLC26A4 gene were amplified with PCR and subjected to directly sequencing.

RESULTS

The patient was found to have carried two mutant alleles of the SLC26A4 gene, namely c.1522A to G and c.1229C to T, which were inherited from her father and mother, respectively.

CONCLUSION

SLC26A4 c.1522A to G is likely to be a pathogenic mutation. Above results may facilitate genetic counseling and prenatal diagnosis for this family.

Superior canal dehiscence with tegmen defect revealed by otoscopy: Video clip demonstration of pulsatile tympanic membrane

Superior canal dehiscence is a pathologic condition of the otic capsule acting as aberrant window of the inner ear. It results in reduction of inner ear impedance and in abnormal exposure of the labyrinthine neuroepithelium to the action of the surrounding structures. The sum of these phenomena leads to the onset of typical cochleo-vestibular symptoms and signs. Among them, pulsatile tinnitus has been attributed to a direct transmission of intracranial vascular activities to labyrinthine fluids. We present the first video-otoscopic documentation of spontaneous pulse-synchronous movements of the tympanic membrane in two patients with superior canal dehiscence. Pulsating eardrum may represent an additional sign of third-mobile window lesion.

Large vestibular aqueduct in distal renal tubular acidosis: High-resolution MR in three cases

High-resolution MR of the inner ear performed in 3 consecutive pediatric patients affected by distal renal tubular acidosis (dRTA) and progressive sensorineural hearing loss (SNHL) revealed enlarged vestibular aqueducts (LVA) (bilateral in 1 case and unilateral in 2). LVA is associated to sporadic, progressive SNHL, often secondary to minor head trauma and activities involving the Valsalva maneuver.

We believe that the presence of LVA may have contributed to the onset of SNHL and its progression in our patients, and therefore want to stress the importance of morphological studies of the inner ear in patients affected by dRTA and SNHL.

The large vestibular aqueduct: A new definition based on audiologic and computed tomography correlation

Objective

The study goal was to determine the prevalence and clinical significance of a large vestibular aqueduct (LVA) in children with sensorineural hearing loss (SNHL).

Study Design and Setting

We conducted a retrospective review of a pediatric SNHL database. One hundred seven children with SNHL were selected and their radiographic and audiometric studies were evaluated. Radiographic comparisons were made to a group of children without SNHL.

Results

A vestibular aqueduct (VA) larger than the 95th percentile of controls was present in 32% of children with SNHL. Progressive SNHL was more likely to occur in ears with an LVA and the rate of progressive hearing loss was greater than in ears without an LVA. The risk of progressive SNHL increased with increasing VA size as determined by logistic regression analysis.

Conclusions

An LVA is defined as one that is ≥2mm at the operculum and/or ≥1 mm at the midpoint in children with nonsyndromic SNHL. An LVA appears to be more common than previously reported in children with SNHL. A linear relationship is observed between VA width and progressive SNHL.

Significance

The finding of an LVA in children with SNHL provides diagnostic as well as prognostic information. © 2007 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

Vestibular pathology in children with enlarged vestibular aqueduct

OBJECTIVES/HYPOTHESIS

To establish the prevalence of abnormal vestibular test findings in children with enlarged vestibular aqueduct (EVA) and determine if these findings correlate with clinical symptoms, radiographic findings (EVA size and laterality), audiometric findings, and genetic testing in these patients.

STUDY DESIGN

Prospective cohort.

METHODS

Patients 3 to 12 years of age with hearing loss and imaging findings consistent with EVA treated at our tertiary care institution were sequentially enrolled from 2009 to 2011. The following six outcome measurements were analyzed: audiometric findings, EVA laterality, temporal bone measurements, genetic testing, vestibular testing (cervical-evoked myogenic potentials, posturography, rotational chair, and calorics), and vestibular symptoms.

RESULTS

Twenty-seven patients with EVA (mean age 9.2 years, 48% female) were enrolled in and completed the study. Vertigo was reported in six patients. Twenty-four of 27 (89%) had at least one abnormal vestibular test result. Midpoint and operculum size correlated with directional preponderance (P = .042 and P = .032, respectively). Also, high-frequency pure tone average (HFPTA) correlated with unilateral weakness (P = .002). Walking at a later age correlated with abnormal posturography results. There was no correlation between EVA laterality and vestibular test findings.

CONCLUSION

We found a high rate of vestibular pathology in children with EVA; however, the prevalence of abnormal vestibular test findings in this patient population was not correlated with vestibular symptoms. Enlarged vestibular aqueduct size, HFPTA, and walking at a later age were correlated with abnormal vestibular test findings. In view of these results, it may be prudent to consider vestibular testing in children with these clinical characteristics.

LEVEL OF EVIDENCE

2b. Laryngoscope, 126:2344-2350, 2016.

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.

[Imaging and audiology analysis of the congenital inner ear malformations]

OBJECTIVE

To investigate imaging and audiology features of temporal bone and analyze the classification and prevalence of inner ear abnormalities in children with sensorineural hearing loss.

METHOD

Children who were diagnosed with sensorineural hearing loss were examined by high resolution CT and the inner ear fluid of MRI. And each chart was retrospectively reviewed to determine the imaging and audiology features.

RESULT

There were 125 patients(232 ears) found with inner ear malformation in 590 children with SNHL. About 21.71% of the inner ear malformation occurred in severe and profound hearing loss ears, and 12.85% occurred in r moderate hearing loss ears. The inner ear malformation rate in normal hearing ears were 13.59%.

CONCLUSION

CT and MRI examinations of temporal bone are important diagnostic tools to indentify inner ear malformations. Inner ear malformations are almost bilateral and hearing loss are profoud. Cochleo-vestibular malformations and large vestibular aqueduct are the 2 most frequent deformities. Among the children with SNHL, deformity rate in the severe and profound hearing loss ears is higher than that in moderate hearing loss ear. Inner ear malformations can exist in people with normal hearing.

[The application value of MRI in the children with sensorineural hearing loss before cochlear implantation]

OBJECTIVE

To investigate diagnostic value and clinical application of MRI in the children with sensorineural hearing loss (SNHL) before cochlear implantation.

METHOD

MRI images of 80 children with the diagnosis of SHNL were retrospectively analyzed in combination with the latest classification of inner ear malformation.

RESULT

There were 152 ears of inner ear malformation of 80 cases (160 ears), including 38 ears of cochlear malformation, 33 ears of vestibular malformation, 41 ears of semicircular canal malformation, 37 ears of vestibular aqueduct enlargement, 40 ears of internal auditory canal malformation, and 46 ears of cochlear nerve malformation.

CONCLUSION

MRI can provide detailed and reliable anatomical information for children with SNHL before cochlear implantation, and help to make the classification diagnosis. Therefore MRI is of great clinical significance for operation plan guidance and prognosis assessment.

Mono-allelic mutations of SLC26A4 is over-presented in deaf patients with non-syndromic enlarged vestibular aqueduct

OBJECTIVES

Recessive mutations of SLC26A4 are the major cause of hearing impairment associated with enlarged vestibular aqueduct (EVA). In a significant percentage of non-syndromic EVA patients, however, only mono-allelic mutations of SLC26A4 can be identified. In this study, we aimed to evaluate whether presence of mono-allelic mutations of SLC26A4 in those patients was coincidental or etiologically associated with the disorder.

METHODS

The exons and flanking splicing sites of SLC26A4 were sequenced in 150 Chinese Han deaf probands with non-syndromic EVA. c.919-2A >G and p.H723R, two frequent mutations of SLC26A4 in Chinese Hans, were screened by an allele-specific PCR-based array in 3056 ethnically-matched normal hearing controls. The frequency of mono-allelic c.919-2A >G and p.H723R mutations was determined in each group. The statistical significance of the difference was analyzed by Fisher's exact test.

RESULTS

Bi-allelic, mono-allelic and no mutation of SLC26A4 were detected in 98 (65.3%), 18 (12%) and 34 (22.67%) deaf probands with non-syndromic EVA, respectively. The frequency of mono-allelic c.919-2A >G and p.H723R mutations were significantly higher in the 150 deaf probands with non-syndromic EVA (8.67%) than in the 3056 normal hearing controls (1.4%, P=1.8×10(-6)).

CONCLUSION

Presence of mono-allelic mutations of SLC26A4 in non-syndromic EVA patients is etiologically associated with this disorder. Additional genetic or environmental causes may be present in those patients and demand further investigation and consideration during the genetic diagnosis and counseling.

Large vestibular aqueduct syndrome: Impedance changes over time with different cochlear implant electrode arrays

OBJECTIVES

The aim of this study was to assess if large vestibular aqueduct syndrome (LVAS), with the increase in perilymphatic pressure, affects impedance changes over time with different types of Cochlear(®) implant electrode arrays Contour, Straight, and CI 422. To report speech perception outcomes for these cochlear implant recipients.

METHODS

Retrospective case review of impedance levels and categories of auditory performance. Impedance data were collected at switch on, 1 month, 3, 6, 12, and 24 months after cochlear implantation and compared with control (non-LVAS cochlear implant recipient) data for each array type. Forty-seven patients with exclusive LVAS and no other vestibulocochlear abnormalities or other identifiable cause of deafness were eligible for inclusion in the study.

RESULTS

In LVAS patients, there was a significant difference in impedance between the three types of device (P < 0.0001). Time since switch on was associated with a decrease in impedance for all three devices (P < 0.0001). The mean impedance reduced between switch on and 1 month and remained relatively constant thereafter. Sound variation with softening of sounds was seen in four CI 422 (Straight Research Array) recipients due to ongoing fluctuations in electrode compliance.

DISCUSSION

For all three array types, there was no significant difference in the mean impedance between the LVAS patients and controls over the first 12 months. In keeping with previous studies cochlear implant recipients with LVAS hear very well through the cochlear implant.

KCNJ10 may not be a contributor to nonsyndromic enlargement of vestibular aqueduct (NSEVA) in Chinese subjects

Background

Nonsyndromic enlargement of vestibular aqueduct (NSEVA) is an autosomal recessive hearing loss disorder that is associated with mutations in SLC26A4. However, not all patients with NSEVA carry biallelic mutations in SLC26A4. A recent study proposed that single mutations in both SLC26A4 and KCNJ10 lead to digenic NSEVA. We examined whether KCNJ10 excert a role in the pathogenesis of NSEVA in Chinese patients.

Methods

SLC26A4 was sequenced in 1056 Chinese patients with NSEVA. KCNJ10 was screened in 131 patients who lacked mutations in either one or both alleles of SLC26A4. Additionally, KCNJ10 was screened in 840 controls, including 563 patients diagnosed with NSEVA who carried biallelic SLC26A4 mutations, 48 patients with nonsyndromic hearing loss due to inner ear malformations that did not involve enlargement of the vestibular aqueduct (EVA), 96 patients with conductive hearing loss due to various causes, and 133 normal-hearing individuals with no family history of hereditary hearing loss.

Results

925 NSEVA patients were found carrying two-allele pathogenic SLC26A4 mutations. The most frequently detected KCNJ10 mutation was c.812G>A (p.R271H). Compared with the normal-hearing control subjects, the occurrence rate of c.812G>A in NSEVA patients with lacking mutations in one or both alleles of SLC26A4 had no significant difference(1.53% vs. 5.30%, χ² = 2.798, p = 0.172), which suggested that it is probably a nonpathogenic benign variant. KCNJ10 c.1042C>T (p.R348C), the reported EVA-related mutation, was not found in patients with NSEVA who lacked mutations in either one or both alleles of SLC26A4. Furthermore, the normal-hearing parents of patients with NSEVA having two SLC26A4 mutations carried the KCNJ10 c.1042C>T or c.812G>A mutation and a SLC26A4 pathogenic mutation.

Conclusion

SLC26A4 is the major genetic cause in Chinese NSEVA patients, accounting for 87.59%. KCNJ10 may not be a contributor to NSEVA in Chinese population. Other genetic or environmental factors are possibly play a role in the etiology of Chinese EVA patients with zero or monoallelic SLC26A4 mutation.

[Analysis the relationship between the found ways and first diagnosis age for large vestibular aqueduct children]

OBJECTIVE

To explore the found ways and first diagnosis age of children with large vestibular aqueduct, and their relations with hearing loss.

METHOD

Medical histories of 122 cases of children diagnosed with large vestibular aqueduct by HRCT or MRI had been collected from January 2009 to April 2014 in our hospital children's hearing diagnosis center clinic. Found ways comprise of accepting universal newborn hearing screening (UNHS) group and unaccepting UNHS group. Accepting UNHS children were divided into two ears unpassing group, single ear unpassing group and passing group. The patients in unaccepting UNHS group were divided into not sensitive to sounds, speech stunting, sudden hearing loss, and other group. Analysis the relationship between the found ways and first diagnosis age and their relations with hearing loss.

RESULT

There are 84 cases (68.85%) accepting UNHS, the average age of first diagnosis was (17.24 ± 17.08) months; 37 cases (31.15%) are not accepting UNHS. The average age of first diagnosis was (30.92 ± 18.21) months. The average first diagnosis age of accepting UNHS group was more earlier than the unaccepting UNHS group. The difference was statistically signif- icant (P < 0.01). There were 57 cases (67.85%) whose two ears not pass UNHS; 15 cases (17.86%) single ear not pass; namely the referral rate was 85.71%; 12 cases (14.29%) pass the test. The first diagnosis age of passing UNHS group was more later than two ears unpassing group (P < 0.001). In the unaccepting UNHS group, the average first diagnosis age of not sensitive to sounds group (19.69 ± 11.16 months) was more earlier than words dysplasia group (37.13 ± 15.62 months) and sudden hearing loss group (47.40 ± 24.70 months) (P < 0.01). The difference in the degree of hearing loss between accepting UNHS and unaccepting UNHS group had no statistical significance (P > 0.05). In unaccepting UNHS group ,the average first diagnosis age of the mild-to-moderate hearing loss group was later than the very severe hearing loss group (P < 0.01).

CONCLUSION

Most of large vestibular aqueduct children can be found and receive diagnosis early by UNHS. But part of these patients with late-onset or progressive hearing loss, especially these with mild-to-moderate hearing loss cannot be found early, which should arouse our attention.

Correlation analysis of genotypes, auditory function, and vestibular size in Chinese children with enlarged vestibular aqueduct syndrome

CONCLUSION

In children with enlarged vestibular aqueduct syndrome (EVAS), their hearing was more related to genotype than VA size, and VA size was related to genotype.

OBJECTIVE

To study genotypes of the SLC26A4 gene, types and levels of hearing loss, and vestibular aqueduct (VA) size in children with EVAS.

METHODS

A total of 271 children with nonsyndromic sensorineural hearing loss and EVA underwent SLC26A4 gene screening. According to genotype typing, the phenotypes including pure tone average (PTA), distribution of subjects, and diameters of the external aperture and middle portion of the VA, were compared by t test or Pearson's χ(2) tests. Further, divided by the dilated level of the VA, subject distribution in different hearing loss levels was compared by Pearson's χ(2) test.

RESULTS

In all, 66 types of mutations were identified and 2 were novel (c.665G >T and c.1639G >A). Biallelic genotype was found in 207 subjects, monoallelic in 56, and no mutation in 8. The hearing loss was more stable in the subjects with monoallelic mutation than in other genotype groups. An air-bone gap was more frequently found in subjects with biallelic missense mutations than in other groups. The patients with no mutation had the most slightly enlarged VA. There was no dominant correlation between hearing loss level and VA size, and between VA size and different genotypes.

[Current status and perspectives of the research in Pendred syndrome]

Pendred syndrome is an autosomal recessive disorder characterized by sensorineural hearing loss, goiter, and a partial defect in iodide organification, and is the most common syndromic hearing loss. Hearing loss is congenital in most cases and is accompanied by an enlarged vestibular aqueduct and a Mondini cochlea. Pendred syndrome and autosomal recessive deafness-4 (DFNB4) with enlarged vestibular aqueduct comprise a phenotypic spectrum caused by mutations in SLC26A4. Recently, mutations in FOXI1 and KCNJ10 have also been identified in DFNB4. Molecular mechanism of hearing loss and goiter remains to be elucidated, and therapies which can reverse or prevent the progression of the symptoms are not available. Here, we describe advances in the basic, clinical, and translational studies on Pendred syndrome.

[Clinical analysis of in-patients with large vestibular aqueduct syndrome]

OBJECTIVE

This study is to investigate the clinical materials of in-patients with the large vestibular aqueduct syndrome (LVAS), and explore the feature, diagnosis and treatment measures of the disease.

METHOD

A retrospective review was conducted including the medical history, audiological examinations, vestibular function examinations, imaging examinations and treatment methods of 44 in patients (87 ears) suffering LVAS admitted to our hospital in the past 4 years(from 2008 to 2012).

RESULT

ln the 44 in patients, there were 24 male cases and 20 female cases, and the male-female ratio was 1.2 :1. The average of the onset age was 3.39 years. Five cases (11. 36%) had related familial history. The profound hearing loss was found in 67 ears (77.01%), and the severe hearing loss was found in 20 ears (22.99%). After systemic treatment,the hearing of 38 ears improved effectively,but that of 49 ears did not improve obviously. The analysis found that patients suffering sudden hearing loss got better curative effect than those with progressive hearing loss. Patients received combined drug therapy improving arterial circulation as well as venous reflux got better therapeutic effect. There was a significant difference on effect between the patients with course of treatment more than 7 days and those less than 7 days. There was no significant correlation between therapeutic effect and other factors.

CONCLUSION

In part of LVAS patients,the hearing level can be effectively improved through a standard internal medicine treatment. We can improve the personalized and standardized treatment strategy for this disease through analysis of diagnosis and treatment of in-patients with complete clinical data.

[The clinical application of gene chips combined with CT examination in the diagnosis of large vestibular aqueduct syndrome patients]

OBJECTIVE

To explore the feasibility and superiority of the gene chip method and temporal bone CT in diagnosis of large vestibular aqueduct syndrome.

METHOD

One hundred and eighty-eight cases of deaf students in Guangzhou were selected,the microarray detection of the SLC26A4 gene locus was performed,and the 26 cases of students with detected SLC26A4 gene mutations received temporal bone CT imaging.

RESULT

Among the detected 26 cases of patients with hearing loss, IVS7-2A>G homozygous mutation was found in 7 cases, 17 cases were heterozygous mutation, 2168A>G heterozygous mutation presented in three cases, including one case of IVS7-2A>G and 2168A>G compound heterozygous mutations. Temporal bone CT findings of 25 cases among the 26 patients showed bilateral large vestibular aqueduct,among which 9 cases exhibited bilateral cochlear malformations, and 1 case was normal.

CONCLUSION

Among the different SLC26A4 gene mutations, IVS7-2A>G point mutation rates the highest, followed by 2168A>G. Most of the CT examination prompted the expansion of the vestibular aqueduct. Deafness gene chip hotspot detection of SLC26A4 gene mutations can diagnose such patients before CT examination,which can be used for screening people with high risk of deafness prenatal screening. The early detection and early diagnosis can guide proper precautionary measures in advance to prevent the occurrence of prelingual deafness.

Compound heterozygous mutations of SLC26A4 in 4 Chinese families with enlarged vestibular aqueduct

OBJECTIVE

Enlarged vestibular aqueduct is the most common inner ear malformation in individuals with sensorineural hearing loss. Mutations in SLC26A4 can cause non-syndromic EVA. To date, more than 170 SLC26A4 mutations have been described. The aim of the present study was to detect and report genetic causes of four unrelated Chinese families with hearing loss.

METHODS

We evaluated 4 families presenting bilateral enlarged vestibular aqueducts and describe the clinical and molecular characteristics of 5 patients.

RESULTS

The SLC26A4 gene was sequenced in 23 members of these 4 Chinese families with EVA, and the patients were found to carry 4 compound heterozygous mutations, p.G197R and p.S391R, IVS7-2A>G, p.I188T and c.1746 del G, p.V659L and p.T410M, and p.T94I and p.G197R, none of which have been reported previously.

CONCLUSIONS

These results emphasize the necessity of considering the complete DNA sequencing of the SLC26A4 gene in molecular diagnosis of deafness, especially when phenotypes such as congenital, invariable, and progressive hearing loss with EVA are present.

Molecular epidemiology and functional assessment of novel allelic variants of SLC26A4 in non-syndromic hearing loss patients with enlarged vestibular aqueduct in China

Background

Mutations in SLC26A4, which encodes pendrin, are a common cause of deafness. SLC26A4 mutations are responsible for Pendred syndrome and non-syndromic enlarged vestibular aqueduct (EVA). The mutation spectrum of SLC26A4 varies widely among ethnic groups. To investigate the incidence of EVA in Chinese population and to provide appropriate genetic testing and counseling to patients with SLC26A4 variants, we conducted a large-scale molecular epidemiological survey of SLC26A4.

Methods

A total of 2352 unrelated non-syndromic hearing loss patients from 27 different regions of China were included. Hot spot regions of SLC26A4, exons 8, 10 and 19 were sequenced. For patients with one allelic variant in the hot spot regions, the other exons were sequenced one by one until two mutant alleles had been identified. Patients with SLC26A4 variants were then examined by temporal bone computed tomography scan for radiological diagnosis of EVA. Ten SLC26A4 variants were cloned for functional study. Confocal microscopy and radioisotope techniques were used to examine the membrane expression of pendrin and transporter function.

Results

Of the 86 types of variants found, 47 have never been reported. The ratio of EVA in the Chinese deaf population was at least 11%, and that in patients of Han ethnicity reached at least 13%. The mutational spectrum and mutation detection rate of SLC26A4 are distinct among both ethnicities and regions of Mainland China. Most of the variants caused retention of pendrin in the intracellular region. All the mutant pendrins showed significantly reduced transport capability.

Conclusion

An overall description of the molecular epidemiological findings of SLC26A4 in China is provided. The functional assessment procedure can be applied to identification of pathogenicity of variants. These findings are valuable for genetic diagnosis, genetic counseling, prenatal testing and pre-implantation diagnosis in EVA families.

[The research progress of large vestibular aqueduct syndrome]

Large vestibular aqueduct syndrome (LVAS) is one of common non-syndromic hearing disorders. With the rapid development of medical imaging, audiology, molecular biology, genetics, cochlear implant surgery, we have made remarkable achievements in the diagnosis and treatment of large vestibular aqueduct syndrome. This article reviewed related researches of the large vestibular aqueduct syndrome.

[Vertigo due to enlarged vestibule with lateral semicircular canal dysplasia: an analysis of clinical characteristics]

OBJECTIVE

To explore the clinical characteristics and possible pathological mechanisms of vertigo due to enlarged vestibule with lateral semicircular canal dysplasia.

METHODS

A retrospective review was conducted for 5 cases of peripheral vertigo due to enlarged vestibule with lateral semicircular canal dysplasia. Their characteristics of medical history, precipitating factors, course of vertigo, auditory tests, vestibular tests and imaging examine results were analyzed.

RESULTS

The clinical characteristics were as follows. (1) Specifics of medical history: 4 cases suffered delays in gross motor development and potential equilibrium dysfunctions. One case failed to recount an earlier medical history, but could maintain normal hearing and vestibular functions for a long time in adulthood. (2) Most cases could identify the precipitating factors of initial attacks, such as head-bumping, nose-blowing and constipation, etc. resulting in sudden rises of intracranial or abdominal pressures. (3) Paroxysmal vertigo and progressive hearing loss were mimicking Meniere disease or large vestibular aqueduct syndrome. But its course of vertigo was different from those of Meniere disease and large vestibular aqueduct syndrome with regards to hearing levels and audiograms. (4) Some cases had positional vertigo. But the results of Dix-Hallpike and Roll tests were different from benign paroxysmal positioning vertigo (BPPV). (5) The inner ear imaging showed enlarged vestibule with lateral semicircular canal dysplasia.

CONCLUSION

The enlarged vestibule with lateral semicircular canal dysplasia is a rare etiology of peripheral vertigo. The history of delays in gross motor development and potential equilibrium dysfunctions in childhood may offer important diagnostic clues. And audiological and vestibular tests, high-resolution computed tomography and magnetic resonance may help to ascertain the diagnosis.

Hearing loss associated with enlargement of the vestibular aqueduct: mechanistic insights from clinical phenotypes, genotypes, and mouse models

Enlargement of the vestibular aqueduct (EVA) is one of the most common inner ear malformations associated with sensorineural hearing loss in children. The delayed onset and progressive nature of this phenotype offer a window of opportunity to prevent or retard progression of hearing loss. EVA is not the direct cause of hearing loss in these patients, but rather is a radiologic marker for some underlying pathogenetic defect. Mutations of the SLC26A4 gene are a common cause of EVA. Studies of an Slc26a4 knockout mouse demonstrate that acidification and enlargement of the scala media are early events in the pathogenesis of deafness. The enlargement is driven by fluid secretion in the vestibular labyrinth and a failure of fluid absorption in the embryonic endolymphatic sac. Elucidating the mechanism of hearing loss may offer clues to potential therapeutic strategies.

Hereditary hearing loss with thyroid abnormalities

Mutations in SLC26A4 can cause deafness and goiter in Pendred syndrome (PDS) or isolated non-syndromic enlargement of the vestibular aqueduct (NSEVA). PDS is one of the most common hereditary causes of deafness. It is characterized by autosomal-recessive inheritance of sensorineural hearing loss, enlarged vestibular aqueducts (EVA), and an iodide organification defect with or without goiter. The diagnosis is confirmed by detection of two mutant alleles of SLC26A4 in a patient with EVA. The perchlorate discharge test can detect the underlying thyroid biochemical defect and is useful for the evaluation of goiter or for the clinical diagnosis of PDS in a patient with a non-diagnostic SLC26A4 genotype. SLC26A4 encodes the pendrin polypeptide, an anion exchanger that, in recombinant expression systems, transports chloride, bicarbonate, and iodide. Investigation of pendrin function in the inner ear has been facilitated by the Slc26a4(Δ) (knockout) mouse model, but the exact mechanism of its hearing loss remains unclear, as does pendrin's principal transport function in the inner ear. Treatment of PDS is focused upon rehabilitation of hearing loss, and surveillance and management of goiter and, less commonly, hypothyroidism.

Novel ATP6V1B1 mutations in distal renal tubular acidosis and hearing loss

CONCLUSION

Novel ATP6V1B1 mutations were found in a patient with distal renal tubular acidosis (dRTA), hearing loss (HL), and enlargement of the vestibular aqueduct (EVA). The deterioration of HL and vertiginous attacks may be associated with the disruption of the endolymph pH homeostasis.

OBJECTIVES

To study the audiovestibular functions and to identify the causative gene.

METHODS

This study enrolled a Japanese family, where the proband showed type 1 dRTA, early onset HL, and bilateral EVA. A deterioration of HL occurred several times in both ears. Vertiginous attacks were always associated with a deterioration of HL. Audiovestibular examinations included distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs), caloric testing, and vestibular evoked myogenic potentials (VEMPs). Direct sequencing was utilized to screen for ATP6V1B1, SLC26A4, and GJB2 mutations.

RESULTS

The findings of DPOAEs and ABRs indicated cochlear HL. The vestibular function was thought to be mildly impaired according to the caloric responses and VEMP findings. Two novel ATP6V1B1 mutations of a heterozygous 15 base-pair deletion (c.756_770del) in exon 7 and a heterozygous 1 base-pair insertion (c.1242_1243insC) in exon 12 were detected in a compound heterozygous state. No mutation was identified in either SLC26A4 or GJB2.

[The clinical significance of ABR testing in the diagnosis of the large vestibular aqueduct syndrome]

OBJECTIVE

To analyse the clinical audiological significance in the diagnosis of large vestibular aqueduct syndrome (LVAS) by the auditory brain stem response (ABR) testing.

METHOD

Patients with sensorineural hearing loss were examined by temporal bone CT scanning from January, 2008 to September, 2009. The result of CT scanning of 70 cases inner ear malformation were analysed. Patients were divided into two groups, LVAS group including 38 cases (76 ears) and other inner ear malformation group including 32 cases (62 ears). All patient accepted clinical audiology analysis and auditory brainstem response (ABR) test.

RESULT

Twenty-four cases (41 ears) of LVAS group were detected with ASNR in 2 3 cm by the ABR testing, the positive rate was 54%, while ASNR was not detected in patients of other inner ear malformations group. There was significant differences (P=0.01) of the ASNR between two groups.

CONCLUSION

There is high incidence of LVAS on the patients with non-syndromic deafness. ASNR by ABR testing could help diagnosing the LVAS.

Hereditary hearing loss and deafness genes in Japan

Hearing loss (HL) is the most common sensory impairment occurring at birth in developed countries. Epidemiological data show that more than one child in 1000 is born with HL, while more than 50% of prelingual HL cases are found to be hereditary. Approximately 70% of hereditary HL is nonsyndromic and subdivided to autosomal dominant (20%), autosomal recessive (75%), X-linked HL (1%), and maternally-inherited HL associated with the mitochondrial DNA mutation. More than 10 deafness genes have been reported to be responsible for nonsyndromic hereditary HL in Japan. Among them, the most prevalent causative genes, GJB2 and the mitochondrial DNA 12SrRNA are introduced. In addition, this study also refers to the specific genes responsible for the unique audiogram, mainly WFS1. Finally, the genes related to the enlargement of vestibular aqueduct of inner ear abnormality, SLC26A4, EYA1 and SIX1 are discussed. The clinical and genetic findings associated with these disorders including the results of a recent study are reviewed.

SLC26A4 genotype, but not cochlear radiologic structure, is correlated with hearing loss in ears with an enlarged vestibular aqueduct

OBJECTIVES/HYPOTHESIS

Identify correlations among SLC26A4 genotype, cochlear structural anomalies, and hearing loss associated with enlargement of the vestibular aqueduct (EVA).

STUDY DESIGN

Prospective cohort survey, National Institutes of Health, Clinical Center, a federal biomedical research facility.

METHODS

Eighty-three individuals, 11 months to 59 years of age, with EVA in at least one ear were studied. Correlations among pure-tone hearing thresholds, number of mutant SLC26A4 alleles, and the presence of cochlear anomalies detected by computed tomography or magnetic resonance imaging were examined.

RESULTS

Linear mixed-effects model indicated significantly poorer hearing in ears with EVA in individuals with two mutant alleles of SLC26A4 than in those with EVA and a single mutant allele (P = .012) or no mutant alleles (P = .007) in this gene. There was no detectable relationship between degree of hearing loss and the presence of structural cochlear anomalies.

CONCLUSIONS

The number of mutant alleles of SLC26A4, but not the presence of cochlear anomalies, has a significant association with severity of hearing loss in ears with EVA. This information will be useful for prognostic counseling of patients and families with EVA.

Hearing loss in patients with enlarged vestibular aqueduct: Air-bone gap and audiological Bing test

The Bing test is based on the principle that occlusion of the external auditory meatus improves the perception of bone-conducted sounds unless there is a conductive hearing impairment. An air-bone gap has been reported in patients with large vestibular aqueduct (LVA) syndrome without apparent middle ear dysfunction. We therefore performed the Bing test on nine patients with this syndrome to evaluate whether it is associated with an air-bone gap or middle ear dysfunction. Bone conduction thresholds did not change significantly during the Bing test in any patient. Because an air-bone gap is observed in patients with abnormal communication between the inner ear and cerebrospinal fluid through the LVA, dehiscent superior canal, or dilated inner ear meatus; we propose that a 'three windows' model (in which the abnormal communication provided by the enlarged endolymphatic duct and sac in LVA acts as the 'third window' for sound conductance) might explain the air-bone gap in such patients.

Do mutations of the Pendred syndrome gene, SLC26A4, confer resistance to asthma and hypertension?

BACKGROUND AND AIMS

Mutations of SLC26A4 cause Pendred syndrome, an autosomal recessive disorder comprising goitre and deafness with enlarged vestibular aqueducts (EVA). Recent studies in mouse models implicate Slc26a4 in the pathogenesis of asthma and hypertension. We hypothesise that asthma and hypertension are less prevalent among humans with SLC26A4 mutations.

METHODS

We reviewed medical histories and SLC26A4 genotypes for 80 individuals with EVA and 130 of their unaffected family members enrolled in a study of EVA. We used Fisher's exact test to compare the prevalence of asthma and hypertension among groups of subjects with zero, one, or two mutant alleles of SLC26A4.

RESULTS

Although none of the 21 subjects with two mutant alleles of SLC26A4 had asthma or hypertension, there were no statistically significant differences in the prevalence of asthma or hypertension among subjects with zero, one, or two mutant alleles.

CONCLUSION

There might be a protective effect of SLC26A4 mutations for asthma and hypertension but our study is statistically underpowered to detect this effect. Study sizes of at least 1125 and 504 individuals will be needed for 80% power to detect an effect at alpha = 0.05 for asthma and hypertension, respectively. Our hypothesis merits a larger study since it has implications for potential strategies to treat hearing loss by manipulating SLC26A4 expression or function.

Mutations of KCNJ10 together with mutations of SLC26A4 cause digenic nonsyndromic hearing loss associated with enlarged vestibular aqueduct syndrome

Mutations in SLC26A4 cause nonsyndromic hearing loss associated with an enlarged vestibular aqueduct (EVA, also known as DFNB4) and Pendred syndrome (PS), the most common type of autosomal-recessive syndromic deafness. In many patients with an EVA/PS phenotype, mutation screening of SLC26A4 fails to identify two disease-causing allele variants. That a sizable fraction of patients carry only one SLC26A4 mutation suggests that EVA/PS is a complex disease involving other genetic factors. Here, we show that mutations in the inwardly rectifying K(+) channel gene KCNJ10 are associated with nonsyndromic hearing loss in carriers of SLC26A4 mutations with an EVA/PS phenotype. In probands from two families, we identified double heterozygosity in affected individuals. These persons carried single mutations in both SLC26A4 and KCNJ10. The identified SLC26A4 mutations have been previously implicated in EVA/PS, and the KCNJ10 mutations reduce K(+) conductance activity, which is critical for generating and maintaining the endocochlear potential. In addition, we show that haploinsufficiency of Slc26a4 in the Slc26a4(+/-) mouse mutant results in reduced protein expression of Kcnj10 in the stria vascularis of the inner ear. Our results link KCNJ10 mutations with EVA/PS and provide further support for the model of EVA/PS as a multigenic complex disease.

Hypo-functional SLC26A4 variants associated with nonsyndromic hearing loss and enlargement of the vestibular aqueduct: genotype-phenotype correlation or coincidental polymorphisms?

Hearing loss with enlargement of the vestibular aqueduct (EVA) can be associated with mutations of the SLC26A4 gene encoding pendrin, a transmembrane Cl(-)/I(-)/HCO(3)(-) exchanger. Pendrin's critical transport substrates are thought to be I(-) in the thyroid gland and HCO(3)(-) in the inner ear. We previously reported that bi-allelic SLC26A4 mutations are associated with Pendred syndromic EVA whereas one or zero mutant alleles are associated with nonsyndromic EVA. One study proposed a correlation of nonsyndromic EVA with SLC26A4 alleles encoding pendrin with residual transport activity. Here we describe the phenotypes and SLC26A4 genotypes of 47 EVA patients ascertained since our first report of 39 patients. We sought to determine the pathogenic potential of each variant in our full cohort of 86 patients. We evaluated the trafficking of 11 missense pendrin products expressed in COS-7 cells. Products that targeted to the plasma membrane were expressed in Xenopus oocytes for measurement of anion exchange activity. p.F335L, p.C565Y, p.L597S, p.M775T, and p.R776C had Cl(-)/I(-) and Cl(-)/HCO(3)(-) exchange rate constants that ranged from 13 to 93% of wild type values. p.F335L, p.L597S, p.M775T and p.R776C are typically found as mono-allelic variants in nonsyndromic EVA. The high normal control carrier rate for p.L597S indicates it is a coincidentally detected nonpathogenic variant in this context. We observed moderate differential effects of hypo-functional variants upon exchange of HCO(3)(-) versus I(-) but their magnitude does not support a causal association with nonsyndromic EVA. However, these alleles could be pathogenic in trans configuration with a mutant allele in Pendred syndrome.