Fluctuating sensorineural hearing loss associated with enlarged vestibular aqueduct maps to 7q31, the region containing the pendred gene

Analysis of SLC26A4, FOXI1, and KCNJ10 Gene Variants in Patients with Incomplete Partition of the Cochlea and Enlarged Vestibular Aqueduct (EVA) Anomalies

Pathogenic variants in the SLC26A4, FOXI1, and KCNJ10 genes are associated with hearing loss (HL) and specific inner ear abnormalities (DFNB4). In the present study, phenotype analyses, including clinical data collection, computed tomography (CT), and audiometric examination, were performed on deaf individuals from the Sakha Republic of Russia (Eastern Siberia). In cases with cochleovestibular malformations, molecular genetic analysis of the coding regions of the SLC26A4, FOXI1, and KCNJ10 genes associated with DFNB4 was completed. In six of the 165 patients (3.6%), CT scans revealed an incomplete partition of the cochlea (IP-1 and IP-2), in isolation or combined with an enlarged vestibular aqueduct (EVA) anomaly. Sequencing of the SLC26A4, FOXI1, and KCNJ10 genes was performed in these six patients. In the SLC26A4 gene, we identified four variants, namely c.85G>C p.(Glu29Gln), c.757A>G p.(Ile253Val), c.2027T>A p.(Leu676Gln), and c.2089+1G>A (IVS18+1G>A), which are known as pathogenic, as well as c.441G>A p.(Met147Ile), reported previously as a variant with uncertain significance. Using the AlphaFold algorithm, we found in silico evidence of the pathogenicity of this variant. We did not find any causative variants in the FOXI1 and KCNJ10 genes, nor did we find any evidence of digenic inheritance associated with double heterozygosity for these genes with monoallelic SLC26A4 variants. The contribution of biallelic SLC26A4 variants in patients with IP-1, IP-2, IP-2+EVA, and isolated EVA was 66.7% (DFNB4 in three patients, Pendred syndrome in one patient). Seventy-five percent of SLC26A4-biallelic patients had severe or profound HL. The morphology of the inner ear anomalies demonstrated that, among SLC26A4-biallelic patients, all types of incomplete partition of the cochlea are possible, from IP-1 and IP-2, to a normal cochlea. However, the dominant type of anomaly was IP-2+EVA (50.0%). This finding is very important for cochlear implantation, since the IP-2 anomaly does not have an increased risk of “gushers” and recurrent meningitis.

Contralateral hearing loss in children with a unilateral enlarged vestibular aqueduct

OBJECTIVE

To evaluate the long-term ipsi- and contralateral hearing of patients with a unilateral enlarged vestibular aqueduct (EVA).

STUDY DESIGN

Multicenter retrospective cohort study.

SETTING

Three tertiary otology and audiology referral centers.

PATIENTS AND DIAGNOSTIC INTERVENTIONS

A total of 34 children with a unilateral enlarged vestibular aqueduct as identified on CT and/or MR imaging were evaluated with pure tone and speech perception audiometry.

MEAN OUTCOME MEASURES

Radiologic measurements of the vestibular aqueduct, ipsi- and contralateral hearing loss, ipsi- and contralateral hearing loss progression over time and DNA test results.

RESULTS

All patients in this cohort with unilateral EVA presented with hearing loss. Hearing loss was progressive in 38% of the ipsilateral ears. In 29% of the children, hearing loss was also found in the contralateral ear without EVA. In 90%, the contralateral hearing was stable, with a mean follow up of 4.2 years. We found a significant correlation between the severity of the hearing loss and the size of the EVA. A genetic diagnosis associated with EVA and/or SNHL was found in only 7%.

CONCLUSION

About a third of the children with unilateral EVA are at risk of developing hearing loss in the contralateral ear. This indicates that at least in some patients with a unilateral EVA, a bilateral pathogenic process underlies the hearing loss, in contrary to what the imaging results suggest. These findings are important for counseling of EVA patients and their parents and have implications for follow up.

Cochlear Implantation in Pediatric Patients With Enlarged Vestibular Aqueduct: A Systematic Review

OBJECTIVE(S)

To describe cochlear implantation (CI) outcomes, with speech perception, auditory, language, and parent-reported auditory and speech behaviors, in children with an enlarged vestibular aqueduct (EVA) and incomplete partition type 2 (IP-II) and compare to control children without inner ear malformations (IEMs) and to determine cerebrospinal fluid gusher rates and effect on outcomes.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

MEDLINE, Embase, Cochrane, and CINAHL databases were searched from inception to February 2020. Studies reporting relevant outcomes in children with EVA or EVA + IP-II and controls without IEMs undergoing CI were included. Mean differences in speech perception, auditory, and language scores between cases and controls were meta-analyzed. Gusher rates were determined by proportion meta-analyses.

RESULTS

Of 214 identified articles, 42 met inclusion criteria, evaluating 775 cases and 2,191 controls. Of -cases, 578 (74.6%) had EVA and 197 (25.4%) had EVA + IP-II. Cases showed a significant improvement in speech perception, auditory and language performance, comparable to controls. Parent-reported auditory and speech production behaviors outcomes were positive among cases and comparable to controls. Pooled gusher proportions in EVA and EVA + IP-II cases were 27.7% (95% CI: 17.6-39.1) and 48.6% (95% CI: 28.6-69.0), respectively, with a proportion difference of 20.9% (95% CI: 11.0-30.1). Gusher occurrence did not impact speech perception or language outcomes.

CONCLUSION

Outcomes in children with EVA or EVA + IP-II undergoing CI are favorable and largely comparable to outcomes in children with hearing loss undergoing CI without IEMs. Intraoperative gusher is more prevalent among children with EVA + IP-II as compared to iEVA. Gusher does not influence speech perception and language development outcomes.

LEVEL OF EVIDENCE

NA Laryngoscope, 2021.

DENTAL ENAMEL FORMATION AND IMPLICATIONS FOR ORAL HEALTH AND DISEASE

Dental enamel is the hardest and most mineralized tissue in extinct and extant vertebrate species and provides maximum durability that allows teeth to function as weapons and/or tools as well as for food processing. Enamel development and mineralization is an intricate process tightly regulated by cells of the enamel organ called ameloblasts. These heavily polarized cells form a monolayer around the developing enamel tissue and move as a single forming front in specified directions as they lay down a proteinaceous matrix that serves as a template for crystal growth. Ameloblasts maintain intercellular connections creating a semi-permeable barrier that at one end (basal/proximal) receives nutrients and ions from blood vessels, and at the opposite end (secretory/apical/distal) forms extracellular crystals within specified pH conditions. In this unique environment, ameloblasts orchestrate crystal growth via multiple cellular activities including modulating the transport of minerals and ions, pH regulation, proteolysis, and endocytosis. In many vertebrates, the bulk of the enamel tissue volume is first formed and subsequently mineralized by these same cells as they retransform their morphology and function. Cell death by apoptosis and regression are the fates of many ameloblasts following enamel maturation, and what cells remain of the enamel organ are shed during tooth eruption, or are incorporated into the tooth's epithelial attachment to the oral gingiva. In this review, we examine key aspects of dental enamel formation, from its developmental genesis to the ever-increasing wealth of data on the mechanisms mediating ionic transport, as well as the clinical outcomes resulting from abnormal ameloblast function.

A novel KCNQ4 mutation and a private IMMP2L-DOCK4 duplication segregating with nonsyndromic hearing loss in a Brazilian family

Here we describe a novel missense variant in the KCNQ4 gene and a private duplication at 7q31.1 partially involving two genes (IMMP2L and DOCK4). Both mutations segregated with nonsyndromic hearing loss in a family with three affected individuals. Initially, we identified the duplication in a screening of 132 unrelated cases of hearing loss with a multiplex ligation-dependent probe amplification panel of genes that are candidates to have a role in hearing, including IMMP2L. Mapping of the duplication by array-CGH revealed that the duplication also encompassed the 3′-end of DOCK4. Subsequently, whole-exome sequencing identified the breakpoint of the rearrangement, thereby confirming the existence of a fusion IMMP2L-DOCK4 gene. Transcription products of the fusion gene were identified, indicating that they escaped nonsense-mediated messenger RNA decay. A missense substitution (c.701A>T) in KCNQ4 (a gene at the DFNA2A locus) was also identified by whole-exome sequencing. Because the substitution is predicted to be probably damaging and KCNQ4 has been implicated in hearing loss, this mutation might explain the deafness in the affected individuals, although a hypothetical effect of the product of the fusion gene on hearing cannot be completely ruled out.

EPS8L2 is a new causal gene for childhood onset autosomal recessive progressive hearing loss

Background

More than 70 % of the cases of congenital deafness are of genetic origin, of which approximately 80 % are non-syndromic and show autosomal recessive transmission (DFNB forms). To date, 60 DFNB genes have been identified, most of which cause congenital, severe to profound deafness, whereas a few cause delayed progressive deafness in childhood. We report the study of two Algerian siblings born to consanguineous parents, and affected by progressive hearing loss.

Method

After exclusion of GJB2 (the gene most frequently involved in non-syndromic deafness in Mediterranean countries), we performed whole-exome sequencing in one sibling.

Results

A frame-shift variant (c.1014delC; p.Ser339Alafs*15) was identified in EPS8L2, encoding Epidermal growth factor receptor Pathway Substrate 8 L2, a protein of hair cells’ stereocilia previously implicated in progressive deafness in the mouse. This variant predicts a truncated, inactive protein, or no protein at all owing to nonsense-mediated mRNA decay. It was detected at the homozygous state in the two clinically affected siblings, and at the heterozygous state in the unaffected parents and one unaffected sibling, whereas it was never found in a control population of 150 Algerians with normal hearing or in the Exome Variant Server database.

Conclusion

Whole-exome sequencing allowed us to identify a new gene responsible for childhood progressive hearing loss transmitted on the autosomal recessive mode.

Identification of SLC26A4 c.919-2A>G compound heterozygosity in hearing-impaired patients to improve genetic counseling

Background

Mutations in the SLC26A4 gene, which encodes the anion transporter, pendrin, are a major cause of autosomal recessive non-syndromic hearing loss (NSHL) in some Asian populations. SLC26A4 c.919-2A>G (IVS7-2A>G) is the most common mutation in East Asian deaf populations. To provide a basis for improving the clinical diagnosis of deaf patients, we evaluated 80 patients with the SLC26A4 c.919-2A>G monoallelic mutation from 1065 hearing-impaired subjects and reported the occurrence of a second mutant allele in these patients.

Methods

The occurrence of a second mutant allele in these 80 patients with a single c.919-2A>G mutation was investigated. Mutation screening was performed by bidirectional sequencing in SLC26A4 exons 2 to 6 and 9 to 21.

Results

We found that 47/80 patients carried another SLC26A4 c.919-2A>G compound mutation. The five most common mutations were: p.H723R, p.T410M, 15+5G>A (c.1705+5G>A), p.L676Q and p.N392Y. We found a Chinese-specific SLC26A4 mutation spectrum and an associated SLC26A4 contribution to deafness.

Conclusion

Our study illustrates that mutation analysis of other SLC26A4 exons should be undertaken in deaf patients with a single heterozygous SLC26A4 mutation. Moreover, a model of compound heterozygosity may partially explain the disease phenotype.

Epithelial cell stretching and luminal acidification lead to a retarded development of stria vascularis and deafness in mice lacking pendrin

Loss-of-function mutations of SLC26A4/pendrin are among the most prevalent causes of deafness. Deafness and vestibular dysfunction in the corresponding mouse model, Slc26a4^−/−, are associated with an enlargement and acidification of the membranous labyrinth. Here we relate the onset of expression of the HCO₃⁻ transporter pendrin to the luminal pH and to enlargement-associated epithelial cell stretching. We determined expression with immunocytochemistry, cell stretching by digital morphometry and pH with double-barreled ion-selective electrodes. Pendrin was first expressed in the endolymphatic sac at embryonic day (E) 11.5, in the cochlear hook-region at E13.5, in the utricle and saccule at E14.5, in ampullae at E16.5, and in the upper turn of the cochlea at E17.5. Epithelial cell stretching in Slc26a4^−/− mice began at E14.5. pH changes occurred first in the cochlea at E15.5 and in the endolymphatic sac at E17.5. At postnatal day 2, stria vascularis, outer sulcus and Reissner's membrane epithelial cells, and utricular and saccular transitional cells were stretched, whereas sensory cells in the cochlea, utricle and saccule did not differ between Slc26a4^+/− and Slc26a4^−/− mice. Structural development of stria vascularis, including vascularization, was retarded in Slc26a4^−/− mice. In conclusion, the data demonstrate that the enlargement and stretching of non-sensory epithelial cells precedes luminal acidification in the cochlea and the endolymphatic sac. Stretching and luminal acidification may alter cell-to-cell communication and lead to the observed retarded development of stria vascularis, which may be an important step on the path to deafness in Slc26a4^−/− mice, and possibly in humans, lacking functional pendrin expression.

Identification of two novel mutations, c.232T>C and c.2006A>T, in SLC26A4 in a Chinese family associated with enlarged vestibular aqueduct

It is known that enlarged vestibular aqueduct syndrome is closely related to the SLC26A4 mutation. Up to date, more than 200 of SLC26A4 mutations have been described, and novel mutations are being continually identified in different countries and ethnic groups. In this study, two novel variations were identified in a Chinese family associated with enlarged vestibular aqueduct. The two novel substitutions, c.232T>C and c.2006A>T, were detected in exon 3 and exon 17 of the pendrin encoding gene, respectively. The T/C transversion at 232 nucleotide caused p.Y78H mutation while the A/T transversion at 2006 nucleotide caused p.D669V mutation.

Pendred syndrome in Tunisia

OBJECTIVES

We report a clinical and genetic study of three consanguineous Tunisian families affected by Pendred syndrome.

PATIENTS AND METHODS

Three families from the south of Tunisia were identified as affected by Pendred syndrome. The patients and their families underwent ENT and general examination and audiovestibular and radiological tests. Molecular DNA analysis was performed by the Sfax Human Molecular Genetics Department.

RESULTS

Forty-three patients (mean age: 21 years [2-60 years]) were affected. Tonal audiometry showed bilateral sensorineural hearing loss in 87.5% of cases, and mixed hearing loss in 12.5% with bilateral high frequency sensorineural hearing loss and conductive hearing loss at lower frequencies. Deafness was severe in 21% and profound in 79% of cases. Thyroid goiter was found in 46.5% of cases. Inner ear CT scan found enlarged bilateral vestibular aqueducts in all cases. Hormone analysis was normal and perchlorate test negative in all cases. A single Pendred syndrome (PDS) gene mutation, L445W, was found.

DISCUSSION

Pendred syndrome is the most frequent congenital deafness syndrome. It is characterized by great intrafamilial phenotype variability.

Identification of a novel mutation in the SLC26A4 gene in an Italian with fluctuating sensorineural hearing loss

Pendred syndrome is an autosomal recessive disorder characterized by congenital sensorineural deafness, goitre and defective iodide organification. Congenital and profound hearing loss is the hallmark of the syndrome, while goitre and thyroid dysfunction are highly variable even within the same family. Clinical features are due to altered formation of pendrin, a chloride/iodide transporter protein expressed in the inner ear, thyroid gland and kidney. A novel substitution was found in exon 7 of the pendrin encoding gene (SLC26A4) that leads to a stop codon, S314X. The new variation was found in compound heterozygosity with L445W mutation in a hearing impaired patient with bilateral Mondini's dysplasia and goitre.

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.

GJB2, SLC26A4 and mitochondrial DNA A1555G mutations in prelingual deafness in Northern Chinese subjects

CONCLUSION

This genetic epidemiological study demonstrated that 26.65% of the prelingual deafness in Northern Chinese patients can be detected at younger ages by genetic testing of three common hearing loss genes (GJB2, SLC26A4 and mtDNA A1555G), and thus, early intervention measures could be undertaken to help them in language acquisition.

OBJECTIVES

The GJB2, SLC26A4 and mtDNA A1555G mutations are the prevalent causes of prelingual deafness worldwide. Numerous studies have revealed that the forms and frequencies of the mutations in the three genes are largely dependent on the ethnic or geographic origins. Hence, this study aimed to characterize the mutation profiles of the three genes in prelingual deafness in Northern Chinese patients. SUBECTS AND METHODS: An investigation of 514 patients with prelingual deafness and 117 controls with normal hearing was conducted. Bidirectional sequencing (or enzyme digestion) was applied to identify sequence variations.

RESULTS

This study revealed that 26.65% patients had two mutated alleles (homozygote or compound heterozygote) of GJB2 (9.14%) or SLC26A4 (8.95%) and/or an mtDNA A1555G (8.56%) mutation. In detail, 19.26% patients carried GJB2 mutations including 10.12% single mutant carriers. 235delC was the most common type, making up 69.18% of all mutants for GJB2. The mutant carrier rate for SLC26A4 was 15.2%, including 6.23% single mutant carriers. The two most common types (IVS7-2A > G and H723R) accounted for 51.61% and 33.06% mutations, respectively. Forty-five patients had mtDNA A1555G, giving a frequency of 8.75%. In the control group with normal hearing, 2.56%, 1.71% and 0% of the subjects carried a single mutant for GJB2, SLC26A4 and mtDNA A1555G, respectively.

Genotype-phenotype correlations for SLC26A4-related deafness

Pendred syndrome (PS) and non-syndromic enlarged vestibular aqueduct (EVA) are two recessive disorders characterized by the association of sensorineural hearing loss (SNHL) with inner ear malformations that range from isolated EVA to Mondini Dysplasia, a complex malformation that includes a cochlear dysplasia and EVA. Mutations in the SLC26A4 gene, coding for the protein pendrin, have been implicated in the pathophysiology of both disorders. In order to determine whether SLC26A4 genotypes can be correlated to the complexity and severity of the phenotypes, we ascertained 1,506 deaf patients. Inner ear abnormalities were present in 474 patients (32%). Mutation screening of SLC26A4 detected two mutations in 16% of patients, one mutation in 19% of patients and zero mutation in 65% of patients. When the distribution of SLC26A4 genotypes was compared across phenotypes, a statistically significant difference was found between PS patients and non-syndromic EVA-Mondini patients (P = 0.005), as well as between EVA patients and Mondini patients (P = 0.0003). There was a correlation between phenotypic complexity of inner ear malformations and genetic heterogeneity--PS patients have the most severe phenotype and the most homogeneous etiology while EVA patients have the least severe phenotype and the most heterogeneous etiology. For all patients, variability in the degree of hearing loss is seen across genotypes implicating other genetic and/or environmental factors in the pathogenesis of the PS-Mondini-EVA disease spectrum.

The large vestibular aqueduct--case report and review of the literature

Patients with a large vestibular aqueduct (LVA) suffer from a loss of hearing in childhood at an early onset. An acute loss of hearing can be precipitated by minor head trauma. Until now there seems to be no sufficient therapy for stopping the progression of a loss of hearing. It has been shown that a cochlear implantation is a worthwhile procedure if the patient is almost deaf. We report the case of a patient with a bilateral LVA. A loss of hearing was confirmed at the age of 16 months. Exposure to loud noise triggered an acute progression of the hearing loss. At the age of 18 years, LVA was confirmed radiologically, revealing an enlarged endolymphatic duct and sac in MRI scans and an enlarged vestibular aqueduct in the CT scan. We successfully performed a cochlear implant (MED-EL, Combi 40+ flex). Proceeding from this case report, the paper reviews the literature on LVA.

Congenital hearing impairment

Establishing the etiology of congenital hearing impairment can significantly improve treatment for certain causes of hearing loss and facilitates genetic counseling. High-resolution CT and MRI have contributed to the evaluation and management of hearing impairment. In addition, with the identification of innumerable genetic loci and genetic defects involved in hearing loss, genetic testing has emerged as an invaluable tool in the assessment of hearing impairment. Some of the common forms of congenital hearing loss are reviewed and their imaging features illustrated.

Characteristics of sensorineural hearing loss in children with inner ear anomalies

PURPOSE

To determine whether hearing loss in children with inner ear anomalies has some distinctive characteristics when compared to children with hearing loss but without inner ear anomalies.

METHODS

Temporal bone computed tomography scans of 69 patients with sensorineural hearing loss were examined for inner ear abnormalities of which 17 were identified. The medical histories of these patients were reviewed for the characteristics of their hearing loss, including initial presentation, natural history, and nature of loss, as well as the family history of hearing loss and risk factors for hearing loss. These were compared to age-matched controls with hearing loss but without inner ear anomalies.

RESULTS

Seventeen patients had inner ear anomalies. Records of 14 of these patients were compared to patients without inner ear anomalies. Regarding age of onset, 71.4% of patients with anomalies had onset of their hearing loss at less than 2 years old vs 78.6% without anomalies. Regarding unilateral vs bilateral, 42.9% of patients with anomalies were unilateral vs 28.6% of patients without anomalies. For patients with anomalies, 85.7% were stable and 14.3% were progressive; without anomalies, 71.4% were stable, 21.4% were progressive, and 7.1% were fluctuating. Regarding family history, only 14.3% of patients without anomalies had a positive family history vs 56% of patients with anomalies.

CONCLUSIONS

Children with inner ear anomalies and sensorineural hearing loss have an increased incidence of unilateral hearing loss and stable hearing loss as compared to controls with sensorineural hearing loss without inner ear anomalies. In addition, children with inner ear anomalies and sensorineural hearing loss are less likely to have a family history of hearing loss.

Large vestibular aqueduct syndrome: audiological, radiological, clinical, and genetic features

PURPOSE

The aim of this study was to analyze the clinical, audiological, radiological, and genetic features of a group of patients affected with large vestibular aqueduct syndrome.

MATERIALS AND METHODS

Seventeen patients affected with large vestibular aqueduct syndrome (LVAS), diagnosed by means of high-resolution magnetic resonance imaging of the inner ear, with 3-dimensional reconstructions of the labyrinth and by high-resolution spiral computed tomography of the temporal bone, performed only on the oldest patients, have been submitted to a complete audiological evaluation, a thyroid functional and ultrasonographic study, and a molecular study of the PDS gene.

RESULTS

The clinical presentation of LVAS was very variable in our group of patients. The enlarged vestibular aqueduct was bilateral in 15 cases and unilateral in 2; it was the only malformation of the labyrinth in 12 patients, whereas it was associated with other inner ear anomalies in the other 5. The hearing loss was very variable in degree (from mild to profound), age at onset, and progression. Moreover, among the 17 patients, 10 were clinically affected by Pendred's syndrome (PS), 3 by distal renal tubular acidosis associated with large vestibular aqueduct, whereas in 3 patients the large vestibular aqueduct was not syndromal. Finally, we identified mutations in the PDS gene in 5 of 10 patients with PS.

CONCLUSIONS

Our data underscore the frequent role of the large vestibular aqueduct syndrome in the pathogenesis of sensorineural hearing loss and the overall wide variability in its audiological features. It is also highlighted that LVAS is often part of some syndromal diseases, most of which are PS, which is often misdiagnosed because of the varying degree of thyroid symptoms. This study also underscores the possible role of hydro-electrolyte and acid-base endolymphatic fluid disorders in the pathogenesis of enlarged vestibular aqueduct syndrome.

[Cochlear implant in a patient with dilatation of the endolymphatic sac and vestibular aqueduct]

We present an 8 years patient old with a giant dilatation of the vestibular aqueduct associated with profound and progressive bilateral sensorineural hearing loss. The patient received a cochlear implant and during the surgery a pulsatile clear fluid via the cochleostomy was observed, without gusher. We present all the problems, and offer some advices for this kind of surgery.

Chronological changes of hearing in pediatric patients with large vestibular aqueduct syndrome

OBJECTIVES

To describe the chronologic changes of hearing in patients with large vestibular aqueduct syndrome (LVAS) and identify the prognostic factors.

STUDY DESIGN

A retrospective chart-review study.

METHODS

Twelve consecutive patients with LVAS were recruited at Taipei Veterans General Hospital between July 1986 and July 2000. The records of serial pure-tone audiogram and high-resolution computer tomography were collected. The chronologic figures of pure-tone average (PTA) were sketched. The investigated variables included sex, laterality and type of hearing loss (HL), size of vestibular aqueduct, and the chronologic changes and configurations of hearing. Data were analyzed statistically.

RESULTS

The degree of HL in early childhood was from moderate to profound. The worst hearing could be estimated by the hearing level in early childhood. Sixteen of 24 ears were stable. Bilateral, chronologically stepwise-downhill hearing occurred in only one patient (1/12) during the follow-up period. Chronologically, high-tone hearings were worse than those of low-tone, but fluctuations of high-tone hearing were smaller than those of low-tone. The sizes of vestibular aqueduct were predictive of the density of major depression and its depth.

CONCLUSIONS

LVAS, a congenital disease, is characterized by fluctuating sensorineural HL. Most hearing at PTA remained stable at least in one ear chronologically. The standard deviation of hearing at 500 Hz was the only prognostic factor for the progression of PTA. An enlarged vestibular aqueduct affects fluctuations of hearing, but the pathogenesis of HL still remains unclear and deserves further investigations.

Enlarged endolymphatic duct and sac syndrome: relationship between MR findings and genotype of mutation in pendred syndrome gene

Pendred syndrome (PDS) is characterized by profound deafness in childhood, positive perchlorate challenge, and goiter. PDS is often associated with enlarged endolymphatic duct and sac (EEDS), and recently, PDS gene mutations have been reported even in those patients with EEDS without classic Pendred syndrome. In a previous report, the number of mutant alleles was correlated with the degree of subclinical thyroid abnormality, but not with hearing loss, in patients with missense mutation H723R. It also has been reported that the hearing loss in EEDS was not correlated with the EEDS volume, cochlear modiolar area, or signal intensity of the endolymphatic sac. We evaluated the correlations between the number of mutant alleles and these parameters in patients with EEDS to investigate the mechanisms underlying this condition. The study group was comprised of 16 Japanese patients with EEDS diagnosed by MR imaging. The H723R mutation was homozygous in six patients and heterozygous in six patients, with no mutation found in four patients. The modiolar area, EEDS volume, and signal intensity ratio (sac signal/cerebrospinal fluid signal) were not significantly correlated with the number of mutant alleles. PDS gene mutations may not be the only cause of EEDS, and the mechanisms underlying EEDS remain unclear.

Cochlear implantation with large vestibular aqueduct syndrome

OBJECTIVES

In this investigation, we report the outcomes of 14 adults (age >18 y) and 9 children (age <18 y) with radiographically proven large vestibular aqueduct syndrome (LVAS) who received cochlear implants at Indiana University School of Medicine.

STUDY DESIGN

This is a retrospective case-control study detailing the outcomes of 23 patients with LVAS and 46 control patients implanted with Nucleus (Cochlear Corp., Englewood, CO), Clarion (Advanced Bionics Corp., Sylmar, CA), or Med-El (MED-EL Corp., Innsbruck, Austria) cochlear implants.

METHODS

Performance data on pure-tone averages, speech detection thresholds, and a variety of auditory and speech recognition tasks from these patients with LVAS were compared with performance data obtained from a matched group of 46 cochlear implant users who did not have LVAS. Specific patient characteristics used in matching included the age of the patient, the age at implant of the patient, and whether the patient was pre- or postlingually deafened. Data for the adult group was analyzed using the Student t test, and data for the pediatric patient group was compared using a chi2 test.

RESULTS

The results indicated positive outcomes for both pediatric and adult groups. With both adult and pediatric groups, auditory and speech recognition performance did not differ significantly between those patients with LVAS and control subjects.

CONCLUSIONS

This study adds further support for the use of cochlear implantation in patients with LVAS. Cochlear implantation is beneficial and can be offered as an eventual treatment of LVAS if hearing loss progresses to profound levels in these patients.

Pendred's syndrome with goiter and enlarged vestibular aqueducts diagnosed by PDS gene mutation

BACKGROUND

Pendred's syndrome (PS) is an autosomal recessive disorder characterized by goiter and congenital sensorineural hearing loss. Recent advances in molecular biology revealed the gene responsible for PS (PDS) and provided an important aid for the diagnosis of this condition.

METHODS

A case of PS with huge goiter and congenital hearing impairment was diagnosed by mutational analysis of the PDS gene.

RESULTS

Physical examination and computer tomography CT revealed a diffuse swelling of the thyroid gland. Thyroid function tests were normal, and the perchlorate discharge test was negative. Audiologic examination confirmed sensorineural hearing loss, and temporal bone CT revealed bilateral enlarged vestibular aqueducts. The mutational analysis revealed that the patient was homozygous for His 723 Arg (2168A-->G) in exon 19, a missense mutation.

CONCLUSIONS

The results of thyroid function tests in PS patients are usually normal, and the positive perchlorate discharge test has been used for the diagnosis. However, this is a nonspecific test and is not sensitive enough for PS. In our case, despite a negative perchlorate test, the patient was diagnosed by mutational analysis and received total thyroidectomy to relieve respiratory distress caused by thyroid enlargement. This is the first report of a mutation detected in the thyroid tissue and clearly shows that the mutation caused histopathologic change in that gland.

[Idiopathic sudden deafness]

PURPOSE

Sudden idiopathic deafness is a sensorineural hearing loss with no recognized causes at the time of onset. The impairment site is usually localized in the cochlea, but some cases of retrocochlear lesions (e.g., cerebellopontine angle tumors, degenerative neural diseases, neuraxial ischemic lesions) can induce sensorineural deafness. The medical management of patients presenting with sudden deafness aims at detecting a causal mechanism, and at administering emergency therapeutic drugs. The diagnosis of idiopathic sudden deafness can be definitely made when no causes are found. Usually, the impairing mechanism involves the cochlea. The pathophysiology of this sensorineural alteration is still unknown. It is most likely that several mechanisms are associated together, their common point being an impairment to the feedback loop of the organ of Corti.

CURRENT KNOWLEDGE AND KEY POINTS

It is very likely that reactivation of neurotropic viruses and/or cochlear ischemia are frequent etiologies. Whatever the cause, the treatment is to be administered urgently, and consists of a high-dose corticotherapy at the least. Other treatments have never really proven to be effective. It is secondarily checked that no retrocochlear pathological processes, such as a cerebellopontine angle tumor, is present, in particular in young people.

FUTURE PROSPECTS AND PROJECTS

One of the current objectives is to determine when cochlear ischemia is involved, in a mini-invasive manner, such as with laser Doppler flowmetry, so that the treatment can be optimized. From a therapeutic point of view, early acoustic protection has been proven to be effective in cases of cochlear ischemia in small laboratory animals. Its efficacy in case of sudden deafness, non-exclusive of other causes than ischemia, is being assessed in a multicentric project.

Fluctuant, progressive hearing loss associated with Menière like vertigo in three patients with the Pendred syndrome

OBJECTIVE

To evaluate vestibular and long-term audiometric findings in patients with Pendred syndrome.

STUDY DESIGN

Retrospective analysis of long-term clinical data.

SETTING

University hospital department.

PATIENTS

Three patients with Pendred syndrome caused by a mutation in the SLC26A4 gene.

METHODS

Perchlorate discharge test, mutation analysis of the SLC26A4 gene, MR imaging of temporal bones, vestibular function test (in two cases) and serial audiometry. A saturation hyperbola with onset age was fitted to the audiometric threshold-on-age data using a nonlinear regression method. The residues remaining after regression were analyzed in a correlation analysis to detect significant ipsilateral or contralateral cofluctuation.

RESULTS

All three patients had a mutation in the SLC26A4 gene and bilateral enlarged vestibular aqueduct; two of them had a positive perchlorate discharge test but in one of two siblings this test was negative. Hearing loss was significantly progressive with significant ipsilateral and contralateral cofluctuation in all evaluable cases, combined with episodes of Menière like vertigo in two cases. The episodes of vertigo are as seen in Menière disease. One case had unilateral caloric areflexia and one had bilateral vestibular hyporeflexia, proven to be progressive in a repeat examination.

CONCLUSIONS

Patients with Pendred syndrome may exhibit progressive and fluctuant hearing loss with episodes of vertigo.

Progressive fluctuant hearing loss, enlarged vestibular aqueduct, and cochlear hypoplasia in branchio-oto-renal syndrome

OBJECTIVE

To study the results of petrosal bone imaging and audiometric long-term follow-up of two patients with branchio-oto-renal (BOR) syndrome and relate them to the clinical features, including caloric responses.

STUDY DESIGN

Longitudinal case study.

SETTING

Tertiary referral center.

PATIENTS

A father and son with the BOR syndrome.

MAIN OUTCOME MEASURES

Both patients underwent imaging studies to detect and evaluate inner ear anomalies. Longitudinal audiometric analysis of the hearing threshold data over the previous 23 years was performed. Caloric tests were performed at various ages.

RESULTS

The son had a short, wide internal acoustic canal, a hypoplastic cochlea, a plump vestibule, and a wide vestibular aqueduct on both sides; the semicircular canals and endolymphatic sac were of normal size. He showed progressive fluctuant sensorineural hearing loss. Caloric tests disclosed hyporeflexia on the left side. The father had a plump internal acoustic canal and hypoplastic cochlea on both sides. The left vestibule was hypoplastic, and the left vestibular aqueduct was marginally enlarged. He showed severe hearing impairment, without substantial progression or fluctuation, and caloric areflexia on the left side.

CONCLUSION

These findings suggest a correlation between progressive fluctuant sensorineural hearing loss with caloric hypofunction and the presence of an enlarged vestibular aqueduct in the BOR syndrome. Additional longitudinal case studies are needed to further evaluate such a correlation.

Molecular analysis of the Pendred's syndrome gene and magnetic resonance imaging studies of the inner ear are essential for the diagnosis of true Pendred's syndrome

Pendred's syndrome is a combination of congenital sensorineural hearing loss and iodine organification defect leading to a positive perchlorate test and goiter. Although it is the commonest form of syndromic hearing loss, the variable clinical presentation contributes to the difficulty in securing a diagnosis. The identification of the disease gene (PDS) prompts the need to reevaluate the syndrome to identify possible clues for the diagnosis. To this purpose, in three Italian families presenting with the clinical features of Pendred's syndrome, the molecular analysis was accompanied by full clinical, biochemical, and radiological examination. A correlation between genotype and phenotype was found in the only patient with enlargement of vestibular aqueduct and endolymphatic duct and sac at magnetic resonance imaging. This subject was a compound heterozygote for a deletion in PDS exon 10 (1197delT, FS400) and a novel insertion in exon 19 (2182-2183insG, Y728X). The present study demonstrates for the first time the value of the combination of clinical/radiological and genetic studies in the diagnosis of Pendred's syndrome. The positivity of a perchlorate discharge test and the malformations of membranous labyrinth fit well with the recent achievements on the role of pendrin in thyroid hormonogenesis and the maintenance of endolymph homeostasis.

Large vestibular aqueduct syndrome treated by hyperbaric oxygen

We report the case of a 14-year-old girl with a large vestibular aqueduct (LVA) in whom hyperbaric oxygen (HBO) therapy was effective for the treatment of sensorineural hearing loss. The patient was referred to Nagoya University Hospital for the treatment of hearing loss on 14 September, 1998, because her right hearing level had declined abruptly on 22 August, 1998, and had not changed for 3 weeks since then in spite of steroid and prostaglandin therapy. Her audiogram revealed bilateral profound deafness of more than 110 dB. She had had profound hearing loss on the left side since she was 9 years old. HBO therapy was performed on 22 occasions from 17 September until 19 October, 1998. During the HBO therapy, her right hearing ability returned almost to the level determined prior to the abrupt loss, 60 dB. We therefore recommend HBO therapy for the treatment of sensorineural hearing loss associated with large vestibular aqueduct syndrome if the hearing ability does not recover following conventional treatment.