Improved diagnostic effectiveness with a sequential diagnostic paradigm in idiopathic pediatric sensorineural hearing loss

Congenital Sensorineural Hearing Loss

Congenital sensorineural hearing loss is highly prevalent in our population, with a wide variety of causes. The key to clinical management is early detection and intervention, to promote language and cognitive development. With expanding genetic knowledge about congenital sensorineural hearing loss, the indiscriminate approach in workup is no longer recommended. Comprehensive genetic evaluation and cytomegalovirus testing are key to identify the underlying cause of the hearing loss. Treatment and prognosis depend on age of hearing loss onset and detection; management plans will typically include audiology consultation, speech therapy, and various hearing amplification devices and technologies when applicable.

Comprehensive medical evaluation of pediatric bilateral sensorineural hearing loss

Children with bilateral sensorineural hearing loss (SNHL) should undergo a comprehensive medical evaluation to determine the underlying etiology and help guide treatment and counseling. In this article, we review the indications and rationale for medical evaluation of pediatric bilateral SNHL, including history and physical examination, imaging, genetic testing, specialist referrals, cytomegalovirus (CMV) testing, and other laboratory tests. Workup begins with a history and physical examination, which can provide clues to the etiology of SNHL, particularly with syndromic causes. If SNHL is diagnosed within the first 3 weeks of life, CMV testing should be performed to identify patients that may benefit from antiviral treatment. If SNHL is diagnosed after 3 weeks, testing can be done using dried blood spots samples, if testing capability is available. Genetic testing is oftentimes successful in identifying causes of hearing loss as a result of recent technological advances in testing and an ever-increasing number of identified genes and genetic mutations. Therefore, where available, genetic testing should be performed, ideally with next generation sequencing techniques. Ophthalmological evaluation must be done on all children with SNHL. Imaging (high-resolution computed tomography and/or magnetic resonance imaging) should be performed to assess for anatomic causes of hearing loss and to determine candidacy for cochlear implantation when indicated. Laboratory testing is indicated for certain etiologies, but should not be ordered indiscriminately since the yield overall is low.

Overview of Medical Evaluation of Unilateral and Bilateral Hearing Loss in Children

Early identification, treatment, and medical evaluation of childhood hearing loss are essential to promoting language and social development, regardless of their age of presentation. Evaluation of hearing loss in children should prioritize reversible and treatable causes. Multiple algorithms have been established to address the changing prevalence of genetic or infectious contributions to hearing loss and include recommendations on laboratory testing, imaging, and genetic testing. Despite these recommendations, significant practice variation remains on assessing the etiology of hearing loss in children.

Torticollis in children with enlarged vestibular aqueducts

OBJECTIVES

To evaluate the association between torticollis and enlarged vestibular aqueduct (EVA).

METHODS

An online/phone survey was administered to parents of 133 children diagnosed with the following disorders: EVA, GJB2 (Connexin 26) mutations associated congenital hearing loss and epistaxis (control). The survey included questions regarding symptoms of torticollis, vertigo, and hearing loss.

RESULTS

Patients with EVA had a 10-fold greater odds of having torticollis than controls (31% vs. 4%; OR = 10.6; 95% CI: 2.9, 39.2). No patients with GJB2 had a reported history of torticollis. Torticollis preceded the diagnosis of hearing loss in most (87%) patients with EVA who had a reported history of torticollis. EVA patients were more likely to have reported motor delay than controls (40% vs. 15%; p = 0.002). EVA patients with prior torticollis (80%; 12/15) were more likely to have balance impairment than EVA patients without prior torticollis (12%; 4/33; p < 0.001). Twelve patients had a reported history of paroxysmal torticollis, all of whom had EVA.

CONCLUSION

Torticollis in infants may be a marker of EVA. Infants with torticollis should be monitored closely for hearing loss and motor delay, especially when the torticollis is paroxysmal.

Assessment of the Clinical Benefit of Imaging in Children With Unilateral Sensorineural Hearing Loss: A Systematic Review and Meta-analysis

Importance

Imaging used to determine the cause of unilateral sensorineural hearing loss (USNHL) in children is often justified by the high likelihood of detecting abnormalities, which implies that these abnormalities are associated with hearing loss and that imaging has a positive contribution to patient outcome or well-being by providing information on the prognosis, hereditary factors, or cause of hearing loss.

Objectives

To evaluate the diagnostic yield of computed tomography (CT) and magnetic resonance imaging (MRI) in children with isolated unexplained USNHL and investigate the clinical relevance of these findings.

Evidence Review

Cochrane Library, Embase, PubMed, and Web of Science databases were searched for articles published from 1978 to 2017 on studies of children with USNHL who underwent CT and/or MRI of the temporal bone. Two authors (F.G.R. and E.N.B.P.) independently extracted information on population characteristics, imaging modality, and the prevalence of abnormalities and assessed the studies for risk of bias. Eligibility criteria included studies with 20 or more patients with USNHL who had CT and/or MRI scans, a population younger than 18 years, and those published in English.

Main Outcomes and Measures

The pooled prevalence with 95% CI of inner ear abnormalities grouped according to finding and imaging modality.

Findings

Of 1562 studies, 18 were included with a total of 1504 participants included in the analysis. Fifteen studies were consecutive case studies and 3 were retrospective cohort studies. The pooled diagnostic yield for pathophysiologic relevant findings in patients with unexplained USNHL was 37% for CT (95% CI, 25%-48%) and 35% for MRI (95% CI, 22%-49%). Cochleovestibular abnormalities were found with a pooled frequency of 19% for CT (95% CI, 14%-25%) and 16% for MRI (95% CI, 7%-25%). Cochlear nerve deficiency and associated cochlear aperture stenosis had a pooled frequency of 16% for MRI (95% CI, 3%-29%) and 44% for CT (95% CI, 36%-53%), respectively. Enlarged vestibular aqueduct (EVA) was detected with a pooled frequency of 7% for CT and 12% for MRI in children with USNHL.

Conclusions and Relevance

Imaging provided insight into the cause of hearing loss in a pooled frequency of about 35% to 37% in children with isolated unexplained USNHL. However, none of these findings had therapeutic consequences, and imaging provided information on prognosis and hereditary factors only in a small proportion of children, namely those with EVA. Thus, there is currently no convincing evidence supporting a strong recommendation for imaging in children who present with USNHL. The advantages of imaging should be carefully balanced against the drawbacks during shared decision making.

The etiological evaluation of sensorineural hearing loss in children

This study aims to evaluate the etiology of pediatric sensorineural hearing loss (SNHL). A total of 423 children with SNHL were evaluated, with the focus on the determination of causative genetic and acquired etiologies of uni- and bilateral SNHL in relation to age at diagnosis and severity of the hearing loss. We found that a stepwise diagnostic approach comprising of imaging, genetic, and/or pediatric evaluation identified a cause for SNHL in 67% of the children. The most common causative finding in children with bilateral SNHL was causative gene variants (26%), and in children with unilateral SNHL, a structural anomaly of the temporal bone (27%). The probability of finding an etiologic diagnosis is significantly higher in children under the age of 1 year and children with profound SNHL.Conclusions: With our stepwise diagnostic approach, we found a diagnostic yield of 67%. Bilateral SNHL often has a genetic cause, whereas in unilateral SNHL structural abnormalities of the labyrinth are the dominant etiologic factor. The diagnostic yield is associated with the age at detection and severity of hearing loss: the highest proportion of causative abnormalities is found in children with a young age at detection or a profound hearing loss. What is Known: • Congenital sensorineural hearing loss is one of the most common congenital disorders • Determination of the cause is important for adequate management and prognosis and may include radiology, serology, and DNA analysis What is New: • Using a stepwise diagnostic approach, causative abnormalities are found in 67% both in uni- and bilateral SNHL, with the highest diagnostic yield in very young children and those suffering from profound hearing loss • Bilateral SNHL often has a genetic cause, whereas in unilateral SNHL structural abnormalities of the labyrinth are the dominant etiologic factor.

Utilization of diagnostic testing for pediatric sensorineural hearing loss

BACKGROUND/OBJECTIVE

Sensorineural hearing loss is a common diagnosis among children. The diagnostic workup varies widely among practitioners. This study's aim was to assess the utilization of diagnostic testing for SNHL and determine the yield of each test.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary care center.

SUBJECTS

827 patients with a diagnosis of SNHL from January 1, 2011 to January 1, 2015.

RESULTS

746 patients met inclusion criteria. Temporal bone imaging was performed on 561 (75%) of patients with 224 (40%) having positive results that explained the etiology of the SNHL. Congenital SNHL was more likely to be associated with abnormal imaging than acquired SNHL (109/299 versus 106/316 respectively) (p = 0.001). Unilateral SNHL was more likely to be associated imaging abnormalities than bilateral SNHL (101/221 and 123/340 respectively) (p = 0.028). Genetic testing was performed on 244 (33%) patients, of which 94 (39%) had abnormalities. Positive genetics results were more common with bilateral than unilateral SNHL (82/191 and 12/53 respectively) (p = 0.007). There was no statistically significant difference in the utility of genetic testing for congenital and acquired SNHL (p = 0.0836). Cytomegalovirus (CMV) testing was available for 104 (14%) of patients with 13 (12.5%) being positive and consistent with congenital CMV. Electrocardiogram, urinalysis, and Lyme titers were less useful.

CONCLUSIONS

Imaging and genetic testing had the highest yield in the evaluation of children with SNHL and were the most commonly performed. CMV testing was valuable in neonates who failed newborn hearing screening.

Concomitant imaging and genetic findings in children with unilateral sensorineural hearing loss

OBJECTIVE

To describe the concomitant imaging and genetic findings in children diagnosed with non-syndromic unilateral sensorineural hearing loss.

METHODS

A retrospective cohort study was conducted of 60 children diagnosed between January 2005 and December 2015 in a tertiary-level paediatric institution.

RESULTS

Average age at diagnosis was 4.3 years. All children were considered non-syndromic. Hearing loss was categorised as mild (17 children), moderate (17 children), severe (7 children) or profound (19 children). Imaging was performed in 43 children (71.66 per cent). Nineteen patients (44.2 per cent) had positive computed tomography or magnetic resonance imaging findings. Genetic testing was performed in 51 children (85 per cent). Sixteen children (31 per cent) tested positive to connexin 26 (GJB2); 1 patient (2 per cent) had a homozygous mutation of GJB2 and 15 were heterozygous carriers. Amongst children who tested positive as heterozygous carriers of a GJB2 mutation, there was a high rate of positive imaging findings (47 per cent compared to 37.2 per cent in the total cohort). A genetic abnormality was confirmed in 50 per cent of children with positive imaging findings who underwent genetic testing.

CONCLUSION

Rates of concomitant imaging and genetic findings suggest that both investigations are of value in the study of these patients.

Molecular diagnostics for hereditary hearing loss in children

INTRODUCTION

Hearing loss (HL) is the most common birth defect in industrialized countries with far-reaching social, psychological and cognitive implications. It is an extremely heterogeneous disease, complicating molecular testing. The introduction of next-generation sequencing (NGS) has resulted in great progress in diagnostics allowing to study all known HL genes in a single assay. The diagnostic yield is currently still limited, but has the potential to increase substantially. Areas covered: In this review the utility of NGS and the problems for comprehensive molecular testing for HL are evaluated and discussed. Expert commentary: Different publications have proven the appropriateness of NGS for molecular testing of heterogeneous diseases such as HL. However, several problems still exist, such as pseudogenic background of some genes and problematic copy number variant analysis on targeted NGS data. Another main challenge for the future will be the establishment of population specific mutation-spectra to achieve accurate personalized comprehensive molecular testing for HL.

Genomic Sequencing Procedure Microcosting Analysis and Health Economic Cost-Impact Analysis: A Report of the Association for Molecular Pathology

The increasing use of advanced nucleic acid sequencing technologies for clinical diagnostics and therapeutics has made vital understanding the costs of performing these procedures and their value to patients, providers, and payers. The Association for Molecular Pathology invested in a cost and value analysis of specific genomic sequencing procedures (GSPs) newly coded by the American Medical Association Current Procedural Terminology Editorial Panel. Cost data and work effort, including the development and use of data analysis pipelines, were gathered from representative laboratories currently performing these GSPs. Results were aggregated to generate representative cost ranges given the complexity and variability of performing the tests. Cost-impact models for three clinical scenarios were generated with assistance from key opinion leaders: impact of using a targeted gene panel in optimizing care for patients with advanced non-small-cell lung cancer, use of a targeted gene panel in the diagnosis and management of patients with sensorineural hearing loss, and exome sequencing in the diagnosis and management of children with neurodevelopmental disorders of unknown genetic etiology. Each model demonstrated value by either reducing health care costs or identifying appropriate care pathways. The templates generated will aid laboratories in assessing their individual costs, considering the value structure in their own patient populations, and contributing their data to the ongoing dialogue regarding the impact of GSPs on improving patient care.

High-frequency sensorineural hearing loss in children

OBJECTIVES/HYPOTHESIS

Determine the prevalence of high-frequency sensorineural hearing loss (HFSNHL) in our hearing loss population and a diagnostic algorithm for these patients.

STUDY DESIGN

Retrospective case series.

METHODS

We identified patients diagnosed with sensorineural hearing loss (SNHL) at our pediatric tertiary care institution from 1981 to 2010. Based on audiometric profiles, these patients were subdivided into those with a flat SNHL configuration and those with HFSNHL. Imaging and genetic testing data and data regarding age at diagnosis, laterality, and risk factors were obtained for both groups. Comparisons were then made between the two groups.

RESULTS

Of 2,867 patients included in the study, 7.6% had HFSNHL. Age at diagnosis was significantly higher in HFSNHL patients (8.3 years vs. 6.1 years; P < .0001). These patients also had a significantly higher proportion of unilateral versus bilateral loss (49.1% vs. 26.1%; P < .0001); unilateral losses were also less severe. Genetic testing showed no significant difference between groups in the proportion of patients tested or in those who tested positive. Similarly, imaging data revealed no difference in the proportion of patients tested in the two groups; however, overall diagnostic yield was significantly higher in flat SNHL patients (29.5% vs.17.3; P = .02).

CONCLUSIONS

The positive predictive value of simple genetic testing is similar to that of imaging studies. However, given cost differences between genetic testing and imaging, it is prudent to perform genetic testing as the initial diagnostic test. Determination of whether high-throughput, multigene diagnostic platforms offer an added benefit in the evaluation of children requires further study.

LEVEL OF EVIDENCE

4. Laryngoscope, 126:1236-1240, 2016.

Etiological approach in patients with unidentified hearing loss

OBJECTIVES

Etiological diagnosis of hearing impairment is of great importance to ensure early and adequate management. Even after thorough history taking, clinical and audiometric evaluation, the cause of hearing loss remains unclear in a majority of patients. Further examinations can imply imaging, ophthalmologic investigations, laboratory tests, electrocardiography and genetic testing. Lately, the latter has taken an increasingly prominent place within this diagnostic work-up. However, clear guidelines about optimal implementation and sequence of these tests are required.

METHODS

Records of patients who visited the consultation for otogenetics at Ghent University Hospital (Belgium) during the period 2006-2012 were retrospectively reviewed. In order to optimize the etiological-diagnostic work-up of unidentified hearing loss, application patterns and results of various diagnostic tests, audiometric and etiological data of each patient were collected and analyzed.

RESULTS

Data of 191 patients were analyzed. In 81.2% of the patients, a cause of hearing loss could be determined or suspected. In total, 65.4% had a (presumably) genetic etiology, with connexin 26 (GJB2) mutations as the leading cause. Inquiry of risk factors, associated with congenital hearing loss, and pedigree analysis were found to have the highest diagnostic gain (61.3% and 41.8%). Connexin 26 gene mutations were only present in bilateral hearing impairment, whereas CT abnormalities were related to unilateral (P=0.003), profound (P<0.001) hearing loss. An enlarged vestibular aqueduct was present in 42.9% of all CT abnormalities. Ophthalmologic anomalies were detected in 35.7% of the studied patients.

CONCLUSIONS

A sequential approach for the etiological diagnosis of unidentified hearing loss could determine or suggest a cause in more than 80% of patients. The approach may vary based on the presenting phenotype.

Connexin-Related (DFNB1) Hearing Loss

Objectives

Determine if routine computed tomography (CT) imaging is necessary in the workup for children with connexin-related (DFNB1) sensorineural hearing loss (SNHL).

Study Design

Case-control retrospective chart and imaging review.

Setting

Tertiary care otolaryngology practice.

Subjects and Methods

High-resolution temporal bone CT scans of children (n = 21) with DFNB1 SNHL were compared to age-matched controls with either conductive hearing loss (CHL, n = 33) or a nonsyndromic, non-DFNB1 SNHL (n = 33). Sixteen measurements of cochleo-vestibular structures were recorded. Statistical analysis was performed using a repeated analysis of variance model that controlled for both age and gender. Area under the curve (AUC) and multidimensional AUC (MAUC) analyses were also performed.

Results

Overall, no statistically significant differences were found between the 3 experimental groups. In addition, comparisons between the DFNB1 and CHL groups, DFNB1 and non-DFNB1 SNHL groups, and CHL and non-DFNB1 SNHL groups failed to demonstrate any statistically significant differences. AUC and MAUC analyses also failed to detect any significant differences between the 3 groups.

Conclusions

Patients with DFNB1 SNHL do not have significant anatomic differences on temporal bone CT scans when compared to non-DFNB1 SNHL and CHL control groups. Based on the above analysis, it is reasonable to avoid routine CT imaging of the temporal bones in children with known DFNB1 SNHL unless otherwise clinically indicated.

Diagnostic yield of MRI for pediatric hearing loss: a systematic review

OBJECTIVE

To perform a systematic review to analyze the diagnostic yield of magnetic resonance imaging (MRI) for pediatric hearing loss, including comparison to computed tomography (CT) and subgroup evaluation according to impairment severity and specific diagnostic findings (cochlear anomalies, enlarged vestibular aqueduct, cochlear nerve abnormalities, and brain findings).

DATA SOURCES

Pubmed, EMBASE, and the Cochrane library were assessed from their inception through December 2013. Manual searches were also performed, and topic experts were contacted.

REVIEW METHODS

Data from studies describing the use of MRI with or without comparison to CT in the diagnostic evaluation of pediatric patients with hearing loss were evaluated, according to a priori inclusion/exclusion criteria. Two independent evaluators corroborated the extracted data. Heterogeneity was evaluated according to the I(2) statistic.

RESULTS

There were 29 studies that evaluated 2434 patients with MRIs and 1451 patients with CTs that met inclusion/exclusion criteria. There was a wide range of diagnostic yield from MRI. Heterogeneity among studies was substantial but improved with subgroup analysis. Meta-analysis of yield differences demonstrated that CT had a greater yield than MRI for enlarged vestibular aqueduct (yield difference 16.7% [95% CI, 9.1%-24.4%]) and a borderline advantage for cochlear anomalies (4.7% [95% CI, 0.1%-9.5%]). Studies were more likely to report brain findings with MRI.

CONCLUSIONS

These data may be utilized in concert with that from studies of risks of MRI and risk/yield of CT to inform the choice of diagnostic testing.

Diagnostic yield of computed tomography scan for pediatric hearing loss: a systematic review

BACKGROUND

Computed tomography (CT) has been used in the assessment of pediatric hearing loss, but concern regarding radiation risk and increased utilization of magnetic resonance imaging (MRI) have prompted us toward a more quantitative and sophisticated understanding of CT's potential diagnostic yield.

OBJECTIVE

To perform a systematic review to analyze the diagnostic yield of CT for pediatric hearing loss, including subgroup evaluation according to impairment severity and laterality, as well as the specific findings of enlarged vestibular aqueduct and narrow cochlear nerve canal.

DATA SOURCES

PubMed, EMBASE, and the Cochrane Library were assessed from the date of their inception to December 2013. In addition, manual searches of bibliographies were performed and topic experts were contacted.

REVIEW METHODS

Data from studies describing the use of CT in the diagnostic evaluation of pediatric patients with hearing loss of unknown etiology were evaluated, according to a priori inclusion/exclusion criteria. Two independent evaluators corroborated the extracted data. Heterogeneity was evaluated according to the I(2) statistic.

RESULTS

In 50 criteria-meeting studies, the overall diagnostic yield of CT ranged from 7% to 74%, with the strongest and aggregate data demonstrating a point estimate of 30%. This estimate corresponded to a number needed to image of 4 (range, 2-15). The most commonly identified findings were enlarged vestibular aqueduct and cochlear anomalies. The largest studies showed a 4% to 7% yield for narrow cochlear nerve canal.

CONCLUSION

These data, along with similar analyses of radiation risk and risks/benefits of sedated MRI, may be used to help guide the choice of diagnostic imaging.

Hereditary sensorineural hearing loss: advances in molecular genetics and mutation analysis

Hearing loss has a genetic etiology in the majority of cases and is very common. The universal newborn hearing screening program, together with remarkable recent progress in the characterization of genes associated with the function of hearing, have resulted in increased demand and exciting possibilities of detecting the molecular basis of hereditary hearing loss through DNA testing. Future molecular diagnostic assays are expected to offer a greater variety of gene-specific tests, as well as combined mutation panels, which will aid in the management of the impressive genetic heterogeneity observed in hereditary hearing loss, especially in individuals with nonsyndromic forms. This review addresses the genetics of hearing loss, discusses the most commonly offered genetic assays for nonsyndromic hearing loss, with advantages and limitations, proposes a practical testing algorithm, and highlights current developments.

Improving the Value of Costly Genetic Reference Laboratory Testing With Active Utilization Management

Context.—Tests that are performed outside of the ordering institution, send-out tests, represent an area of risk to patients because of complexity associated with sending tests out. Risks related to send-out tests include increased number of handoffs, ordering the wrong or unnecessary test, specimen delays, data entry errors, preventable delays in reporting and acknowledging results, and excess financial liability. Many of the most expensive and most misunderstood tests are send-out genetic tests.

Objective.—To design and develop an active utilization management program to reduce the risk to patients and improve value of genetic send-out tests.

Design.—Send-out test requests that met defined criteria were reviewed by a rotating team of doctoral-level consultants and a genetic counselor in a pediatric tertiary care center.

Results.—Two hundred fifty-one cases were reviewed during an 8-month period. After review, nearly one-quarter of genetic test requests were modified in the downward direction, saving a total of 2% of the entire send-out bill and 19% of the test requests under management. Ultimately, these savings were passed on to patients.

Conclusions.—Implementing an active utilization strategy for expensive send-out tests can be achieved with minimal technical resources and results in improved value of testing to patients.

Epidemiology of unilateral sensorineural hearing loss with universal newborn hearing screening

OBJECTIVES/HYPOTHESIS

Compare the epidemiology of pediatric unilateral sensorineural hearing loss before and after implementation of universal newborn hearing screening in Missouri.

STUDY DESIGN

Inception cohort.

METHODS

Charts of 134 children born between January 1, 1990 and December 31, 2007, diagnosed with unilateral sensorineural hearing loss at a single institution in Missouri were reviewed to determine the effects of universal newborn hearing screening on age of detection and etiology of hearing loss.

RESULTS

Mean age of detection declined from 4.4 (standard deviation [SD] 1.8) to 2.6 (SD 2.6) years of age, whereas the rate of detection by 6 months of age increased from 3% to 42%. The majority (58%) of cases had normal hearing at birth. The most common etiological category was unknown (41%) before screening and congenital (45%) after screening. The use of magnetic resonance imaging has increased by 21% (2-fold), whereas use of computed tomography has declined by 8% since 2002. Yields of connexin, Pendred, electrocardiogram, and syphilis testing were 0/48 and 2/31 before and after screening, respectively.

CONCLUSIONS

Implementation of universal newborn hearing screening in Missouri is associated with a decrease in age of detection of unilateral sensorineural hearing loss. The majority of cases are either not present or not detectable at birth. The combination of hearing status at birth and imaging findings suggests that the majority of cases are congenital rather than of unknown etiology.

Significance of unilateral enlarged vestibular aqueduct

OBJECTIVES/HYPOTHESIS

To describe the clinical phenotype of pediatric patients with unilateral enlarged vestibular aqueduct (EVA) and then to compare the findings to two clinically related phenotypes: bilateral EVA and unilateral hearing loss without EVA. In view of clinical observations and previously published data, we hypothesized that patients with unilateral EVA would have a much higher rate of contralateral hearing loss than patients with unilateral hearing loss without EVA.

STUDY DESIGN

Retrospective cohort study.

METHODS

Patients with unilateral or bilateral EVA were identified from a database of children with sensorineural hearing loss who were seen at a tertiary care institution between 1998 and 2010. Those with imaging findings consistent with well-established EVA criteria were identified. A comparative group of patients with unilateral hearing loss without EVA was also identified. The following specific outcome measurements were analyzed: 1) hearing loss phenotype, 2) laterality of EVA and hearing loss, 3) midpoint and operculum vestibular aqueduct measurements, and 4) genetic test results.

RESULTS

Of the 144 patients who met our inclusion criteria, 74 (51.4%) had unilateral EVA. There was a strong correlation between the presence of hearing loss and ears with EVA. Fifty-five percent of patients with unilateral EVA had hearing loss in the contralateral ear; in most of these patients, the hearing loss was bilateral. Contralateral hearing loss occurred in only 6% of patients with unilateral hearing loss without EVA. No significant differences were found in temporal bone measurements between the ears of patients with unilateral EVA and ipsilateral hearing loss and all ears with EVA and normal hearing (P = .4). There was no difference in the rate of hearing loss progression in patients with unilateral EVA between ears with or without EVA (16 of 48 [33.3%] vs. 9 of 27 [33.3%], respectively; P = 1.0). There was no difference in the rate of hearing loss progression in patients with bilateral and unilateral EVA (41 of 89 ears [46.1%] vs. 25 of 75 ears [33.3%], respectively; P = .1); however, both EVA groups had higher rates of progression compared to patients with unilateral hearing loss without EVA. There was a strong correlation between the presence of hearing loss at 250 Hz and the risk of more severe hearing loss and progressive hearing loss. Patients with bilateral EVA and SLC26A4 mutations had a higher rate of progression than patients who had no mutations (P = .02). No patients with unilateral EVA had Pendred syndrome.

CONCLUSIONS

Children with unilateral EVA have a significant risk of hearing loss progression. Hearing loss in the ear contralateral to the EVA is common, suggesting that unilateral EVA is a bilateral process despite an initial unilateral imaging finding. In contrast to bilateral EVA, unilateral EVA is not associated with Pendred syndrome and may have a different etiology. Temporal bone measurements, hearing loss severity, and hearing loss at 250 Hz were all correlated with the risk of progressive hearing loss. Clinicians should become knowledgeable regarding the implications of this disease process so that families can be counseled appropriately.

Evaluation of pediatric sensorineural hearing loss: a survey of pediatric otolaryngologists

OBJECTIVES

We sought to determine the trends in the evaluation of pediatric patients with sensorineural hearing loss (SNHL) and to determine evaluation patterns based on respondents' demographic data.

METHODS

All members of the American Society of Pediatric Otolaryngology were invited to voluntarily and anonymously complete an online survey. The survey was available from September 2009 to January 2010 and addressed demographic data and tests obtained in evaluating new pediatric patients with SNHL at different age points and with different degrees of hearing loss.

RESULTS

The response rate was 22.9% (79 of 345). For all ages and all types of SNHL, the most common consultations were genetics (26% to 76%) and ophthalmology (31% to 66%) consultations. Computed tomography of the temporal bones (49% to 66%), genetic testing (25% to 68%), and electrocardiography (13% to 43%) were the most commonly performed tests. Although there was no consistent difference in practice patterns by gender or years of practice, there were differences in the use of thyroid function tests, TORCH titers, and autoimmune studies by hospital affiliation.

CONCLUSIONS

Type of SNHL and age are factors in the evaluation of pediatric patients with SNHL. Additionally, evaluation patterns differ according to region and hospital affiliation. The results of this study may provide guidance for otolaryngologists in making information-based and cost-effective evaluations.

[Hereditary hearing loss: genetic counselling]

The aim of this review is to provide an updated overview of hereditary hearing loss, with special attention to the etiological diagnosis of sensorineural hearing loss, the genes most frequently mutated in our environment, the techniques available for their analysis and the clinical implications of genetic diagnosis. More than 60% of childhood sensorineural hearing loss is genetic. In adults, the percentage of hereditary hearing loss is unknown. Genetic testing is the highest yielding test for evaluating patients with sensorineural hearing loss. The process of genetic counselling is intended to inform patients and their families of the medical, psychological and familial implications of genetic diseases, as well as the risks, benefits and limitations of genetic testing. The implementation of any genetic analysis must be always preceded by an appropriate genetic counselling process.

Diagnostic yield in the workup of congenital sensorineural hearing loss is dependent on patient ethnicity

HYPOTHESIS

Diagnostic yield on GJB2 sequencing and computed tomography in the workup for idiopathic congenital sensorineural hearing loss is related to patient ethnicity.

BACKGROUND

GJB2 sequencing and computed tomography of the temporal bones are important initial diagnostic tests in the workup of idiopathic congenital sensorineural hearing loss. Previous studies showed an association between mild or unilateral hearing loss and positive imaging findings and between severe or bilateral deafness and GJB2 mutations. Recent studies on connexin 26-associated deafness demonstrate a wide range of phenotypes that vary with ethnicity.

METHODS

We present a retrospective case series of 271 consecutive ethnically diverse patients evaluated for idiopathic congenital sensorineural hearing loss. Results of genetic testing and imaging were correlated with audiologic findings and ethnicity.

RESULTS

All patients with asymmetric hearing loss had more positive findings on imaging. With respect to the severity of hearing loss, however, differences were noted between ethnic groups. Whereas white patients conformed to previous findings, Hispanics with severe hearing loss had similar rates of positive imaging and genetic testing results. Asians with mild hearing loss had significantly greater yield on genetic testing rather than on imaging. This reflects the high prevalence of the p.V37I mutation in GJB2 among Asians, which gives rise to a mild, frequently progressive phenotype.

CONCLUSION

Ethnicity should be considered when determining the optimal sequence of diagnostic testing for idiopathic congenital sensorineural hearing loss. Asian patients, in particular, should all be screened for mutations in GJB2, especially in the case of mild hearing loss.

Cochlear implantation in the very young child: issues unique to the under-1 population

Since the advent of cochlear implantation, candidacy criteria have slowly broadened to include increasingly younger patients. Spurred by evidence demonstrating both perioperative safety and significantly increased speech and language benefit with early auditory intervention, children younger than 12 months of age are now being successfully implanted at many centers. This review highlights the unique challenges involved in cochlear implantation in the very young child, specifically diagnosis and certainty of testing, anesthetic risk, surgical technique, intraoperative testing and postoperative programming, long-term safety, development of receptive and expressive language, and outcomes of speech perception. Overall, the current body of literature indicates that cochlear implantation prior to 1 year of age is both safe and efficacious.

Impact of gene patents and licensing practices on access to genetic testing for hearing loss

Genetic testing for heritable hearing loss involves a mix of patented and unpatented genes, mutations and testing methods. More than half of all hearing loss is linked to inherited mutations, and five genes are most commonly tested for in the United States. There are no patents on three of these genes, but Athena Diagnostics holds exclusive licenses to test for a common mutation in the GJB2 gene associated with about 50% of all cases as well as mutations in the MTRNR1 gene. This fragmented intellectual property landscape made hearing loss a useful case study to assess whether patent rights in genetic testing can proliferate or overlap, and whether it is possible to gather the rights necessary to perform testing. Testing for hearing loss is widely available, primarily from academic medical centers. Based on literature reviews and interviews with researchers, research on the genetics of hearing loss has generally not been impeded by patents. There is no consistent evidence of a premium in testing prices attributable to patent status. Athena Diagnostics has, however, used its intellectual property to discourage other providers from offering some tests. There is no definitive answer about the suitability of current patenting and licensing of commonly tested genes because of continuing legal uncertainty about the extent of enforcement of patent rights. Clinicians have also expressed concerns that multiplex tests will be difficult to develop because of overlapping intellectual property and conflict with Athena's sole provider business model.

High-throughput detection of mutations responsible for childhood hearing loss using resequencing microarrays

BACKGROUND

Despite current knowledge of mutations in 45 genes that can cause nonsyndromic sensorineural hearing loss (SNHL), no unified clinical test has been developed that can comprehensively detect mutations in multiple genes. We therefore designed Affymetrix resequencing microarrays capable of resequencing 13 genes mutated in SNHL (GJB2, GJB6, CDH23, KCNE1, KCNQ1, MYO7A, OTOF, PDS, MYO6, SLC26A5, TMIE, TMPRSS3, USH1C). We present results from hearing loss arrays developed in two different research facilities and highlight some of the approaches we adopted to enhance the applicability of resequencing arrays in a clinical setting.

RESULTS

We leveraged sequence and intensity pattern features responsible for diminished coverage and accuracy and developed a novel algorithm, sPROFILER, which resolved >80% of no-calls from GSEQ and allowed 99.6% (range: 99.2-99.8%) of sequence to be called, while maintaining overall accuracy at >99.8% based upon dideoxy sequencing comparison.

CONCLUSIONS

Together, these findings provide insight into critical issues for disease-centered resequencing protocols suitable for clinical application and support the use of array-based resequencing technology as a valuable molecular diagnostic tool for pediatric SNHL and other genetic diseases with substantial genetic heterogeneity.

Distinct and novel SLC26A4/Pendrin mutations in Chinese and U.S. patients with nonsyndromic hearing loss

Mutations of the human SLC26A4/PDS gene constitute the most common cause of syndromic and nonsyndromic hearing loss. Definition of the SLC26A4 mutation spectrum among different populations with sensorineural hearing loss is important for development of optimal genetic screening services for congenital hearing impairment. We screened for SLC26A4 mutations among Chinese and U.S. subjects with hearing loss, using denaturing HPLC (DHPLC) and direct DNA sequencing. Fifty-two of 55 Chinese subjects with deafness accompanied by enlargement of the vestibular aqueduct (EVA) exhibited at least one mutant SLC26A4 allele, whereas SLC26A4 mutations were found in only 2 of 116 deaf Chinese patients without EVA. The spectrum of SLC26A4 mutations differed among Chinese and U.S. subjects and included 10 previously unreported SLC26A4 variants: 4 in the Chinese population (p.E303Q, p.X329, p.X467, p.X573) and 6 in the U.S. population (p.V250A, p.D266N, p.F354S, p.D697A, p.K715N, p.E737D). Among the seven novel in-frame missense mutations, five encoded SLC26A4 proteins with substantially reduced Cl(-)/anion exchange activity as expressed and measured in Xenopus oocytes, but four of these were sufficiently active to allow study of anion selectivity. The only mutant polypeptide exhibiting complete loss of anion exchange function, p.E303Q, was expressed at or near the oocyte surface at near-wild-type levels. Two variants, p.F354S and p.E737D, displayed selective reduction in relative rate of Cl(-)/HCO(3)(-) exchange compared with similarly measured rates of Cl(-)/Cl(-) and Cl(-)/I(-) exchange. Our data show that mutation analysis of the SLC26A4 gene is of high diagnostic yield among subjects with deafness and bilateral EVA in both China and the U.S. However, the pathogenicity of monoallelic SLC26A4 gene variants in patients with hearing loss remains unclear in many instances.

Audiologic and temporal bone imaging findings in patients with sensorineural hearing loss and GJB2 mutations

OBJECTIVES/HYPOTHESIS

Our objectives were to determine genotype-phenotype correlations in patients with sensorineural hearing loss (SNHL) who undergo testing for GJB2 mutations and to examine the relationship of temporal bone anomalies seen on computed tomography (CT) and GJB2 mutations.

STUDY DESIGN

We conducted a retrospective review of all children diagnosed with SNHL and who underwent GJB2 testing from 1997 to 2006.

RESULTS

Of 840 patients, 146 (17.4%) had mutations. Seventy-six (9.1%) had biallelic GJB2 mutations and 70 (8.3%) had heterozygous mutations. When biallelic mutations were categorized as missense or nonsense mutations, the presence of at least one missense mutation was associated with mild or moderate SNHL. Biallelic nonsense mutations were associated with severe to profound SNHL. Among patients with GJB2 mutations, those with heterozygous mutations (n = 14 [20%]) had a higher rate of asymmetric SNHL loss than those with biallelic mutations (n = 6 [7.9%], P = .03). Those with heterozygous mutations were more likely to experience progression than were those with biallelic mutations, though this difference was only marginally significant (26.5% vs. 12.3%, respectively; P = .06). Patients who were wild type for GJB2 were more likely to have an enlarged vestibular aqueduct (EVA) than were those with biallelic and heterozygous mutations (29% vs. 11.9%, respectively; P = .004). Compared to patients who were wild type, those with biallelic mutations had a significantly lower rate of EVA.

CONCLUSIONS

This is the largest single-institution study of pediatric patients with GJB2 mutations and SNHL. The functional consequences of GJB2 mutations correlated with the degree of hearing loss. Patients with M34T mutations and/or mild SNHL had a low risk of progression. Temporal bone anomalies were uncommon in patients with GJB2 mutations.

SLC26A4 c.919-2A>G varies among Chinese ethnic groups as a cause of hearing loss

PURPOSE

Mutations in the SLC26A4 gene are second only to GJB2 mutations as a currently identifiable genetic cause of sensorineural hearing loss. In most areas of China, genetic testing for sensorineural hearing loss is unavailable because of limited knowledge of the mutation spectrum. Although SLC26A4 c.919-2A>G (IVS7-2A>G) is a common mutation among some Asian populations, the mutation prevalence among various ethnic groups within China has not been studied.

METHODS

DNA specimens from 3271 subjects with moderate to profound sensorineural hearing loss from 27 regions of China were genotyped for the c.919-2A>G mutation by polymerase chain reaction/restriction-fragment-length polymorphism. Normal hearing controls from Han (n = 185) and Uigur (n = 152) populations were also tested.

RESULTS

Overall, 408 subjects with sensorineural hearing loss (12.5%) carried at least one c.919-2A>G allele, with 158 (4.8%) homozygotes and 250 (7.6%) heterozygotes. Within the subpopulations examined, the rate varies from 0% to 12.2% for c.919-2A>G homozygotes and from 0% to 17.6% for heterozygotes. Based on this cohort, Chinese subjects with sensorineural hearing loss seem to have a relatively higher c.919-2A>G frequency than that of other Asian populations.

CONCLUSION

These results demonstrate that a simple and efficient genetic test for the c.919-2A>G mutation alone would identify the molecular cause in up to 8-12% of individuals with sensorineural hearing loss in a few eastern and central regions of China. Those who are negative for the c.919-2A>G mutation would be candidates for further mutational analysis of SLC26A4 or other deafness-related genes. This would greatly improve genetic diagnosis and counseling for a huge number of Chinese individuals and family members with sensorineural hearing loss in China, and many more ethnic Chinese in other countries, which might be up to one million.

Two patients with the V37I/235delC genotype: are radiographic cochlear anomalies part of the phenotype?

We present two East Asian patients with sensorineural hearing loss (SNHL) and compound heterozygosity for the 235delC and V37I mutations in the GJB2 gene. One patient has a unilaterally enlarged vestibular aqueduct, which underscores the importance of routine CT examination in children with SNHL, even if GJB2 (connexin 26) mutations have been identified. The second patient was not available for evaluation by CT. The pathogenic role of the V37I mutation has been controversial. We review the literature and present evidence in support of pathogenicity. Larger studies in compound heterozygous individuals and co-transfection studies will allow better genotype-phenotype correlations and prognostication.