Additional clinical manifestations in children with sensorineural hearing loss and biallelic GJB2 mutations: who should be offered GJB2 testing?

Concurrent genetic and standard screening test for hearing reduction

Reduction of hearing is the most common sensory impairment among newborns with an incidence of 1-3 per 1000 births. Introduction of an Auditory Newborn screening program allows early identification of hearing impairment. Mainly, congenital hearing loss in early childhood is a result of genetic changes. Due to high frequency of GJB2 pathogenic variants, its molecular characterization among sensorineural hearing reduction cases is already conducted as a routine analysis in many countries. The aim of this study is to show our initial results in the effort to determine whether genetic screening along with the standard hearing screening in newborns is justified. Otoacoustic emission (OAE) method was conducted in 223 newborns at risk of hearing impairment. Among them, 7 did not pass the test in both ears while 9 exhibited one-sided hearing loss. In all 7 children with indication of profound bilateral deafness, the diagnosis was confirmed using auditory brainstem response. Genetic screening of GJB2 gene was performed in 6 of them. Genetic analysis of GJB2 revealed homozygous state of the most common pathogenic variant 35delG in 3 (50%) of the analyzed infants. In the remaining 3 no pathogenic variant was determined. The results indicate that performing auditory OAE together with genetic screening is justified. In newborns who have not passed the hearing screening test and have profound hearing loss, without other syndrome traits, screening for mutations of GJB2 gene should be conducted. Genetic screening enables establishment of early definite diagnosis for deafness and helps in conducting adequate therapy providing timely rehabilitation and social inclusion of deaf child. Key words: hearing loss, genetic screening, auditory screening, GJB2 gene

The OTOGL p.Arg925* Variant is Associated with Moderate Hearing Loss in a Syrian Nonconsanguineous Family

AIM

To screen for the genetic basis of congenital hearing loss in a Syrian family.

METHODS

A Syrian patient living in Lebanon presented with moderate congenital hearing loss. The patient's large nonconsanguineous family was recruited. DNA was extracted from blood samples and sent for whole-exome sequencing. A detailed clinical examination along with audiograms was obtained for all subjects.

RESULTS

Hearing loss was noted to be mild to moderate in the low and mid frequencies, sloping to moderate to severe in the high frequencies for all affected members. Results of DNA analysis showed the presence of a previously described p.Arg925* mutation in the OTOGL gene on both alleles in affected family members, whereas nonaffected members either had the wild type or one copy of the mutated allele.

DISCUSSION

Mutations affecting the OTOGL gene have been recently connected with nonsyndromic sensorineural hearing loss. Seven such mutations have already been described. The p.Arg925* reported in this study has been found once in a French family. The current report is the first to describe this mutation in a Middle Eastern family.

Outcomes of evaluation and testing of 660 individuals with hearing loss in a pediatric genetics of hearing loss clinic

Hearing loss is a relatively common condition in children, occurring in approximately 2 out of every 1,000 births with approximately 50% of reported diagnoses having a primary genetic etiology. Given the prevalence and genetic component of hearing loss, coupled with a trend toward early diagnosis with the institution of universal newborn hearing screening, The Genetics of Hearing Loss Clinic was established at The Children's Hospital of Philadelphia to manage the diagnosis, testing, and genetic counseling for individuals and families. This paper described a cohort of 660 individuals with a diagnosis of hearing loss evaluated between July 2008 and July 2015 in the Genetics of Hearing Loss Clinic. To elucidate the cause of hearing loss in this cohort for better management and prognostication, testing included single nucleotide polymorphism chromosomal microarray, hearing loss next generation sequencing panel, and additional clinical tests inclusive of thyroid and renal function studies, temporal bone magnetic resonance imaging, and electrocardiogram. Of those evaluated, most had bilateral sensorineural hearing loss, occurring in 489/660 (74%). Additionally, 612/660 (93%) of patients presented with a nonsyndromic form of hearing loss (no other observed clinical findings at the time of exam), of which pathogenic mutations in GJB2 were most prevalent. Of the individuals with syndromic manifestations (48/660), Usher and Waardenburg syndrome were most commonly observed. A family history of hearing loss (first degree relative) was present in 12.6% of families with available information. Through molecular analyses, clinical examination, and laboratory testing, a definitive etiologic diagnosis was established in 157/660 (23.8%) of individuals. © 2016 Wiley Periodicals, Inc.

Chorioretinal scars and visual deprivation are common in children with cochlear implants after congenital cytomegalovirus infection

AIM

The aim of this study was to compare visual function and ocular characteristics in children with cochlear implants, due to severe hearing impairment caused by the congenital cytomegalovirus (CMV) infection, with control children fitted with cochlear implants due to connexin 26 mutations (Cx26), a genetic cause of hearing impairment.

METHODS

We carried out ophthalmological assessments, including visual acuity, ocular alignment, Ocular Motor Score, biomicroscopy and fundus photography, on 26 children with congenital CMV (median age 8.3 years, range 1.4-16.7) and 13 Cx26 controls (median age 5.6 years, range 1.7-12.5).

RESULTS

We found unilateral chorioretinal macular scars that reduced best-corrected visual acuity ≤0.3 in five (19%) of the children with congenital CMV, but in none of the children with Cx26 (p = 0.15). Ocular motility problems were more common among children with congenital CMV, but the difference was not significant (p = 0.20). The vestibulo-ocular reflex was more frequently pathological in children with congenital CMV (p = 0.011).

CONCLUSION

Ocular complications with central chorioretinal scars and ocular motility disturbances were common in children treated with cochlear implants due to severe hearing impairment caused by the congenital CMV infection. Ophthalmological assessments are advisable in such children for early identification, intervention and follow-up.

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.

Impaired balance and neurodevelopmental disabilities among children with congenital cytomegalovirus infection

AIM

Although cytomegalovirus (CMV) is the most common congenital infection, existing research has not provided us with a full picture of how this can affect children in the future. The aim of this case-control study was to evaluate disabilities in a well-defined group of children with congenital cytomegalovirus (CMV) infection, who had been fitted with cochlear implants because of severe hearing impairment.

METHODS

A multidisciplinary team assessed 26 children with congenital CMV infection for balance difficulties, neurodevelopmental disabilities and language and visual impairment. We also included a control group of 13 children with severe hearing impairment due to connexin 26 mutations.

RESULTS

The majority of the children with congenital CMV infection (88%) displayed balance disturbances, including walking at a later age, but there were no cases in the control group. The CMV group also displayed frequent neurodevelopmental disabilities and feeding difficulties.

CONCLUSION

Congenital CMV infection affects the general development of the brain and gives rise to a complex pattern of difficulties. Identifying comorbid conditions is very important, as children with associated difficulties and disabilities need more support than children with just hearing impairment. Congenital CMV infection needs to be considered in children with hearing impairment and/or balance disturbance and/or neurodevelopmental disabilities.

Prevalence of DFNB1 mutations among cochlear implant users in Slovakia and its clinical implications

Hereditary etiology plays an important role in bilateral profound deafness as a main indication for cochlear implantation. Mutations in DFNB1 locus account for most of the inherited deafness cases in Caucasians. To provide actual data on mutation prevalence among implanted deaf subpopulation, we performed DNA analysis of GJB2 and GJB6 genes in 131 unrelated Slovak cochlear implant users. Eight previously described causal mutations and one probably pathogenic missense variant (c.127G>A) were detected in the GJB2 gene in 58 (44.28%) subjects. The most common mutation found was c.35delG with frequency 83.02% of all disease alleles, followed by c.71G>A, c.1-3201G>A, c.313_326del14, c.109G>A, 167delT, c.269T>C, and c.333_334delAA. GJB6 deletion delD13S1830 was identified in only one subject, in double heterozygosity with a GJB6 mutation. Thus, the deafness cause could be clearly attributable to DFNB1 mutations in 36.64% of the patients examined. In summary, the mutation profile found in our cohort was similar to the mutation spectrum reported for Central European deaf populations. The mutation prevalence in cochlear implant users was, however, almost by 25% higher than previously established for non-implanted hearing-impaired population in Slovakia. Finally, we also demonstrate a certain variability in deafness onset in patients with causal genotype and coincidence with other risk factors for deafness. Our results underline the importance of genetic tests in all cochlear implant candidates.

Molecular diagnosis of hearing loss

This unit discusses an approach to identifying a genetic etiology in an individual with nonsyndromic hearing loss. The unit begins with a discussion of the decision-making process that can be used to determine whether specific genes and/or a large gene panel should be used for molecular diagnosis of a patient presenting with nonsyndromic hearing loss. Next, two protocols are presented: (1) a full gene-sequencing assay to identify mutations in the GJB2 gene (encoding connexin 26), the most common cause of congenital hearing loss, and (2) an assay to detect the presence of the GJB6-D13S1830 deletion, a 342-kb deletion that causes hearing loss in homozygosity or in combination with a single GJB2 mutation. Finally, the unit ends with a strategy for determining the clinical significance of the test results, which can be challenging given the extensive genetic heterogeneity associated with hearing loss.

Impact of co-occurring birth defects on the timing of newborn hearing screening and diagnosis

PURPOSE

Early detection of hearing loss in all newborns and timely intervention are critical to children's cognitive, verbal, behavioral, and social development. The initiation of appropriate early intervention services before 6 months of age can prevent or reduce negative developmental consequences. The purpose of this study was to assess, using large, population-based registries, the effect of co-occurring birth defects (CBDs) on the timing and overall rate of hearing screening and diagnosis.

METHOD

The authors linked statewide data from newborn hearing screenings, a birth defects registry, and birth certificates to assess the timeliness of newborn hearing screening and diagnosis of hearing loss (HL) for infants with and without CBDs in 485 children with confirmed HL.

RESULTS

Nearly one third (31.5%) of children with HL had 1 or more CBDs. The presence of CBDs prolonged the time of the initial infant hearing screening, which contributed to further delays in the subsequent diagnosis of HL.

CONCLUSIONS

Better coordination of HL assessment into treatment plans for children with CBDs may enable earlier diagnosis of HL and provide opportunities for intervention that will affect long-term developmental outcomes for these children.

Vestibular dysfunction in DFNB1 deafness

Mutations of GJB2 and GJB6 (connexin-26 and 30) at the DFNB1 locus are the most common cause of autosomal recessive, nonsyndromic deafness. Despite their widespread expression throughout the vestibular system, vestibular dysfunction has not been widely recognized as a commonly associated clinical feature. The observations of vertigo accompanying DFNB1 deafness in several large families prompted our hypothesis that vestibular dysfunction may be an integral, but often overlooked, component of DFNB1 deafness. Our aim was to define the prevalence of vestibular dysfunction in Cases of DFNB1 deafness and Controls with other forms of deafness. We developed and used a survey to assess symptoms of vestibular dysfunction, medical, and family history was distributed to Cases with deafness due to pathogenic GJB2 and/or GJB6 mutations and deaf Controls without DFNB1 deafness. Our results showed: Surveys were returned by 235/515 Cases (46%) with DFNB1 mutations and 121/321 Controls (38%) without these mutations. The mean age of Cases (41) was younger than Controls (51; P < 0.001). Vestibular dysfunction was reported by 127 (54%) of Cases and was present at significantly higher rates in Cases than in deaf Controls without DFNB1 deafness (P < 0.03). Most (63%) had to lie down in order for vertigo to subside, and 48% reported that vertigo interfered with activities of daily living. Vertigo was reported by significantly more Cases with truncating than non-truncating mutations and was also associated with a family history of dizziness. We conclude that vestibular dysfunction appears to be more common in DFNB1 deafness than previously recognized and affects activities of daily living in many patients.

Temporal bone abnormalities in children with GJB2 mutations

OBJECTIVES

To determine the incidence of temporal bone abnormalities in children with sensorineural hearing loss (SNHL) and pathogenic biallelic GJB2 mutations.

STUDY DESIGN

Retrospective analysis of a large cohort of pediatric patients with biallelic GJB2 mutations and SNHL (observational case series).

METHODS

Blinded review of all available temporal bone computed tomographic (CT) and magnetic resonance imaging (MRI) studies in this cohort.

RESULTS

Out of 158 patients with biallelic GJB2 mutations, 113 had CT and/or MRI studies available for review. Definite, although generally subtle, inner ear abnormalities were present in 12/113. There were malformations of the semicircular canals (SCC) in 4/12, of the internal auditory canal in 2/12, of the cochlear nerve canal (CNC) in 6, and unilateral cochlear malformation in 1/12. MRI in 1/5 showed mildly hypoplastic cochlear nerve. There was no correlation between SNHL severity and presence/absence/type of malformations or genotype.

CONCLUSIONS

Our study of 113 biallelic GJB2 patients with SNHL and temporal bone imaging is the largest study to date. We found only 10% had any abnormalities, most subtle, and none had EVA. Additionally, there was no correlation between SNHL severity and presence/absence/type of malformations or genotype. Disparities between our group and previous reports may be due to differences in degree of hearing loss, types of mutations, populations studied, and radiologic factors for both image acquisition and interpretation.

The clinical features of patients with the homozygous 235delC and the compound-heterozygous Y136X/G45E of the GJB2 mutations (Connexin 26) in cochlear implant recipients

OBJECTIVE

This study aimed to investigate the prevalence of GJB2 gene for the 235delC mutations, the clinical features and the outcomes of patients who had undergone cochlear implantation.

METHODS

We have sequenced the coding region of GJB2 gene for 135 patients with sensorineural deaf from September 2000 to May 2009. Of the 135 patients, the patients with the homozygous 235delC and the compound-heterozygous Y136X/G45E were detected and were investigated clinically.

RESULTS

The GJB2 gene for the 235delC mutations was found in 39 alleles of 270 alleles (14.4%), especially for the homozygous of 235delC was detected in 26 alleles (9.6%), the single heterozygous of 235delC was 1 allele (0.4%), the compound heterozygous of 235delC was found in 12 alleles (4.4%). Of 16 subjects (29 alleles) with the homozygous 235delC and the compound-heterozygous Y136X/G45E, 2 subjects (4 alleles) were found to have complications. All of the subjects were found to show severe hearing loss and some of them have indicated progressive hearing loss. However, they showed better performance regarding the thresholds after implantation. The subjects with complications, although, suggested poorer performance in the auditory speech performance.

CONCLUSION

The findings of poorer outcomes might depend on complications and brain functions. In addition, considering the blood test parameters, an independent elevated LDH and ChE at diagnosis were found to be associated with hereditary enzyme's metabolic disease. Therefore, the value of LDH measurements in patients might be a helpful predictive parameter in hereditary diseases.

Etiological diagnosis in the hearing impaired newborn: proposal of a flow chart

OBJECTIVE

Most industrialized countries have introduced some form of universal newborn hearing screening program. Both identification and rehabilitation of hearing loss in newborns have evolved to an acceptable standard and the need for a standardized etiological protocol is emerging.

METHODS

Extensive literature search to determine which investigations can help identifying the cause of congenital hearing loss and how to limit extensive testing in these children by taking into account the most prevalent causes.

FINDINGS

A stepwise approach to detect the cause of hearing loss in children with congenital sensorineural hearing loss was developed.

CONCLUSION

In general it is advised to first rule out Cx26/Cx30 and infectious causes (cytomegalovirus and, if indicated, toxoplasmosis and rubella), and to preserve more extensive investigations for those children in whom these causes do not explain the hearing loss.

Neurodevelopmental disorders in children with severe to profound sensorineural hearing loss: a clinical study

AIM

The effects of sensorineural hearing loss (SNHL) are often complicated by additional disabilities, but the epidemiology of associated disorders is not clearly defined. The aim of this study was to evaluate the frequency and type of additional neurodevelopmental disabilities in a sample of children with SNHL and to investigate the relation between these additional disabilities and the aetiology of deafness.

METHOD

One hundred children with severe/profound SNHL (60 males, 40 females; mean age 5 y 7 mo, SD 3 y 6 mo, range 8 mo-16 y) were investigated using a diagnostic protocol including neurodevelopmental, genetic, neurometabolic, and brain magnetic resonance imaging (MRI) assessment.

RESULTS

Forty-eight per cent of the sample exhibited one or more additional disabilities, with cognitive, behavioural-emotional, and motor disorders being the most frequent. The risk of additional disabilities varied according to the type of aetiology. Thirty-seven out of 80 individuals with available MRIs showed signal abnormalities, in particular brain malformations (46%) and white matter abnormalities (54%). Frequency and type of disability were associated with aetiology (p=0.015) and MRI data (p<0.001).

INTERPRETATION

A multidimensional evaluation, including aetiological, neurodevelopmental, and MRI investigation, is needed for planning therapeutic intervention, such as cochlear implantation in children with severe to profound hearing impairment. The aetiology of deafness is a relevant risk indicator for the presence of an associated disorder.

Prevalence of the c.35delG and p.W24X mutations in the GJB2 gene in patients with nonsyndromic hearing loss from North-West Romania

OBJECTIVE

In Central and South-Eastern European countries, the most frequent mutation types responsible for congenital nonsyndromic sensorineural hearing loss (NSHL) are c.35delG and p.W24X (15-55.8% and 2.5-4.3%, respectively). The aim of the study was to determine for the first time in Romania the prevalence of c.35delG and p.W24X mutations in patients with NSHL.

MATERIAL

75 unrelated children with NSHL from Transylvania (North-West Romania).

METHODS

a. Audiological examination (otoscopy, tympanogram, acoustic otoemission and tonal audiogram or auditory evoked potentials); b. detection of the c.35delG (semi-nested-PCR, RFLP and ARMS-PCR analysis) and p.W24X (ARMS-PCR analysis) mutations.

RESULTS

Audiological examination allowed the diagnosis of hearing loss of various degrees: moderate in 8 patients (10.7%), severe in 14 cases (18.7%), profound in 53 patients (70.6%). The number of reported mutation cases as against the number of alleles indicates a 33.3% frequency rate for c.35delG mutation and respectively 5.3% for p.W24X mutation. All 22 patients with 35delG/c.35delG genotype (19 patients), c.35delG/p.W24X genotype (2 patients) or p.W24X/p.W24X genotype (1 patient) presented profound/severe hearing loss.

CONCLUSION

Our study confirms that the frequency rate of the two mutations analyzed in patients with NSHL from North-West Romania is comparable to that seen in other Central and South-Eastern European countries. The homozygote or compound heterozygote states represent a major risk factor for profound or severe deafness. Audiological screening in newborns and genetic testing in confirmed congenital hypoacusis cases are compulsory for early therapeutic intervention (hearing prosthesis or cochlear implant) and genetic counselling.

Genetic evaluation of American minority pediatric cochlear implant recipients

OBJECTIVE

To review the results of genetic evaluation of American minority pediatric cochlear implant recipients over a 5-year period.

METHODS

Case series review of pediatric cochlear implant recipients of Caribbean Hispanic and African American admixture descent with severe to profound sensorineural hearing loss at a tertiary care children's hospital.

RESULTS

Out of 28 patients receiving cochlear implants, 14 were of Caribbean Hispanic or African American admixture ancestry. Six (43%) had environmental risk factors for sensorineural hearing loss. Eight (57%) patients had presumed genetic sensorineural hearing loss; two of whom were syndromic and six non-syndromic. Patients with no clear etiology for hearing loss were tested for Gap Junction Beta 2 (GJB2) mutations. Within this admixture group, we found no biallelic mutations in GJB2, while two patients, both with environmental risk factors for sensorineural hearing loss, had monoallelic GJB2 variants. One patient of mixed ethnicity (Caribbean Hispanic, Turkish, Macedonian), not included as part of the 14, had the common Caucasian founder mutation, 35delG, along with a heterozygous polymorphism in the GJB2 gene. This extends previous data showing a paucity of GJB2 mutations in these admixture populations.

CONCLUSIONS

We found no biallelic GJB2 mutations in our admixture cochlear implant population, and two sequence variants of the gene, only one of which was disease causing. This suggests that the incidence of GJB2 mutations in these admixture populations is low. Hence, there may be low cost-benefit of GJB2 mutation analysis in these admixture populations with severe to profound non-syndromic sensorineural hearing loss.

Genetics of congenital hearing impairment: a clinical approach

Hearing impairment (HI) is the most frequent sensory disorder, with a genetic etiology in >50% of all cases, due to mutations in >44 identified genes. Autosomal recessive inheritance explains the majority, with GJB2 (connexin 26) mutations accounting for 15-50% of paediatric HI. Delayed presentation of HI to 11-60 months in cases of biallelic GJB2 mutations is a concern, necessitating a good audiological follow-up in addition to neonatal hearing screening. Providing a genetic diagnosis in congenital HI has implications for the prognosis, the possible risk of associated medical manifestations, and precise genetic counseling of the family, and should be integrated into the medical examinations done in order to diagnose syndromic features. Large-scale mutation detection methods, such as micro arrays, are promising for wider genetic testing, but few studies on their clinical utility have been published, so far. Limitations of interpretation of genetic test results, combined with significant ethical issues, currently do not justify to institute genetic screening for GJB2 mutations in neonates before a diagnosis of HI is established.

Infant hearing screening

PURPOSE OF REVIEW

Infant hearing screening has progressed markedly over the past year. Although uncommon in the past, now almost 95% of infants in the United States are screened for hearing loss. Recent literature has expanded on several important components of hearing screening.

RECENT FINDINGS

A major revision of the American Academy of Pediatrics policy statement on infant hearing screening was published. This statement identifies a number of important principles and guidelines for infant hearing screening. Improvements in diagnostic techniques have been described including the need for auditory brainstem response screening in premature infants. Risk factors for congenital-hearing loss have been updated. An etiologic diagnosis for infants with hearing loss is increasingly possible with advances in genetics and molecular diagnosis. Finally, several articles provide further information on optimizing follow-up and diagnostic testing as well as early intervention.

SUMMARY

Despite the challenges still present in infant hearing screening, screening continues to identify infants at a very young age, and improve the early communication skills of infants with hearing loss through early diagnosis and early intervention.