Genetic Testing for Congenital Bilateral Hearing Loss in the Context of Targeted Cytomegalovirus Screening

Genetic testing for pediatric sensorineural hearing loss in the era of gene therapy

PURPOSE OF REVIEW

To summarize indications, methods, and diagnostic yields for genetic testing for pediatric hearing loss.

RECENT FINDINGS

Genetic testing has become a cornerstone of clinical care for children with sensorineural hearing loss. Recent studies have shown the efficacy of gene panels and exome sequencing for any child with sensorineural hearing loss. Recent findings have underscored the importance of a diagnosis in clinical care. Clinical trials for gene therapy for hearing loss have begun.

SUMMARY

Genetic testing has become critical for personalized care for children with hearing loss. Recent studies have shown a 43% overall diagnostic yield for genetic testing for pediatric hearing loss, though the diagnostic yield may range from 10 to 60% depending on clinical features. Syndromic diagnoses comprise 25% of positive genetic tests for pediatric sensorineural hearing loss. While diagnostic yield is lower for children with unilateral or asymmetric sensorineural hearing loss, the likelihood of syndromic hearing loss finding is higher. An early and accurate genetic diagnosis is required for participating in clinical trials for gene therapy for hearing loss.

Congenital Cytomegalovirus and Hearing Loss: The State of the Art

In developed countries, congenital cytomegalovirus (cCMV) infection is the most common congenital viral infection, representing the leading non-genetic cause of sensorineural hearing loss (HL). Diagnosis of cCMV infection can be performed by detection of CMV DNA in urine or saliva within 2-3 weeks after birth, or later in dried blood samples on the Guthrie card. Currently, there are many controversies regarding the preventive, diagnostic, and therapeutic approaches to cCMV infection. HL secondary to cCMV is highly variable in onset, side, degree, audiometric configuration, and threshold changes over time. Therefore, it is of paramount importance to perform a long and thorough audiological follow-up in children with cCMV infection to ensure early identification and prompt treatment of progressive and/or late-onset HL. Early cochlear implantation appears to be a valid solution not only for children with bilateral profound HL, but also for those with single-sided deafness, improving localization ability and understanding speech in noisy environments. Moreover, the decision to apply a unilateral cochlear implant in children with cCMV is strengthened by the non-negligible possibility of hearing deterioration of the contralateral ear over time.

Is CMV PCR of inner ear fluid during cochlear implantation a way to diagnose CMV-related hearing loss?

To evaluate the diagnostic performance of cytomegalovirus (CMV) polymerase chain reaction (PCR) on inner ear fluid collected during cochlear implantation and to assess its interest in current practice. This monocentric prospective study included consecutive children presenting with severe to profound sensorineural hearing loss (SNHL) who were candidates for unilateral and/or bilateral cochlear implantation. The etiology of the SNHL was determined before cochlear implantation when possible. During the surgery, drop-like samples of inner ear fluid and blood were collected. CMV PCR was then performed on both samples. Between January 2017 and September 2021, 113 children with severe to profound SNHL underwent cochlear implantation with inner ear fluid collection. Among these children, 77 of them presented with a known cause of SNHL (68%) and 36 of them had an unknown cause of SNHL at the time of surgery (32%). Sensitivity and specificity of the CMV PCR on inner ear fluid were 60% (95% CI: [49-71]) and 98% (95% CI: [96-100]), respectively. Positive and negative predictive values were 90% (95% CI: [83-97]) and 92% (95% CI: [86-98]), respectively. A sensitivity analysis according to age at cochlear implantation showed a decrease with age.

CONCLUSION

Sampling of inner ear fluid during cochlear implant surgery is an interesting, simple and safe way to diagnose CMV-related hearing loss, especially when the diagnosis of congenital infection can no longer be confirmed. However, the sensitivity decreases with age.

TRIAL REGISTRATION

NCT04724265 What is Known: • Congenital cytomegalovirus infection is the leading infectious cause of neurological disabilities and sensorineural hearing loss in children. In the absence of systematic screening at birth, many cCMV infections go undetected and are often undiagnosed despite the development of sensorineural sequelae.  • Nearly 40% of indications for cochlear implantation are of unknown etiology.

WHAT IS NEW

• Performing CMV PCR on inner ear fluid at the time of cochlear implantation is a safe way with high diagnostic performance (PPV = 90%, NPV = 92%) to detect a CMV-related hearing loss. • This sample may be interesting in cases of unknown cause of hearing loss in order to identify undiagnosed cCMV infections.

Genetic testing for pediatric hearing loss: no time to waste

Since the discovery of the first human deafness gene a quarter of a century ago, our approach to clinical evaluation of children with hearing loss has changed dramatically. What was once a low-yield scattershot approach has changed to a clearly definable pathway involving genetic testing, imaging, and congenital cytomegalovirus testing. There still however is a great deal of work to be done to expand the correct use of this testing, particularly genetic testing.

Genetics of Childhood Hearing Loss

Compelling evidence indicates that some newborns harboring genetic variants associated with hearing loss might not be identified by current physiologic newborn hearing screening (NBHS) rendering current NBHS protocols suboptimal. Incorporating genomic sequencing into NBHS would improve clinical diagnosis and decrease time to early intervention efforts.

Early Identification and Management of Congenital Cytomegalovirus

Congenital cytomegalovirus (cCMV) is the most common nongenetic cause of sensorineural hearing loss. Despite its prevalence, universal screening for cCMV is not currently performed. Hearing loss caused by cCMV is most often severe to profound, often bilateral, and may be fluctuating or progressive. Infants with hearing loss at birth and confirmed cCMV might benefit from antiviral therapy. Roughly half of hearing loss cases owing to cCMV are delayed in onset, and consequently, these children pass newborn hearing screening. Children with cCMV require close audiologic monitoring, require appropriate management with hearing aids, and should be monitored for cochlear implant candidacy.

Congenital Cytomegalovirus Infection: Epidemiology, Timely Diagnosis, and Management

Congenital cytomegalovirus (cCMV) infection is common because of the ubiquitous nature of the virus and the lack of an effective prevention strategy during pregnancy. Most infants with cCMV are asymptomatic, although a notable subset can have sequelae including, most commonly, sensorineural hearing loss and neurodevelopmental disability, which may not be present at birth. Timely screening for cytomegalovirus in the first weeks after birth is critical to appropriately diagnose congenital infection, evaluate affected infants, and determine the treatment course. Antiviral therapy with valganciclovir can optimize end hearing and neurodevelopmental outcomes in symptomatic infants. This review discusses the epidemiology and clinical manifestations of cCMV, targeted and universal screening approaches, and treatment and monitoring of infants with cCMV.

The History of Pediatric and Adult Hearing Screening

OBJECTIVES/HYPOTHESIS

To document the history of hearing seeing in children and adults.

STUDY DESIGN

A literature search in all languages was carried out with the terms of hearing screening from the following sources: Pub Med, Science Direct, World Catalog, Index Medicus, Google scholar, Google Books, National Library of Medicine, Welcome historical library and The Library of Congress.

METHODS

The primary sources consisting of books, scientific reports, public documents, governmental reports, and other written material were analyzed to document the history of hearing screening.

RESULTS

The concept of screening for medical conditions that, when found, could influence some form of the outcome of the malady came about during the end of 19th century. The first applications of screening were to circumscribe populations, schoolchildren, military personnel, and railroad employees. During the first half of the 20th century, screening programs were extended to similar populations and were able to be expanded on the basis of the improved technology of hearing testing. The concept of universal screening was first applied to the inborn errors of metabolism of newborn infants and particularly the assessment of phenylketonuria in 1963 by Guthrie and Susi. A limited use of this technique has been the detection of genes resulting in hearing loss. The use of a form of hearing testing either observational or physiological as a screen for all newborns was first articulated by Larry Fisch in 1957 and by the end of the 20th century newborn infant screening for hearing loss became the standard almost every nation worldwide.

CONCLUSIONS

Hearing screening for newborn infants is utilized worldwide, schoolchildren less so and for adults many industrial workers and military service undergo hearing screening, but this is not a general practice for screening the elderly.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:S1-S25, 2021.

Hearing Loss Caused by HCMV Infection through Regulating the Wnt and Notch Signaling Pathways

Hearing loss is one of the most prevalent sensory disabilities worldwide with huge social and economic burdens. The leading cause of sensorineural hearing loss (SNHL) in children is congenital cytomegalovirus (CMV) infection. Though the implementation of universal screening and early intervention such as antiviral or anti-inflammatory ameliorate the severity of CMV-associated diseases, direct and targeted therapeutics is still seriously lacking. The major hurdle for it is that the mechanism of CMV induced SNHL has not yet been well understood. In this review, we focus on the impact of CMV infection on the key players in inner ear development including the Wnt and Notch signaling pathways. Investigations on these interactions may gain new insights into viral pathogenesis and reveal novel targets for therapy.

Future directions for screening and treatment in congenital hearing loss

Hearing loss is the most common neurosensory deficit. It results from a variety of heritable and acquired causes and is linked to multiple deleterious effects on a child's development that can be ameliorated by prompt identification and individualized therapies. Diagnosing hearing loss in newborns is challenging, especially in mild or progressive cases, and its management requires a multidisciplinary team of healthcare providers comprising audiologists, pediatricians, otolaryngologists, and genetic counselors. While physiologic newborn hearing screening has resulted in earlier diagnosis of hearing loss than ever before, a growing body of knowledge supports the concurrent implementation of genetic and cytomegalovirus testing to offset the limitations inherent to a singular screening modality. In this review, we discuss the contemporary role of screening for hearing loss in newborns as well as future directions in its diagnosis and treatment.