Hearing loss is complex, but its effects are relatively straightforward. In adults with late onset hearing loss, progressive decline in hearing can significantly reduce quality of life. In newborns and children with hearing loss, potential negative effects on speech and language development can have long-lasting developmental consequences if not accurately diagnosed and treated early. Because of this danger, newborn hearing screening has been mandated in the United States since 2001.
Explore this issue:August 2017
Contributing to the complexity of hearing loss are the multiple variables in the environment and genetics that cause it. Although mandatory screening has helped to identify newborns with hearing loss, accurate diagnosis of the etiology of the hearing loss remains challenging, given the heterogeneity of the condition. To date, more than 110 genes and 8,000 genetic variants linked to hearing loss have been reported, and more are discovered each day, according to Richard J. Smith MD, a professor in the department of otolaryngology at the University of Iowa Carver College of Medicine in Iowa City.
The importance of identifying the etiology of hearing loss, particularly in newborns and infants, lies in first classifying the condition appropriately to ensure that appropriate treatments are offered. Of the newborns with hereditary hearing loss, most (70%) will have nonsyndromic hearing loss (NSHL), while 30% will have syndromic hearing loss (SHL) (Curr Opin Pediatr. 2012;24:679-686). Distinguishing the type of genetic hearing loss a child has is one critical step to ensuring she receives the appropriate treatment, for her hearing as well as for other comorbidities if the condition is syndromic. For newborns and children in particular, accurate and early diagnosis is critical to providing the appropriate needed interventions that will ensure that these children can develop normally.
Genetic testing is a powerful tool that can augment more traditional diagnostic methods in identifying and diagnosing the etiology of hearing loss. Although available for years, this testing has only recently become a feasible tool in the clinical setting, given new technologies that can provide more comprehensive data. “Genetic testing for hearing loss has emerged over the past decade as the most important first diagnostic test to order in a new evaluation of sensorineural hearing loss,” said Dr. Smith. “After a thorough history, including family history of hearing loss, complete head and neck examination, and appropriate audiometric testing, we recommend genetic testing with a multi-gene testing panel.”
The multi-gene testing panel Dr. Smith refers to is one of the new technologies for genetic testing that has emerged over the past several years. Referred to as next-generation sequencing (NGS) technologies, these tests are replacing older technology that relied on sequencing single genes.