Advances in understanding the many different genetic causes of childhood hearing loss suggest that genetic testing can help plan treatment, including the optimal timing of treatment.
Even if a child with hearing loss was not diagnosed through genetic testing a few years ago, rapid advances in genomics recently make retesting worthwhile, according to scientists in the field.
Hearing loss, usually caused by sensory problems in the inner ear, affects about 1 in 400 newborns in the United States. About half of these children have a genetic cause for their hearing loss.
More than 120 genes and thousands of different genetic variants can lead to childhood hearing loss. Almost all children with genetic hearing loss have a mutation or mutations in only one gene.
A recent study reported, Jan. 12 in JAMA Otolaryngology, Head and Neck Surgeryexamined a group of more than 400 young adults with bilateral sensorineural hearing loss affecting both ears.
Researchers from UW Medicine and Seattle Children’s Hospital sought to determine the genetic causes of hearing loss in this group and how each genetic cause relates to a specific type of hearing loss. They also assessed whether the genetic cause of hearing loss was related to the success of treatment with a cochlear implant, a surgically placed electronic device that enables a person to sense sound through impulses transmitted to the brain.
The results show that genetic testing is a valuable tool in determining a diagnosis of hearing loss in a child and in predicting the benefit of a cochlear implant for a child’s understanding of speech.
“Through genetic diagnosis, it is possible to predict future hearing loss across acoustic frequencies and progression with age,” the researchers noted in their paper. “This information can be combined with the current severity of hearing loss to make a treatment decision.”
The study was led by Ryan J. Carlson, MD/PhD. Student in the Medical Scientist Training Program at the University of Washington School of Medicine in Seattle.
It was conducted during his training with Marie Claire King, lead author and professor of medicine and genome sciences at the University of Washington School of Medicine and with Jay Rubinstein, professor of otolaryngology and head and neck surgery at the University of Washington School of Medicine.
“For more than half of pediatric patients, genomic testing can now identify the genetic cause of their hearing loss and often provides important information about its clinical characteristics,” explained Carlson.
The study participants included 449 children from 406 families. Genetic analysis resulted in genetic diagnoses for 210 of the 406 families, including 55 of the 82 families with more than one child with a hearing impairment and 155 of the 324 families with one child with a hearing impairment. Genetic diagnosis rates were similar for all strains in the study cohort.
In this study population, the researchers discovered variants responsible for hearing loss in 43 different genes. With one exception, each child’s genetic diagnosis involves only one gene.
The severity of hearing loss, the sound frequencies most affected, and changes in hearing loss over time vary by gene and, in some cases, by the type of variant within the gene. Children with causative mutations in the genes MYO6, OTOA, SLC2644, TMPRSS3, or severe mutations in the GJB2 gene have progressive hearing loss.
All of the children with cochlear implants had better speech perception than they did before they received their implants. The degree of cochlear implant success varied somewhat based on the participant’s genetic diagnosis.
Taking into account the child’s age at implantation and the length of time the implant was in place, speech perception was higher for children with hearing loss due to mutations in the MITF or TMPRSS3 genes.
However, the researchers concluded that differences in cochlear implant success related to genetic diagnosis were not significant enough to rule out a cochlear implant for any patient who met the criteria for the implant.
The ancestors of the study participants were 17 (4%) African/African American, 32 (8%) East Asian, 219 (54%) European, 53 (13%) Hispanic, and 16 (4%) Hispanic. South Asia, 61 (15). %) who cited more than one origin. Just over half of the children (51%) were female
The study was conducted from 2019 to 2022 at the otolaryngology and audiology clinics at Seattle Children’s Hospital and the University of Washington, including the Center for Human Development and Disability.
DNA from the participants was analyzed by genetic sequencing and analysis of structural variants in the Mary Claire King Genomic Sciences Laboratory at the University of Washington School of Medicine. The severity and progression of hearing loss was measured with audiological tests, and the success of their cochlear implantation was assessed by a test of speech perception of children or adults.
The research team identified several key conclusions from their findings:
- First, genetic testing for hearing loss can identify a genetic cause in most pediatric patients. Newborn hearing screening misses hearing loss in about a third of affected babies, because the hearing loss cannot be detected at birth. Genetic testing can fill this gap.
- Second, genetic analysis techniques are improving rapidly. If a child has already had genetic testing, and the results are negative, retesting may find a previously undetected genetic cause.
- Third, genetic testing can identify syndromic forms of hearing loss and lead to necessary referrals of children to key specialists.
- Finally, genetic diagnostics can be used more effectively to inform the accurate treatment of childhood hearing loss. Once the expected clinical characteristics of a particular genetic cause are known, this information can be used to assess prognosis and guide treatment.
Overall, the researchers emphasized that “detection of hearing loss at the earliest possible age is important for cognition and social development, regardless of management approach.”
Carlson noted that the study had a direct positive impact on its participants.
He explained: “We were able to provide genetic testing to more than 400 families with hearing loss in this one study. Many of the participants received new genetic diagnoses that were important to their care.” “I am proud to have directed a project that provided direct benefits to the participants and indirect benefits to all patients with hearing loss.”
Ryan J. Carlson et al., Association of Genetic Diagnostics of Childhood Hearing Loss with Cochlear Implant Outcomes, JAMA Otolaryngology – Head and Neck Surgery (2023). DOI: 10.1001/jamaoto.2022.4463
Provided by the University of Washington School of Medicine
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