Of every 1,000 live births, two to three children are born with permanent bilateral hearing loss, and the majority of children will experience a period of hearing loss related to ear infections prior to the age of 10.4
The auditory pathway is a complex system made up of several different structures. The three main parts of the ear include the outer ear, the middle ear, and the inner ear. The outer ear contains the cartilaginous structure on the side of the head (the pinna), the ear canal, and the eardrum. The middle ear includes the three bones that attach the eardrum to the inner ear. Those three bones are called the ossicular chain, and they make up some of the smallest bones in the human body. Finally, there is the inner ear (the cochlea) that contains thousands of “hair cells,” and the nerve that connects the inner ear to the brain. In order to hear, sound must pass through the ear canal to reach the eardrum. The ossicular chain then stimulates the hair cells within the cochlea. The hair cells send the signals to the auditory nerve, which then travel through the brainstem, to the auditory cortex in the brain.
The pinna begins developing at the fetal stage and continues to grow until nine years of age, while the inner ear is fully developed by 20 weeks gestation. An infant may develop congenital hearing loss any time in-utero, but is particularly susceptible to complications of the inner ear after four weeks gestation.4 The anatomical connections between the inner ear and the brain are developed between 20 to 30 weeks gestation.6
How is a Baby’s Hearing Tested?
There are several ways to test an infant’s hearing. Of course one cannot expect a newborn to participate in traditional hearing tests. An audiometric evaluation for the adult population requires the patient to indicate a response to given stimuli, typically by raising a hand or pressing a button. Due to this, objective ways of testing a person’s hearing has been developed.
95% of infants born in the United States of America have their hearing screened in the neonatal period. In fact, most states in America have mandated newborn hearing screening protocols.3 How were newborn hearing screening programs implemented? The Joint Committee on Infant Hearing (JCIH), established in 1969, pioneered these programs. JCIH is composed of audiologists, otolaryngologists, and pediatric specialists. The goal of JCIH is to establish recommendations for children with hearing loss, and children at risk for developing hearing loss. Secondly, JCIH aims to bring newborn hearing screenings to as many children as possible.2
JCIH lists five primary risk factors for hearing loss. The first risk factor is a stay in the neonatal intensive care unit (NICU) for five or more days. Infants born prematurely or who require more invasive medical procedures such as needing to be intubated or need blood transfusions may need to be admitted to the NICU. The second risk factor is if the infant is diagnosed with a syndrome that is known to include hearing loss. Third is a family history of permanent sensorineural hearing loss beginning in childhood. The fourth risk factor is the presence of craniofacial abnormalities. Lastly, includes in-utero infections including the following: cytomegalovirus, herpes, toxoplasmosis, rubella, or syphilis.2
Infants born without complications and who do not have any prior risk factors related to hearing loss are typically placed in the well baby nursery after birth. Infants born with complications or who have risk factors for hearing loss may be placed in the NICU after birth.
The two primary ways of screening an infant for hearing loss include testing and measuring otoacoustic emissions (OAEs) and the auditory brainstem response (ABR). The majority of hearing screening programs will test OAEs in the well baby, and ABRs for infants in the NICU or the infants who have any of the above mentioned risk factors for hearing loss.
In order to test OAEs, a probe tip needs to be placed in the ear canal. Tones are presented and the probe measures the responses generated by the inner ear. This test evaluates the health of the hair cells within the cochlea. However, the results may be negatively impacted by any disruptions within the outer or middle ear, such as an ear infection. An ABR test evaluates the majority of the auditory pathway, from the outer ear to the brainstem. Several electrodes are placed on the head of the infant and earphones are inserted into the ear canal. “Click” sounds are played through the earphones, and the brain waves produced in response to hearing the sounds are measured.
The primary reason why two different test methods are used is because of the previously discussed risk factors. Testing the auditory brainstem response is ideal for at-risk infants because it tests further into the auditory pathway than otoacoustic emissions. An at risk infant may have more complex disorders that impact areas other than the outer, middle, and inner ears. After a child passes six months of age, they are typically able to participate in tests that include behavioral responses, and by five years of age, it is common for them to advance to the testing that adult patients undergo.4
A lesser known risk factor for hearing loss that is still being investigated is the connections between socioeconomic status and race.3 Individuals from low socioeconomic areas may not have access to effective healthcare services, including prenatal care. Due to this lack of access, a pregnant woman may be unable to receive treatment for infections, or the identification of possible disorders associated with hearing loss, both of which are included in the JCIH list of risk factors for hearing loss. One study suggests that children born into a low socioeconomic status are twice as likely to be born with hearing loss when compared to infants born into an affluent family.3 Further investigation of this association should be explored.
Early ziagnosis and Treatment
In 1994, JCIH introduced a three step process for identifying and treating children with hearing loss, known as the Early Hearing Detection and Intervention 1-3-6 Goals. The 1-3-6 Goals include the following: infants should undergo a newborn hearing screening prior to one month of age; infants identified as needing additional testing should complete a comprehensive audiologic evaluation to confirm hearing loss by three months of age; after confirming and diagnosing hearing loss, infants should begin early intervention, but no later than six months of age. The 2019 JCIH position statement aims to shorten this timeline for better early detection and intervention, “States who meet the 1-3-6 benchmark should strive to meet a 1-2-3 month timeline.”2 With this newer goal, infants may be able to access early intervention services by three months of age.
What are the Benefits of Early Intervention?
Early intervention with audiologists, ear, nose, and throat physicians, pediatricians, and speech language pathologists allows for caregivers to make the best decisions for their child’s future. This begins with caregiver education. When a caregiver is aware of different options available through early intervention, they are able to choose a model that suits the child and family.
Early intervention may take place in the infant’s home, at clinics, in schools, or at hospitals. The ideal location for daily intervention services to be conducted is in the most natural environment for the child: the home. There are many different models of early intervention. The models can include fitting hearing aids or evaluating for cochlear implants, family counseling, speech language pathology services, communication consultations, and more. An early intervention team can also connect families of children with hearing loss to support groups.
Additionally, early intervention for children with hearing loss can allow for any other disorders to be detected and diagnosed. In one study that included 42,361 children with hearing loss, 40% of them had additional disabilities.4
What are the Effects of a Mild Hearing Loss?
Children with hearing loss are more likely to have delays of speech and language. A child learns how to communicate by mimicking what they see and hear. If a child is unable to hear what is going on in their environment, they may produce speech that appears abnormal. These children may also be delayed in pragmatic aspects of communication. Pragmatic skills allow for a person to use the rules of social communication. When a person struggles with implementing pragmatic skills, they may have difficulty interacting with their peers, which can lead to social isolation.7
Children with mild hearing loss struggle with understanding speech in background noise when compared to their peers, which can significantly impact academics. Children with untreated mild to moderate hearing loss are at an increased risk of falling one to four grades behind their peers.1 In a study with 1,218 children with mild sensorineural hearing loss, 37% of them repeated at least one grade. 25% to 40% of children with mild hearing loss are at risk for academic challenges.7 Despite this, when a child has access to appropriate support services, they can be successful in their academic environments.
Resources/Tips for Parents of a Baby with Hearing Loss
Parents or caregivers of an infant diagnosed with hearing loss may go through a period of grieving after receiving the news. It is important to address the grief of losing the future they hoped for their child, but it is essential to understand that hearing loss is manageable and that their child will most likely be able to live a relatively normal life when compared to their peers. Establishing care with a multidisciplinary team will allow for parents to get the information and support they need. The multidisciplinary teams may include, but are not limited to: pediatricians, audiologists, ENT physicians, counselors or therapists, and more.
The caregivers should be given information regarding support groups for families of children with hearing loss. Oftentimes, caregivers of children with disabilities may feel isolated and they need to know that they are not alone. In 2017, a survey on the perceived informational and emotional support received by families of children with hearing loss was conducted. Out of the 445 respondents, 87% of them reported satisfaction with the support they received from other families.5
Hearing loss is the most common disability an infant can be born with.4 The auditory system is a complex pathway that needs to be fully developed without disruption to function properly. When a child is identified as being at risk for hearing loss, they should be monitored closely by a multidisciplinary team, and be provided with early intervention when necessary. Families of children with hearing loss should be given the proper education and support that they need to feel confident in their decisions for their child’s future.
References
1American Speech Language Hearing Association (ASHA). (n.d.). Effects of hearing loss on development. American Speech Language Hearing Association. Retrieved from: https://www.asha.org/public/hearing/effects-of-hearing-loss-on-development/
2Joint Committee on Infant Hearing (JCIH). (2019). Year 2019 position statement: Principles and guidelines for early hearing detection and intervention programs. Journal of Early Hearing Detection and Intervention, 4. DOI: https://doi.org/10.15142/fptk-b748
3Lantos, P. M., Maradiaga-Panayotti, G., Barber, X., Raynor, E., Tucci, D., Hoffman, K., Permar, S. R., Jackson, P., Hughes, B. L., Kind, A., & Swamy, G. K. (2018). Geographic and racial disparities in infant hearing loss. Otolaryngology-Head and Neck Surgery, 159.
4Northern, J. L. & Downs, M. P. (2014) Hearing in children (6th edition). Plural Publishing, Inc.
5Scarinci, N., Erbasi, E., Moore, E., Ching, T., & Marnane, V. (2017). The parents’ perspective of the early diagnostic period of their child with hearing loss: Information and support. International Journal of Audiology, 57.
6Tharpe, A. M. & Seewald, R. (2017). Comprehensive handbook of pediatric audiology (2nd edition). Plural Publishing, Inc.
7Yoshinaga-Itano, C., Sedey, A., Mason, C., Wiggin, M., Chung, W. (2020). Early intervention, parent talk, and pragmatic language in children with hearing loss. Pediatrics, 146.
