OVERVIEW: What every practitioner needs to know
Are you sure your patient has congenital or early onset hearing loss? What are the typical findings for this disease?
Infants with congenital or early-onset hearing loss (CHL) are typically asymptomatic until delayed speech and language development is evident. Risk-factor screening to detect infants with CHL are largely unsuccessful because more than 50% of these infants have no known risk indicators for deafness (see below). Therefore, newborn hearing screening is necessary to detect all infants with CHL.
Role of Newborn Hearing Screening in detecting infants with congenital/early-onset hearing loss
Every state in the United States has established early hearing detection and intervention (EHDI) programs and many countries throughout the world have developed or are developing such programs. In the United States and its territories, EHDI programs are typically a component of the state’s department of public health. The recommended goals of EHDI programs are to ensure the following:
Infants receive hearing screening by 1 month of age.
Infants who refer (do not pass) hearing screening receive audiologic diagnostic evaluation by 3 months of age.
Infants with confirmed hearing loss receive appropriate intervention by 6 months of age.
How are newborns screened for congenital/early-onset hearing loss?
Newborn hearing screening is conducted by physiologic techniques. Two techniques are currently available (1) automated auditory brainstem response (A-ABR) and (2) otoacoustic emissions (OAEs). Using surface electrodes attached to the infant’s scalp, A-ABR measures the electrical response of the auditory nerve and brainstem pathways in response to short-duration sounds. Using a miniature microphone inserted into the infant’s external ear canal, OAEs measure the acoustic response of outer hair cells in the cochlea in response to short-duration sounds. As screening measures, both techniques reliably detect cochlear hearing loss of 40 dB hearing level (HL) or more. A-ABR can also detect auditory neuropathy, a complex auditory condition most commonly observed in infants who require neonatal intensive care unit (NICU) care. Babies who receive care in the well-baby nursery may be screened by either A-ABR or OAEs. Babies who receive care in the NICU should be screened by A-ABR.
What should I do when an infant should be referred on newborn hearing screening?
Families should be strongly encouraged to follow up promptly with diagnostic audiologic evaluation conducted by an audiologist with expertise in pediatric assessment. Audiologic measures will include physiologic tests and observation of the infant’s behavioral response to sound.
Common physiologic measures include the following:
-Diagnostic auditory evoked potentials, including ABR to clicks and tone bursts, and/or auditory steady-state response.
-Acoustic immittance measures, including tympanometry.
Common behavioral response measures include the following:
-Behavioral observation audiometry for infants from birth to 6 months’ developmental age.
-Visual reinforcement audiometry for infants/toddlers 6 months’ to approximately 3 years’ developmental age.
Using these combinations of physiologic and behavioral procedures, the audiologist will estimate the infant’s hearing sensitivity by frequency to determine the degree and nature (conductive, mixed, or sensorineural) of the hearing loss. Frequency-specific measures will delineate whether the hearing loss is equivalent at all frequencies tested or if hearing sensitivity is better in low versus high frequencies.
If audiologic evaluation confirms CHL, the infant should be referred to an otolaryngologist for thorough history, physical examination, imaging, and/or laboratory studies to determine the cause of hearing loss and possible medical or surgical treatment options. Based on his/her findings, the otolaryngologist may recommend additional consultations with members of other fields, such as genetics, ophthalmology, and/or neurology.
What other disease/condition shares some of these symptoms?
Delayed development – such as specific language disorder, autism, or general developmental delay – produces patterns of language delay similar to that in children with CHL. Approximately 30%-40% of children with CHL will have additional developmental delays, underscoring the importance of ruling out hearing loss in children with developmental delay or other disabilities.
What caused this disease to develop at this time?
In general, causes associated with CHL are as follows:
Environmental and unknown: 40%
Prenatal infections, most commonly congenital cytomegalovirus infection
Prematurity, hypoxia, hyperbilirubinemia, other perinatal conditions
Per the Joint Committee on Infant Hearing 2007 Position Statement, specific risk indicators associated with permanent congenital, delayed-onset, or progressive hearing loss in childhood include the following (those marked with a ‘*’ are of greater concern for delayed-onset hearing loss):
-Caregiver concern* regarding hearing, speech, language, or developmental delay
-Family history* of permanent childhood hearing loss
-Neonatal intensive care of more than 5 days or any of the following regardless of length of stay: ECMO,*assisted ventilation, exposure to ototoxic medications (gentamicin and tobramycin) or loop diuretics (furosemide), and hyperbilirubinemia that requires exchange transfusion
-In utero infections, such as CMV,* herpes, rubella, syphilis, and toxoplasmosis
-Craniofacial anomalies, including those that involve the pinna, ear canal, ear tags, ear pits, and temporal bone anomalies
-Physical findings, such as white forelock, that are associated with a syndrome known to include a sensorineural or permanent conductive hearing loss
-Syndromes associated with hearing loss or progressive or late-onset hearing loss,* such as neurofibromatosis, osteopetrosis, and Usher syndrome; other frequently identified syndromes include Waardenburg, Alport, Pendred, Jervell, and Lange-Nielson
-Neurodegenerative disorders,* such as Hunter syndrome, or sensory motor neuropathies, such as Friedreich ataxia and Charcot-Marie-Tooth syndrome
-Culture-positive postnatal infections associated with sensorineural hearing loss,* including confirmed bacterial and viral (especially herpesviruses and varicella) meningitis
-Head trauma, especially basal skull/temporal bone fracture,* that requires hospitalization
What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?
The otolaryngologist will determine what, if any, laboratory studies are needed to identify the cause of the child’s hearing loss. The following might be ordered: CMV titers for a newborn, tests for connexin 26/30, an electrocardiogram, urinalysis if there is a family history of renal dialysis or hematuria, and renal ultrasonography if the child has other branchial abnormalities, such as preauricular tags, auricular anomalies, or branchial cleft pits.
Would imaging studies be helpful? If so, which ones?
The otolaryngologist will determine what, if any, imaging studies are needed. Either computed tomography (CT) or magnetic resonance imaging (MRI) of temporal bones will be ordered if the child is a candidate for a cochlear implant and the family is considering this option. This imaging is needed to detect any abnormalities of the inner ear that might compromise electrode insertion into the cochlea. MRI is used to identify small or absent cochlear nerves. Small cochlear nerves compromise expected benefit from cochlear implantation; absence of cochlear nerves precludes cochlear implantation.
Confirming the diagnosis
The sequence for confirming the diagnosis and initiating intervention for infants with congenital or early-onset hearing loss
Newborn hearing screening (up to two screenings during birth admission if infant does not pass initial screening). If infant passes, no further testing* is needed.
If infant does not pass birth admission screenings, hearing rescreening is performed on an outpatient basis within 7-10 days of discharge from birth admission. If infant passes, no further testing.*
If infant does not pass outpatient rescreening, diagnostic audiologic assessment is performed by 2-3 months of age. If normal hearing is diagnosed, no further testing.*
If hearing loss is confirmed, otolaryngologic assessment and clearance for hearing aid use (if recommended) takes place by 4-5 months of age.
Initiate hearing aid fitting and family-centered intervention by 6 months of age.
This sequence may be delayed for infants in the NICU, infants with auditory neuropathy, or infants with coexisting middle ear disorders.
*No further testing unless the infant has a condition associated with late-onset hearing loss, such as family history of progressive childhood hearing loss, or conditions develop associated with childhood hearing loss such as bacterial meningitis.
If you are able to confirm that the infant has congenital or early-onset hearing loss, what treatment should be initiated?
On confirmation that an infant has CHL, the family should be referred for the following:
-Evaluation by an otolaryngologist to determine the cause of hearing loss and any potential medical or surgical interventions; based on his/her findings, genetic counseling and other consultations may be recommended,
-Ophthalmologic assessment to detect any vision problems
-Audiologic intervention, including hearing aids and other assistive listening devices
-Early intervention services provided through the local educational unit or other public agency, which will include development of the individualized family service plan as mandated by federal law
-Family support through parent-to-parent organizations for families of children who are deaf or hard-of-hearing
In general, the pediatrician/primary care provider can expect the audiologist who confirmed the diagnosis of CHL to provide the family with information about options for hearing aids, early intervention, and family support.
What are the adverse effects associated with each treatment option?
Adverse effects associated with medical or surgical treatment options (if appropriate) will be discussed and managed by the pediatric otolaryngologist.
Adverse effects of audiologic intervention with hearing aids will be discussed and managed by the audiologist.
What are the possible outcomes of congenital or early-onset hearing loss?
Children with CHL may experience speech and language delay, which in turn leads to diminished academic success and social/emotional distress. These factors are exacerbated by late identification and delayed intervention. Thus, early identification and intervention, preferably before the infant is 6 months of age, are important to provide the child with the opportunity to develop age-equivalent speech and language skills.
Families should be informed about the importance of the following:
-Audiologic recommendations for consistent hearing aid use and audiologic follow-up
-Early intervention recommendations for providing a rich language environment
Families should also be informed about the importance of monitoring their child for ear infections and seeking prompt medical attention if ear infections are suspected.
Pediatricians/primary care providers should be vigilant about assessing the child’s overall development and referring any child with other suspected developmental delays for evaluation and treatment.
What causes this disease and how frequent is it?
How frequent is congenital and early-onset hearing loss?
Hearing loss is the most common congenital sensory disorder, affecting 2-3 infants/1000. By school age, an additional 2-3 children/1000 will have acquired permanent hearing loss.
How do these pathogens/genes/exposures cause the disease?
What is the pathophysiology of congenital or early onset hearing loss?
CHL may be conductive, sensorineural, mixed, and/or neural.
Conductive hearing loss is associated with outer or middle ear disorders. Permanent conductive hearing loss present in newborns or very young infants is typically associated with aural atresia (unilateral approximately 70% of the time; often associated with other craniofacial anomalies) and ossicular malformations. Hearing loss ranges from mild to moderate (up to 50-60 dB HL) in conductive hearing loss.
Sensorineural hearing loss is typically associated with damage to the sensory cells in the cochlea and the outer and inner hair cells. There are approximately 13,000 outer hair cells in the human cochlea and these are vulnerable to a number of insults, including hypoxia, noise, ototoxic medications, and infection. There are approximately 3500 inner hair cells in the human cochlea, which are typically more robust than the outer hair cells. Damage or destruction of all hair cells in the cochlea results in profound hearing loss, hearing loss greater than 90 dB HL.
Mixed hearing loss is the combination of conductive and sensorineural hearing loss. Each component is additive such that a 20 dB HL conductive hearing loss adds to a 40 dB HL sensorineural hearing loss to produce a mixed hearing loss of 60 dB HL. Infants with sensorineural hearing loss should receive active management of otitis media with effusion to prevent a decrease in hearing thresholds associated with middle ear fluid.
Neural hearing loss is relatively uncommon; causes associated with neural hearing loss include small or absent cochlear nerves or progressive neuropathies. Total absence of the cochlear nerve is associated with profound deafness and precludes the use of hearing aids or a cochlear implant.
How can congenital or early onset hearing loss be prevented?
Routine childhood immunizations have significantly decreased CHL, especially CHL associated with congenital rubella syndrome and bacterial meningitis. Although knowledge about the genetics of deafness is expanding rapidly, no genetic interventions are currently available to prevent or ameliorate CHL.
What is the evidence?
This article provides evidence supporting universal newborn hearing screening:
“2007 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Program”. Pediatrics. vol. 120. 2007. pp. 898-921.
The following articles provide evidence supporting early identification and intervention:
Ongoing controversies regarding etiology, diagnosis, treatment
Previous controversies regarding cochlear implantation in children, as well as education and communication mode (auditory-oral versus sign language), have been largely attenuated by emphasis on family informed choice and unbiased presentation of all treatment options. Optimal management of children who are deaf or hard of hearing includes family choice of treatment modalities and access to other families and adult role models in the deaf and hard-of-hearing communities.
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- OVERVIEW: What every practitioner needs to know
- Are you sure your patient has congenital or early onset hearing loss? What are the typical findings for this disease?
- What other disease/condition shares some of these symptoms?
- What caused this disease to develop at this time?
- What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?
- Would imaging studies be helpful? If so, which ones?
- Confirming the diagnosis
- If you are able to confirm that the infant has congenital or early-onset hearing loss, what treatment should be initiated?
- What are the adverse effects associated with each treatment option?
- What are the possible outcomes of congenital or early-onset hearing loss?
- What causes this disease and how frequent is it?
- How do these pathogens/genes/exposures cause the disease?
- How can congenital or early onset hearing loss be prevented?
- What is the evidence?
- Ongoing controversies regarding etiology, diagnosis, treatment