Hearing loss, the other newborn screen

The dried blood spot collects at 24 to 48 hours of life, and the chemistry assays follow. Newborn hearing screening is the second universal screen in the same time window, performed at the bedside with an instrument the size of a paperback book. The hearing screen has nothing in common with the metabolic and endocrine assays that share its timing, but it is on every state's screening protocol for the same reason: a treatable condition with a catastrophic untreated developmental course, a reliable bedside test, and an intervention pathway that depends on early identification.

Permanent congenital hearing loss affects roughly 1 to 3 of every 1,000 newborns, which is more than every other condition on the metabolic and endocrine portion of the panel combined. The case for screening is the strongest case of the universal screening program. The intervention infrastructure that has been built around it, including the early intervention services, the cochlear implant centers, and the sign language and oral education programs, is one of the larger applied developmental programs in pediatrics.

What hearing loss is

Permanent hearing loss in newborns spans a wide range of causes. Roughly half of cases are genetic, with the most common cause being biallelic variants in GJB2, encoding connexin 26, a gap junction protein in the cochlea. Other genetic causes include variants in GJB6, SLC26A4 (Pendred syndrome), MYO7A and other usher syndrome genes, and dozens of other syndromic and non-syndromic genes. Roughly a quarter of cases are caused by congenital cytomegalovirus infection, which can produce hearing loss at birth or progressive hearing loss in the first years of life. Other causes include perinatal complications (prematurity, severe hyperbilirubinemia, neonatal sepsis, hypoxic-ischemic encephalopathy), in-utero exposures, and congenital structural abnormalities of the inner ear.

The clinical consequence of unrecognized hearing loss in infancy is failure of language acquisition during the critical window for spoken or signed language development. Children identified by newborn screening and provided with appropriate amplification or implantation in the first months of life develop spoken or signed language on a near-typical trajectory. Children identified later, after the first year, lag substantially even with subsequent intervention, and the gap widens with later identification.

How the screen works

Two technologies are used in newborn hearing screening: otoacoustic emissions (OAE) and automated auditory brainstem response (AABR). OAE measures the cochlear response to a sound stimulus and detects most cochlear hearing loss. AABR measures brainstem electrical activity in response to sound and additionally detects auditory neuropathy spectrum disorder. Many programs use a two-step protocol: OAE first, with AABR for any infants who do not pass OAE, before referral to formal audiology. The two-step approach reduces false positives and the rate of unnecessary diagnostic referrals.

A positive screen prompts diagnostic audiology evaluation, typically within the first 1 to 3 months of life, including diagnostic ABR or auditory steady-state response, behavioral observation audiometry, otoacoustic emissions, and tympanometry. The diagnostic evaluation establishes the type, degree, and laterality of hearing loss. Imaging (CT or MRI) and genetic testing follow to characterize the cause when not obvious.

Permanent congenital hearing loss is on the federal Recommended Uniform Screening Panel and is universally screened in the United States. Screening protocols are coordinated through the Early Hearing Detection and Intervention (EHDI) program of the Centers for Disease Control and Prevention.

What management looks like

Management depends on the type and degree of hearing loss and on family preference for communication mode. Mild to moderate sensorineural hearing loss is managed with hearing aids, fitted as early in infancy as the diagnosis is established. Severe to profound sensorineural hearing loss can be managed with hearing aids in the first months and, when amplification does not provide adequate access to speech, with cochlear implantation. Cochlear implants are FDA-approved for children as young as 9 months for bilateral severe to profound hearing loss, and many centers implant earlier when the diagnosis is established.

Auditory neuropathy spectrum disorder, in which OAE may be present but ABR is abnormal, requires individualized management because hearing aids and cochlear implants produce variable results and the underlying mechanism affects amplification choice.

Communication mode decisions are family-led, with information from a multidisciplinary early intervention team. American Sign Language acquisition in deaf children of hearing parents requires deliberate parental learning and exposure to fluent ASL users. Spoken language development with hearing aids or implants requires intensive auditory-verbal therapy and early intervention services. Many families choose bilingual approaches that combine signed and spoken language. The choice is the family's. The role of the medical team is to support whatever mode the family chooses with the necessary technology and therapy access.

Genetic counseling and genetic testing for the cause of hearing loss are part of the diagnostic workup. The information matters for family planning, for surveillance of additional features in syndromic forms (cardiac in Jervell and Lange-Nielsen, vestibular and visual in Usher syndromes, thyroid in Pendred), and for understanding prognosis (whether the loss is likely to be progressive or stable).

What this looks like for a family

A baby is born. At 24 hours of life, the OAE screen is performed. The baby does not pass on either ear. AABR follows and confirms an abnormal pattern bilaterally. The family is referred to a pediatric audiology clinic. At 6 weeks of life, diagnostic ABR establishes severe to profound sensorineural hearing loss bilaterally. Imaging shows cochlear nerve presence and an unremarkable cochlea. Genetic testing returns biallelic GJB2 variants. The family meets the early intervention team. Hearing aids are fitted at 8 weeks. The family begins ASL instruction and auditory-verbal therapy. Cochlear implant evaluation begins at 9 months.

That child grows up with the language environment that early identification made possible. The same child, identified at age 3 in a state without screening, would have entered language development a year or more behind the critical window for the first acquisition of either signed or spoken language. The catch-up trajectory after late identification is well-documented and shows persistent deficits.

That is what newborn hearing screening looks like in practice. The screen identifies the loss. The family chooses the mode. The infrastructure of audiology, early intervention, and cochlear implant centers makes the rest of the developmental trajectory possible.