The Newborn Who Passed but Shouldn't Have
A 6-week-old infant is brought to your clinic after passing a newborn hearing screening (automated ABR, 35 dB nHL) in both ears at the hospital. The parents report the baby startles to loud sounds but does not calm to the mother's voice and has not begun to coo. The infant was born at 36 weeks, spent 5 days in the NICU on gentamicin for suspected sepsis, and had hyperbilirubinemia requiring phototherapy. Otoscopy shows normal canals and mobile tympanic membranes. You perform a diagnostic ABR: click thresholds are 30 dB nHL in the left ear and 65 dB nHL in the right ear. OAEs are absent in the right ear and present in the left.
1. Reconcile the passed screening with the diagnostic ABR results. What is the most likely diagnosis and why did screening miss it?
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The infant has a right-ear sensorineural hearing loss (moderate, ~65 dB nHL click ABR) with absent OAEs on the right and present OAEs on the left. The passed screening is explained by several factors:
- Screening ABR at 35 dB nHL is a pass/fail screen; a 65 dB nHL loss should fail, but screening is susceptible to false passes from probe placement, calibration, or a noisy environment, and some automated algorithms tolerate borderline responses.
- Risk factors were present but not acted upon: NICU stay, gentamicin (ototoxic), and hyperbilirubinemia (auditory neuropathy risk) are all risk indicators that mandate diagnostic follow-up regardless of screening result.
- The left ear is normal by ABR and OAEs, so a unilateral loss can be missed if the screening focused on the better ear or if the right-ear response was contaminated.
Diagnosis: right moderate sensorineural loss. The key teaching point: risk factors trump a passed screen - the Joint Committee on Infant Hearing recommends diagnostic ABR for NICU graduates and infants with risk indicators even after a pass.
2. What additional testing should you order, and what condition must you rule out given the hyperbilirubinemia and gentamicin exposure?
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Order diagnostic ABR with frequency-specific (tone-burst) stimuli to define the audiogram across octaves, plus bone-conduction ABR to distinguish conductive from sensorineural components. Repeat OAEs and add acoustic reflexes (often absent in auditory neuropathy). Given hyperbilirubinemia and gentamicin, rule out auditory neuropathy spectrum disorder (ANSD) - the hallmark is present OAEs or cochlear microphonic with absent/abnormal ABR. In this infant OAEs are absent on the right, which argues against classic ANSD on that side, but you must check the cochlear microphonic on ABR and consider imaging (MRI) if ANSD or structural anomaly is suspected. Also screen for vestibular and developmental concerns and refer to genetics and ophthalmology per JCIH. Do not delay: the critical window for language is before 6 months.
3. What is the immediate management plan, and how do you counsel parents who were told their baby "passed"?
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Management: Refer immediately for hearing aid fitting on the right ear (and consider FM/remote microphone technology), enroll in early intervention (Part C), and schedule frequent audiological monitoring (every 3 months in infancy) because thresholds can change. Refer to ENT and genetics. If ANSD is confirmed, hearing aids may help but cochlear implant candidacy must be considered early.
Counseling: Acknowledge the confusion honestly - explain that screening is a quick check and can miss losses, especially with risk factors like NICU care, gentamicin, and jaundice. Emphasize that acting now (before 6 months) gives the best language outcomes. Avoid blaming the hospital; focus on the plan. Provide written information, connect them with parent support networks, and confirm they understand the follow-up schedule. Document the risk factors and the rationale for diagnostic testing despite the passed screen.