Hearing loss in high-risk neonates — short-answer question

Part A — Screening and the OAE-versus-AABR distinction (10 marks)

a) State the 1-3-6 framework and explain why this infant is screened with AABR rather than OAE (6 marks)

The Joint Committee on Infant Hearing 1-3-6 framework requires screening by one month of age, diagnostic confirmation by three months, and fitting of hearing aids with enrolment in early intervention by six months. [1]

This infant must be screened with automated auditory brainstem response rather than otoacoustic emissions because the NICU population carries the highest burden of auditory neuropathy spectrum disorder. Otoacoustic emissions test only the cochlear outer hair cells and return a normal result in auditory neuropathy, where the cochlea is intact but the nerve or brainstem misfires. Automated auditory brainstem response tests the whole pathway from sound to brainstem and therefore detects auditory neuropathy, which is precisely why it is the mandated modality for the NICU infant. [1] [2]

b) List the JCIH risk indicators present in this infant and explain why a pass does not end surveillance (4 marks)

The risk indicators present are a prolonged NICU stay well beyond five days, repeated ototoxic drug exposure (gentamicin and furosemide), and severe hyperbilirubinaemia at exchange level. Hypoxic-ischaemic insult from respiratory failure and prolonged assisted ventilation are additional relevant exposures. [1]

A pass on the newborn screen does not end surveillance because a substantial fraction of permanent loss is progressive or late-onset. Congenital CMV in particular can produce loss that is absent at birth and emerges in the first year, and several genetic causes behave similarly. Infants with JCIH risk indicators therefore require ongoing audiological surveillance to at least 30 months regardless of a normal newborn screen. [3]

Part B — Diagnosis, cause and management (10 marks)

a) Describe the diagnostic pathway and the aetiological work-up you would arrange (6 marks)

A refer on the AABR screen is repeated once; a second refer triggers referral for a diagnostic frequency-specific auditory brainstem response, performed by a paediatric audiologist by three months of age under sedation or natural sleep. The diagnostic ABR defines the degree, configuration, and type of loss in each ear and characterises the waveform for evidence of auditory neuropathy spectrum disorder. [1]

The aetiological work-up runs in parallel. A genetic panel including connexin 26 (GJB2) with clinical genetics referral is first-line because genetic causes predominate. A urine CMV PCR must be sent before 21 days of life to confirm congenital infection, because after that point congenital CMV cannot be distinguished from later-acquired infection. Cranial MRI of the temporal bone and brain identifies inner-ear malformation and brainstem injury, and an ophthalmology review screens for syndromic causes such as Usher syndrome. [3]

b) Outline the management and state the prognosis principles (4 marks)

If permanent loss is confirmed, hearing aids are fitted by six months of age and the family is enrolled in a family-centred early-intervention programme offering auditory-verbal therapy or sign language support according to the family's chosen communication approach. For severe-to-profound sensorineural loss with insufficient benefit from hearing aids, cochlear implantation is evaluated around twelve months. For confirmed symptomatic congenital CMV, valganciclovir improves audiologic and developmental outcomes when started early. [1] [3]

The prognosis is determined less by the severity of the loss than by the age at which it is addressed. Children confirmed by three months and amplified by six months acquire language at rates comparable to hearing peers, and this benefit is sustained into adolescence, which is the entire justification for early universal screening. [4]