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]