Hearing assessment and childhood hearing loss — formative SAQs

SAQ 1 — The baby who refers on the newborn hearing screen (20 marks, ~15 minutes)

A term baby is born after an uneventful pregnancy. The otoacoustic emissions newborn hearing screen gives a refer result in both ears. The parents are anxious and ask what happens next. The baby has a small head circumference and was noted to have petechiae at birth, but is otherwise well. ^[6]

Questions

1. State the milestones of the universal newborn hearing screening programme that govern this baby's timeline, with the specific ages. (4 marks) ^[6]
2. Explain the diagnostic test that confirms the hearing loss and how it distinguishes conductive from sensorineural loss. (4 marks) ^[5]
3. Given the petechiae and small head circumference, name the congenital infection that is the commonest acquired cause of permanent childhood hearing loss, and state how and when it is confirmed. (4 marks) ^[7]
4. Outline the definitive management of a confirmed permanent sensorineural hearing loss in an infant. (4 marks) ^[1]
5. State why a child with neonatal risk factors should be screened with automated auditory brainstem response rather than otoacoustic emissions, and why a passed screen does not guarantee hearing for life. (4 marks) ^[4]

Model answer (must-hit)

1. The programme follows the one-three-six milestones: every baby is screened by one month of age, a baby who refers has a diagnostic auditory brainstem response by three months, and a child with confirmed loss is enrolled in early intervention by six months. The aim is to protect the critical period of auditory development, and a lost-to-follow-up baby is the preventable catastrophe. ^[6]
2. The diagnostic test is a full auditory brainstem response, performed with the baby asleep or sedated, which gives frequency-specific thresholds without cooperation. Adding bone conduction distinguishes a conductive loss (the air thresholds are raised but bone thresholds are normal, an air-bone gap) from a sensorineural loss (both air and bone thresholds are raised together). ^[5]
3. The commonest acquired cause of permanent childhood hearing loss is congenital cytomegalovirus infection, suggested here by the petechiae and small head circumference. A congenital infection is confirmed by polymerase chain reaction on saliva or urine within the first three weeks of life; the dried blood spot can be tested retrospectively. Symptomatic congenital CMV is treated with a six-month course of valganciclovir, which improves hearing and developmental outcomes. ^[7]
4. Management is rehabilitation, chosen by degree and site: mild to severe losses are managed with hearing aids fitted early and adjusted as the child grows; profound loss with insufficient aid benefit is treated with cochlear implantation, ideally in infancy within the critical period. The family is enrolled in a family-centred early intervention programme for language support, and referred to genetics for aetiological counselling. ^[1]
5. Neonatal intensive care graduates carry the highest risk of auditory neuropathy spectrum disorder, in which outer hair cells survive and emissions are present but neural synchrony is disordered; an emissions-only screen can read as normal in a baby who cannot hear speech, so AABR is used. A passed screen does not guarantee hearing for life because congenital CMV, the enlarged vestibular aqueduct and some GJB2 variants cause delayed-onset or progressive loss, so any speech delay or regression must trigger re-assessment. ^[4]