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]

SAQ 2 — The preschool child with persistent glue ear (20 marks, ~15 minutes)

A 3-year-old has had three months of fluctuating hearing loss, worse after colds, with speech that the nursery describes as mumbled. Tympanometry shows a flat type B trace in both ears and the audiogram shows a 32 dB conductive loss with an air-bone gap bilaterally. The parents want grommets to protect his development. [10]

Questions

1. Give the diagnosis and explain the pathophysiology of the conductive loss. (4 marks) [10]
2. State the criteria for offering ventilation tubes and whether this child meets them. (4 marks) [10] [11]
3. Summarise what the Paradise randomised trials showed about early versus delayed grommet insertion and developmental outcome, and the implication for counselling these parents. (5 marks) [12]
4. State which children have a lower threshold for grommets and why. (4 marks) [10]
5. State your disposition and the safety-netting advice for this child. (3 marks) [11]

Model answer (must-hit)

1. The diagnosis is bilateral otitis media with effusion, or glue ear. The pathophysiology is Eustachian tube dysfunction failing to ventilate the middle ear, so trapped gas is absorbed and a sterile effusion accumulates. The fluid mass-loads the tympanic membrane and ossicular chain, damping their movement and producing a conductive loss with an air-bone gap, typically 20 to 40 dB, that fluctuates with the effusion. [10]
2. The accepted threshold for offering ventilation tubes is persistent bilateral otitis media with effusion for three months or more with a hearing level of 25 to 30 dB HL or worse, particularly when it affects speech or behaviour. This child meets the criteria: three months of documented duration, bilateral type B tympanograms, and a 32 dB conductive loss with speech impact. [10] [11]
3. The Paradise randomised trials found that inserting tympanostomy tubes early rather than waiting made no difference to developmental, language, cognitive or academic outcomes at three, six and nine to eleven years. The Cochrane review confirms only a modest, time-limited hearing improvement that fades as tubes extrude. The implication for counselling is that grommets are offered for the functional hearing and speech benefit they provide over the 12 to 18 months they sit in place, not as a developmental safeguard, and the parents' expectation of protected development should be gently corrected. [12]
4. Children at higher risk of developmental impact have a lower threshold for grommets, including those with Down syndrome, cleft palate, permanent hearing loss in the other ear, blindness, and developmental delay, because even a small additional conductive loss compounds their existing disadvantage. These children are offered grommets earlier and at a lower hearing threshold. [10]
5. This child meets grommet criteria, so I would refer to otolaryngology for discussion and insertion of bilateral ventilation tubes. The safety-netting is that effusions recur after tubes extrude at 12 to 18 months, so hearing is rechecked; and if any feature suggested something other than glue ear, such as a non-fluctuating or asymmetric loss, I would arrange full audiology to exclude a sensorineural component. [11]