A DEAF BOY
History
Ronan is a 3-year-old boy with Down’s syndrome. He is brought to his GP because his parents are worried about his hearing. He does not seem to notice when his parents call his name if he is not looking directly at them, his speech has become less clear and his nursery teachers are concerned that his behaviour has become more difficult to manage. He has also started to snore when asleep. Ronan was born at 36 weeks’ gestation. He required admission to the neonatal unit for poor feeding and also needed a partial volume dilutional exchange transfusion for polycythaemia with hypoglycaemia and seizures. He had a normal newborn hearing screen. He has a small ventricular septal defect and he had bacterial endocarditis 6 months ago, necessitating a long course of intravenous antibiotics. His mother is a 30-year-old teacher and his father is a 43-year-old manager of a computer company. They are both well. Ronan has been fully immunized, including an influenza vaccine last winter.
Examination
Ronan’s weight and length are on the 25th centile on the Down’s syndrome growth chart. He smiles at you when you approach and seems to follow visual cues and be affectionate with his parents. His speech is difficult to understand. Cardiovascular examination reveals a heart rate of 110 beats/min, a grade 3 pansystolic murmur, loudest at the lower left sternal edge, and no signs of cardiac failure. His respiratory and abdominal examinations are unremarkable. Both tympanic membranes have a dull retracted appearance with loss of the light reflex and some bubbles visible behind the membrane. He has large tonsils that almost touch in the middle.
Questions
• What is the most likely cause of his hearing difficulties?
• What other possibilities are there?
• How could his hearing be assessed?
Medicine
Ronan is most likely to have conductive hearing loss secondary to chronic otitis media with an effusion (OME, or ‘glue ear’). This diagnosis is consistent with the fact that his hearing has recently deteriorated, that he snores (indicating partial upper airway obstruction in sleep) and the findings on examination of his ears. Children with Down’s syndrome are particularly vulnerable to OME because their large adenoids, small nasopharynx and narrow Eustachian tubes make aeration of the middle ear less efficient. For these reasons, children with Down’s syndrome should have regular screening for hearing impairment. In addition to conductive deafness, sensorineural deafness is more common in children with Down’s syndrome. The normal newborn hearing screen (otoacoustic emissions) makes congenital sensorineural deafness unlikely. Sensorineural hearing loss can be acquired, and a potential risk factor is the use of aminoglycoside antibiotics, e.g. gentamicin, which may have been used in the treatment of his bacterial endocarditis. Aminoglycosides cause doserelated ototoxicity and some individuals also have an underlying genetic susceptibility. Another possibility is that Ronan has autism. This is more common in children with Down’s syndrome and can present with abnormal speech, language and behaviour, which may initially be attributed to hearing difficulties.
Features of conductive and sensorineural hearing loss
Conductive Sensorineural
Causes Glue ear Genetic Congenital ear Infections: congenital / postnatal abnormalities Birth asphyxia Head injury
Severity Milder; intermittent More severe; static or progressive 20–60 dB loss 20–120 dB loss
Management Conservative Hearing aid Grommets Cochlear implant
Ronan should be referred urgently to a paediatric audiology clinic, so that there is minimal delay in detection of any significant hearing impairment, and to minimize further delay of his speech and language development. Ideally, he would already have regular follow-up in such a clinic. His hearing will be assessed using techniques appropriate to his developmental age. These may include visual reinforcement audiometry (where a visual signal reinforces a correct head-turning response to localize a sound), free field conditioning (where an auditory stimulus is the cue for an action in a simple game), and speech discrimination tests (where toys are named at a set volume and identified by the child). He would also have tympanometry performed to confirm negative middle ear pressures typical of OME. It would also be important to ask if Ronan has sleep apnoea, which is associated with severe upper airway obstruction and which may necessitate an adenotonsillectomy.
KEY POINTS
• It is important to recognize and refer hearing problems at an early stage.
• Conductive hearing loss due to glue ear is the most common cause of hearing impairment.
• Children with Down’s syndrome have an increased risk of hearing problems and require surveillance.
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