Hearing loss in children is a common problem that encompasses a broad differential diagnosis. Knowledge of normal auditory developmental milestones, risk factors and common causes of hearing loss are essential in managing the child with hearing loss. Early intervention is important in preventing delays in speech and language development.
The incidence of hearing loss (moderate or greater) in Australia is estimated to be between nine and 12 children per 10,000 live births. Furthermore, 23 per 10,000 children will acquire a hearing impairment severe enough to require hearing aids by the age of 17. Indigenous children in Australia experience a greater burden of ear and hearing problems than non-Indigenous children. Indigenous infants less than one year of age are four times as likely as nonIndigenous infants to develop acute otitis media (AOM) and three times as likely to have otitis media with effusion (OME).
Hearing loss in children may be classified by the child’s age and type of the hearing loss. Conductive hearing loss (CHL) occurs when there is a problem with the conduction of sound waves from the environment to the inner ear. Sensorineural hearing loss (SNHL) occurs when there is a problem with the transduction of soundwaves into neural impulses, and the conduction and interpretation of these by higher centres. Mixed hearing loss occurs when there is both a conductive and sensorineural component to the hearing loss.
In infants with congenital hearing loss, the cause is often sensorineural in nature. About 60% of cases of congenital SNHL will have a genetic cause and of these, 15-30% are syndromic, with over 400 syndromes described to include hearing loss. In the infant with hearing loss, a thorough perinatal history to exclude in-utero infections known as TORCH (toxoplasmosis, other [such as syphilis, varicella, mumps, parvovirus and HIV], rubella, cytomegalovirus and herpes simplex virus) is required.
Other important risk factors include: a family history of congenital hearing loss, perinatal ototoxic exposure, hyperbilirubinaemia requiring exchange transfusion and admission to neonatal ICU. In children, infection is the most common cause of hearing loss, predominantly due to AOM and OME which result in a conductive hearing loss. Table 1 summarises the risk factors and red flags for hearing loss in children. The differential diagnosis of hearing loss in children is extensive.
Normal hearing is within the range of 20-20,000Hz. Most human speech lies within the range of 250-8000Hz and the loudness of conversational speech is about 65dB. There are various methods used to measure hearing in children. Newborn screening uses auditory brainstem response, which involves measuring action potential responses of the eighth cranial nerve to an auditory stimulus.