Hearing Loss In Children
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.
Signs and Symptoms
These are the early signs and symptoms of hearing loss in infants and children.
Infants:
- Does not startle at loud noises
- Does not turn their head toward sounds
- Does not say at least some words by 12 months of age
Older children:
- Delayed speech development
- Speech that does not sound clear
- Does not follow directions
- Frequently asks you to repeat what you have said
- Listens to music or television at a high volume
Most infants are screened for hearing loss at birth and children are usually tested again before starting school. However, if your infant or child shows symptoms of hearing loss at any time, it is important to have them tested as soon as possible to minimize any effects that hearing loss might have on their development.
Hearing Loss and Child Development
These are the signs and symptoms of hearing loss and the effect on child development.
- Delayed speech development: the child does not say 50 individual words by their second birthday or form two-word sentences by their second birthday.
- Vocabulary develops much more slowly in children who have hearing loss. The gap in vocabulary development between children with and without hearing loss widens with age.
- Children with hearing loss have difficulty hearing and subsequently pronouncing certain sounds such as “s”, “sh”, “f”, “t”, and “k”. This affects the way they speak and can make them difficult to understand.
- Children with hearing loss often have difficulty with complex sentence structure.
- The child may have difficulty hearing word endings such as -s or -ed.
- They sometimes cannot hear their own voices when they speak or hear only a distorted version of themselves when they speak causing them to speak too loudly or too softly.
- Children with hearing loss often struggle academically.
- Communication problems can lead to social problems and feelings of isolation among children with hearing loss and speech delays.
As previously mentioned, early detection of any hearing loss and early appropriate intervention is crucial for the best outcomes. The type of intervention used depends on the type and degree of hearing loss and usually involves a team of professionals. The intervention will be different for each child.
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