The effects of hearing loss on a child's development can be devastating, impairing the development of communication and language which are the gateway to participation in social interaction and education. In addition to vocational effects, hearing loss can affect mental health as there may be bonding problems between the child and mother. Consequently it is essential that hearing loss is identified early and appropriate interventions offered to the child and their family. Ideally, hearing loss should be identified by three months of age and interventions commence by six months of age. Where this occurs the child can develop age appropriate communication and language. Medical practitioners need to be aware of the known risk factors for permanent congenital hearing impairment (listed in Box 1) and refer babies immediately if any of these risk factors apply. No baby is too young to refer. Unfortunately, the risk factor approach will pick up at most 40 percent of children with hearing impairment - the other 60 percent do not have known risk factors. In the absence of a universal newborn hearing screening programme the medical practitioner should be alert to parental concerns - parents who suspect that their infant can not hear should be responded to by appropriate referral to an audiologist. Parents are by far the most common source of initial suspicion of hearing loss.
Paediatric assessment of hearing loss
The audiologic assessment of a baby or infant can be conducted at any age although a different range of tests will be offered depending on the age of the child. The most precise test is Auditory Brainstem Response Audiometry (ABR). Older infants with suspected severe to profound loss will usually require ABR testing under a general anaesthetic. Very young babies can simply sleep through an ABR - another advantage of early identification. Mild to moderate hearing loss would not usually require older children to go through an ABR. The various tests a qualified audiologist may conduct are described in Box 2. If a child is diagnosed with a significant hearing loss it is important to remember the needs of the family as well as the child. Families may need grief counselling and will want information to support them through what can be a difficult period of adjustment. Your audiologist can provide appropriate referrals and fulfil the hearing aid requirements of a baby or infant with hearing loss.
Dilworth Hearing offers full paediatric hearing assessment. We can offer consultations in conjunction with an ENT specialist who can provide immediate support and advice to a family with a newly diagnosed baby or infant with significant hearing loss.
Box 2 - Audiological Tests
Birth to 5 months
ABR - while baby is in a natural sleep state. Electrodes on the babies head measure responses through the auditory pathways following a sound impulse fed into the ear. Provides separate ear and frequency information.
Otoacoustic emissions (OAE) - measure the response of the ear up to the cochlear (but not from the inner ear to the brainstem). A good test of cochlear function and frequency.
6 to 36 months
Visual reinforcement audiometry (VRA) or Puppet in the window illumination (PIWI) - is an accurate but subjective test which gives frequency information but not necessarily separate ear information.
OAE
ABR - under general anaesthetic. Used if severe or profound loss is suspected.
36 months and over
Play audiometry - the child responds to sound during a game. This provides separate ear information through the use of headphones.
OAE
ABR - under general anaesthetic.
Box 1 - RISK FACTORS FOR PERMANENT
If any of the following risk factors apply the baby should be referred to an audiologist for a hearing assessment without delay.
- Family history of hearing loss
- Severe jaundice
- Craniofacial abnormalities
- Ototoxic drugs, eg. Aminoglycosides
- Mechanical ventilation lasting 5 or more days
- Low Apgar scores (0-4 at one minute or 0-6 at five minutes)
- Birth weight 1500 grams
- Bacterial meningitis
- Maternal infections including rubella, CMV, Toxoplasmosis, syphilis and herpes
Parents are often the first to suspect hearing loss in their infant - respond to this suspicion by immediate audiology referral. Maori and Pacific babies are at far greater risk of hearing loss.
Nearly half (49%) of deafness notifications are Maori children, although they make up less than a quarter (19%) of the population (NAC, 2003).
