The Importance of Hearing Tests

by DR KIRSTY DONALD – Red Cross Childrens Hospital

Early detection and intervention for hearing impairment has become an increasingly important aspect of neonatal care in well-resourced countries. Rising numbers of universal newborn hearing screening (UNHS) programmes have been implemented to facilitate an optimal outcome for infants with hearing impairment.

These programmes have been established for the following reasons:

  • Prevalence of hearing impairment is significantly higher than other birth defects. Screening for sensorineural hearing impairment will identify 260/100 000 afflicted infants compared with 50/100 000 with congenital hypothyroidism, the most common congenital condition routinely screened for in the USA.
  • Undetected hearing impairment leads to irreversible language, speech and cognitive delays, with far reaching social and economical ramifications (persistent language delay of 2 – 4 years for infants identified after 6 months of age)
  • Infants whose hearing impairment is identified before 6 months of age have significantly better language abilities than those whose hearing impairment is identified later. This is providing that intervention (hearing aid fitting and supportive services) also occur before the age of 6 months.

South Africa has taken the first step towards UNHS in the form of a Hearing Screening Position Statement and proposes screening of high-risk infants, i.e. targeted hearing screening. These are infants with a family history of permanent childhood hearing impairment, craniofacial abnormalities, a syndrome associated with hearing impairment, exposure to an infection due to herpesvirus, cytomegalovirus, toxoplasmosis, rubella or syphilis in pregnancy, and infants who had been admitted to a neonatal intensive care unit for more than 48 hours.

According to this policy, infants should be identified and screened before discharge. If missed, they should be screened at the 6-week immunisation visit. Diagnosis of the type, degree, and configuration of hearing impairment should be completed by 3 months of age and intervention initiated before 6 months of age.

Targeted infants are also at risk for delayed and progressive hearing impairment. These infants must be screened periodically, as well as those with the following additional risk indicators:

  • caregiver concern regarding hearing, speech, language, and/or developmental delay;
  • postnatal infections associated with sensorineural hearing impairment including bacterial meningitis;
  • neonatal conditions in particular hyperbilirubinaemia requiring exchange transfusion and those complicated by severe hypoxaemia such as persistent pulmonary hypertension of the newborn;
  • recurrent or persistent otitis media with effusion for at least 3 months;
  • head trauma

Contemporary physiological hearing screening methods, oto-acoustic emissions (OAEs) and auditory brainstem responses (ABRs) can reliably pick up hearing problems and can be done from birth. However, failing the hearing screening does not necessarily mean that the baby has a hearing loss. Not all babies pass the hearing screening the first time. Infants who do not pass a screening should be given a second screening to confirm the findings.

Even if your baby is given a clear response at the hearing screening test, it is still a good idea to monitor their hearing, as children can develop a hearing loss as they grow older

Later on, once children have head control, pure tone audiometry can used to further define the degree of hearing loss as well as differences in perception of varying frequencies (high and low pitch). The older and more co-operative the child, the more information can be achieved from this test.

The high-risk indicators for hearing impairment are evident in approximately 10% of all newborn infants and this group comprises approximately 50% of infants with congenital hearing impairment. The remaining 50% are term, normal infants whose hearing impairment is missed using targeted screening. It is for this reason that screening of high-risk infants should be seen as only an interim step towards UNHS.

A useful reference site for parents who have concerns:

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