What is auditory screening for the newborn?
The newborn auditory screening is an objective hearing test that does not require a newborn to respond. This test is designed to identify children who have hearing impairments in the first few days of life. It also helps to determine if there are any permanent hearing problems (1-2 children per 1,000). Permanent and transient hearing disorders can be detected by the test. These disorders will usually resolve within the first few days or weeks of life. Children with hearing loss are diagnosed on average at 2.5 years old if there is no hearing screening. This means that the child will have a prolonged period of hearing loss, which can negatively impact their language acquisition, psycho-social, and cognitive development. A newborn hearing screening allows for early intervention so that delays in language development are minimized.
Hearing screening should be done
The newborn’s auditory screening is performed in the first few days of life. It can be done either one day before or on the day of discharge. The result can be expressed as a PASS (passed the test) or REFER (did not pass the test). PASS is a healthy result that includes all structures of the ear and the external hair cells. REFER means that the test has to be repeated if something is preventing the inner ear from receiving the signals. The tests should be repeated around the age 1 month. The child should pass the test if he/she is not able to do so by the end of the first month. Children who have failed the test (PASS) but are at risk of developing complications (premature or immature, hyperbilirubinemia), intensive care for more then two days, ototoxicity, and so on. Retests are recommended.
What is auditory screening? How do you interpret the results?
Acoustic otoemissions and auditory evoked potentials can be used to screen the auditory system. Acoustic self-emissions capture signals from the external hair cells within the cochlea. To be captured, all structures in the ear must be healthy. Auditory evoked screen potentials are used to test the health of the auditory structures, down to the brainstem. Over 90% of congenital hearing impairment can be detected by acoustic self-emissions. Newborns with risk factors – perinatal problems (hypoxia, hyperbilirubinemia), premature, immature, hereditary-collateral history of hearing loss, hearing loss-associated syndromes, administration of ototoxic drugs, intensive care (NICU) more than 48 hours – require screening testing with auditory evoked potentials to assess and auditory pathways.
Acoustic self-emissions testing: This involves inserting a probe in the infant’s external auditory channel. The probe emits sounds, and the outer hair cells of the cochlea emit sounds, which the probe picks-up from the ear. The test takes between 2 and 5 minutes. It does not require a soundproof area, but only a child who is quiet and an environment that is quiet. The PASS response indicates the presence or absence of sound from the ear. REFER is the absence of sound. PASS is a sign that the outer ears are free, the structures are healthy, and the outer cells are healthy. REFER means that the response of external hair cells was not recorded. It could be because the cells are unable to emit the sound or there is a permanent hearing impairment. These conditions may resolve when the test is retaken the next day or over the following weeks.
Screening uses the auditory evoked possibilities to evaluate the auditory system at the brainstem level. This qualitative evaluation is similar to otoemissions in that it can detect hearing impairments beyond external hair cells, such as auditory neuropathy. Three electrodes are placed on the skin and a probe emits sounds similar to acoustic echolocations. The electrodes pick up signals from both the auditory nerve and the nuclei. These signals are interpreted as PASS or REFER (present or absent response).
The National Program currently has acoustic self-emission devices. This test must be performed for all children. Children with risk factors should have their auditory evoked potentials performed. Even if the result from acoustic self emissions is positive, they should be referred for audiological follow-up.
What should you do if the “test didn’t pass”?
It is recommended that you retest the pregnancy test in the next few weeks until your child turns one month old. To be able send the child to a reassessment, the family doctor must verify that the test was performed. Most children pass the second test as the secretions in their ears that block the test disappear. Only a few require an audiological evaluation to diagnose the problem. This is done in a specialized center.
Screening tests are not able to raise suspicions of hearing loss. This is a qualitative and not quantitative test. Children who fail the initial test may pass the test again later without permanent hearing loss diagnosis.
A child with hearing loss should be retested between 3 and 6 months of age.
The hearing screening process involves a collaboration between the neonatologist, the family doctor, who does the initial screening, and the doctor who guides the child to a diagnostic center.