It Is Important To Have Universal Hearing Screening For All Newborns

Question: My son passed a hearing screening test shortly after he was born. The device that was used made a sound and he seemed to startle. Later, when I was concerned that he didn’t seem to respond much to sound, I was told that babies’ hearing cannot be tested before six months of age. My son was finally diagnosed with significant hearing loss when he was almost one, and he needed two hearing aids. He has since received excellent help from speech-language specialists, and he is developing his listening and speech fairly well. I am wondering how early can children be tested reliably. Is it possible to test a newborn baby?

Answer:

It looks like your son was tested by a very crude screening device that is still in use in many hospitals around Canada. This type of equipment generates a loud noise, children with normal hearing are expected to make a startle response. Unfortunately this way of testing is extremely inaccurate. There are many false positive and false negative results. Children with perfectly normal hearing are falsely identified with hearing loss, and are referred to audiologists (specialists who test children’s hearing). Those who have true hearing loss are missed, and would not be diagnosed until much later. The end result is valuable time being wasted on children with normal hearing, and delay in helping those who need it most.

Before any further discussion, I want to congratulate you for noticing that your son has had hearing problem, and pursued until you found the answer. Many parents would likely assume that passing the newborn screening means normal hearing, and would not be watching for telltale signs of hearing loss. The fact that your son was diagnosed fairly early likely prevented him from life-long speech impediment, which can affect his academic and social development, ultimately giving him better career opportunities and quality of life.

Advance in technology over the last few decades has produced equipments that are very reliable in screening newborn babies for hearing loss. It is not possible for me to describe these technologies in detail, but I will explain about them in more general terms so that everyone can understand. There are two types of equipment available: automated auditory brainstem response (AABR) and otoacoustic emissions (OAE).

AABR is actually a modification of the standard ABR technique which is already widely used by audiologists for testing children suspected of hearing problem. Instead of requiring a highly skilled audiologist to perform the test, computer technology will interpret the results with high degree of accuracy. The AABR machine delivers a series of clicks at 30 to 40 dB (about the normal hearing level of young adults) and look for electrical brain wave response from the baby, using electrodes attached to the head. This test is totally safe for the baby. If conducted with care and in a quiet environment, especially if the baby is sleeping, it is extremely accurate with very few false alarms.

There are actually two kinds of OAE. Both of them generate sounds delivered through little probes inserted into the ear canals of newborn babies. When sound passes through normal eardrums and small bones in middle ear, it will reach the inner ear called cochlear, where tiny cells convert sound waves into electrical signals. Normal cochlear produces an ‘echo’ in response to the sound from the machine. This echo is a very faint sound which can be detected by a minute transducer inside the little probe in the baby’s ear. The presence of the echo implies normal conduction of sound waves and normal function of cochlear, which detects the sound.

Both of these technologies are extremely safe and accurate. In United States, over 32 states already have universal newborn hearing screening programs mandated by law. Similar programs are also in place in 20 health districts in Great Britain. Unfortunately, Canada is lacking far behind in mandating newborn screening, and putting our children at risk.

Extensive research has shown that 1 to 3/1000 children are born with severe hearing loss. This can be due to problem in conducting sound waves from the eardrum through the small bones in middle ear to the cochlear. This is called conductive hearing loss.

Another type of hearing loss is called sensorineural. These children have normal conduction of sound waves. However, conversion of sound waves to electrical signals, and passage of these signals to the brain, is impaired. Some children can have a combination of both types of problem.

In normal children, the whole system involved in hearing is fully developed well before they are born. Normal foetus can hear the mother’s heart beat and voice. That is why babies often stop crying when they hear their mother speaking or singing. Although babies do not have understandable speech for the first few months of life, they do produce cooing sounds before real speech develops.

These children with normal hearing are constantly stimulated by sounds in their environment, even when they are sleeping. They turn their head to familiar sounds like the voice of parents or siblings, or get startled by loud noise. Over time, normal speech will develop, with ever increasing number of words, and putting words together in short phrases and then sentences.

When children are born with severe hearing loss, they usually appear completely normal. They sleep and eat like all other babies. They will cry whenever they are hungry, or if the diaper is wet or dirty. However, their world is a silent one. They cannot hear their own crying, let alone any sound from their environment. Over time, they will utter less and less sound.

As they get older, these children discover that adults around them don’t understand their needs. Many develop aggressive behaviour as a result, which is extremely stressful for the family. When they do make any noise, it is usually loud screaming, which is again interpreted as behaviour problem.

Without universal newborn hearing screening, the average age of identification of hearing impairment is about 30 months. This is very late for speech development of these children. Even with assistance like hearing aids and remedial speech therapy, many continue to have significant speech impediment for many years. Some may never learn to speak and rely on sign language and reading lips.

A lot of resource is required to assist a single child with significant hearing loss that is diagnosed after the first few months of life. The later the diagnosis, the more resource is required, for longer periods of time, and less satisfactory final outcome for the child and the family. This will ultimately impact on future career opportunity and quality of life. For the society, it would imply a significant loss of contribution from this individual.

With universal newborn screening, these children can be identified shortly after birth. They can be provided with hearing aids earlier, so that they can start to hear what other children are able to hear. This will provide much better chance for normal hearing, and require less resource from speech-language specialists, ultimately save money for the whole health care system.

With our emphasis on prevention and good health, this is the kind of program federal and provincial governments should invest in for the future of Canada. The initial financial and personnel requirement will be well compensated by the ultimate savings and improved outcome, especially in view of the shortage of well qualified speech-language specialists throughout North America.

Finally, it is important to emphasize to all parents that children can still develop hearing loss after birth. This can happen as a result of infection in the womb, birth defects, meningitis, severe head injury, and recurrent ear infections. Parents should be vigilant and watch for signs of hearing loss and delayed speech in their children, even if the universal newborn screening program is available. If there is any suspicion, get in touch with your doctor, or talk to the public health nurse. Your child can be tested safely and effectively by an audiologist at any age.

I hope this column answered your question and provided information to all parents out there. Good luck with your son’s progress.