Overview of Hearing Loss Assessment in Children
Hearing loss is fairly common in newborns and kids, affecting approximately 1-3.5 in 1,000 babies screened and up to 1 in 5 children by the time they are 18 years old. Therefore, it’s very important to have the right testing and treatment methods to stop any negative impacts of hearing loss. If not detected and treated, hearing loss can cause lots of issues including delays in speech and language development, balance problems, increased feelings of anxiety and depression, and a decrease in overall happiness and self-esteem.
In 1993, the National Institutes of Health suggested that all babies should have a routine hearing test by the time they are 3 months old. The Joint Committee on Infant Hearing agreed with this in 1994 and has updated its guidelines a few times with the most recent update in 2019. As per the 2007 guidelines, all newborns must have a hearing test within 1 month of birth. If a baby fails this test, they should undergo another detailed hearing test by 3 months of age, and if required, treatment should begin by 6 months of age. These guidelines are followed broadly across the United States. Recent data show that 98% of all newborns had their first hearing test within one month of birth, which leads to the updated 2019 suggestion that screening, diagnostic testing, and treatment should take place within 1, 2, and 3 months, respectively, wherever possible.
Hearing loss may affect one ear (unilateral) or both ears (bilateral). Hearing loss in one ear used to be considered less of an issue than hearing loss in both ears, but recent findings show that it’s more clinically significant than earlier thought. Balanced hearing from both ears is vital for the proper development of hearing pathways early in life. If this doesn’t happen, it can be tough for patients to figure out where sounds are coming from, particularly when there’s background noise. Kids with unilateral hearing loss are ten times more likely to repeat a grade at school than children with normal hearing, with up to 40% needing extra educational help. Moreover, hearing loss in one ear can also progress to hearing loss in both ears in around 7.5 to 11% of cases, which highlights the importance of actively diagnosing and treating hearing loss, whether it’s in one or both ears. In children, more than 50% of hearing loss in one ear is due to Deformations in the cochlea, such as Mondini dysplasia or an enlarged vestibular aqueduct.
Anatomy and Physiology of Hearing Loss Assessment in Children
Hearing is a complex process that allows us to convert sound waves into something our brain can understand. It involves various parts of our ear working together to amplify sound and convert it into an electronic signal. Normally, sounds enter our ear and are amplified by the middle ear, making them about 82.5 times louder than they were when they first entered.
The inner ear is responsible for hearing and is divided into three sections, like a three-part tunnel. This section is filled with fluid that is similar to the fluids in and around our cells. It also contains a special structure called the organ of Corti, which contains hair cells that respond to sounds. Different sounds stimulate different areas of the inner ear. Low-frequency sounds, like a deep bass in music, stimulate one end of the cochlea, while high-frequency sounds, like a bird chirping, stimulate the other end.
Different types of tests are used to screen newborns for hearing problems. Two of these tests are called otoacoustic emissions (OAE) and automated auditory brainstem response (AABR). OAE involves detecting movements in the ear in response to sounds. This is done by placing a probe in the baby’s ear. Two types of OAE tests are usually done during newborn screening. If the OAE test shows that the baby’s ear is responding correctly to sounds, this is taken as an indication that the baby’s hearing system is working fine. However, if the baby’s ear does not respond to sounds, this could mean a hearing problem and further tests will be needed. The OAE test mainly checks the mechanical function of the inner ear.
The AABR test checks the electrical function of the hearing pathway. This is done by placing electrodes on the baby’s head to detect electrical activity along the pathway that sound travels. Different waves in the results represent different parts of the hearing pathway. Delayed or low wave readings could indicate a hearing problem. Some infants with hearing loss are diagnosed with a condition called auditory neuropathy spectrum disorder (ANSD), which means that signals generated in the inner ear are not properly transmitted to the brain.
In ANSD, the ear can pick up sounds, but there is a problem with transmitting this information to the brain, leading to hearing problems. This condition can occur in one or both ears. A common symptom is the absence of reflex responses to sounds, although this is not always the case and is not used as a diagnostic criteria.
Why do People Need Hearing Loss Assessment in Children
Before newborns leave the hospital, it’s important that they have their hearing checked. Kids who pass the first check-up should continue with regular check-ups as they grow. If a baby doesn’t pass the first hearing test, they should be tested again before leaving the hospital. The second test should be a few hours after the first one.
Often, doctors use a test called Otoacoustic Emissions (OAEs) to check a baby’s hearing. This test measures sounds that the ear produces when the cochlea gets stimulated. However, for babies who might be at a higher risk of having hearing problems, they should be tested using Automated Auditory Brainstem Response (AABR). This test measures how the hearing nerve responds to sound.
Now, you might be wondering what makes a baby at risk. Well, some of these risk factors include being in the newborn intensive care unit (NICU) for more than 5 days, having very high bilirubin levels that need a blood transfusion, having a severe bloodstream infection, and if they have been given medications that could harm the ear.
Babies who have been in the NICU are about 7 times more likely to have hearing problems than those who didn’t need NICU care. Other risk factors include infections while the baby was still in the womb, infections after birth, and abnormal physical features or inherited conditions.
Generally, healthy newborns who pass the initial hearing test using the OAE method don’t need additional testing, because the risk of them having Auditory Neuropathy Spectrum Disorder (ANSD), a hearing disorder, is quite low.
Of course, testing should not stop at birth. As kids grow, if parents, teachers, or doctors notice something off with a child’s hearing, they should have their hearing tested again. Research shows that parents, even though they live with their child every day, often miss signs of hearing loss. In fact, only about 61% of parents who think their child might have hearing problems are right. Speech therapists do slightly better at spotting the problem, at 36%, and teachers pick up on the issue about 18% of the time.
When a Person Should Avoid Hearing Loss Assessment in Children
There’s no reason why newborns and children shouldn’t have their hearing checked. However, babies born with conditions like congenital aural atresia (a birth defect where the ear canal is not open) or other visible ear deformities might not need this test right away in the nursery. This is because their hearing test might be expected to show abnormal results due to these conditions. But, they should always be quickly referred to a hearing specialist for a thorough hearing check-up to determine what to do next.
Equipment used for Hearing Loss Assessment in Children
Standard hearing testing equipment should be ready for use, tailored to the person’s age. Here’s what the tests might look like for different ages. For kids under 2 who can sit up by themselves and have good control of their head and neck, we use something called visual reinforcement audiometry (VRA). This is when we play a sound and see if the child can turn their head towards it. Normally, this starts to be possible when the child is about 6 months old.
From ages 2 to 5, or until the child can interact more meaningfully with the test, we use a method called conditioned play audiometry (CPA). After age 5, or as soon as a child is able to take part in it, we use standard pure-tone audiometry (PTA), which tests a person’s ability to hear pure tones of varying pitches and volumes.
Sound reflex testing, i.e. testing how the muscles in your ear react to sounds, is commonly used when testing adults and older kids. However, it’s not often used for newborns and young children.
Who is needed to perform Hearing Loss Assessment in Children?
A team of different medical experts is necessary to effectively check and treat children with hearing loss. This team should include an audiologist, who tests hearing levels and is trained to work with children, an ear, nose, and throat specialist, known as an otolaryngologist, and a child doctor, or pediatrician. If the child’s hearing loss might be due to Auditory Neuropathy Spectrum Disorder (ANSD) or inherited factors, a geneticist, who specialises in understanding and interpreting genetic conditions, should also be involved. This is because ANSD and certain types of inherited hearing loss are known to be passed down through families.
The team should also pay special attention to children suffering from genetic conditions such as sickle cell disease because these children have a higher chance of experiencing hearing loss. Therefore, these children need thorough hearing tests.
Children with a type of hearing loss that is not associated with other symptoms, known as non-syndromic sensorineural hearing loss, are more likely to have eye problems. Hence, an eye doctor, known as an ophthalmologist, should also check these children.
Preparing for Hearing Loss Assessment in Children
To get accurate results from a child’s medical test, it’s important that they are able to cooperate during the process. For older kids, they should be well-fed, rested, and have good hygiene, like having diapers changed, right before the test. This increases their comfort and their ability to cooperate.
On the other hand, newborns should not be fed or put to sleep before coming for the test, especially if it’s a non-sedated ABR (a test that checks the function of the hearing nerves and brain). Instead, once they arrive at the clinic, they would be connected to the test monitors. After that, they should be fed and allowed to sleep during the examination. By doing so, we increase the chances of getting an accurate test result.
How is Hearing Loss Assessment in Children performed
There are many methods to check if babies and children have hearing difficulties. Newborns usually get their hearing checked by two tests called the Otoacoustic Emissions (OAE) test and Auditory Brainstem Response (ABR) test. Additional tests like tympanometry, behavioral testing, and pure-tone audiometry may be used as needed. Also, imaging and genetic testing can also be used to better understand a child’s hearing loss. Let’s discuss these terms:
Otoacoustic Emissions
This involves placing a small device in the child’s ear which plays sounds and then records the ear’s response. This test checks for certain frequencies (or pitches) of sound. The results will either be “pass” or “refer” deciding whether the ear’s response is normal or not.
Auditory Brainstem Response
With this test, headphones are put in the child’s ear, and sensors are put on the head to measure brain activity. The headphones play a variety of sounds to check how the brain responds to them. The test is usually easier to do if the child is sleeping.
Tympanometry
This test involves placing a soft-tipped probe into the child’s ear which changes pressure while the child hears low-pitched noise. The test measures how the eardrum moves and can help determine if there’s fluid behind it.
Acoustic Reflex Testing
This test is less common for newborns and children but may be used in certain cases. This involves putting a probe into each ear and playing a certain pitch of sound into one ear to see if the other ear responds. This test helps to assess ear functioning.
Behavioral Audiometry
This is best for children between 6 to 24 months old and involves responding to a sound by turning the head toward it. As they grow older, up to age 5, children participate in the test by playing a game that involves responding to a sound.
Pure-tone Audiometry
This is the standard hearing test, usually for children over the age of 5. They wear headphones and press a button each time they hear a sound. This helps determine the quietest sound the child can hear at different pitches.
Imaging and Genetic Testing
These are less frequently used but can provide useful information. For example, some children might have a CT scan or an MRI to look at the structure of their ears. Genetic tests can help figure out if hearing loss might run in the family, as about half of all hearing loss in children is due to genetic causes.
Babies may also be tested for a common virus called cytomegalovirus (CMV), which can cause hearing loss. This test can be done through collecting spit or urine within the first three weeks of the baby’s life. If positive for the virus, the baby might be given a medication to help reduce the risk of hearing loss.
Possible Complications of Hearing Loss Assessment in Children
Testing for hearing loss in children doesn’t usually lead to major complications, but the main worry is the chance of incorrect results. These could be false positives, where the test wrongly shows that a child has hearing loss, or false negatives, where the test misses that a child does in fact have hearing loss.
A false positive result might lead to extra tests and worry for parents, but doesn’t cause any lasting problems for the child. However, a false negative result, where a child with hearing loss gets a normal result, could delay the discovery and treatment of the child’s hearing loss.
This delayed diagnosis could affect the child’s social, emotional and intellectual development in a negative way. It’s very rare, but there can be minor complications from hearing tests, like a small hole in the eardrum or an injury to the ear canal, but these don’t usually cause long-term issues. These risks are always there when any tools are used to examine the ear.
If a child behaves disruptively during the evaluation, it can make the test more difficult and increase the risk of complications or inaccurate results.
What Else Should I Know About Hearing Loss Assessment in Children?
Hearing loss can have serious impacts on one’s life, but studies show that if it’s caught early, effective treatments can help. These remedies can increase the chance for someone to maintain or regain normal hearing function. The main forms of treatment are regular hearing aids, bone-anchored hearing aids (BAHA) for children under 5, contralateral routing of signals (CROS) hearing aids, and remote microphone systems. If the hearing loss is severe, a cochlear implant may be considered.
The effectiveness of these treatments can vary. Hearing aids can help reduce hearing loss by up to 25 decibels. However, for severe or profound hearing loss, cochlear implants perform much better. Cochlear implants can bring hearing levels close to those without any hearing impairment, with word recognition scores of around 85%. Furthermore, 95% of those who receive the implants do not need learning adaptations or full-time educational support, which can lead to fewer developmental delays.
Hearing loss screening is essential. If hearing loss is not identified early and treated, it could lead to difficulties as the brain’s ability to adapt (plasticity) decreases over time. If abnormal results are not followed up promptly, the patient can experience social, developmental, and intellectual delays. Out of every four patients with early signs of hearing loss, one may not receive adequate follow-up care. This highlights the importance of newborn hearing screening programs and the need to close the gap between diagnosis and the start of treatment.
In some cases, genetic testing and imaging might be needed to determine the cause of hearing loss, but this is not necessary for everyone. By following a timeline of screening and starting treatment within the first few months of life, children with hearing loss can lead high-quality lives.