Hearing Tests for Children: How They Work
Diagnosing hearing loss in children can be difficult if the child is still too young to properly express himself to adults. On the other hand, an older child can be given standard hearing tests that adults would take, as long as he or she has the ability to respond accordingly. How a doctor tests for hearing loss in the child will be related to the child's age, physical condition, and developmental progress.
Over the last decade there has been a push among the nation's hospitals to do newborn screenings which include, among other things, a hearing test. In some states, infant hearing tests are required by law. In other states they are optional. As a parent, you have the right to insist a hearing test be done as part of a newborn screening program. If it's not required by law in your state, be sure to request it during routine discussions with your obstetrician.
If you're concerned that your child might be suffering from some of hearing loss there are some typical symptoms you can look for including:
- little or no reaction to sudden, loud noises
- no recognition of parents voices by the third month
- failure of a child to turn his head in the direction of sound
- difficulty in recreating simple words
- poor speech development
- inattentiveness
- learning difficulties
Types of Hearing Loss in Children
There are five different types of hearing loss recognized by the medical community. However, the two most common in young children are conductive and sensorineural hearing loss. Conductive hearing loss occurs when something is blocking the transmission of sound waves to the inner ear. Typical causes of conductive hearing loss include ear infection, a perforated eardrum, a foreign object lodged in the ear, or a buildup of ear wax. In any of these cases, the issue can easily be corrected once it's identified.
It's important to note that if conductive hearing loss is being caused by ear infections then repeated infections could cause permanent damage. Doctors may suggest tubes be inserted in the child's ear to help drainage and prevent permanent damage.
Sensorineural hearing loss is the result of the physical damage done to one of the components in the hearing system. This damage can be caused by a genetic defect, injury to the ear or skull, infections, reactions to certain types of medications, and other factors. When sensorineural hearing loss is detected, the only effective treatment is typically the use of hearing aids.
Different Types of Hearing Tests for Children
For all intents and purposes there are two categories of hearing tests for children: behavioral and physiologic. Behavioral tests are those that measure the level of hearing by producing sound and observing a child's behavior. Physiologic tests are used for infants and children whose developmental disabilities make their behavior unreliable enough to be considered an inaccurate measure. We will discuss both categories of testing here.
Behavioral Testing - Behavioral testing involves observing a child's behavior in reaction to noises produced or instructions given. For example, one type of test might measure a child's response to speech, while another might test a response to specific frequencies of sound.
In infants, one of the most common behavioral tests observes head and eye movement in response to sound. Most infants will demonstrate eye movement somewhere before the third or fourth month. Head movement typically begins no later than the sixth month. As long as an infant demonstrates the proper response to sound through eye and head movement, it is assumed he is hearing at least moderately well.
Physiologic Testing - Physiologic testing involves using sophisticated testing equipment to measure the response of nerves and brain pathways. They are used for newborn screening as well as for children whose behavioral responses to sound can't be relied upon. The most common forms of physiologic testing are:
- auditory brainstem response (ABR)
- auditory steady state response (ASSR)
- otoacoustic emissions (OAE)
- tympanometry
Auditory Brainstem Response (ABR)
ABR is a test which uses tiny earphones and small electronic receptors placed on the forehead and behind the ears. With the earphones gently inserted into the outer ear, various sounds are broadcast. The electronic receptors measure the response of the brain and nerves to these sounds. Those measurements are fed into a sophisticated computer program which calculates the response and displays them visually as waveforms. If those waveforms fall within normal parameters, it's a good sign that the child is hearing properly. Those that fall outside the parameters may be an indication of hearing loss or some other medical issue.
Auditory Steady State Response (ASSR)
The ASSR test is performed alongside the ABR test. For infants, it's necessary that they be asleep or sedated during this test. Older children who are able to sit still might be able to sit for the test without sedation. The test is conducted by introducing sound into the ear canal and measuring the brain's response in a way that establishes volume levels. In other words, while the ABR test simply establishes that sound waves are being correctly interpreted by the brain, the ASSR test helps to measure the "volume" of those signals as they reach the brain.
Otoacoustic Emissions (OAE)
In this test, doctors are measuring the echo of sound waves in the inner ear. The construction of the inner ear produces some measure of echo which is then interpreted by the cochlea and transmitted into auditory signals sent to the brain. With this test a small probe is inserted into the ear canal which will be used to create sound pulses and measure their echo effect. The echoes are recorded and run through a computer program which averages them together in order to produce the results.
Tympanometry
The tympanometry test does not actually measure hearing function as a physical response to sound. Rather, it tests the reaction of the eardrum when a sound is introduced. For this test, the audiologist will inject a slight puff of air as well as a soft sound into the ear canal and then measure the response of the eardrum to the pressure. If the eardrum shows little responsiveness it could mean hearing loss is present. A normal response by the eardrum is an indication that it is functioning properly.
A combination of these physiological tests is used for newborn screening. They also may be used on older infants and toddlers who demonstrate symptoms that would indicate moderate to severe hearing loss. In either case, young children can easily adapt to hearing issues if they are discovered and treated early enough. This is why it's important to have newborn screening done then followed up by regular hearing tests with your pediatrician. Hearing loss can certainly be challenging to children but it doesn't need to be the controlling factor in their lives or their development.