Hearing tests
Hearing tests are essential assessments designed to determine the presence, type, and severity of hearing impairment in individuals of all ages, from newborns to adults. These tests are typically administered by audiologists, although some screening procedures can be performed by trained technicians. Hearing loss can be classified based on severity—ranging from mild to profound—and also by the anatomical region affected, such as conductive or sensorineural loss. The choice of testing methods often depends on the patient's age and their ability to follow instructions. For patients who cannot cooperate, objective tests like the auditory brainstem potential (ABR) and evoked otoacoustic emissions (EOAE) are utilized, requiring minimal patient involvement. Behavioral techniques, such as visual reinforcement audiometry and play audiometry, are effective for younger children and those with developmental disabilities. Early detection of hearing loss is crucial, especially in infants, as it significantly impacts language development and social adaptation. Screening initiatives, particularly for newborns, have been implemented in many regions to address this issue, although challenges remain in ensuring all children receive the necessary follow-up evaluations.
Hearing tests
Anatomy or system affected: Ears, nervous system
Definition: Evaluation techniques for determining the type and severity of hearing loss in children and adults
Indications and Procedures
Hearing tests are done to establish the presence, type, and severity of hearing impairment in children and adults. Such tests are conducted by an audiologist, although screening tests can also be done by a technician under the supervision of an audiologist. The severity of hearing loss is classified as mild, moderate, moderately severe, severe, and profound. It is also classified according to the anatomic region affected: conductive, sensorineural, or mixed hearing loss.
The selection of tests to evaluate hearing will depend on the patient’s age and ability to follow directions and the ability of the audiologist to elicit responses from the patient. When a patient cannot follow instructions, such as lifting a hand or pressing a button, a test that does not require the patient’s cooperation is used. Two tests that do not require the patient’s cooperation are the auditory brainstem potential (ABR) test and the evoked otoacoustic emissions (EOAE) test. Both tests require only that the patient be quiet. For this purpose, the patient may need sedation if normal sleep cannot be induced.
The ABR test requires the placement of four electrodes on the patient’s head: in both mastoid regions and in the mid-forehead and upper center of the head. A stimulus is sent through a small microphone placed in the patient’s external ear canal or via headphones. The instrument records the average of the electrical discharges generated by the auditory nerve in response to sound stimuli and produces a tracing of waves that correspond to the different electrical potentials generated in response to the stimuli. Analysis of the waves can determine the presence of hearing loss and measure its severity. The ABR test may be used for screening, to determine whether the subject can hear, or for the clinical evaluation of hearing loss. It can be done at any age. An automated method of ABR testing is available for screening newborn infants for hearing loss; it automatically determines if the patient has passed or failed. The clinical ABR test requires specially trained personnel and takes forty-five to fifty minutes to perform. The automated method can be applied by a technician.
The EOAE test involves recording the sound produced by hair cells within the cochlea by way of a microphone placed in the outer ear canal. Normally, when sound enters the cochlea, the hair cells produce a sound that bounces backward and can be recorded. This sound correlates with the sound sent to the auditory nerve. If there is damage to the hair cells in the cochlea, then no sound is elicited. The EOAE test can be performed without sedation if the patient cooperates by staying quiet. It can be done by a technician and takes approximately ten minutes or less. The EOAE test is used for universal screening of newborn infants. It can be done at all ages to help determine the integrity of the cochlea and, thus, whether an observed hearing defect is within the cochlea.
Behavioral techniques are the most practical, cost-effective, and time-efficient methods for the accurate assessment of hearing. They give more complete information on the child’s hearing as well as functional information about how the child uses their hearing. The simplest test is behavioral observation audiometry, in which the audiologist records the behavioral response to applied sound stimuli of a known frequency. This test can be done with infants, toddlers, and uncooperative patients, such as children or adults with developmental disabilities. Visual reinforcement audiometry (VRA) is done with infants and toddlers from six months to twenty-four months of age. It is also used with uncooperative patients. In this test, the patient is submitted to sounds of different intensity and trained to respond to the sound stimuli by means of an attractive stimulus. Every time that the sound appears, the stimulus illuminates. When the patient hears the sound, he or she will look for the reinforcement. Play audiometry is a test that can be used in children over two years of age. The child is taught to move a block or place a puzzle piece every time they hear a sound.
In 2002, Ruth Litovsky, a University of Wisconsin–Madison communicative disorders professor, introduced a binaural hearing test to evaluate how people respond to sounds in a noisy environment resembling public areas and schools. Using computers showing images related to words broadcast on loudspeakers, her test assesses which sounds people ignore and which sounds secure their attention.
In 2003, the Ear, Nose, and Throat Journal provided information describing the Otogram from Tympany, a Sonic Innovation subsidiary. This device enables patients to test their hearing at sites using automated technology. During the twenty-minute testing period, patients undergo an audiogram that thoroughly evaluates their acoustic capabilities with tympanometry and other standard diagnostic tests, responding to the tests via touchscreens with results recorded by computer.
In 2005, Bio-Logic Systems Corporation and House Ear Institute researchers introduced the hearing-in-noise test (HINT), which assesses how hearing functions in police and emergency personnel whose hearing is vital to their work. The test involves subjects repeating sentences while exposed to a variation of noise and quiet. The source azimuth identification in noise test (SAINT) evaluates subjects’ ability to detect where sounds are located.
Perspective and Prospects
Early detection of hearing loss has become a priority among early intervention services for infants and young children because it has devastating effects on language development, and consequently, on social adaptation. It has been found that the mean age at which deafness is diagnosed is around three, which is after speech development should have occurred. Thus, children with hearing loss are placed at a disadvantage with their peers.
In 1993, the National Institutes of Health (NIH) developed a consensus statement by which all newborn infants in the United States were to be screened for hearing loss. The aim was that by the year 2000, all newborns would have been screened before being discharged from the hospital. By 1999, many US states had passed legislation requiring hearing screening of newborns. Still, by the 2020s, success was incomplete, as only forty-three states had legislation that addressed universal mandatory newborn hearing screening.
The rate of success in implementing newborn hearing screening may have been slowed by studies suggesting that infant screening was more valuable. In October 2001, the Journal of the American Medical Association evaluated nineteen studies, emphasized that screening newborns was not superior to tests by pediatricians when infants were several months old and stressed that determining the value of newborn screening required additional study. A further issue was noted when, in October 2005, the Archives of Pediatrics & Adolescent Medicine estimated that more than half of children whose hearing test results revealed that they needed additional tests never underwent such testing. What remained clear as the twenty-first century progressed, however, was the importance of evaluating a child’s hearing issues before the age of three so that early intervention methods could be initiated should they be necessary.
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