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 from 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 his or her hearing. The simplest test is behavioral observation audiometry, in which the audiologist records the behavioral response to an applied sound stimuli of a known frequency. This test can be done with infants up to six months of age, toddlers, and uncooperative patients, such as children or adults with developmental delays. 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 he or she hears a sound.
In 2002, Ruth Litovsky, an 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 being broadcasted on loudspeaker, 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 intervention services 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, but a study described in the July, 1999, issue of American Journal of Otology recommended screening only babies with a risk for impaired hearing, stating that pediatricians and child care providers would detect deafness in infants and toddlers.
The October, 2001, the Journal of the American Medical Association
evaluated nineteen studies, emphasizing that screening newborns was not superior to tests by pediatricians when infants were several months old and stressing that determining the value of newborn screening required additional study. 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.
The role of otitis media (middle-ear infections
) in producing hearing impairment is an area of great concern and controversy. Special attention to the hearing evaluation of children with recurrent and chronic otitis media is indicated.
Bibliography
"Audiometry." MedlinePlus, August 30, 2012.
Bess, Fred H., and Judith S. Gravel, eds. Foundations of Pediatric Audiology. San Diego, Calif.: Plural, 2006.
Dobie, Robert A. and Susan B. Van Hemel, eds. Hearing Loss: Determining Eligibility for Social Security Benefits. Washington, D.C.: National Academies Press, 2005
de la Rocha, Kelly. "Audiometry." Health Library, November 11, 2012.
Elder, Nina. “Now Hear This—Check Your Baby’s Hearing.” Better Homes and Gardens 78, no. 5 (May, 2000): 264.
Glaser, Gabrielle. “Pediatricians Urge Hearing Tests at Birth.” The New York Times, April 6, 1999, p. 7.
Hall, James W., III. New Handbook of Auditory Evoked Responses. Boston: Pearson Education, 2006.
Hearing Exchange. http://www.hearingexchange.com.
Koike, Kazunari J. Everyday Audiology: A Practical Guide for Health Care Professionals. San Diego, Calif.: Plural, 2006.
Montemayor-Quellenberg, Marjorie. "Newborn Hearing Test." Health Library, March 15, 2013.
McCormick, Barry, ed. The Medical Practitioner’s Guide to Paediatric Audiology. New York: Cambridge University Press, 1995.
Martin, Frederick N., and John Greer Clark. Introduction to Audiology. 10th ed. Boston: Pearson, 2010.
Northern, Jerry L., and Marion P. Downs. Hearing in Children. San Diego, Calif.: Plural, 2011.
Roush, Jackson, ed. Screening for Hearing Loss and Otitis Media in Children. San Diego, Calif.: Singular, 2001.
Sataloff, Robert T., and Joseph Sataloff. Hearing Loss. 4th ed. New York: Taylor & Francis, 2005.
No comments:
Post a Comment