OAE Pediatrician Booklet
OAE Pediatrician Booklet
OAE Pediatrician Booklet
Introduction
Hearing loss is not uncommon in children. According to recent estimates, 31.5 million people in the United States report difficulty with hearing. Approximately 6 out of every thousand children have some type of unilateral or bilateral hearing loss. When present from birth, or acquired in the pre-school years, hearing loss of any degree, even mild hearing loss, interferes with speech and language development. Hearing loss among school age children contributes to poor academic performance, including reading disorders. Indeed, in a policy statement approved by the American Academy of Pediatrics, The Joint Committee on Infant Hearing (JCIH) endorses early detection of and intervention for infants with hearing loss. The goal of early hearing detection and intervention (EHDI) is to maximize linguistic competence and literacy development for children who are deaf or hard of hearing. Without appropriate opportunities to learn language, these children will fall behind their hearing peers in communication, cognition, reading, and social-emotional development. (Joint Committee on Infant Hearing, 2007, p. 898) The Joint Committee on Infant Hearing (2007) identified risk factors or indicators for childhood hearing impairment. Factors associated with congenital, delayed onset, or progressive hearing loss, are summarized in Appendix A at the end of this booklet. At the top of the list of risk factors is caregiver concern regarding hearing, speech, language, or developmental delay, followed by family history of permanent childhood hearing loss. A number of risk factors for sensory or conductive hearing loss can be identified in the perinatal period. Others are associated with syndromes or neurodegenerative disorders. Hearing screening with otoacoustic emissions, sometimes in combination with tympanometry, is warranted for children whose medical histories reveal one or more of these risk factors. In addition to, and related to, obvious communication deficits, the consequences of hearing loss in children include psychosocial problems, such as frustration, irritability, anxiety, the tendency to withdraw from social interactions, and even depression. The psychosocial problems, of course, affect relationships between the person with the hearing impairment and family members, classmates, teachers, friends, and others. Otoacoustic emissions (OAEs) permit early detection of inner ear abnormalities associated with a wide variety of diseases and disorders, including non-pathologic 1
etiologies like metabolic dysfunction of outer hair cells caused by potentially ototoxic medications. With early detection, the serious consequences of hearing loss can sometimes be prevented. And, fortunately, with proper identification and diagnosis of hearing impairment, medical and non-medical (e.g., audiologic) treatment options almost always lead to effective management. Tympanometry provides clinically valuable information on the functional status of the tympanic membrane and the middle ear system. Middle ear disorders, a common occurrence in young children, can almost always be detected, and sometimes differentiated, by simple analysis of the results of tympanometry. Tympanometry is easily and quickly performed in a physicians office, or any clinical setting.
Figure 1. Simplified diagram of three portions of the ear (external, middle, and inner ear), the auditory (8th cranial) nerve, and auditory regions of the brain Illustration appears with permission of artist Anuradha Bantwal.
The middle ear consists of the tympanic membrane and the ossicles (malleus, incus, and stapes). Sound waves reaching the tympanic membrane are amplified by the middle ear system, providing an increase in sound intensity of almost 30 dB. Mechanical energy from sound waves is converted to electrical signals by specialized hair cells located within the inner ear (the cochlea). The term hair cells is used because there are extending from the top of each cell hundreds of thin hair-like proteinbased cilia. There are about 15,000 hair cells in the human ear. One third of the hair cells, the inner hair cells located medially in the cochlea (see Figure 1), communicate (synapse) with auditory (8th cranial nerve) fibers. Activation of the inner hair cells leads to firing of auditory nerve fibers and stimulation of auditory regions of the central nervous system (also shown in Figure 1). The remaining two-thirds of the hair cells located more laterally within the cochlea, referred to as outer hair cells, are capable of motility (movement). Upon activation, metabolism within the outer hair cells increases dramatically, and the outer hair cells rapidly elongate (during hyper-polarization) and become shorter (during depolarization). Changes in outer hair cell length generate energy within the cochlea that contributes to hearing sensitivity and the ability to distinguish small differences in the frequencies of sounds. Outer hair cell movement also produces otoacoustic emissions, as reviewed briefly in the next section. At this point, its important keep in mind that although the ear is clearly important in hearing, we really hear with our brain. High level auditory processing, including speech perception, occurs within a complex network of central nervous system pathways and centers (nuclei) containing millions of neurons. Clinically, hearing evaluation is not complete unless it includes procedures for evaluating how the brain processes relatively sophisticated sounds, such as speech. Audiologists regularly perform such procedures in hearing assessment. Audiologic tests used to evaluate function of the ear, such as otoacoustic emissions (OAEs), are very important in the diagnosis of hearing loss. However, OAEs alone are not a test of hearing.
The stimuli vibrate the tympanic membrane and mechanical energy is transmitted through the middle ear to the cochlea. Tiny waves in the cochlear fluids vibrate a thin membrane, activating outer hair cells located on the membrane. Energy associated with outer hair cell movement, in the frequency region of the stimulus, is propagated back through the middle ear system and, as sound, into the ear canal. A miniature microphone within the probe assembly detects OAE-related sound, as well as any other sound in the ear canal during the recording. By means of sophisticated algorithms in the OAE device, OAE activity is differentiated from other ambient and physiological noise in the ear canal and the presence of OAEs is statistically confirmed. Amplitude values for the OAEs are then compared to normative data for the device (refer again to Figure 2).
Figure 2. Illustration of the measurement of distortion product otoacoustic emissions (DPOAEs) showing a probe assembly that fits into the external ear canal, the delivery of the signals to the ear via the middle ear, the generation of OAEs by outer hair cells in the cochlea and, finally, propagation of OAE energy as sound into the external ear canal Illustration appears with permission of artist Anuradha Bantwal.
PASS REFER
_________________
30 25 20 dB 15 10 5 0 0 1 2 3
Protocol:
DP QuickScreen
Test Number: 26 Test Date: 2009-10-15 15:13:15 Instrument and Probe Serials: 0835019 T0840102 Number of frequencies: 4, minimum for a pass: 3 F2 2000 3000 4000 5000 P1 66 66 64 65 P2 55 55 55 55 DP -4.0 0.0 3.0 5.0 NF SNR Result -14.0 10.0 P -16.0 16.0 P -18.0 21.0 P -18.0 22.0 P dB SPL
10 11 12
25 15 5 -5 -15 -25 0 1 2 3
4 5 6 7 8 Frequency (kHz)
10 11 12
REFER
_________________
30 25 20 dB 15 10 5 0 0 1 2 3
Protocol:
DP QuickScreen
Test Number: 26 Test Date: 2009-10-15 15:13:15 Instrument and Probe Serials: 0835019 T0840102 Number of frequencies: 4, minimum for a pass: 3 F2 2000 3000 4000 5000 P1 66 66 64 65 P2 55 55 55 55 DP -7.0 -7.0 -4.0 -2.0 NF SNR Result -10.0 3.0 R -10.0 3.0 R -12.0 8.0 P -14.0 12.0 P dB SPL
10 11 12
25 15 5 -5 -15 -25 0 1 2 3
4 5 6 7 8 Frequency (kHz)
10 11 12
Figure 3
Etymotic Research Inc. - Copyright 2009
Table 1. Selected applications of otoacoustic emissions (OAEs) in pediatric patient populations __________________________________________________________ Infant hearing screening Screening hearing in pre-school (e.g., Head Start) years Screening in school age children Monitoring for possible cochlear ototoxicity Early detection of noise induced cochlear dysfunction Diagnosis of pediatric hearing impairment __________________________________________________________
Tympanometry begins with insertion of a probe assembly into the external ear canal. The probe assembly, coupled to a soft rubber tip, usually consists of three small tubes for: 1) presentation of a pure tone sound (known as the probe tone), 2) detection via a miniature microphone in the probe assembly of sound level within the ear canal, and 3) air pressure changes in the ear canal. Disposable probe tips are available in a variety of sizes to accommodate patients from newborn infants to school age children. Tympanometry requires an airtight (hermetic) seal between the probe tip and the walls of the external ear canal. An airtight seal is confirmed when positive or negative pressure in the external ear canal is developed at +200 or 300 mmH2O (daPa). If neither positive nor negative pressure can be created in the external ear canal, the probe tip should be replaced and reinserted in an attempt to adequately seal the external ear canal. Tympanometry is very quick. The systematic change in external ear canal from +200 to -200 or -300 mmH2O (daPa), and measurement of the resultant change in middle ear compliance, takes only 5 to 10 seconds.
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TYMPANOMETRY
150 135 120 105 90 Type C 75 60 45 Type A 30 15 0 -200 -250 -150 -100 -50 0 50 100 150 200 Type B
With an abnormal type B tympanogram, there is no clear peak as air pressure is varied across the range of +200 mmH2O to -300 mmH2O. Often the type B tympanogram appears as essentially a flat line. The finding of a type B tympanogram indicates a severely restricted mobility of the middle ear system, and often is consistent with otitis media. At this point its important to emphasize that tympanometry can be conducted only after an airtight (hermetic) seal is obtained between the probe tip and the external ear canal walls. With a hermetic seal, its possible with clinical immittance devices to estimate the ear canal volume between the probe tip and the tympanic membrane. For children, ear canal volumes are in the range of 0.30 to 1.0 cc (ml) depending on body size. When a hermetic seal is confirmed, the finding of an ear canal volume exceeding 1.0 cc (ml) or, a 11
large asymmetry in ear canal volume, suggests the possibility of either a tympanic membrane perforation or a patent (open) ventilation tube in the tympanic membrane. Estimation of ear canal volume is a clinically useful feature of tympanometry. However, when the tympanic membrane is not intact, air pressure cannot be varied within the ear canal and the requirement for tympanometry cannot be met. A type C tympanogram, also abnormal, has a negative pressure peak exceeding the normal limits (less than -150 mmH2O). Sometimes the type C tympanogram has a rounded maximum point, rather than a distinct peak. The finding is most often a indicator of Eustachian tube dysfunction, and the inadequate ventilation of the middle ear space. Examples of the Pass and Refer outcomes for tympanometry screening with the Maico EroScan device are illustrated in Figure 5. The, probe tone frequency (e.g., 226 Hz) and findings for specific tympanometry measures (e.g., ear canal volume, middle ear compliance, and the pressure at which the tympanogram peak was recorded) are displayed in tabular form to the left. A tympanogram is shown graphically to the right. The shaded box indicates the normal region for the tympanogram peak.
Figure 5
PASS
_________________ ml 1 .5 0 -300 0 +300 daPa
Protocol:
Tymp 226 Hz
Test Number: 28 Test Date: 2009-10-15 15:41:48 Instrument and Probe Serials: 0835019 T0840102 Frequency: Ear volume: Gradient: Compliance: Peak Pressure: 226 Hz 0.69 mL 96 daPa 0.48 mL 4 daPa
REFER
_________________ ml 1 .5 0 -300 0 +300 daPa
Protocol:
Tymp 226 Hz
Test Number: 27 Test Date: 2009-10-15 15:39:50 Instrument and Probe Serials: 0835019 T0840102 Frequency: Ear volume: Gradient: Compliance: Peak Pressure: 226 Hz 1.16 mL 169 daPa 1.74 mL -190 daPa
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Tympanometry is a sensitive indicator of middle ear functional status, often revealing evidence of abnormalities not clearly visible upon visual examination. However, tympanometry is not a valid measure of hearing, or even hearing sensitivity. Normal tympanograms may be recorded in children with sensory hearing loss affecting speech and language development, including severe to profound hearing impairment. Conversely, abnormal tympanometry findings are not always associated with communicatively or clinically significant deficits in hearing sensitivity. The clinical value of tympanometry in children is confirmed by the requirement for inclusion of the procedure in the JCIH recommended test battery for auditory assessment of infants and for toddlers (see Appendix B). In short, OAE and tympanometry findings in isolation cannot be used to diagnose auditory dysfunction or to predict the degree of hearing loss. For diagnostic assessment of auditory function, OAEs and tympanometry must be included within an appropriate test battery. It is important to keep in mind that neither OAEs nor tympanometry are tests of hearing.
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Descriptors for OAE CPT Codes 92587: Evoked otoacoustic emissions; limited (single stimulus level, either transient or distortion products). 92588: Comprehensive or diagnostic evaluation (comparison of transient and/ or distortion product otoacoustic emissions at multiple levels and frequencies.) The CPT code for tympanometry is 92567. CPT codes also are available for other immittance measurements, including acoustic reflex recordings (92568 and 92569). Other billing and reimbursement considerations, including diagnosis (ICD-9) codes appropriate for use with OAE measurement, are summarized at the end of this booklet.
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Selected References
Dhar S & Hall JW III. (2010). Otoacoustic Emissions: Principles, Procedures, and Protocols. San Diego: Plural Publishing Hall JW III. (2000). Handbook of Otoacoustic Emissions. San Diego: Singular Publishing Company Hall JW III & Swanepoel, D. (2010). Objective Measures of Hearing. San Diego: Plural Publishing National Center for Hearing Assessment and Management (NCHAM). (2006). Early identification of hearing loss: Conducting periodic otoacoustic emissions (OAE) hearing screening with infants and toddlers during well-child visits. For more information, contact NCHAM at Utah State University, Logan UT 84322. Available online at: www. infanthearing.org or www.hearandnow.org/periodicscreening Year 2007 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs. Joint Committee on Infant Hearing Pediatrics, 120, pp. 898-921
NOTE: Anyone with Internet access can quickly perform a literature review on the topic of otoacoustic emissions at the National Library of Medicine website (www.nlm.nih.gov, Health Care Professionals). A search will produce abstracts of thousands of articles containing the word otoacoustic emissions. A more refined search can be performed with combinations of terms, such as otoacoustic emissions and dementia. Articles of interest can then be requested via email of the author designated for correspondence.
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Credits
James W. Hall III, Ph.D. contributed to the preparation of this booklet. Dr. Hall earned his Masters degree from Northwestern University and his Ph.D. in Audiology from Baylor College of Medicine. He is the author of over 150 journal articles and book chapters, plus 10 textbooks including the Handbook of Otoacoustic Emissions and the recently published Otoacoustic Emissions: Principles, Procedures, and Protocols. Dr. Hall is Clinical Professor in the Department of Communicative Disorders at the University of Florida where he maintains a clinical practice, teaches doctoral level students, and conducts externally funded research. David Adlin contributed as a consultant to the direction of this booklet. Since 1993 Adlin has been the National Sales Manager for Maico Diagnostics. Kathryn May served as production coordinator for this booklet. Anuradha Bantwal provided the artwork appearing in Figure 1 and Figure 2 of this booklet. Ms. Bantwal is an Audiologist and Speech-Language Pathologist working in India.
Additional Resources
American Academy of Audiology. www.audiology.org American Academy of Pediatrics. www.aap.org Better Hearing Institute. www.betterhearing.org National Center for Hearing Assessment and Management (NCHAM). www.infanthearing.org Otoacoustic Emissions Portal Zone. www.otoemissions.org
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Reference: International Classification of Diseases, 9th Revision, Clinical Modification, ICD-9-CM 2009, Volumes 1 and 2, American Medical Association, AMA Press. ISBN: 1-57947-575-2 Notes
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Appendix A. Evidenced-based risk indicators that are associated with hearing loss in childhood, including permanent congenital, delayed onset, or progressive hearing loss, according to the Joint Committee on Infant Hearing.* ________________________________________________________________ Caregiver concern regarding hearing, speech, language, or developmental delay Family history of permanent childhood hearing loss Neonatal intensive care of more than 5 days or any of the following regardless of length of stay: ECMO, assisted ventilation, exposure to ototoxic medications (gentimycin and tobramycin) or loop diuretics (furosemide/Lasix), and hyperbilirubinemia that requires exchange transfusion In utero infections, such as CMV, herpes, rubella, syphilis, and toxoplasmosis Craniofacial anomalies, including those that involve the pinna, ear canal, ear tags, ear pits, and temporal bone anomalies Physical findings, such as white forelock, that are associated with a syndrome known to include a sensorineural or permanent conductive hearing loss Syndromes associated with hearing loss or progressive or late-onset hearing loss, such as neurofibromatosis, osteopetrosis, and Usher syndrome other frequently identified syndromes include Waardenburg, Alport, Pendred, and Jervell and Lange-Nielson Neurodegenerative disorders, such as Hunter syndrome, or sensory motor neuropathies, such as Friedreich ataxia and Charcot-Marie-Tooth syndrome Culture-positive postnatal infections associated with sensorineural hearing loss, including confirmed bacterial and viral (especially herpes viruses and varicella) meningitis Head trauma, especially basal skull/temporal bone fracture that requires hospitalization Chemotherapy ______________________________________________________________________ * Source: Joint Committee on Infant Hearing. (2007). Year 2007 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs. Pediatrics, 120, pp. 898-921
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Appendix B. Joint Committee on Infant Hearing* recommendations for audiological assessment of children less than 3 years of age. ________________________________________________________________ Children from Birth to 6 Months Developmental Age Child and family history. A frequency-specific assessment of the ABR using air-conducted tone bursts and bone-conducted tone bursts when indicated to determine the degree and configuration of hearing loss in each ear for fitting of amplification devices. Click-evoked ABR testing using both condensation and rarefaction single-polarity stimulus, if there are risk indicators for neural hearing loss (e.g., auditory neuropathy/auditory dyssynchrony),to determine if a cochlear microphonic is present. Distortion product or transient evoked OAEs. Tympanometry using a 1000-Hz probe tone. Clinician observation of the infants auditory behavior as a cross-check in conjunction with electrophysiologic measures. Children from 6 to 36 Months of Age Child and family history. Parental report of auditory and visual behaviors and communication milestones. Behavioral audiometry, including pure-tone audiometry across the frequency range for each ear and speech-detection and -recognition measures. OAE testing. Acoustic immittance measures (tympanometry and acoustic reflex thresholds). ABR testing if responses to behavioral audiometry are not reliable or if ABR testing has not been performed in the past. ________________________________________________________________ * Source: Joint Committee on Infant Hearing. (2007). Year 2007 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs. Pediatrics, 120, pp. 898-921
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