20Q: The Cross-Check Principle in Pediatric Audiometry - Forty Years Later

From the Desk of Gus Mueller

The 1970s were an exciting time for clinical audiologists.  Prior to this decade, audiologic “special testing” usually was limited to the behavioral measures of speech recognition, Bekesy audiometry, the SISI, and tone decay.  But, two new clinically-friendly objective measures arrived in the 1970s: immittance audiometry (referred to as impedance or admittance in those days) and the auditory brainstem response (ABR).  These tests were extremely helpful in adult differential diagnosis, but also played a major role in the evaluation of the pediatric patient, where often basic audiometric findings such as pure-tone thresholds were questionable or not attainable.

Gus Mueller

In those days, many of us struggling with the clinical interpretation of the findings from these new objective measures looked toward The Methodist Hospital in Houston for guidance. It was there where audiologist James Jerger, PhD, and his staff always seemed to have recognized the critical issues surrounding each clinical measure, and kindly provided easy-to-understand explanations for the rest of us in a variety of workshops, published articles and book chapters.  One of the many articles that emerged during this time was authored by Dr. Jerger and Deborah Hayes, titled “The Cross-Check Principle in Pediatric Audiometry.”  Using five illustrative pediatric cases, the authors showed how immittance findings and the ABR can be used in conjunction with behavioral results to make important clinical decisions.  The article quickly became the “go-to” reference for anyone involved in the assessment of the pediatric patient.

It’s been 40 years since that classic article was published, and we’re pleased to bring one of the authors, Deborah Hayes, PhD, to our 20Q pages for an update.  Dr. Hayes is Professor, Physical Medicine and Rehabilitation at University of Colorado School of Medicine and Chair, Audiology, Speech Pathology, and Learning Services at Children’s Hospital Colorado. She is an audiologist with more than 40 years of professional experience, most of which has focused in the area of pediatric audiology.  

Deborah mentions that those indeed were exciting days at The Methodist Hospital.  She states: “We experienced new discoveries in hearing science and audiology that changed the profession forever.  There was nothing routine or usual about our practice back then.  Every day the audiologists reviewed their cases with Dr. Jerger to mine his insights into hearing and hearing loss.  I fondly remember him counseling that ‘every patient is interesting’ and how right he was.”   

Dr Hayes is the author of numerous journal articles, book chapters, monographs, and proceedings, and textbooks. She is a Fellow of the American Speech-Language-Hearing Association, has received the Distinguished Achievement Award from the American Academy of Audiology, and the Lifetime Achievement Award from the Colorado Academy of Audiology.

Deborah was a little surprised when I approached her to revisit the “Cross-Check Principle” after 40 years.  “That little article . . . just a compilation of a few case examples”, she said modestly.  But after some thought she added, “The article does remind us that pediatric audiology requires both science and skill - science of evidence-based practice to provide contemporary, valid, and reliable tools to assess the child’s hearing, and skill to interpret the relationship among measures in arriving at an accurate diagnosis.” 

Thanks to people like Deborah, the Cross-Check Principle for pediatric audiology is alive and thriving today.   

Gus Mueller, PhD

Contributing Editor
October, 2015

To browse the complete collection of 20Q with Gus Mueller CEU articles, please visit www.audiologyonline.com/20Q

20Q: The Cross-Check Principle in Pediatric Audiometry - Forty Years Later

Deborah Hayes

1.  You’ll have to help me out with your title.  I wasn’t even born 40 years ago!  Cross-check principle?

You missed some good times.  Exciting things were happening in audiology in the mid-1970s.  The cross-check principle, however, is not specifically unique to that time frame, as it more or less applies to all aspects of diagnostic audiology.  Over time, the key measures used for the audiologic cross-check will change, but the principle remains the same. Unless you have one particular test with excellent sensitivity and specificity, it is considered good practice to “cross-check” your findings with another test.  This is especially critical for pediatric audiology, where the findings for one of the tests might be ambiguous.  And this principle isn’t just for diagnostic audiology.  With hearing aid fittings we frequently cross-check our probe-microphone real-ear findings with behavioral tests in the clinic or outcome measures in the real world.

2.  What’s the significance of 40 years?

In the 1970s, the hotbed for clinical audiology was Baylor College of Medicine and The Methodist Hospital in Houston, headed by Dr. James Jerger.  I was there obtaining my PhD and also working part-time in the clinic.  We had just finished some research related to using speech audiometry for clinical hearing aid selection.  It turned out to be my first professional publication (Jerger & Hayes, 1976a).  I was excited to be a published author and felt fortunate that Dr. Jerger asked me what I wanted to do next. I remembered a particularly challenging case of an almost three-year old youngster who had been diagnosed with a moderate conductive hearing loss by behavioral hearing tests before being referred to Methodist Hospital. This child, referred to as Case 2 in the article, had a severe, high-frequency mixed hearing loss bilaterally. Dr. Jerger suggested that we gather a series of case examples to illustrate how some of our then newer diagnostic tools could be used to cross-check behavioral results obtained in children.  We put the cases together and quickly submitted the paper, which led to a 1976 article in the Archives of Otolaryngology titled, ”The cross-check principle in pediatric audiometry” (Jerger & Hayes, 1976b).  At the time, our “cross-checks” for behavioral findings were immittance audiometry and the auditory brainstem response (ABR).  These two measures were just emerging as clinical tests, and audiologists were very interested in the clinical applications, so our article became more popular than I would have ever imagined.  I even remember to this day the name of that youngster (and how difficult he was to test behaviorally) who made such an impression on me and got me started with the paper.

3.  What was the outcome for this youngster who inspired you to write about the cross check principle? Do you remember?

Unfortunately, in those days, there were limited options for both hearing aids and early intervention for young children. Audiologists did not routinely dispense hearing aids and available hearing aid technology did not provide the signal processing features we expect today. There was no federal mandate for preschool programs for children with disabilities. I don’t know the ultimate outcome for this specific youngster, but I speculate that he entered public school at kindergarten with significantly delayed language skills and continuing behavioral challenges.

4.  What was the environment of pediatric audiology 40 years ago?

Much different than today! Clinically useful auditory evoked potentials were just emerging with the discovery of the ABR, and acoustic immittance (AI) measures were being explored to provide more information than just the status of the eardrum and middle ear. I recall the excitement of applying the ABR in pediatric assessment and understanding the utility of acoustic reflexes in predicting sensorineural hearing loss as well as auditory nerve and brainstem auditory pathway dysfunction.

5.  Let’s talk a bit about the ABR. In your opinion, what were some highlights of the ABR research back then that have impacted clinical practice today?

Two areas of early ABR research were important for application of this technique in pediatric audiology. First, in this early research, there was considerable energy focused on defining the effects of various subject-related variables on the click-evoked ABR such as: 1) age (important for understanding maturation of the response and developing age-related latency norms); 2) degree and configuration of hearing loss (important for predicting the audiogram and fitting amplification); and, 3) site of auditory dysfunction (important for differentiating conductive, sensory, neural, and brainstem disorders). There was also considerable discussion and some disagreement on the generators of the ABR during this era. In the 1970s, each new publication about the ABR was eagerly devoured to apply clinically relevant information to our practice with children. 

Second, understanding the optimum stimulus and recording parameters for extracting frequency-specific information from the ABR was a critically important research endeavor at many laboratories. Dr. Jerger and I conducted some research on this topic in the early 1980s when we evaluated the predictive accuracy of ABR recorded to tone-pip stimuli (Hayes & Jerger, 1982). I recall that we specifically included children who were hard-of-hearing as subjects in this study because the target population for frequency-specific ABR techniques would be children.

6.  You mentioned the click ABR. Do you think it still has a role in audiological assessment?

Click ABR is a very powerful tool that provides significant information in a very short period of time. In infants and young children, the latency, interwave intervals, and response morphology can provide an insight into middle ear function, degree and configuration of conductive or sensory hearing loss, presence of auditory neuropathy, and eighth nerve and brainstem auditory pathway integrity. As our colleague Jay Hall says, “…don’t ditch the click…”

7.  Can you be more specific about using the click ABR in this manner, say, for detecting auditory neuropathy?

A hallmark of “classic” auditory neuropathy is presence of normal cochlear function and absence of auditory nerve conduction. Normal cochlear function can be measured by demonstrating the presence of the pre-neural, polarity-reversing cochlear microphonic (CM) by first obtaining an ABR to a rarefaction click then obtaining an ABR to a condensation click. Presence of a cochlear microphonic with absent neural responses is a strong indicator of auditory neuropathy. This perplexing auditory disorder is not infrequently diagnosed in infants who received care in the neonatal intensive care unit.  I should mention that the clinical identification of this disorder relates directly to the cross-check principle that we are discussing.  That is, when you conduct your typical battery of tests, the findings in patients with auditory neuropathy do not “line up” like you would expect for a more common cochlear pathology.

8.  So the click ABR is important. What other thoughts do you have about auditory evoked potentials in pediatric assessment?

I’m a fan of objective response detection techniques in auditory evoked potentials. The options available for frequency-specific ABR and auditory steady-state response (ASSR) for objective response detection are powerful tools that reduce or eliminate observer bias and improve confidence in threshold predictions by these techniques. Of course, the audiologist must fully understand the theory and application of these response detection techniques to understand their application and limitations. I became interested in objective response detection in the late 1970s when I conducted two studies addressing observer bias. In one study, I explored blinded vs. unblinded response identification in respiration audiometry (Hayes & Jerger, 1978). You probably haven’t heard of this interesting technique; see Kankunnen and Liden (1977) for a description of its use in infants. A few years later, Jim Martin, an auditory neurophysiologist working at Baylor, and I explored frequency decomposition using the Fast Fourier Transform to identify objectively presence of a response in the 40-Hz auditory event-related potential (ERP) (Martin & Hayes, 1982). Ultimately, the 40-Hz ERP stimulated investigators in Canada and Australia to develop a related response, the ASSR, into a commercially-available auditory evoked potential technique. The respiration audiometry and 40-Hz ERP studies convinced me that objective response detection criteria should be applied to auditory evoked potentials whenever possible.  

9.  I’ve seen articles suggesting we use cortical auditory evoked potentials for evaluating infants and children.  What are your thoughts about that?

Both cortical auditory evoked potentials and new stimuli for brainstem evoked potentials are emerging as fascinating windows into central auditory development and auditory processing in infants and young children. Anu Sharma’s groundbreaking research on maturation of the P1 response shows the importance of sensory stimulation during sensitive periods of cortical development and the utility of cochlear implants on restoring delayed development in children who are deaf or hard of hearing. Similarly, Nina Kraus’ current work on complex stimuli, including speech and patterned sound sequences, for eliciting the ABR has explored the role of brainstem plasticity in processing complex auditory signals. I think we are all fascinated by her research on the effect of musical training on enhanced neural differentiation of specific speech sounds and how individuals with musical training exhibit improved speech perception in noise. These results suggest an important role of musical training throughout the lifespan.

10.  You mention that immittance testing was also part of your cross-check in the 1970s. Are immittance measures of today for infants and children different than they were then?

Well, yes and no. We continue to use the techniques of tympanometry, equivalent ear canal volume, and acoustic reflex measures today as in the past. I think today we better appreciate the importance of age-appropriate normative values for middle ear measurements, especially in very young infants. For example, 40 years ago, we used low-frequency probe tones for almost all patients from infants to older adults. By better understanding the anatomy and physical properties of the newborn external and middle ear, we have identified the appropriate use of higher frequency probe tones for immittance measures in the earliest months of life. Research in the past decade on wideband acoustic immittance shows great promise for improving detection of middle ear dysfunction and conductive hearing loss in newborns, thereby enhancing newborn hearing screening programs.

11.  Wideband acoustic immittance?

Yes, also known as wideband energy reflectance (ER), wideband acoustic immitance measures transfer of energy through the external and middle ear system to a broadband stimulus (approximately 200 – 10,000 Hz) rather than to a single frequency such as 226 Hz or 1,000 Hz. This technique has been investigated for more than two decades and two wideband acoustic immittance systems are now commercially available. In general, the measurement technique is similar to that used in standard single-frequency tympanometry; a wideband stimulus is introduced into the hermetically-sealed ear canal either at ambient air pressure or with varying air pressure. The sound input to the ear canal is compared to the sound recorded in the ear canal to derive energy transfer through the middle ear, either as energy reflected back to the ear canal or energy absorbed (or admitted) into the middle ear.

The advantage of wideband acoustic immittance is improved detection of middle ear disorders, especially in newborns and very young infants.  Research has shown that wideband acoustic immittance is a better predictor of which newborn ears will pass distortion product otoacoustic emission (OAE) screening than 1,000 Hz probe-tone tympanometry that is typically used today. This result suggests that coupling wideband acoustic immittance measures with newborn hearing screening may improve performance of newborn hearing screening programs. For example, Lisa Hunter and her colleagues (2010) recommended that newborns with high wideband ER scores who refer on OAEs should be rescreened within a short period of time based on the assumption that these infants have transient middle ear disorder. In contrast, newborns with normal wideband ER scores who refer on OAEs should be referred for diagnostic audiological testing as they are unlikely to have transient middle ear disorder. 

Despite the apparent advantages of wideband acoustic immittance, it has not been widely accepted in clinical settings. This is probably related to complexity of response interpretation and audiologist lack of familiarity with this technique. I think that these measures show great promise for improving audiological evaluation of infants and young children. Hopefully, we will see more rapid uptake of these procedures in the next few years.   

12.  I just checked out your 1976 article, and I see you mentioned something called the "SPAR."  Is that still used today?

Frankly, no.  The SPAR (Sensitivity Prediction by the Acoustic Reflex) was a test we used quite successfully back then.  Today, when I ask my younger colleagues about this technique, most are puzzled by the acronym and have no idea what I’m talking about.

13.  How did this test come about and how do you do it?

Well, I mentioned that a lot was happening at the audiology clinic at the Methodist Hospital in Houston in the 1970s, and this is yet another test developed at that time (Jerger et al., 1974).  Simply stated, you compare the acoustic reflex thresholds for pure tones to that of a broadband noise, and the difference value will help predict the presence and degree of a cochlear pathology (in normal ears, the acoustic reflex to broadband noise occurs at an approximately 20 dB lower intensity than the acoustic reflex to pure tones, related, in part, to loudness summation across critical bands).  The authors of the original 1974 article provided a handy chart for clinical use.  In general, if the difference is 20 dB or greater, you can be fairly certain that hearing thresholds are at or near normal, and smaller differences (e.g., <20) allow for the prediction of the mild to severe loss, depending on the difference score and the absolute value of the broadband finding.  

14.  Why isn’t the SPAR test used today?

I think this technique fell out of favor for a number of reasons, including expanded availability of auditory evoked potential techniques and inability to measure acoustic reflexes due to otitis media or PE tubes in many children - the target population for most predictive techniques. Unfortunately, I fear that too many audiologists have “thrown out the baby with the bathwater” because I don’t see acoustic reflexes being used to their full potential in many pediatric assessments today. Either they are not completed at all, or the audiologist defaults to just a single frequency ipsilateral reflex to determine integrity of this important auditory pathway from the external ear through brainstem.

15.  We weren’t using OAEs in the clinic when you wrote your 1970s article.  How do they fit in to the cross-check principle?

They are definitely very important. OAEs have such a wide variety of uses in pediatric audiology from newborn hearing screening to monitoring children receiving treatment with ototoxic medications to informing the assessment of youngsters with suspected auditory neuropathy. Echoing Dr. Jerger’s assertion about acoustic immittance measures years ago, I must say about OAEs, "I don’t know how we lived without them”.

For newborn hearing screening, OAEs have appealing characteristics. They are: 1) quick and simple to conduct; 2) virtually risk-free; 3) valid and reliable; and, 4) easy to interpret. These characteristics also make them attractive for monitoring hearing in children receiving treatment with ototoxic medications. We use them routinely in an extended high-frequency configuration (up to 12,000 Hz) to identify onset of hearing loss in children receiving these treatments. For children with suspected auditory neuropathy, OAEs are another indicator of normal cochlear function. Like the cochlear microphonic mentioned earlier, presence of OAEs in the absence of auditory neural response on the ABR is a hallmark of “classic” auditory neuropathy.

16. It sounds like OAEs are the perfect test for pediatric audiology. Are there any limitations or shortcomings of OAE testing?

Sure!  Nobody’s perfect. Remember that OAEs are not a “hearing test” in the common sense of the expression, but rather a measure of cochlear function. If cochlear function is normal, we expect OAEs to be present, provided they were conducted in appropriate test conditions (quiet subject, relatively quiet test environment, ability to obtain and maintain a seal in the ear canal, absence of middle ear pathology). If cochlear hearing loss exceeds about 30 – 40 dB HL, however, OAEs are typically absent and have limited utility.

OAEs also have limitations in youngsters with middle ear disorder. In children with otitis media, responses are typically absent, precluding their use for predicting cochlear function. In contrast, however, in children with PE tubes, OAEs are often present. I always encourage audiologists to use OAEs as a cross-check even in children with PE tubes (or tympanic membrane perforation for that matter). If a response is present, great; you have more information about cochlear status. If OAEs are absent, however, you cannot interpret the result as indicating cochlear dysfunction.

For children with auditory neuropathy, OAEs frequently disappear over time. For this reason, current thinking on diagnosing auditory neuropathy is presence of either otoacoustic emissions or the cochlear microphonic as the signature of normal cochlear function.

17.  The cross-check principle usually involves behavioral measures. Are behavioral measures less important now that we have reliable non-behavioral measures to diagnose hearing loss in children?

Accurately diagnosing hearing loss in infants and young children is, of course, a primary responsibility of pediatric audiologists. In addition, however, we should be highly skilled in suspecting or detecting delays in a child’s auditory, speech-language, and cognitive development. Behavioral measures remain the cornerstone of pediatric audiology because these provide insight into both hearing sensitivity and overall development.

18.  What are some of the new procedures for conducting behavioral testing with young children?

I would characterize “new” procedures as improved technology for getting the job done. We continue to use classic conditioning procedures and a variety of reinforcement techniques to obtain valid audiometric results. Of course, the visual reinforcers available today are much more sophisticated and engaging then they were 40 years ago. When I first started practicing, we had a homemade visual reinforcement system consisting of a plastic Halloween pumpkin with a light bulb inside. When the child responded with the appropriate head-turn, we flashed the light bulb to illuminate the pumpkin. Clearly, video reinforcement systems available today with multiple screens and a variety of video clips are much more appealing for holding a child’s attention.

I appreciate the recent discussion regarding unconditioned behavioral response testing. As you may know, the American Academy of Audiology is recommending that this technique be called simply “behavioral observation” rather than “behavioral observation audiometry.” While observing an infant’s or young child’s unconditioned response to sound is an important component of an audiologist’s evaluation, it does not yield reliable thresholds and should not be equated with techniques that do.

19.  How exactly does a child’s behavior contribute to the audiological diagnosis?

Behavioral measures begin in the waiting room when the audiologist first greets the infant or child and his/her caregivers. Observing how an infant interacts with his sensory environment provides insight into his emerging social, pre-language, and cognitive development. For preschool and older children, interacting with the child prior to testing allows the audiologist to assess the child's speech, language, and cognitive development. These insights help the audiologist develop the most efficient audiological test battery for the individual child. In addition, if the audiologist suspects delays in any area of development, he or she can gently question the caregiver about these observations and discuss options for a thorough developmental evaluation.

20.  So after 40 years, any new thoughts on the cross-check principle?

I’d say that the cross-check principle has aged better than most of us with a 40-year career in audiology! It is as robust and valid today as it was in 1976. A basic premise underlying the cross-check principle is incorporation of new, validated test techniques - acoustic immittance measures and the auditory brainstem response in the 1970s - to improve accuracy in audiological diagnosis and management of children who are deaf or hard-of-hearing. I hope that in the next 40 years, audiologists will continue to enthusiastically adopt new and improved audiological techniques to cross-check test results in infants and young children and thereby improve care of this precious population.

References

Hayes, D., & Jerger, J. (1978).  Response detection in respiration audiometry. Archives of Otolaryngology, 104(4), 183-185.

Hayes, D., & Jerger, J. (1982). Auditory brainstem response (ABR) to tone pips: Results in normal and hearing-impaired subjects. Scandinavian Audiology, 11(3), 133-142.

Hunter, L. L., Feeney, M. P., Lapsley Miller, J. A., Jeng, P. S., Bohning, S. (2010). Wideband reflectance in newborns: Normative regions and relationship to hearing-screening results. Ear & Hearing 31(5), 599-610.

Jerger, J., & Hayes D. (1976a). Hearing aid evaluation: Clinical experience with a new philosophy. Archives of Otolaryngology, 102, 214-225.

Jerger, J., & Hayes, D. (1976b). The cross-check principle in pediatric audiometry. Archives of Otolaryngology, 102(10), 614-620.

Jerger, J., Burney, P., Mauldin, L., & Crump, B. (1974). Predicting hearing loss from the acoustic reflex. The Journal of Speech and Hearing Disorders, 39(1), 11-22.

Kankunnen, A., & Liden, G. (1977). Respiration audiometry. Scandinavian Audiology, 6(2), 81-86.

Martin, J., & Hayes, D. (1982). Use of an FFT criterion to identify presence of auditory evoked response (40 Hz ERP) at behavioral threshold. Abstracts, International Congress of Audiology, 23-27 May, 1982, Helsinki, Finland.