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Is evaluating auditory processing disorders in your scope of practice?

Keith, Robert W.

doi: 10.1097/01.HJ.0000294659.33133.83
Page Ten

Much has been learned in recent years about auditory processing disorders and their effects, and it is now time, the author contends, for audiologists in most work situations to be prepared to conduct a basic test battery for APD and to provide their patients with information and advice. This article provides help for the clinician in evaluating APD and providing follow-up.

1 How did you become interested in auditory processing disorders, and are you surprised at the growth of interest in the subject?

Many years ago, after hearing a presentation by Jack Willeford at the American Speech-Language-Hearing Association (ASHA) Convention, I became interested in auditory processing disorders (APD) and began to read about and investigate the topic. In the early days, there was much controversy over APD, especially from speech-language pathologists, who believed that all auditory processing disorders were simply language disorders. Since then we have come a long way in developing an understanding of auditory processing and its disorders.

As we have come to understand APD better, I am not surprised that interest in the subject has grown. What does surprise me is how slow our progress has been. Despite interest by many clinicians and demands for services from parents, there are few new developments in behavioral tests, and even less documentation supporting approaches to remediation and measuring outcomes.

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2 I'm used to hearing the term “central auditory processing disorders” (CAPD). Why do you use “auditory processing disorders”?

For years I believed that using the term “central” was confusing to professionals and parents alike, and I preferred to use “auditory processing disorders” (though I must admit I often succumbed to the common usage of CAPD). For example, in 1986 the original Scan test was subtitled “A screening test for Auditory Processing Disorders.”

I agree with the recent suggestion by Jerger and Musiek that the label auditory processing disorder (APD) seems more appropriate in both avoiding attribution of anatomic loci and in emphasizing the interactions of disorders at both peripheral and central sites.1

3 Okay, I get your point. I'll use APD. You mention James Jerger and Frank Musiek. That makes me wonder, is this testing something that can be conducted only at major medical centers and clinics?

Not at all. I believe that audiologists in most work situations should be prepared to do a basic test battery, provide their patients with information on auditory processing abilities, and advise them on follow-up. Testing is as appropriate for the dispensing audiologist—and certainly for the educational audiologist—as it is for those working in a medical center. The availability of quality tests on CDs facilitates conducting the tests, and interpretation of results is within the grasp of anyone willing to put in the time to study the issues.

4 Good, I'm ready to start. Wasn't there a special conference on APD a year or 2 ago?

There have been several, but you might be thinking of the Bruton Conference, held at the Callier Center in Dallas in April 2000. Jerger and Musiek published a report of the conference.1 At that meeting, 14 individuals (13 audiologists and one lone SLP) met to discuss screening for APD, differential diagnosis of APD, a minimal test battery, and directions for future research. The purpose was to reach a consensus on the problem of diagnosing auditory processing disorders in school-aged children.

5 Sounds interesting. What do you think of the Bruton Conference proceedings and recommendations?

The conference worked toward an understanding of APD as a deficit in the processing of information that is specific to the auditory modality. I agree that it is desirable to use test approaches that minimize attention, cognition, and language. But, while that is a desirable goal, it should be recognized that it is not always an obtainable goal. The conference recommendations for future research needs are excellent.

The conference did not address management of APD, and, perhaps due to the makeup of the panel, it follows more closely a medical than a psycho-educational model. There is emphasis on electrophysiologic and electroacoustic measures as being central to the diagnosis of APD. Some would argue that tests like ABR and MLR (middle latency response) are not useful in the management of children with APD and contribute little to the overall evaluation.

My take on the conference is that the recommendations were hastily done, and the attendees needed more time to work on the statement. While the conference made a good start, it was not definitive and follow-up is needed.

6 Has the American Academy of Audiology (AAA) or ASHA made APD consensus statements or recommendations?

In 1993, ASHA convened a task force on how to define central auditory processing and its disorders and how the disorders can be identified and ameliorated through intervention. (The proceedings were published in the American Journal of Audiology.2) The conference was attended by a broad group of audiologists, speech-language pathologists, speech scientists, and others. As a result, the consensus statement is more inclusive than that of the Bruton conference.

Both the Bruton and the ASHA documents recommend a team approach to assessment and management planning. I have always liked the organization of the ASHA statement on auditory system mechanisms and processes, and find it a useful outline for designing a diagnostic test battery. The implications for professional education and research priorities at the end of the document are often overlooked, and they are excellent.

7 When I was in graduate school, our APD protocol consisted of nothing more than delivering W-22 words in white noise. Do you still recommend speech testing?

You and I must have attended the same graduate school! We've come a long way since then, haven't we? I remember an editorial by Jerger many years ago, in which he stated that most important measures we do are of speech understanding. I agree that we need to develop auditory-specific tests of auditory processing, but in the end I want to know the individual's speech-perception ability under various listening conditions. The best way to measure that is with sensitized speech signals of various kinds.

8 Whoa! You're getting ahead of me. What do you mean by “sensitized speech”?

Sensitized speech tests are any speech measure that is enhanced to identify auditory processing disorders. We know that we cannot identify APD with normal speech stimuli in quiet. Sensitized speech stimuli include filtered words, speech in noise, time-compressed speech, or other techniques that reduce the acoustic redundancy of the signal and make it more difficult to understand.

9 It sounds as if I have a lot of possibilities. I know you don't want to answer this, but if I'm testing an adult and have time to do just one APD speech test, which one should I do?

You do like to corner a guy! I think that the single most powerful diagnostic test using speech is a dichotic test. If I had one test to administer I would go for dichotic words using a directed-ear listening test. Interpretation of dichotic words testing provides a great deal of information about the status of the auditory system and hemispheric dominance for language. It is also very useful in identifying a disordered auditory system.

10 Okay, I'll remember that. But what if I'm testing a child? What do I do then?

The evaluation of a child is more complex and requires more thoughtful planning. The auditory processing test battery is designed around the child's primary complaint, based on observing what problems the child is having. The examiner should look at different auditory processes using both verbal and non-verbal signals. I also want to know something about the child's expressive and receptive language abilities, and the verbal and performance IQ. All of these factors will impact on test administration and interpretation.

11 You're obviously an advocate for this testing, but I seem to recall reading that APD tests are so unreliable that they aren't even worth doing. How do you respond to that?

The auditory tests aren't unreliable, but children sometimes are. Remember, you are not always dealing with a typical child. Some children are inconsistent in their behavior. They will do well one day and not another, or perform differently under different listening situations. For all these children, the tests are well worth doing; however, it takes skill to interpret the results.

12 You mentioned electrophysiologic testing. What is its role in assessment of APD in children?

According to the Bruton conference, electrophysiologic measures are central to the diagnosis of APD. However, most educational audiologists do not consider physiologic measures to play a critical role in auditory processing assessment.

Personally, I prefer behavioral tests of auditory processing, though I do understand the application of OAE and ABR for identifying auditory neuropathy. I find MLR responses to be variable in young children, and doubt the value of measuring them routinely. I think the most important role for electrophysiology at the moment is in group studies to develop our understanding of APD. For individual children, I find most of the late cortical evoked potentials to be primarily investigational, especially mismatch negativity and the P-300.

13 Are your thoughts the same about testing adults?

No, electrophysiologic responses are more stable in adults, and are generally more appropriate. Still, electrophysiology may be more useful in group studies to help understand APD than in the diagnosis of an individual subject.

14 What is the role of APD testing in adults?

Research has been conducted in various adult patient populations, including persons with Parkinson's disease, chronic alcoholism, Alzheimer's disease, multiple sclerosis, head trauma, stroke, learning disabilities, and AIDS. In all of these patient groups, results of central auditory tests were poorer than predicted on the basis of peripheral hearing levels.

These findings are interesting for monitoring the status of the auditory system in patients with progressive disease. However, the greater need may be to describe disorders of functional communication in patients who have increasing difficulty understanding speech in difficult listening conditions, even though their hearing levels are not that poor, and who do not fall into the dramatic diagnostic categories listed above. Other groups that we should investigate include patients with lupus, fibromyalgia, and other categories of disease.

15 What are some possible uses of AP testing in a hearing aid dispensing practice?

Recent evidence indicates that tests of auditory processing help explain why some elderly hearing aid clients do not do well with binaural amplification. It may be that not all persons should have two hearing aids.

On the other hand, AP findings may support the need to provide binaural amplification to slow the deterioration of auditory processing abilities in the aging patient. It is probably true that large differences in performance between ears on clients who are administered monaural sensitized speech tests may not benefit from amplification, especially at first. The acclimatization studies reported by Silman, however, indicate that these scores may improve given exposure to amplification and time.3 I am not sure that we know the answers to these questions at this time. For audiologists who have a dispensing practice these issues are important for satisfying hearing aid clients.

16 If I were interested in adding tests of auditory processing to my pre-hearing aid fitting test battery, what would you recommend?

Since these patients all have hearing loss of one degree or another it is necessary to limit the linguistic content of the signal. For example, dichotic digits or words will provide comparison of ear advantage and decreased performance in an ear that may do less well with amplification. Similarly, a simple test of speech in noise with comparison of results between ears may give some clue of asymmetry in auditory perception in ears that are otherwise symmetrical for pure-tone sensitivity. It's important to remember, however, that hearing loss can confound the results. There are tests, however, such as the DSI (dichotic sentence identification) that are more resistant to hearing loss.

17 What other findings might be important for assessment of auditory processing in hearing aid candidates?

Jerger has published studies showing the effects of aging on auditory processing abilities. One of the interesting findings is the re-emergence of the right-ear advantage on dichotic tests. That is, older subjects who are cognitively intact begin to show the right-ear advantage on dichotic testing that they “grew out of” during adolescence. That finding is also reported by Hallgren et al.4 The auditory asymmetry may explain why some patients have difficulty coping with binaural amplification. Your readers should understand, however, that this is speculation and more research on auditory processing and hearing aid satisfaction is required.

18 Let's talk about remediation for a moment. What do you think about the computer-assisted remediation of APD?

As far as I know, there are two computer-assisted remediation programs available. There have been many claims about the success of these programs with children who have gone through the remediation process. There are also some powerful anecdotal stories told about individual children who have done extremely well. But anecdotal stories don't make good science, and there is accumulating evidence to suggest that the claims may be exaggerated.

My take on the situation is that the present remediation programs serve to show what may be possible in the future. Whether or not the current programs work, the profession should continue to investigate new, innovative programs for computer-assisted remediation.

19 Most audiologists don't seem too interested in APD testing. Why is this?

There are several factors, but I would include (1) the fact that few training programs incorporate the study of APD in their curriculum, (2) the uncertainty of what to do when one is finished with the test battery, and (3) audiologists' discomfort with problems of language, reading, and learning. Most of us made a conscious decision not to become speech-language pathologists, and APD is sometimes halfway up the staircase between SLP and audiology.

There are several other issues that also come to mind. First among them is the poor reimbursement most audiologists receive for their services in this area. Unlike other areas of audiology, the reimbursement for AP testing is abysmal.

Secondly, there are many remediation schemes floating around that have no scientific basis or construct. Parents are spending a great deal of money and having their hopes raised for no benefit. These schemes, offered by professions other than audiology, are a scam and discredit the entire endeavor.

Third, while there is excellent information available on the Internet, there is also a great deal of bad information. Parents and consumers need to be careful about what they read and believe, and audiologists have to be well-informed and diligent about correcting misinformation.

20 What are the greatest needs in APD?

I am a strong believer in the use of standardized measures to assess auditory performance, in any dimension. We spend a great deal of time in the literature discussing the science of our measures. We know precisely the percent increase in word recognition for every decibel increase from 0 to 24 dB HL in an articulation gain function, and we know exactly the mean and standard deviation of the latency of each wave of the ABR.

But, somehow audiologists have accepted tests of auditory processing that do not have normative data or utilize only cut-off scores. We don't know how the tests were normed, the demographics of the standardization sample, the mean of the sample and variance, the test-retest reliability, etc. In my opinion we need measures that withstand psychometric scrutiny, on a par with psychological tests and the best of the available speech-language measures.

We also need to develop better auditory-specific tests of auditory processing abilities. For example, psychoacoustic tests like differential thresholds for frequency and intensity might yield valuable information. Finally, we need more basic research using fMRI and electrophysiology to investigate both causes of APD and effects of remediation.

You regular readers of Page Ten will recall that, last year, Gail Chermak provided us with an excellent review of the current status of the evaluation and treatment of auditory processing disorders (APD). It's a topic that is worth visiting regularly, so here's a second edition.

If you attended the ASHA convention back in 1975, you would have heard Jack Willeford, a professor from Colorado State, talk about a battery of tests that he had developed for assessing APD in children. While the “Willeford battery” is seldom administered today, the notion of using sensitized speech material to assess auditory processing in children stuck with one audience member—this month's Page Ten author.

Robert W. Keith, PhD, is professor and director of the Division of Audiology at the University of Cincinnati Medical Center. A former president of the American Academy of Audiology, he currently chairs the academy's board certification program. As most of you already know, Dr. Keith's greatest audiologic interest lies in the area of auditory processing and its disorders. He supervises many master's theses and doctoral dissertations on APD, and teaches a distance-learning course on the topic for the CMU/Vanderbilt AuD program.

Even if you're a rookie in APD testing, I'm betting you've heard of a test for children called the SCAN (which, by the way, is not an acronym for anything). Thanks to Bob, we now have the SCAN-C (for children) and the SCAN-A (for adolescents and adults). And, if the sub-tests of the SCAN battery don't fit your needs, Bob also is the author of the Random Gap Detection Test and the Time Compressed Sentence Test (acronyms pending). And, there also is SCANWARE—software for the analysis and interpretation of SCAN-A and SCAN-C (which makes life much easier for the busy clinician). You can read about all these tests and software at his web site, www.capdtest.com, no doubt designed so that Dr. Keith can remember all his tests!

When Bob isn't concentrating on processing disorders, you can probably find him somewhere on a bike trail, enjoying his longtime outdoor love. Or, you might see him flailing away in the deep rough, since he says he's committed to learning golf.

In his review, Dr. Keith reminds us that regardless of what area of audiology we work in, we must always remember that ears are connected to a brain.

Gus Mueller

Page Ten Editor

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REFERENCES

1. Jerger J, Musiek F: Report on the consensus conference on the diagnosis of auditory processing disorders in school-aged children. JAAA 2000;11:467–474.
2. American Speech-Language-Hearing Association: Task Force on Central Auditory Processing Consensus Development. AJA 1996;5:41–54.
3. Silman S, Silverman C, Emmer M, Gelfand S: Adult onset auditory deprivation. JAAA 1992;3:390–396.
4. Hallgren M, Larsby B, Lyxell B, Arlinger S: Evaluation of a cognitive test battery in young and elderly normal-hearing and hearing-impaired persons. JAAA 2001;12:357–370.
© 2002 Lippincott Williams & Wilkins, Inc.