Editor’s note: This is an edited transcript of an AudiologyOnline live webinar.
I want to begin with a scenario: a school-aged child presents at your clinic, and they have difficulty hearing and listening in the presence of background noise. You know there is an old adage in medicine that says, "When you hear hoof beats, think horses." So when most audiologists hear this complaint from parents or teachers, they automatically think that this is possibly a sensorineural hearing loss.
However, this child also has a long-standing inconsistency in responding to auditory information and difficulty following auditory information presented at a "typical" rate. The parents may have also noticed these behaviors since the preschool years, and the parents will talk about the fact that these things may be subtle, but they certainly seem significant for that child.
From our perspective as audiologists, we might go through a range of potential explanations and etiologies. If you look at some of the research on unilateral hearing loss, we might see some of those kinds of behaviors. We might look at either mild or high-frequency sensorineural hearing loss. Maybe we would consider a fluctuant conductive hearing loss. The other things that we may need to be aware of is the range of non-audiologic factors to be considered in a child like this, which might include attentional issues, cognitive impairments, and learning disabilities.
From an audiologist's perspective, this also presents a philosophical decision. Obviously, this child needs to have audiometric testing completed to assess their hearing status. Think about how many children were screened in schools whose hearing loss was actually missed. We have to consider the screening protocol, the screening environment, and the frequency of screenings (the grades the child in when the screenings occurred). If the child passes the hearing test, what does "pass" mean? If they have a "normal" audiogram, is your work done with this child?
This scenario is designed to introduce this presentation about school-aged children who may present with "normal hearing" per the audiogram. We will talk about the audiologist’s role in addressing both hearing and listening in children, which ties into Dr. Flexer’s presentation in this seminar series, The Auditory Brain: Conversations for Pediatric Audiologists about auditory brain development.
We are going to look at opportunities for assessment and management of these children. In the next hour, I hope to whet your whistle a little bit when it comes to talking about auditory processing disorders (APD) and the challenge we have in assessing both hearing and listening skills.
In children, we know that hearing is often assumed and generally overlooked. I would venture to guess any of you who have been in practice for more than a few years can go back and think of several children who were struggling in school, who had behavioral issues, and when they arrived at the audiologist's office and were diagnosed with a hearing loss and were given appropriate amplification, their school situation turned around. Unfortunately in those cases, hearing was assumed to be normal and not really assessed.
If that is true for hearing, it is even more true for listening, which is more subtle and complex. Dr. Flexer talked yesterday about hearing being a first-order event. I would address hearing and listening skills in the same way - they are a scaffold for other types of information processing such as language, attention, pragmatics, and of course, literacy.
Some thoughts to frame this presentation
An auditory processing disorder should be viewed as a disorder of the auditory system on the same continuum as hearing loss. There are a lot of people who do not believe in APD, and that is okay. It can be frustrating to look for a disorder that sometimes may feel like a needle in a haystack. I am going to ask you to do something very difficult; I really want you to think about a child's auditory system and try to believe in something you cannot always see.
Auditory processing disorders often present as part of a complex issue. Many audiologists shy away from this area because they want to be able to separate APD from other related disorders. That can be done. When looking at the life of a child, I describe children to parents as pies, and my job as an audiologist is to figure out what part of the pie contributes to hearing, listening and auditory perceptual issues. However, that does mean that there are not other things that could also be contributing, such as attention deficient disorder (ADD). There is research that talks about how we can look at the difference between APD versus ADD or attention deficit hyperactivity disorder (ADHD).
The other important thing we have to recognize is that APD often has a subtle presentation. We may not always see it in our testing in a sound-treated booth, which does not reflect most listening environments, including school. There are significant environmental variations presented to our auditory system on a daily basis. When you think about the wonder of our auditory system, how flexible it needs to be, how it has to accommodate in so many environments, it is really quite amazing. The last critical thing to mention to set the foundation today is that APD is low-incidence disorder.
Top down and bottom up processing
One of the basic premises to understanding the auditory system is the difference between bottom-up and top-down processing. While these are somewhat artificial differentiations, it is helps us frame some of the points in our discussion today. Bottom-up processing addresses how information is carried from the ear to the brain. As audiologists, we are looking at an entire system from the pinna to somewhere deep within the cortex. Peripheral hearing loss and auditory processing skills impacts all the information that is available to the person. So, information that is available to the person to ‘work on’ using top down processing is impacted by both peripheral hearing loss and auditory processing skills. Bottom up processing is generally in the purview of the audiologist.
Top-down processing refers to how information is acted on once it gets to the brain. One of my colleagues, Marcia Taber, described the auditory cortex as a "filing cabinet." Once the information arrives at the brain, how is it available for organization, retrieval, and categorization of information? Top-down processing often falls in the purview of the speech-language pathologist. While our perspectives may be different as audiologists and speech-language pathologists, we need to think about APD from an interdisciplinary perspective. I’m going to talk later about the American Academy of Audiology’s position statement on APD that came out in 2010, and one important take away from this statement is that as audiologists, we need to own the auditory system as the leaders on the APD team.
The concept of redundancy: Internal v. external
Another concept important for understanding auditory processing is redundancy. Intrinsic or internal redundancy is built into the auditory system both on the peripheral level and on the central level. We know that there are multiple representations in this very complex network, and there are many things that can influence the representations negatively such as tumors, demyelinating diseases such as multiple sclerosis, or head injuries.
Our historical view about APD was a "site of lesion" approach, where we thought we could pinpoint the location of the problem. However, we now know that both auditory development and specific auditory disorders, what Frank Musiek and colleagues refer to as “cerebral morphologic abnormalities”, are involved in auditory processing abilities in children, and they can influence what happens to the internal redundancy of the auditory system. So, if APD is really a brain issue, why can't it be located on imaging studies? One of the first things that we discovered in the APD research is that we were looking on a macro level, when much of auditory communication happens on the cellular level – the micro level - and we do not have great ways to measure that yet.
Additionally, much of our assessment is focused on the afferent, ear-to-brain auditory connection. However, one of the things that we know from the research (including looking at contralateral suppression data) is that the efferent, brain-to-ear connection is also very important. It is very possible that some patients we see have efferent disorders. Just because we cannot easily measure efferent disorders clinically yet does not deny that they exist. As an audiologist for 30 years now, I see a parallel between APD and auditory neuropathy. For years we saw children who presented with auditory neuropathy, but we didn’t have a name for it or a good understanding of what it was. It is very difficult to assess and manage something that you can’t wrap your arms around, as was the case for auditory neuropathy in the past, and is the case for APD today. In the near future, we will go through periods of discovery with APD as we did in the past with auditory neuropathy. One of the reasons I say this is because there are imaging studies that are now being done, such as fMRI, that demonstrate evidence of differences in the auditory systems of children with these kinds of disorders as compared to children with typically developing auditory systems. This was not possible with previous imaging studies.
Extrinsic or external redundancy refers to the redundancy that is built into the signal to which we are listening, such as in the syntax, morphology, semantics, pragmatics, etc. Extrinsic redundancy enhances our comprehension of the signal. We know that extrinsic redundancy can be impacted by a number of things such as a cognitive impairment or language impairment, or issues like environmental noise. For example, the presence of background noise can significantly impact the extrinsic redundancy of the system.
Some additional points to help build the foundation for today’s presentation include the fact that APD assessment requires an interdisciplinary approach as I mentioned earlier; it is not just the audiologist, although I believe we should take the lead in this area. In addition, there is not yet a cure for APD. While this may seem discouraging, consider that we also work with patients who suffer from tinnitus and sensorineural hearing loss, and our treatments such as tinnitus maskers and hearing aids do not cure those disorders either. Another issue that we have to resolve as a profession is how clinical significance and statistical significance are not synonymous. One of the most frustrating aspects of dealing with APD testing is trying to figure out how people develop their test batteries and what kind of statistical cutoffs we see. This is an area that needs more work.
Lastly, our current and future knowledge of auditory development and psychoacoustics will likely change the face of APD assessment, and this has already started to happen. For those of you who may have felt like APD testing is really just advanced language testing performed by audiologists, we will look at some of the assessment philosophies. Certainly this new knowledge will come from an evidence-based approach. I commend the American Academy of Audiology’s (AAA) position statement on APD (AAA, 2010) because it really focused on the different levels of evidence and presented the best evidence currently available, which also allows people who are going to be doing research in this area to be forward-thinking.
Listening in Children: Beyond the Audiogram
There are many considerations that we need to make as we study the auditory development in children. We know that the central auditory nervous system has one of the longest developmental time courses in the body. One of the things that we see in the course of auditory development is an improvement in listening in noise that continues to develop through approximately age 13. In addition, increases in myelination of the corpus callosum, important for transferring auditory information quickly between the two hemispheres of the brain, continue through the late teens.
Auditory processing is closely related to the science of developmental psychoacoustics, as well. We know that children, in general, have wider critical bands than adults. These wider bands allow more noise into the system, so children’s auditory systems are inherently noisier. Consequently, children do not perform as well in less-than-optimal listening environments. One of the challenges that we have is looking at what is developmental versus what is disordered in these children’s auditory systems.
Considerations and biases
The first bias is that audiologists have to "own" the auditory system. That is our job. My other bias is that not every audiologist has to do formal APD testing; however, every audiologist needs to know how to screen for APD and how to facilitate appropriate referrals. Remember that this is a low incidence disorder, and as audiologists we need to own the auditory system and to be essential in the lives of these children.
To illustrate this point, I’m going to share a story with you. I work on an amazing interdisciplinary team with several physical therapists, occupational therapists, speech-language pathologists, dieticians, and others. Last week we had a parent who came in with her toddler, who had a history of chronic middle ear pathology and was struggling to process information. During the case history, the mother spent a lot of time talking about the child’s bowel function. It got to the point that everyone in the room was wondering where the conversation was going.
We finished the assessment, and the child’s auditory processing skills looked good, and hearing was normal on an audiogram. When we went to talk to the mother, she said, "Well, I'm a little confused, because our occupational therapist spent a lot of time talking about middle ear pathology impacting the pathway that runs from the middle ear to the large intestines."
It reinforces the point that if we are not willing to be the ones to at the very least say to the parents, “This isn’t auditory processing disorder” and facilitate appropriate recommendations, they will search and shop for other professionals who do not have the same knowledge that we have as audiologists.
Another consideration is the audience to which we are directing our diagnosis. You may be in an educational setting. If you are in a medical model, you may choose a different type of test battery and reporting. We see a lot of adults in our clinic following motor vehicle accidents or traumatic brain injuries, and we may have a different perspective for them in terms of what we do or recommend, than if we know the audience is in an educational setting.
APD: Definitions and descriptions
Psychoacoustics may be viewed as one of the underpinnings of auditory processing. One definition of APD is based on this philosophical construct. In Great Britain, they are moving away from the model of APD that is similar to the United States’ model, and looking at a different kind of model. Currently, they define auditory processing this way: “APD results from impaired neural function, and is characterized by poor recognition, discrimination, separation, grouping, localization, or ordering of non-speech sounds. It does not result solely from a deficit in general attention, language, or other cognitive processes (British Society of Audiology, 2011).” This is an interesting viewpoint, because it frees us in some ways, and it challenges us in others. This means that when we are looking at auditory processing assessment tools, we have to make sure that we take some of that non-speech sound information into account.
One of the other aspects of that though is that we have to be aware that when we’re looking at this there is a correlation of processing of non-speech information in the auditory system and generalizing to the larger issue. We don’t have time to review Erber’s hierarchy, but it is one of those things that guides how I make decisions about children I see, regardless of diagnosis. I try to look at detection, discrimination, comprehension and identification as being included in a test battery, whether the child has hearing impairment or APD.
A basic functional definition of APD is as follows: “APD is a breakdown in auditory abilities resulting in diminished learning (e.g. comprehension) through hearing, even though peripheral hearing sensitivity is normal.” By "normal," I mean detection at 15 dB HL or better.
The AAA Clinical Practice Guidelines (2010) states that APD is: “…associated with a number of behavioral manifestations and a variety of symptoms, some of which may be quite subtle.” It also includes, “The processing of auditory information within the central auditory nervous system (CANS) is…complex, involving both serial and parallel processing within the auditory structures of the CANS itself, as well as shared processing with other sensory and/or higher order brain structures and systems (e.g. language, attention and executive control).” This means that the central auditory nervous system has to multi-task.
The AAA position statement also talks about the fact that behaviors, symptoms, and the level of impairment observed in individuals with APD are very diverse and heterogeneous. The brain is not compartmentalized, and there is significant interaction between auditory areas and areas responsible for other types of issues in the brain. An auditory processing disorder may have a significant impact on another type of skill, such as language processing or attention.
I've been interested in auditory processing since I was an undergraduate, and in grad school at Michigan State University I had coursework and clinical experience in APD that whet my whistle for the next 30 years of interest in this area. When I was first an audiologist, I was confused about why we didn’t see APD as separate kinds of disorders. It wasn't until I started looking at the greater neurology and learning more, that I understood some of the issues related to the fact that the brain isn't compartmentalized. We need to recognize that an auditory processing disorder may have a significant interaction or impact on other skills such as language processing and/or attention.
Dennis Phillips has published several articles related to auditory processing disorders and the central auditory nervous system. He talks about the fact that there are generalizations of behavior and expectations that we have about sites of lesions (Phillips, 2002). He explains that it is hard to generalize APD, because the auditory system is very idiosyncratic and most auditory processing disorders do not have origins that are identifiable at a structural level. If we are looking for an explanation such as a demyelinating disease or a very specific tumor, those cases are rare. Phillips (2002) also explains that brains are individualized, and whether APD is developmental or acquired, a central auditory nervous system pathology does not respect functional neurological boundaries. It presents very differently in different individuals.
Some of the early descriptions of auditory perceptual difficulties included impairment in phoneme recognition and discrimination, a defective capacity for storing a spoken message, or impairment in processing speech at “normal” rates. Many people think about APD as a deficit in understanding speech in noise. That is not the only aspect of this. It is much more multifaceted than that. When building a test battery and contemplating remediation, many other factors have to come into play also.
Prevalence of APD
I previously mentioned that APD is a low-incidence disorder. According to Chermak and Musiek (2007), about two to five percent of school-aged children are estimated to have APD. The etiology is not clear; however, this is not unique to auditory processing disorders. It is also true for attention deficit disorders, learning disabilities, and other types of issues that can impact learning in children. One of the things we've gotten more sophisticated at in our clinic is looking at the concept of delay versus disorder. It’s important to define what kinds of things we would look at in terms of monitoring a child over time versus those that we would consider a disorder of the auditory system. I'm going to talk later about the seven-year-old cutoff that we use for thinking about that and making clinical decisions.
In our clinic, we believe that assessment begins before the child even arrives at our office, and we typically begin the assessment on the telephone when the family calls to make an appointment. We ask many questions, such as the age of the child. The current literature suggests that age seven is the earliest age for formal assessment of APD. But what about parents who have a concern about their child who is younger than that? There is value in early assessment, and we have to define the audiologist’s role in this capacity.
We often hear that parental concern is one of the first indicators of hearing problems for children who may have passed a newborn hearing screening. However, parental concern must be validated by audiologists also. We find that sometimes when we talk with parents, even of children younger than seven, they say, "We've mentioned this to the pediatrician," or, "We're really concerned about our child's hearing." One of the important roles we have as audiologists is to put the parents’ minds at ease. We can let them know, "Yes, their hearing looks like it is developing typically. They look like they are doing great things. But we do want to monitor their progress."
We also have to recognize that there is tremendous variability in listening behavior in very young children. We have to look at the fact that the auditory system development varies across children, and if a child is on the low end of development, are there things we can do to help bring that development along? Are we prepared to help parents know a little more about reading to their child or rhyming games or things that they might do during that preschool time? We need to be comfortable in making an assessment regarding development versus disorder in the pediatric population.
When the family calls to make an appointment, we also ask about cognitive ability of the child. In our clinic, we have decided that we will only see children with typical or normal cognitive abilities. That is a tough call, because we know that with IQ testing, depending on the IQ test used, verbal IQ can really skew the results, especially for a child who has high performance IQ and low verbal IQ. There’s also the issue of psychologists and how they might assess children and what information we might ask from them, and that is a talk for another day. We like to have any reports from the psychologist prior to the child arriving for testing. The other factor on which we disqualify children is if they carry the diagnosis of autism spectrum disorder (ASD). If a child has an ASD, we do not assess them for auditory processing. We look at the criteria for learning disabilities. We look at the language bias and IQ testing, and we look at who the referral source is.
We also try to get a handle on functional behaviors. Not everyone has the opportunity of making an in-person functional assessment in the classroom or interviewing the teacher face-to-face. That is why we look for authentic assessment tools. One that we use frequently in our clinic is the Children's Auditory Performance Scale (CHAPS; Smoski, Brunt, & Tannahill, 1998.) The SIFTER (Anderson, 1989) and the school age SIFTER also provide a lot of good information. We use Fisher’s Auditory Problems Checklist (Fisher, 1976) from time to time as well. All of these tools are available online at no charge, and you can visit www.edaud.org for additional information about these tools.
The critical point here is that the audiogram does not tell the entire story. However, when APD is suspected, an audiologic evaluation must first be performed. Speech-in-noise difficulties also have to be addressed. We perform speech testing in noise routinely with adults using tools such as the QSIN, HINT and SPIN. In our clinic, we wouldn’t communicate results to an adult patient without first doing some real-world assessment and the same goes for children. The Bamford-Kowal-Bench Speech-in-Noise test (BKB-SIN; Etymotic Research, 2005) is an outstanding tool that can be incorporated into your test battery for children.
We are not going talk about the various APD tests today. One of the recommendations that I would make to you if you are building an APD battery is to be familiar with the significant number of tests currently available. I would also encourage you to examine the normative data on the testing and look at what is psychometrically sound and what is not. Build your test battery based on who your audience is, the population that you see and on the skill areas that you are interested in looking at. The ASHA position statement (ASHA, 1996) has a lot of ideas about specific skill areas, and that's one way to build a test battery. I think it is also important to vary linguistic loading or linguistic demand between very low linguistic demands to very high language demand. There is no cookbook for this.
The AAA guidelines indicate that although APD requires interdisciplinary input, other types of tests, such as speech/language or psychological tests, cannot be used to diagnose APD even if they have the word "auditory" or "auditory processing" in the title. There are a number of these tests that are used including one called the TAPS, the Test of Auditory Perceptual Skills (Martin & Brownell, 2010). However, there is a certain level of control that needs to be applied when testing for APD. Audiologists have the ability to control the test environment, stimulus parameters including speed and intensity and high frequency versus low frequency, and the test parameters.
There is controversy that needs to be considered. One of the great questions is, is there difference between language processing and auditory processing? As I've mentioned before, sometimes linguistic loading can provide insight to this question.
APD assessment options
There are many formal APD assessment tools that can be used clinically. The newly-updated SCAN-3 (Keith, 2009) is available from Pearson Publishing. This test includes the original SCAN, with new additional testing, a screening versus diagnostic battery, child and adolescent/adult versions, and new normative data. If you just want to get your feet wet with APD testing, this is a wonderful screening tool that can be completed in a relatively short period of time. Bob Keith has done an outstanding job of addressing the criticisms of the earlier versions of the SCAN in development of this new version.
The LiSN-S (Cameron & Dillon, 2007) is a spatialized noise test available from Phonak. They have had success with it in particular in Australia and New Zealand. It is easy to administer, and I have been pleased with some of the results. I'm not sure if it is looking at just speech in noise or a more globalized APD issue, so I think it needs some additional information, but the information you get from a functional behavior perspective is very good.
The Multiple Auditory Processing Assessment (MAPA; Schow, Seikel, Brockett, & Whitaker, 2007) is available from Auditec of St. Louis. This test was developed to identify auditory processing disorders for children age eight through adults and is set up into five different subtests. The MAPA uses auditory skills in three of the ASHA domains: monaural low redundancy, auditory pattern temporal ordering, and binaural integration/binaural separation.
The Gaps in Noise test (GIN; Musiek, Shinn, Jirsa, Bamiou, Baran, et al., 2005) is based on psychoacoustic literature for gap detection and is very similar to the British model. It looks at the maturation of a very specific skill: the temporal or time demand. It is appropriate for children age seven years and older and is easy to administer. One of the other advantages is that it requires low cognitive demand.
There is also an Auditory Skills Assessment (ASA; Geffner & Goldman, 2010) available from Pearson for three-and-a-half to seven-year-olds. It includes tasks such as speech discrimination in quiet and in noise, phonological awareness, non-speech processing, and mimicry. We have used the ASA on approximately 30 - 40 children so far and really have been pleased with how it correlates to what the speech-language pathologists and parents are asking about. We do not make a diagnosis of APD based on this test alone, but we can look at some at-risk skills and make recommendations of things that families can do to boost the child's learning opportunities.
Electrophysiologic assessment for APD is something in which the majority of pediatric audiologists may be uncomfortable. It is certainly different than an ABR to estimate hearing. The pros of electrophysiology are that it bypasses language processing, so all those arguments about linguistics are gone. It maintains a specific focus on the auditory system, and it may be a unique measure of system and improvement, which we will talk about shortly.
The cons are: It lacks a functional link, it is speculative; it is based on a site-of-lesion or disease model; it may not be specific enough to address issues on a cellular level; and, the cost of the testing may outweigh the benefit of the information obtained.
Interestingly, a lot of the early position statements on auditory processing focused on including electrophysiology as part of the standard test battery, and now they have backed away from that a little bit, at least in considering AAA’s 2010 position statement. This statement points out that there may be limitations to available equipment, and that it may only be available in a laboratory setting. The recommendation is to define clinical situations where there are clear indicators for auditory evoked responses tests. These may include situations where behavioral assessment fails to demonstrate a clear pattern of deficits, where neurological disorder is suspected, or to perform a site-of-lesion assessment.
One of the strategies that underlies the value of electrophysiology in the functional listening world is what is called the BioMARK, or biological marker of auditory processing. It originally was introduced as BioMAP and is a sub-test in the Biologic EP system. It came out of the research at Northwestern where they used speech stimuli to assess neurological processing of sound. One of the great things is that it differentiates between children with certain types of APD and children who do not have those types of APD. It also allows us to monitor progress objectively using electrophysiologically in conjunction with aural rehabilitation programs that are designed for APD. Additional information regarding BioMARK can be found at http://www.soc.northwestern.edu/brainvolts/projects/clintech/biomark/faq.php
Linking Assessment to Management
The basic things we will look at in terms of management are environmental modifications, compensatory strategies, and direct intervention. One of the important questions that we have to ask is, “How does noise affect a listener's perception of speech?” Noise has a significant detriment on the perception of consonant sounds. Because consonants carry the meaning of speech, if a child has a breakdown in the auditory system and a breakdown in the extrinsic redundancy, we consequently have some significant issues of listening and learning in that environment.
The acoustical condition in a given listening environment can be challenging for any listener, but it is most remarkable for those who Carol Johnson describes as "high risk listeners." These are children who are both on a continuum of peripheral and central hearing losses.
One of the common solutions often recommended to enhance the listening environment is preferential seating. It is inexpensive, easy, and has face validity. It makes sense that if you reduce the distance between the speaker and the listener, a more favorable listening situation results.
However, if you want the best argument against using preferential seating, particularly for kids who are high-risk listeners such as those with APD, the only true preferential seat is about six inches away from the speaker's mouth (Leavitt & Flexer, 1991). That is a really unfortunate situation, because most kids do not like their teachers that well, and six inches is a little too close for most teachers, even if they love the children they teach!
One of the things we can consider is sound-field amplification, and some people get really crazy with this and want to have sound-field systems in every classroom. One of the important things to know is that sound-field amplification is that it is not a substitute for good acoustical treatment. It is very beneficial if the major issue in the room is ambient noise, and it can also offset the effect of distance, but it is not effective if the underlying issue is reverberation. In some cases, it can make the situation worse if the child is not close to the speaker (Boothroyd, 2004).
There are a number of great sound-field options available, including:
(Simeon, http://fmhearing.com) and a new option, Phonak’s Dynamic Soundfield system.
I particularly like the Simeon system by Supportive Hearing Systems. It sounds incredibly clean. Although this is not intended as a commercial for Phonak, we have been installing the Phonak Dynamic Soundfield systems, and I have to say that teachers love the system. The quality of the sound that comes from it is quite amazing, in my opinion. For a very small system, it has a lot of power, and it is on the Phonak’s dynamic digital platform.
One of the things that we know from Arthur Boothroyd (2004) is that the most effective way to enhance and optimize speech audibility for a child with a hearing loss of any variety is through the use a personal FM system. We know that FM can enhance the signal-to-noise ratio up to 15 dB for the child farthest from the teacher, so it addresses both the issues of proximity, (the six-inch distance to the speaker) and noise.
For kids with APD, we frequently use the iSense personal FM product by Phonak because we have had good success with it. It adapts the volume automatically based on the presence and intensity of the background noise. The output also stays within safe limits for these children who have normal peripheral hearing. Additionally, school districts have been more willing to purchase this after a trial period for child with APD. While I am aware that this kind of technology assistance does not fall under IDEA or state guidelines, when we start thinking outside the audiogram box it also frees us to talk about the educational impact of APD, and we have had good success and great feedback from teachers with this specific product.
I want to spend a few minutes talking about direct therapeutic approaches. There is recent evidence that supports the impact of auditory training on neural plasticity. In turn, changes in neural plasticity actually build on changes in functional auditory behaviors.
Dennis Phillips (2002) points out that changes in the auditory cortex representing the neural plasticity of the system are seen as a result of behavioral training. This has been well-documented for decades in animal models. Cynthia Thompson (2000) talks about "representational plasticity" of the central auditory nervous system, meaning that we are engaging new growth in neural networks post-treatment. That should be our goal.
Some of the best evidence for changes in auditory function related to environmental changes and experiences are from children and adults who have received cochlear implants. Anu Sharma and colleagues (2004) talk about the fact that improvements in communicative behaviors following implantation appear to be positively influenced by the rate of plastic changes in the central auditory pathways.
Some of the problems with many listening programs is that they are copies of things out of books that are very generalized, they are not specific for the individual child, and they do not adjust to the learning style. Two of the key words for all of us to keep in mind when it comes to neural plasticity are: Adaptive and challenging. The way we capitalize on treating auditory processing is making sure that we are always adapting the program so that if it is easy today, it is harder tomorrow.
I heard a personal trainer talking about the reason people fail at exercise is because they go on an exercise program and do the same exercises over and over again, and they do not get any results. A lot of what we have seen in the past with APD is similar. The programs were not really challenging or adaptive for the child, and then we thought that these programs were ineffective. Now we know better, so we can do better.
The Listening and Communication Enhancement (LACE) program available from Neurotone.com, was developed to address listening deficits in adults with peripheral hearing loss (Sweetow & Henderson-Sabes, 2004). We have used this program in a number of older children and teenagers to prime them for higher-level listening. LACE is inexpensive at roughly $100.00. It has to be done in a certain time period, however, because there is a critical period we are working with for language learning and auditory processing. If we are going to capitalize on the brain’s auditory plasticity, we have to do it very intensely within a certain time period.
There are currently two programs that we have used in our clinic for dichotic listening. One is dichotic interaural intensity difference training (DIID; Musiek, 2004), and the other is the Aural Rehabilitation for Interaural Symmetry (ARIA; Moncrieff & Wertz, 2008). The DIID aims to strengthen the less-dominant ear. We have had a positive experience with the ARIA, although it is not commercially available yet. Those kinds of programs take into account all the needs that we have with neural plasticity: to be adaptive, to be challenging, and to give positive feedback.
The first of several compensation strategies is environmental modifications. While environmental modifications may sound like common-sense approaches to you as an audiologist, they truly do have impact for kids in the classroom.
Friel-Patti, Finitzo, and Freeman (1993) talked about the fact that comprehension is dually the responsibility of the listener and the speaker, and when failure occurs it is as much the responsibility of the speaker as the listener. The speaker’s rate, pausing, phrasing, prosody, and predictability are all factors that can enhance or degrade communication. When I have presented this concept to teachers, many have told me that they’ve never thought about that before.
When asking a child with APD what makes listening difficult in the classroom, they often talk about things like the teacher’s voice and how it sounds like Charlie Brown’s teacher or how the blinds rattle in the windows. These things significantly impact their ability to hear clearly. These things can be addressed by environmental modifications, not just by changing the direct auditory system or by use of an FM system. It is also important to recognize that teachers are public speakers, and clear speech is important when addressing students.
I’ve included some other examples of environmental modifications and compensation strategies in your handout.
Some audiologists indicate an interest in looking at APD in adults that have a known injury such as a stroke or traumatic brain injury, but shy away from the developmental aspects of the disorder in children. If we're going to be essential in meeting the needs of children and their families, and making audiology essential to patient care on a global perspective, looking at APD is critically important, particularly for patients who have normal hearing acuity.
I often see children who come in wearing hearing aids who will say they don’t want to wear them, but many of the children I see with APD don't baulk at using an FM system. They will tell me how much it helps them, how excited they are, and how they want the assistance it offers them.
I also hear APD referred to as something new or ‘vogue’. If we look back on the literature, Mykelbust defined central auditory processing disorder back in 1954, and the information on APD in children grew in the 1970s.
Whenever in doubt, we come back to a quote by Jerger. He talks about the fact that: “The reality of CAPD can no longer be doubted.” He goes on to say that: “It is a distinct entity across the entire age range. It appears to derive from at least two analogies of auditory perception--loss in the ability to separate auditory foreground from auditory background and failure of the fine temporal resolution necessary to the analysis of speech…” (Jerger, 1998).
So, when we, as audiologists, can move beyond the audiogram, we can meet the needs of our patients and their families and contribute to the development and success for each child.
Question & Answer
From a testing point of view, how do we deal with kids with sensorineural hearing loss who we know clinically must have something in addition to the hearing loss when we look at their auditory skills?
That's a really tough question, and one of the things that I think we have to get better at is developing normative data on what the typically-developing hearing-impaired kids look like when it comes to things we know that are developmental skills like temporal processing and speech in noise. The BKB-SIN should just be the first of many tools, and it has great normative data for children with hearing loss, but I think we are just kind of behind on that.
Depending on the degree of hearing loss, we can expand our reach a little bit with the SCAN-3 or the ASA, but it is truly a tough area to assess at this point in time.
Have you had any experience with music-based auditory stimulation?
Yes, we have some experience with that, and it's generally the occupational therapy programs that bring that in. If we look at some models that we are being used with tinnitus, research suggests incorporating music into in those programs. However, we haven't found any programs that correlate strongly with the use of music and APD specifically.
Can a speech-language pathologist use the Auditory Skills Assessment for informational purposes?
Yes, I believe that you could use that for informational purposes. It very similar to the original SCAN test battery, and I think it is a really nice complement to some of the things that an SLP might be doing. The only caveat on that would be to make sure that you have some control over the level at which the test is presented and the quality of the headphones you use. Some of the ASA is not performed under headphones, so the intensity level and the testing environment is very important.
Is it true that if a child has been diagnosed with ADHD, that they could not be reliably diagnosed with APD?
I don't believe that's true. We see children all the time who have been diagnosed with ADHD, and there is a perception among teachers that even a child who is well-controlled with ADHD still has something else going on. A lot of that does depend on how the child is managed. One of the things in this country that we don't do well is medication management for kids with ADHD. We find our best success is with children who have been monitored or followed by psychiatrists, not pediatricians or prescriptions.
As an early interventionist, I see a lot of children diagnosed with agenesis of the corpus callosum. Is there any information that can be given to parents of these children?
There are a couple of good things on that specific topic. These are kids who I think are really tough to work with, but certainly improving the listening environment is key. These children need a controlled listening environment with a lot of repetition. They require a lot of information related to expanding auditory information, such as rhyming, for example.
Note: Please refer to the handout from the presentation (available as a download with this article) for a full list of references used in the slide presentation. The references listed here were mentioned, but several others appear in information on the slides.
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