20Q: CAPD - Diagnosis and Intervention

From the Desk of Gus Mueller

We’re pleased to have Gail Chermak, PhD, back with us this month at 20Q, to continue the discussion on the topic of central auditory processing disorders (CAPD).  Dr. Chermak is professor of audiology and chair of the Department of Speech and Hearing Sciences, Elson S. Floyd College of Medicine, at Washington State University Health Sciences Spokane, Washington.  Among her many publications, she is best known for her two-volume Handbook of Central Auditory Processing Disorder, edited with Frank Musiek, now in its 2^nd edition—a must-have reference source for anyone involved with CAPD. 

In last month's 20Q, Dr. Chermak reviewed many of the fundaments of CAPD, and discussed some of the challenges in the management of this disorder, relating these concepts and research findings to our typical clinical practice.  This background information no doubt left many clinicians with the obvious questions of how do I screen for this condition, how do I diagnose it, and what treatment strategies are available once the diagnosis is made?   As you will see in this month’s 20Q, Gail answers all these questions, and offers clinical guidance including some intriguing thoughts regarding auditory training and neurorehabilitation.  Along the way she provides a sage assessment of the progress we’ve made in assessing and treating CAPD, and what we might expect to see in the future.

Gus Mueller, PhD
Contributing Editor
August 2016

 

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

20Q: CAPD - Diagnosis and Intervention
 

      Gail Chermak

1.  Thanks for joining me for another session.  Do you remember exactly where we left off?

Oh, yes.  In last month's 20Q, we finished up by talking about services in the schools.  I think you became a bit overwhelmed when within two paragraphs, I talked about the individualized education plan (IEP), the Individuals with Disabilities Education Act (IDEA), the ICD-10 classification (H93.25), the 1973 Rehabilitation Act (Section 504 plan of accommodations), and the Response to Intervention (RTI) approach.

2.  You’re right.  But let’s back up—as a clinical audiologist, how do I first identify CAPD?

Dichotic digits and gap detection (non-verbal or minimally language or cognitively loaded behavioral tests) are most frequently recommended to screen for central auditory processing disorder (CAPD). Some have recommended questionnaires; however, questionnaires generally are poor predictors of CAPD (Wilson et al., 2011). Questionnaires may be more appropriately used, however, to highlight concerns about a child, but not to determine whether a diagnostic central auditory processing assessment is warranted.

In addition to screening children, adults should be screened for CAPD when one or more of the following is observed: hearing difficulties despite normal hearing sensitivity; hearing complaints exceed expectations based on the pure tone audiogram; amplification benefit less than anticipated; and clinical observation or case history suggests possible central nervous system disease or dysfunction (e.g., head injury, dementia).

3.  How is CAPD diagnosed?

To be clear, the tests I just described are for screening.  If performance falls below normative cut-off values, then more comprehensive testing is conducted. CAPD is diagnosed on the basis of performance on a battery of auditory tests, which may include electrophysiological procedures as well as behavioral tests, administered under acoustically controlled conditions. The sensitivity and specificity of the behavioral and electrophysiological central auditory tests and procedures recommended for inclusion in the test battery have been established on patients with known lesions of the CANS. Electrophysiological measures can serve an important role in the objective demonstration of neural deficits in the auditory system, may be more sensitive than comparable behavioral indices, and can provide an objective measure of treatment efficacy. The test battery generally consists of two or more behavioral central auditory processing tests that are sensitive to the integrity of the CANS. Diagnosis requires failure in one or both ears, on two tests, beyond two standard deviations (AAA, 2010). The complexities and redundancies of the CANS require multiple tests to assess multiple processes, and levels and sites of CANS function. Musiek, Chermak, Weihing et al. (2011) reported that dichotic digits (DD) and frequency patterns (FP) comprised the most efficient test battery in adults with confirmed CANS lesions. Weihing, Guenette, Chermak et al. (2015) reported that FP and low-pass filtered speech (LPFS) were most commonly failed by children with CAPD, although including DD and competing speech (CS) in the battery benefited specificity. Given the relatively high linguistic load of LPFS, Weihing et al. recommended using DD and FP with children. Recommendations regarding the test battery approach can be found in ASHA (2005), AAA (2010), and Musiek & Chermak (2014).

4. Could you be more specific about the testing?  Exactly what tests should I order?

Tests with documented reliability, as well as sensitivity and specificity to known involvement of the central auditory nervous system (CANS) should comprise the test battery. The tests/test battery should: provide norms appropriate for the patient being assessed; assess several central auditory processes and behaviors that may be affected by the disorder, increasing the likelihood that the affected process will be measured (e.g., dichotic listening, temporal processing, recognition of degraded signals or signals presented in competition [i.e., monaural low-redundancy]); and evaluate the integrity of the CANS at multiple sites and levels. Patient symptoms and complaints should be considered in selecting the tests and processes to examine because they provide insights as to possible site(s) of dysfunction/lesion and demonstrate an individual’s auditory strengths and weaknesses, which is useful for planning intervention. Although not routinely used in the clinical diagnosis of CAPD, electrophysiological measures in combination with behavioral tests might lead to increased sensitivity to underlying CANS dysfunction and to greater diagnostic accuracy (Musiek et al., 2011). Electrophysiological measures are crucial in clinical situations where there is significant likelihood of neurological involvement (e.g., central deafness, post traumatic brain injury), or when behavioral results are inconclusive or incomplete due to the patient’s age, cognitive status, etc.

5.  And I use the same tests for children and adults?

The same tests may be administered to children (age 7 years and older) and adults under certain conditions. As I stated in response to your last question, appropriate norms must be available. Without appropriate norms, the test has no clinical utility. Moreover, we must be sure that the patient has the cognitive ability and language and motor skills to satisfy the task and response requirements to minimize the introduction of confounds. That said, tests employing nonverbal or simple speech stimuli (e.g., frequency or duration patterns, gaps-in-noise, dichotic digits) may be, under these conditions, appropriately used in both pediatric and adult test batteries.

6.  So it sounds like the screening tests and the diagnostic tests are fairly similar?

While some of our tests can be used both for screening and diagnosis, these tests were originally developed as diagnostic procedures. Unfortunately, research has lagged on the development of screening tests. Presently, dichotic digits and gap detection may be used for screening as well as diagnostic purposes because they pose minimal language and cognitive load and they are sensitive to dysfunction across CANS.

7.   It seems to me that CAPD is observed rather frequently with other developmental disorders in children?  Is this true?

Yes. The co-morbidity of CAPD and other neurodevelopmental disorders can be most easily explained on the basis of brain organization and function. Simply stated, perceptual, language, and cognitive functions rely on extensive networks of shared neurophysiologic and vascular substrate. Networks are nonmodular, temporally coupled, interfacing, polymodal or multisensory, overlapping, interconnected, and synchronized (Buschman & Miller, 2007; Musiek, Bellis, & Chermak, 2005; Price, Thierry, & Griffiths, 2005).

8.   So is CAPD also a precursor to cognitive decline in older adults?

From the seventh decade (age 60’s) and beyond, central auditory function may decline more that pure tone sensitivity or outer hair cell function (Gates, Feeney, & Mills, 2008b). Some have suggested that CAPD may be a precursor of cognitive impairment (Gates et al., 2008a, 2011). A number of mechanisms have been suggested to explain the relationship between CAPD and cognitive decline, including an aging brain in which widespread neural degeneration (e.g., corpus callosum demylenization) (Zaidel & Icoboni, 2003) and vascular changes (Willott, 1991) could impact either cognitive or sensory ability or both (Lin et al., 2013, 2014). Other explanations suggest the depletion of cognitive resources when a degraded sensory signal is sent to the brain, which may lead to increased neural resource allocation for auditory processing and may impact (or limit) the resources available for cognitive functioning.

9.  What exactly is the relationship between the auditory and cognitive systems?

The brain is organized around networks that are nonmodular, temporally coupled, interfacing, polymodal, overlapping, interconnected, and synchronized. A review of the published literature reveals that attention can modulate auditory processing; however, the literature also confirms that auditory processing is not completely dependent on attention. For example, selective attention improves perception of high-priority stimuli in the environment at the expense of other less relevant stimuli (e.g., cocktail –party phenomenon) (Golumbic et al., 2013). Stimulus-focused attention increases stimulus processing speed by increasing sensory gain as seen in a shorter latency of the auditory N1 event-related potential (Folyi, Fehér, & Horváth, 2012).

10.  So does attention then also play a role in central auditory processing tests?

Not to a great extent. Attention has relatively little effect on gap detection, as indexed by N1 amplitude, and gap detection can be observed during sleep, as indexed by a large P2 amplitude (Campbell & Macdonald, 2011). Gyldenkaerne, Dillon, Sharma, and Purdy (2014) reported the absence of significant correlations between sustained attention and masking level differences or the Gaps-In-Noise (GIN) test (Musiek et al., 2005). Similarly, Campbell and Macdonald (2011) reported weak correlations between sustained auditory attention, dichotic digits, and frequency patterns, accounting for only 8% of shared variance. Based on a factor analysis, Weihing et al. (2015) confirmed that central auditory processing tests load on separate factors, suggesting that unique variance is associated with each test, and that central auditory processing tests are not likely governed by one construct (i.e., cognition). Moreover, it is clear that CAPD does not merely reflect attention deficits. Abnormal performance on central auditory processing tests often occurs despite sustained attention within normal limits (Gyldenkaerne, Dillon, Sharma, & Purdy, 2014). These findings suggest that the extent of cognitive influence on central auditory processing is limited and that central auditory processing performance is not driven by cognition alone. The interaction between central auditory processing and attention may perhaps be best described as one in which a common factor contributes to performance on central auditory processing tests and tests of attention, while neither central auditory processing nor attention serves as the sole determinant of performance in the other domain (Musiek & Chermak, 2016).

11.  Once we have the diagnosis, what types of interventions are used to treat and manage CAPD?

Chermak and Musiek (2014) recommend a comprehensive, multidisciplinary approach to strengthen auditory and listening skills and strategies, provide compensatory methods to minimize functional listening deficits and promote efficient allocation of perceptual and higher-order (central) resources (e.g., language, memory, attention, executive control), and enhance signal accessibility through technology and environmental modifications. We recommend coupling of ‘bottom-up’ approaches, including auditory training and enhanced signal accessibility (e.g., using remote microphone technology), with ‘top-down’ compensatory approaches that harness language, cognitive, and metacognitive strategies. See Chermak and Musiek (2014) for extensive discussion of this approach.

12.  I will indeed check out that resource, but could you give me a few specific examples?

Of course—examples of auditory training include: speech recognition in degraded/competing environments, pattern identification, gap detection, glide discrimination/identification, and dichotic interaural intensity difference training (DIID). Parenthetically, many recall that Frank Musiek first introduced the DIID back in 1998 based on dichotic processing in adults with neurological lesions of the corpus callosum and in children with suspected maturational delays of these same regions (Musiek & Schochat, 1998). Cognitive and metacognitive approaches include focus on augmenting working memory, strategy training, and metamemory techniques. Language skill training includes semantic network expansion and contextual derivation of word meaning to build vocabulary and auditory closure skills.

13.   Metacognitive strategies? Language strategies?  I’m not even sure what these are, nor do I understand why they are in intervention programming for CAPD?

The auditory system is extensive and, as noted in last month's 20Q, overlaps the neural substrate of other systems. This shared neural substrate underlies co-morbidity and leads to complex clinical profiles. However, it also provides opportunities for intervention by a multidisciplinary team through several different ‘doors’. Allow me to elaborate— Metacognition refers to the active monitoring and self-regulation of attention, memory, listening, language, and learning processes to achieve some goal. Metacognitive control maximizes the efficient allocation of resources across sensory and cognitive systems (Pichora-Fuller et al., 1995; McCoy et al., 2005; Piquado et al., 2010; Tun et al., 2012). Listening in noise, particularly for an individual with a compromised CANS, requires a disproportionate allocation of processing resources directed to the auditory system (Sullivan et al., 2015). If we can buttress central auditory processing by strengthening metacognitive control (i.e., resource allocation) and language skills (e.g., build vocabulary that supports listening comprehension), intervention efforts are likely to be more effective.  In fact, the foregoing explains why a comprehensive approach to intervention for CAPD is likely to be more effective and efficient than a sole modality approach. But to be clear, CAPD is not a disorder of working memory, metacognition, or language; however, the interactions among central auditory processing, cognition, metacognition, and language processing provide considerable opportunities to buttress auditory skills and maximize the efficient allocation of resources.  

14.  What about cognitive skill building?

It is well understood that working memory organizes sounds that occur simultaneously and sequentially and as such supports auditory processing, listening, and music appreciation. Working memory underpins auditory localization/lateralization (Martinkauppi et al., 2000), auditory pattern processing (Zatorre et al., 2002), speech recognition in noise (Akeroyd, 2008; Salvi et al., 2002; Wong et al., 2009), dichotic listening (Jancke & Shah, 2002; Martin, Jerger, & Mehta, 2007), and indeed most all behavioral measures of the CANS. Working memory capacity correlates with the amplitude of cortical potentials (e.g., N100, P300) (Yurgil & Golob, 2013). Moreover, working memory modulates attention (de Fockert et al., 2001), promotes successful self-regulation (Hofmann et al., 2010), and shows strong correlations with academics, vocabulary, and listening and comprehension (Boudreau & Costanza-Smith, 2011). Strengthening working memory in individuals with CAPD should reduce the burden on the central auditory system and lead to improved listening.

15.  How effective is auditory training?  Does it really work?

There is a body of published reports involving both animal and human studies that substantiates both structural reorganization and functional improvement of auditory behaviors, as well as neurophysiologic representation of acoustic stimuli following auditory training (Krakauer et al., 2012; Ohl & Scheich, 2005; Recazone, Schreiner, & Merzenich, 1993). In fact, we recently published a review of these reports (Weihing, Chermak, & Musiek, 2015).

16.  That sounds like reasonable evidence.  So why have I heard some people say that auditory training doesn’t work?

Perhaps you’ve heard it doesn’t work because there are folks out there with an axe to grind? I’d prefer to think that you have heard such reports because the efficacy of auditory training is highly dependent on a number of factors that underlie neurorehabilitation. It has to be conducted correctly.  These factors include graded task difficulty presented through adaptive trials, timely reinforcement and feedback, intensive and cumulative practice, and of course, motivation, sustained attention, and emotional engagement.  Auditory training is intended to improve auditory deficits as identified by valid tests of auditory function in a targeted, deficit-specific manner.

17.  Does auditory training also improve language skills?

Although the goal of auditory training is not to improve spoken or written language or skills, improvements in auditory function may support improvements in those domains that are dependent upon audition. Hence, improvements in language skills may be an ancillary positive outcome of auditory interventions, particularly when the auditory training is used in combination with environmental modifications and central resources (top-down) training in a multidisciplinary fashion, as I recommended earlier based on current guidelines for CAPD intervention (Bellis, Chermak, Weihing, & Musiek, 2012).

18.  I would guess that there are computerized auditory training tools available?

Most certainly. There are several computerized auditory training programs and exercises available. CAPDOTS (CAPD Online Therapy System) and CIAT (Constraint-Induced Auditory Therapy) are both available for dichotics (binaural integration and/or binaural separation) training.  Sound Auditory Training^TM (SAT), a soon to be released web-based toolbox, provides auditory exercises designed to train a range of auditory processing skills in children, adults, and older adults with CAPD, as well as other clinical populations, such as patients with cochlear implants or language impairment, for whom auditory skills training is recommended to improve listening skills, communication, and learning (Chermak, Weihing, & Musiek, 2016). Clinicians with sufficient computer skills might use MatLab or Adobe Audition (formerly Adobe Cool Edit Pro) to develop measures of auditory skills.

19.   Looking at the big picture, what are some classroom management strategies audiologists might recommend to educators?

Many children with CAPD experience listening difficulties in the classroom and academic challenges due to auditory discrimination difficulties processing rapid spectro-temporal acoustic changes (especially in background noise) that may lead to poor speech sound representation, which has been linked to poor reading and spelling skills, as well as to difficulties in phonological awareness skills. Associated co-morbidities (e.g., ADHD, language impairment) exacerbate the challenge (Bellis, 2003; Kraus et al.1996; Tierney & Kraus, 2013). The following suggestions might be shared with teachers and parents to improve students’ academic success.

• Instructional modifications:  Pre-teaching or previewing material
• Use of computers/learning management systems: Post syllabi, notes, lectures/class presentations, and curricular resources to a school’s website or electronic blackboard and/or directly to a student’s personal storage device (e.g., tablets, cell phones)
• Message delivery modifications: Ensure listener’s attention, speak clearly, use appropriate level vocabulary
• Modify language:  Break long messages into shorter (5-6 word) sequences, add or emphasize connectives (‘tag’ words [e.g., first, last, before, after, if, then, etc.]) to enhance message salience and understanding (Ellis, 1989)
• Group auditory skills training to Develop all students capacity for listening in noise (e.g., teacher asks students questions about a story presented in noise, teach ‘active listening’ [including eye contact and posture])
• Learning accommodations: Consider use of a recording device (e.g., smart pen which digitizes notes and transmits them wirelessly to the students’  devices)
• Staff development: Train teachers on use of amplification systems (ALDs/HATs)

20.  You’ve devoted much of your career to this topic.  Are we making progress, and what do you see for the future?

Considerable progress! Research in auditory neuroscience, especially in the decades since President George H. Bush proclaimed the 1990’s the “Decade of the Brain,” coupled with extensive clinical research have increased our understanding of central auditory processing and its disorders, and advanced the diagnosis and treatment of CAPD. The inclusion of CAPD in the ICD-10 (diagnosis code H93.25), which went into effect in the United States on October 1, 2015, is a major milestone confirming that CAPD is indeed an accepted clinical entity that can be diagnosed and treated, leaving those who attempt to argue against the reality of the disorder and deny services to those affected by the disorder with little support. In addition to the inclusion of CAPD in the ICD-10, the U.S. Ninth District Circuit Court set precedent recently in ruling that children with CAPD are entitled to receive services in schools under the category of 'other health impaired' (OHI), and that audiologists are the professionals qualified to diagnose CAPD.

I am so excited to think about the future when we can identify and diagnose CAPD in children at younger ages and intervene with the most effective treatments during times of maximum neuroplasticity. On the other end of the spectrum, I am eager to see the unfolding of science that explores the relationship between ‘central presbycusis’ and the pathways that lead to cognitive decline and dementia in older adults. Both will be served by new tests and new approaches to assessing the CANS—and not only using efficient behavioral tests, but also auditory event-related potentials (AERPs) and imaging tools (fMRI, PET DTI) to allow audiologists to determine the integrity of the neural substrate underlying the behavioral task, as well as the neural substrate of the pathways responsible for generating the potentials (Musiek & Chermak, 2016). New testing (screening and diagnostic) approaches will provide powerful research and clinical tools—for example, recording AERPs while patients passively listen to (complex) stimuli used in behavioral central auditory tests and/or while the individual actually performs a central auditory test (Jerger et al., 2002; Palmer & Musiek, 2013, 2014). These same tools might become the standard measures to monitor treatment and outcomes. And, speaking of treatment, I look forward to additional, well-designed, clinical research to further document the efficacy and outcomes of auditory interventions in patients with CAPD.

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