Introduction
In a previous article we considered Central Auditory Processing Disorder (CAPD) and its overlap with ADHD, and introduced some concepts for thinking about the relationships between these and similar learning challenges.
For the current article I've posed some questions directly to CAPD researchers, Drs. Frank Musiek and Anthony Cacace. We'll take a look at their responses. I'll also share a Symptom Overlap Checklist - a side-by-side comparison of behaviors associated with the two conditions - which clinical neuropsychologist Dr. David Kent uses in his work with students with ADHD and CAPD.
Modularity versus Nonmodularity (Huh?)
Dr. Frank Musiek , Professor of Audiology and Otolaryngology at the University of Connecticut , has suggested that many students have been incorrectly diagnosed with ADHD when they actually demonstrate a set of limitations best described by the term CAPD. He points out that while impairments associated with ADHD affect multiple domains, CAPD deficits are specific to auditory processing.
Dr. Anthony Cacace, associate professor of surgery at Albany Medical College , observes that one challenge for researchers is to determine whether CAPD and ADHD are separate and/or comorbid disorders, part of the same disorder, or mistakes in diagnosis. Dr. Cacace and his colleagues (2005) define central auditory processing disorder (CAPD) as a "modality-specific perceptual dysfunction that is not due to peripheral hearing loss" and that "should be distinguishable from cognitive, language-based, and/or supramodal attentional problems" (p. 113).
We addressed this issue of "supramodal attentional problems" in the previous article hyperlinked above, using the language "upstream" and "downstream" to discuss the sequence of cognitive events of which language and focused attention are a part.
As a neuropsychologist, I am particularly interested to know whether a student's limitations are with attention in general (suggesting an ADHD type symptom constellation) or are indeed specific to language. CAPD researchers are currently interested to know whether the human central nervous system (CNS) demonstrates modularity or nonmodularity , which in a nutshell seems to come down to the issue of whether a CAPD evaluation can "tease out" these issues of cognitive limitation in other areas "upstream" or "downstream" from central language functions.
Drs. Musiek and Cacace Respond
Below are some responses of Drs. Musiek and Cacace to questions about this clinical and research challenge.
Dr. Nowell: Dr. Cacace, your work makes reference to the "sensitivity" and "specificity" of CAPD screening. What are the practical implications for teachers and parents of sensitivity/specificity issues?
Dr. Cacace: When using auditory tests alone, in our view it would be very difficult to delineate between an auditory modality specific perceptual disorder (CAPD) from one that is much more complex and probably supramodal in nature (ADHD). Conceptually, we would view a test battery that uses auditory tests alone as being incomplete and the resultant diagnosis as being indeterminant.
Dr. Nowell : Dr. Musiek, one issue in the current academic literature is that of "modularity" versus "nonmodularity" of the CNS. What does that mean for parents and teachers of students who might have CAPD type limitations?
Dr. Musiek : At this point, not a thing. This is all theoretical and has no impact at all at this point. (However) if you are more interested see our discussion in last issue of American Journal of Audiology.
Dr. Nowell : When parents first come to the APD Clinic, what are some of their main concerns?
Dr. Musiek:
1. that someone can help their child
2. that the Professional really is qualified to do the evaluation &
recommendations
3. that the result will come back normal!
How one clinical neuropsychologist handles the ADHD/CAPD challenge
Dr. David A. Kent is a clinical neuropsychologist in private practice, working with students and families in central Massachusetts . He reports that a point of confusion for many families is the overlap among the various descriptive and diagnostic terms used by clinicians and educators.\
In his own psychodiagnostic work, Dr. Kent found it useful to develop the following chart for reviewing symptom overlap between the two terms CAPD and ADHD. He notes that, in reviewing results of neuropsychological evaluation with patients and families, and in preparation for report writing, he refers to the chart to sort out the key concerns of the specific family or student being evaluated.
Symptom Overlap in CAPD and ADHd
|
Symptom
|
ADHD
|
Capd
|
|
Aggressiveness
|
X
|
|
|
Decreased auditory attention
|
X
|
X
|
|
Decreased frustration tolerance
|
X
|
X
|
|
Decreased visual attention
|
X
|
|
|
Difficulty with transitions
|
X
|
|
|
Difficulty following directions
|
X
|
X
|
|
Diminished mental flexibility
|
X
|
|
|
Diminished motivation
|
X
|
X
|
|
Diminished memory
|
X
|
X
|
|
Diminished memory
|
X
|
|
|
Diminished memory w/ daily activites
|
X
|
|
|
Diminished self-awareness
|
X
|
X
|
|
Diminished social skills
|
X
|
X
|
|
Diminished verbal abstraction
|
X
|
|
|
Diminished Verbal IQ
|
X
|
|
|
Dislike for music and singing
|
X
|
|
|
Distractibility
|
X
|
X
|
|
Elevated activity level
|
X
|
|
|
Impulsivity
|
X
|
|
|
Impaired peer relationships
|
X
|
|
|
Sensitivity to overstimulation
|
X
|
X
|
|
Task avoidance
|
X
|
X
|
|
Withdrawn/sullen
|
X
|
X
|
Similarities and Differences
A review of the Symptom Overlap chart reveals the following behavioral similarities between students with ADHD and those termed CAPD:
- Decreased auditory attention
- Decreased frustration tolerance
- Difficulty following directions
- Diminished motivation
- Diminished memory
- Diminished self-awareness
- Diminished social skills
- Distractibility
- Sensitivity to overstimulation
- Task avoidance
- Withdrawn/sullen
Symptoms unique to ADHD include:
- Aggressive behavior
- Decreased visual attention
- Difficulty with transitions
- Diminished mental flexibility
- Diminished motor coordination
- Excessive motor activity
- Impulsivity
- Impaired peer relationship
CAPD-specific symptoms include:
Diminished verbal abstraction
Diminished Verbal IQ
Dr. Kent emphasizes that the Symptom Overlap checklist is a heuristic device, best used to guide the clinician to ask more, and better, questions. That is, this is not a diagnostic tool or a "test." He adds that individual students are unique and may not fall into the neat categories suggested by the columns in such a checklist. Dr. Kent has found, though, that this list of behaviors and problems helps him think through a families' chief concerns, leading them towards a clearer understanding of what obstacles are preventing academic success or age-appropriate skill development.
A neuropsychological model
A review of the differences as well as the symptom overlap between ADHD and CAPD reveals an interesting neuropsychological pattern. Specifically, ADHD is more likely to be associated with frontal or executive dysfunction - especially the motor expressions of that dysfunction - than is CAPD.
Behavioral examples of the executive dysfunction which is more suggestive of ADHD include blurting out before a question has been completed, difficulty waiting in line or otherwise tolerating delayed gratification, and difficulty self-directing to complete a task. Children with ADHD might impulsively engage in dangerous or inappropriate, usually with guilt or remorse afterwards.
A review of Dr. Kent's Symptom Overlap Checklist reveals the challenge experienced by neuropsychologists in clinical practice when faced with the ADHD vs. CAPD dilemma: many symptoms of the CAPD presentation can be accounted for by a brain-based, largely frontal lobe, attentional dysfunction (i.e., ADHD). And while CAPD is poorly understood at this time in terms of neurological substrate, a reasonable body of literature does offer the practicing neuropsychologist a coherent model for understanding the brain-behavior relationship of the ADHD symptom complex.
Dr. Russell Barkley (1998) has articulated a model of core deficits/impairments which give rise to the observable and problematic ADHD symptom complex. This model emphasizes the developmental importance of developing motor control and fluency . By these terms Dr. Barkley is including the mental (visual or verbal) representation of parental directives and if-then relationships which we use to bridge from present behavioral choices to desired future outcomes. For example, we inhibit most aggressive impulses in order to obtain (or avoid) some probable future outcome.
With neurological maturation of the frontal lobes, and with experience, we are able to make use of this type of "motor control and fluency" to manage our behavior, our mood, and our moment to moment motivation. Very young children, and students with ADHD, demonstrate specific difficulties with just this mental representation. They don't use self-talk or mental pictures to guide their behavior towards desired outcomes.
The current understanding of CAPD, however, does not propose these types of frontal (or "executive") deficits. These additional behavioral/self-management problems (over and above attention and concentration issues), then, might tip us off that we are dealing with a student with a more general attentional disorder (ADHD) than with a more specific language processing impairment.
Summary
Because of the availability of a coherent model and research base, many clinical neuropsychologists will examine a student carrying a CAPD classification with a view towards carefully ruling out the other prominent symptoms of ADHD. A student with the prominent CAPD symptoms who also demonstrates the impulsivity, hyperactivity, and other hallmarks of ADHD might best be characterized by the latter diagnostic term.
On the other hand, if these classic motor/behavioral manifestations of executive dysfunction are not striking, and if the student demonstrates the additional limitation of specific verbal weaknesses, the CAPD classification might be more appropriate.
Neuropsychological test data which might point in this direction include relative weakness on Verbal IQ and/or tests of verbal processing (higher- and lower-order) and abstraction.
The tendency to rely on the best current model for understanding brain-behavior relationships is conservative and appropriate, but is neither heroic nor "correct" in some fixed sense. As researchers and clinicians continue to communicate, and as our understanding of ADHD and CAPD sharpens, our choices of models for understanding the students with whom we work will broaden. And while details of "CAPD versus ADHD" and certainly issues of "nonmodularity" and "specificity" seem arcane - and removed from the work of most clinicians and educators - it is just this type of theoretical "tightening up" that will facilitate our best work with challenged students.
References
Barkley, R.A. (1998). ADHD: A handbook for diagnosis and treatment. New York : Guilford Press.
Cacade, A.T. (2006). Personal communication.
Cacace, A.T., & McFarland, D.J. (1998). Central auditory processing disorder in school-aged children: a critical review. Journal of Speech Language and Hearing Research. 41(2):355-73.
Cacace, A.T., & McFarland, D.J. (2005). The importance of modality specificity in diagnosing central auditory processing disorder . American Journal of Audiology. 2005 Dec;14(2):112-23.
Carter, L.S. (2000). Scrambled sounds. Dartmouth Medicine , 24:32-37.
Katz, J., Tillery, K.L. (2005). Can central auditory processing tests resist supramodal influences? American Journal of Audiology. 14(2): 124-7; discussion 143-50.
Musiek, F.E. (2006). Personal communication.
Musiek, F.E., Bellis, T.J., & Chermak, G.D. (2005). Nonmodularity of the central auditory nervous system: implications for (central) auditory processing disorder American Journal of Audiology. 14(2):128-38; discussion 143-50.
Rosen, S. (2005). "A riddle wrapped in a mystery inside an enigma": defining central auditory processing disorder. American Journal of Audiology , 14(2):139-42.