by Teri James Bellis
Auditory processing disorder (APD) is a deficit in the perceptual
processing of auditory information in the central nervous system.
According to the 1996 ASHA technical report on APD, the disorder is
characterized by poor performance in one or more basic auditory behaviors
or skills, including sound localization and lateralization, auditory
performance with competing or degraded acoustic signals, auditory
discrimination, auditory pattern recognition, and temporal aspects of
audition. APD can affect individuals of any age, from birth through
elderly, and it has been associated with difficulties in a variety of
communication and learning arenas. In fact, some estimates suggest that as
many as half of all children identified with learning disabilities and up
to 75% of elderly listeners may exhibit APD.
Yet, despite an extensive body of literature that dates back to the
1950s, the topic of APD continues to be shrouded in a veil of mystery and
misconception. Controversy still rages over how to diagnose and treat the
disorder, as well as the relationship between APD and learning, language,
and related difficulties. In some circles, there is even a question as to
whether APD exists as a viable diagnostic entity at all. This is likely
due to the heterogeneity of different types of APD, which precludes
demonstration of a direct one-to-one relationship between deficits in
fundamental auditory skills and learning or related difficulties across
large groups of subjects.
At the same time, awareness of APD is steadily increasing among the lay
population and those in other disciplines, and audiologists and
speech-language pathologists are being called upon more and more
frequently to address the disorder in their practices. As a result, many
clinicians are entering into the APD arena with little, if any,
educational preparation, leading to further misdiagnoses and
misconceptions about the disorder. Many clinicians are now providing APD
diagnosis and treatment services, and it is essential that clinicians who
provide APD diagnosis and treatment services do so accurately.
In response to this crisis, ASHA has recently convened a working group
for the purpose of updating the 1996 technical report to reflect current
conceptualizations of the disorder and its assessment, diagnosis, and
treatment. It is hoped that this document will be made available for peer
review later this year. However, clinicians hoping for simple answers and
cookie-cutter style procedural guidelines will be sorely disappointed. In
fact, as we learn more about auditory processing, it becomes increasingly
clear that, as with any disorder that involves the complex brain, there
will never be one simple solution to the APD puzzle. Nevertheless, there
are some general principles that guide the working group's
conceptualization of APD and the means of diagnosing and treating it.
First, it should be emphasized that diagnosis of APD falls under the
scope of practice of the audiologist. In collaboration with the SLP, who
has a different focus in conducting assessments, an effective functional
treatment and management plan can be developed for children with APD who
also exhibit speech and language concerns. Although one may find many
speech and language, psychological, and educational tests that include the
term "auditory processing" in their titles, these are not to be considered
diagnostic tests for APD. Instead, only those tests that exercise
sufficient acoustic control and have been shown to be sensitive to
disorders of the central auditory nervous system-while, at the same time,
minimizing higher-order confounds such as language, memory, cognition, and
related factors-should be used for APD diagnosis. The test battery used to
diagnose APD should include both speech and non-speech signals that assess
various processes and levels within the auditory system, and may involve
both behavioral and physiologic measures (see sidebar on page 23 for
examples). Further, because APD is a heterogeneous disorder that impacts
different people in different ways, the selection of diagnostic test
battery components must be individualized and appropriate for the child or
adult in question.
A second guiding principle is that interpretation of APD test results
should never occur in a vacuum. That is, in order to differentially
diagnose APD from other disorders that may have similar symptoms, it is
necessary to examine performance in other sensory modalities and
disciplines, as well as across a variety of auditory tests. It is not
enough simply to compare an individual's performance on a given central
auditory test against available normative data and determine whether the
overall score is within normal limits or not, as many different types of
disorders may affect performance on even the most controlled auditory
measure. Instead, audiologists should look for inter- and intra-test
patterns that support the presence of specific auditory deficits. For
example, the finding of ear differences on behavioral tests, hemispheric
differences on topographic physiologic tests, and inter-test and
cross-disciplinary patterns that correlate to well-established
neurophysiologic tenets provide evidence for a diagnosis of APD. On the
other hand, poor or inconsistent performance across all test measures and
the absence of neurophysiologically tenable patterns would more likely be
reflective of a global or higher-order attention, cognitive, motivational,
or related confound.
Therefore, to be fully competent in diagnosis of APD, audiologists must
have a working knowledge of the underlying science-including general and
auditory neuroscience, cognitive neuroscience, cognitive psychology, and
neuropsychology. However, education and training in these areas typically
does not occur in most university-based professional preparation programs
at present. As a result, those audiologists desiring to engage in APD
service provision may need to seek out additional educational
opportunities and study the pertinent literature in other disciplines in
order to provide optimal patient care in the area of APD.
Although the responsibility for APD diagnosis falls to the audiologist,
the full understanding of the functional ramifications of an individual's
APD and the development of a comprehensive management and treatment plan
requires multidisciplinary cooperation. SLPs, psychologists, educators,
and others collaborate in the overall assessment and intervention process.
Just as the diagnostic test battery must be individualized, so must the
management and treatment recommendations. A comprehensive intervention
plan for APD should include three primary components:
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environmental modifications designed to optimize the communication,
learning, and listening environment and improve access to auditory
information
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compensatory strategies that strengthen higher-order cognitive,
language, and related resources so that they may be recruited to
assist with comprehension and retention of auditory information
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direct remediation activities, usually in the form of auditory
training, that target specific auditory skill areas found to be
deficient
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The specific recommendations made in each of these areas will differ
depending upon the individual's unique pattern of symptoms and test
findings. Once again, there are no simple, cookie-cutter intervention
recommendations appropriate for all children or adults with APD. Instead,
the development of an intervention plan requires accurate diagnosis of the
auditory deficit(s), familiarity with the literature regarding auditory
neuroplasticity, interdisciplinary collaboration, and an inherent
appreciation and understanding of the functional difficulties exhibited by
the individual child or adult in question.
Although there is much that is known about auditory processing and its
disorders, much remains to be discovered. Recent advances in neuroimaging
and topographical brain mapping are helping us to have a better
understanding of how auditory information is processed in the brain, and
these findings will have a significant impact on our ability to diagnose
and treat APD more efficaciously.
Clinicians interested in providing APD services are encouraged to avail
themselves of the literature and continuing education opportunities on the
subject so that many of the misconceptions that fuel the continued
controversies may be dispelled and the focus can shift to where it is
needed most: accurate diagnosis and treatment of children and adults with
APD.
Teri James Bellis is an associate professor of
audiology in the department of communication disorders at The University
of South Dakota. She publishes and lectures extensively on the topic of
APD and is a member of the ASHA Working Group on Auditory Processing
Disorders. Contact her by e-mail at
tbellis@usd.edu.
