DIAGNOSIS AND MANAGEMENT
CENTRAL AUDITORY PROCESSING DISORDER
Part II: Assessment
Gail D. Chermak, Ph.D.
Washington State University
The brief article below is
the second installment of a three part series of brief articles by Dr. Chermak
on central auditory processing disorder.
Given the heterogeneous nature of central auditory processing disorder (CAPD)
and the range of listening and learning deficits that often coexist with CAPD,
comprehensive evaluation requires a multidisciplinary team approach. CAPD is
diagnosed by the audiologist on the basis of an extensive audiologic evaluation.
Additional evaluation of language development, speech understanding and learning
is necessary, however, to identify associated (co-morbid) conditions, as well
as clarify the functional impact of CAPD. Speech-language pathologists, psychologists
and educators contribute to this more comprehensive assessment. Speech-language
and psychoeducational assessment of children with CAPD is beyond the scope of
this article. Rather, a minimum test battery for diagnosing CAPD is outlined
Behavioral tests are most
commonly used to assess the auditory system. Electrophysiological (e.g., auditory
brain stem response and middle latency response) and electroacoustic (e.g.,
immittance measures and otoacoustic emissions) tests are more objective (i.e.,
less influenced by extraneous factors); however, they are more time consuming
and expensive and are not as widely used at this time. Neuroimaging, a third
approach to assessment, offers great promise as a tool that will someday be
useful in the clinical assessment of auditory system structure and function.
At this time, diagnosis of CAPD is based on the outcomes of behavioral tests,
supplemented by electroacoustic tests, and to a lesser extent supplemented by
Behavioral assessment begins
with a basic audiologic evaluation consisting of pure-tone audiometry, immittance
measures, and speech recognition testing. Otoacoustic emissions is a strongly
recommended component of the basic evaluation. While the presence of mild-to-moderate
peripheral hearing loss confirmed by the basic evaluation does not preclude
evaluation of the central auditory system, care must be taken in selecting central
tests and in interpreting outcomes in the presence of peripheral hearing impairment.
Evaluation of central auditory
processing requires administration of multiple tests spanning the processing
categories delineated in the first article of this series. This provides information
as to the nature of the CAPD (i.e., which processes are deficient) and guides
intervention planning and implementation. The author recommends that a minimum
test battery for assessment of central auditory function include at least one
measure from each of the following categories: 1) temporal processing (e.g.,
pitch or duration pattern perception, gap detection); 2) binaural integration
(e.g., dichotic listening for digits or words); and 3) monaural low-redundancy
speech recognition (e.g., filtered or compressed speech, speech in competition).
The audiologist diagnoses CAPD on the basis of test outcomes. Because these
tests employ different tasks to measure different auditory processes, subjects
may perform unevenly across tests. The audiologist must determine whether the
overall profile confirms CAPD. Diagnosis of CAPD on the basis of one failed
test score should only be made if that score is at least 3 standard deviations
below the mean performance for the subject's peer group. In such cases, it is
helpful to re-test the subject to ascertain the reliability of that measure.
Visit the American
Academy of Audiology and the American
Speech-Language-Hearing Association web sites for additional information
and/or to locate an audiologist or speech-language pathologist in your area.
Academy of Audiology
8300 Greensboro Dr., Suite 750
McLean, Virginia 22102
10801 Rockville Pike
Rockville, Maryland 20852
Gail D. Chermak Ph. D.,
is an Edward R. Meyer Distinguished Professor of Audiology and Chair of the
Department of Speech and Hearing Sciences at Washington State University. She
earned her doctorate in speech and hearing sciences from the Ohio State University,
holds the Certificate of Clinical Competence in Audiology, and is a fellow of
the American Academy of Audiology.
Dr. Chermak chaired the
ASHA Ad Hoc Committee on Central Auditory Processing which prepared the 1992
report entitled, Issues in Central Auditory Processing Disorders. She served
as a member of the ASHA Task Force on Central Auditory Processing Consensus
Development responsible for the 1995 report, Central Auditory Processing: Current
Status of Research and Implications for Clinical Practice. She was among 14
senior scientists and clinicians who met recently at the University of Texas
at Dallas (the Bruton Conference) to reach consensus on best practices in diagnosis
of auditory processing problems in school-age children.
Dr. Chermak has published
articles and delivered numerous workshops on assessment and management of central
auditory processing disorders. Her co-authored articles on central auditory
processing disorder and attention deficit hyperactivity disorder have been named
by her peers as among the best in diagnostic audiology for the past two consecutive
years. Her 1997 book, Central
Auditory Processing Disorders: New Perspectives, co-authored with Frank
Musiek and published by Singular Publishing Group, has become a landmark volume
in the field.