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It takes a team to differentially diagnose APD

Chermak, Gail D. PhD

Section Editor(s): Musiek, Frank E. PhD

doi: 10.1097/01.HJ.0000293914.81047.29
Path Ways

How can one distinguish auditory processing disorder from multimodal or supramodal disorders that may involve the auditory modality?

Pathways editor

Professor of Audiology and Chair of the Department of Speech and Hearing Sciences at Washington State University.

Correspondence to Dr. Chermak at chermak@wsu.edu.

Readers are invited to suggest future topics to Frank E. Musiek, PhD, editor of Pathways, at frank.musiek@uconn.edu.

Figure. F

Figure. F

Auditory processing disorder (APD) is a deficit in the processing of information that is specific to the auditory modality.1 APD typically involves deficits in dichotic listening, selective attention, and temporal processing. APD has been observed in diverse clinical populations, including those where central nervous system pathology or neuromorphologic disorder is suspected (e.g., developmental language disorder, dyslexia, learning disability, attention deficit disorder) and those where evidence of central nervous system pathology is clear (e.g., aphasia, multiple sclerosis, epilepsy, traumatic brain injury, Alzheimer's disease).2

This co-morbidity occurs because all auditory tasks, from pure-tone perception to spoken language processing, are influenced by higher-level, non-modality specific factors such as attention, learning, motivation, and decision processes.3–6 Moreover, there is a complex arrangement of shared physiologic and neurologic networks across these processes and mechanisms.7–11

Given the heterogeneous nature of APD and the range of listening and learning deficits that often accompany it, comprehensive evaluation requires a multidisciplinary team approach. APD is a perceptual disorder diagnosed by the audiologist on the basis of an extensive audiologic evaluation that employs challenging auditory tasks involving sensitized stimuli (e.g., speech presented in dichotic competition, filtered or time-compressed speech, etc.). Currently, diagnosis of APD is based on the outcomes of auditory behavioral tests, supplemented by electroacoustic and electrophysiologic measures.1

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DIFFERENTIATION REQUIRES MANY TESTS

To more definitively differentiate perceptual, modality-specific APD from multimodal perceptual deficits (i.e., polysensory deficits occurring in multiple sensory modalities), one must compare similar behavioral tasks in at least two modalities.12 And, to differentiate APD from non-perceptual cognitive deficits (i.e., supramodal deficits that are independent of sensory modality), one must examine cognitive and executive functions. The multidisciplinary team also must evaluate language and psychoeducational achievement to identify associated conditions, clarify the functional impact of the APD, and plan and implement therapy.

Analogous testing in the visual modality has been recommended as an optional procedure in the APD diagnostic test battery.1 It is important that audiologists either administer these additional tests or refer patients for analogous testing in the visual domain. These tests might include behavioral tests and event-related potentials.13,14 Auditory and visual continuous performance tests (CPTs) can be used to examine both multimodality sensory function and executive control (i.e., response inhibition). As such, CPTs can provide information to assist in the differential diagnosis of APD and attention deficit hyperactivity disorder (ADHD).15 Neuroimaging also offers great promise for differential diagnosis.13

Given the overlapping symptomatology across diverse clinical populations and the range of listening and learning deficits associated with APD, comprehensive evaluation of patients suspected of APD must be multidisciplinary. Comparing analogous tasks across sensory modalities should help differentiate auditory-specific, perceptual modality deficits (APD) from supramodal, cognitive deficits and from multisensory deficits.1,12,16

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© 2003 Lippincott Williams & Wilkins, Inc.