Auditory processing disorder is a term used to describe listening difficulties resulting from dysfunction in the central auditory nervous system (CANS). APD may be suspected in individuals who display such difficulties but are found to have normal hearing sensitivity.
The terms “Auditory Processing Disorder” and “Central Auditory Processing Disorder” are used interchangeably in the literature to describe the same entity. A third, hybrid term “(Central) Auditory Processing Disorder” ([C]APD), also exists.
The American Academy of Audiology (AAA) and American Speech-Language-Hearing Association (ASHA) report that common signs/symptoms of APD may include:
These, and other common signs of APD, are not unique to APD and should not be treated as definitive signs that an APD is present. It is also important to note that in children, APD may coexist with other disorders, including language, reading, learning, or attention deficit
The etiology of APD is often unknown, although evidence suggests that causes and risk factors for APD may include:
There is no uniform criteria for the assessment and diagnosis of APD and therefore estimates to the prevalence of APD are variable. Common estimates regarding the prevalence of APD in the pediatric population are low (2-3%), with a higher estimated prevalence in older adults.
Age is a primary consideration for the evaluation of APD in children. Individuals 7 years of age or older can be tested for APD. This is due to age-related variability in brain function, language proficiency, and cognitive status.
A comprehensive audiologic evaluation (CAE) is recommended for all individuals suspected of having APD, as even a mild hearing loss can cause difficulties similar to those commonly associated with APD. A recent CAE (within the last 6 months) is required for review before an auditory processing evaluation (APE) can be considered.
Once normal hearing sensitivity is confirmed, the individual’s case history information will be reviewed to determine if they are a candidate for testing (age 7 or older, normal language skills and cognitive status, etc.).
Similar to a hearing test, the APE is completed in a soundproof test booth by an audiologist. A test battery assessing a variety of auditory processes (ex: tests of temporal processing, dichotic listening, monaural low-redundancy speech perception, etc.) is administered. The listener may be asked to listen to different sounds, numbers, words, or sentences throughout testing. These test stimuli may be presented to one or both ears, in quiet or in background noise. Specific instructions are given prior to each test.
APEs are scheduled as 3-hour evaluations. This timeframe allows for a case history review prior to testing, multiple breaks throughout the evaluation, and a discussion of preliminary results upon completion.
In some cases, particularly when attention-related concerns exist, testing may be broken up into more than one session. This is done in an effort to limit possible negative effects of patient fatigue on test results.
APD is diagnosed by an audiologist following administration of a test battery that assesses a variety of auditory processes. According to the American Academy of Audiology, a diagnosis of APD can be made when the individual scores two standard deviations or more below the mean in at least one ear on two or more tests within the battery.
Intervention options for APD should be individualized and specific to the patient’s case history and test results. A multi-disciplinary team management approach is often used, and may include speech-language pathologists, teachers, parents, etc. Recommendations made on a case-specific basis may include direct skills training, compensatory strategies, and environmental modifications, just to name a few.