Auditory Processing Disorder

Auditory processing disorder (APD), rarely known as King-Kopetzky syndrome or auditory disability with normal hearing (ADN), is a neurodevelopmental disorder affecting the way the brain processes auditory information.[rx] Individuals with APD usually have normal structures and functions of the outer, middle, and inner ear (peripheral hearing). However, they cannot process the information they hear in the same way as others do, which leads to difficulties in recognizing and interpreting sounds, especially the sounds composing speech. It is thought that these difficulties arise from dysfunction in the central nervous system. It is highly prevalent in individuals with other neurodevelopmental disorders, such as Attention Deficit Hyperactivity Disorder, Autism Spectrum Disorders, Dyslexia, and Sensory Processing Disorder.

Signs and symptoms of CAPD may include one or more of the following behavioral characteristics:

  • Difficulty localizing sound
  • Difficulty understanding spoke the language in competing messages, in noisy backgrounds, in reverberant environments, or when presented rapidly
  • Taking longer to respond in oral communication situations
  • Frequent requests for repetitions, saying “what” and “huh” frequently
  • Inconsistent or inappropriate responding
  • Difficulty comprehending and following rapid speech
  • Difficulty following complex auditory directions or commands
  • Difficulty learning songs or nursery rhymes
  • Misunderstanding messages, such as detecting prosody changes that help to interpret sarcasm or jokes
  • Poor musical and singing skills
  • Difficulty paying attention
  • Being easily distracted
  • Poor performance on speech and language or psychoeducational tests in the areas of auditory-related skills
  • Associated reading, spelling, and learning problems
  • Difficulty learning a new language

This list is illustrative, not exhaustive, and these behavioral characteristics are not exclusive to CAPD. They may be present with other disorders (e.g., learning disability, language impairment, ADHD, and autism spectrum disorder). The variability in specific auditory processing skill deficits may contribute to the variability in observed behaviors.

The etiology of CAPD may be linked to a specific lesion or disorder or may be unknown. Causes and risk factors for CAPD may include the following (Bamiou, Musiek, & Luxon, 2001; Baran & Musiek, 1999; Chermak & Musiek, 2011):

  • Age-related changes in CANS function
  • Genetic determinants
  • A neurological disorder, disease, or damage
    • Brain injury (e.g., head trauma, meningitis)
    • Cerebrovascular disorder (e.g., stroke)
    • Degenerative diseases (e.g., multiple sclerosis)
    • Exposure to neurotoxins (e.g., heavy metals, organic solvents)
    • Lesions of the central nervous system (CNS)
    • Seizure disorders
  • Neuromaturational delay secondary to deafness/auditory deprivation
  • Otologic disorder, disease, or injury (e.g., auditory deprivation secondary to recurrent otitis media)
  • Prenatal/neonatal factors
    • Anoxia/hypoxia
    • Cytomegalovirus (CMV)
    • Hyperbilirubinemia
    • Low birth weight
    • Prematurity
    • Prenatal drug exposure

Diagnosis

Case history information is obtained by one or more professionals involved in the comprehensive assessment process and may include the following:

  • Age, including chronological and mental age in early childhood and age-related decline in older adults
  • Auditory/behavioral complaints (e.g., difficulty understanding speech in noisy or reverberant environments, difficulty localizing sound, difficulty hearing on the phone, difficulty following rapid speech, difficulty following directions, inability to detect humor or sarcasm [prosody], distractibility, inattention)
  • Cognitive status and psychological factors (e.g., attention, memory, motivation)
  • Cultural and linguistic background (e.g., native language)
  • Educational achievement (e.g., academic, learning, reading difficulties)
  • Family/genetic history
  • Health status (e.g., medical history and medications, previous illness or injury)
  • Hearing status (e.g., peripheral auditory system)
  • Pre-, peri-, and postnatal course (e.g., congenital and early infancy events)
  • Prior and current related therapies
  • Risk factors and comorbidities (e.g., learning disabilities, traumatic brain injury [TBI], epilepsy)
  • Social development
  • Speech, language, and literacy concerns

Audiologic Assessment Components

Audiologic Evaluation of Peripheral Auditory System

An undiagnosed hearing loss may contribute to behavioral complaints. The presence of peripheral hearing loss does not necessarily preclude the assessment of CAPD; however, it may differentially affect testing (Baran & Musiek, 1999). When evaluating an individual with hearing loss, tests that use stimuli minimally affected by peripheral impairment should be used whenever possible (Musiek, Baran, & Pinheiro, 1990). In some cases (e.g., profound hearing loss), testing cannot be completed.

Peripheral auditory disorders include conductive, sensorineural, and mixed hearing loss, as well as auditory neuropathy (Norris & Velenovsky, 2014) and cochlear synaptopathy (i.e., hidden hearing loss; Liberman, Epstein, Cleveland, Wang, & Maison, 2016). These disorders can affect an individual’s ability to hear and understand speech in background noise to varying degrees. See the assessment sections of ASHA’s Practice Portal pages on Hearing Loss in Adults and Permanent Childhood Hearing Loss for information on assessing the peripheral auditory system.

Audiologic Evaluation of Central Auditory System

The audiologist selects the appropriate CAP test battery, based on findings from the case history, interdisciplinary assessment (e.g., results of language and cognitive assessments), and peripheral audiological evaluation. Audiologists should know the strengths and weaknesses of the individual tests, the required response mode, and areas of the CANS to which each test is most sensitive (Chermak, Bamiou, Iliadou, & Musiek, 2017).

The test battery may be used to diagnose impairment in one or more neurophysiologic processes that occur as auditory signals travel through the CANS. The identification of specific deficits in the CANS can lead to targeted recommendations and treatment plans.

Two types of audiology evaluation measures can be used to assess auditory processing skills.

  • Behavioral—assesses the functional capabilities of the auditory system
    • Auditory discrimination tests assess the ability to differentiate similar acoustic stimuli that differ in frequency, intensity, and/or temporal parameters.
    • Auditory temporal processing and patterning test to assess the ability to analyze acoustic events over time.
    • Dichotic speech tests assess the ability to separate (i.e., binaural separation) or integrate (i.e., binaural integration) disparate auditory stimuli presented to each ear simultaneously.
    • Monaural low-redundancy speech tests assess the recognition of degraded speech stimuli presented to one ear at a time, including speech-in-noise, speech-in-competition, low-pass filtered speech, or compressed (rapid) speech.
    • Binaural interaction tests assess the ability to combine complementary inputs distributed between the ears, synthesizing intensity, time, or spectral differences of otherwise identical stimuli presented simultaneously or sequentially.

    For a discussion of behavioral tests, see McNamara and Hurley (2017).

  • Electrophysiologic—assesses neural processes in the central auditory pathway and provides information about the integrity of the CANS from the vestibulocochlear nerve (also known as the “auditory vestibular nerve” or “eighth cranial nerve”) to the auditory cortex. These measures include auditory brainstem response (ABR), middle latency response (MLR), late cortical response, P300, and mismatch negativity.Electrophysiologic measures may be useful in cases where behavioral procedures are not feasible (e.g., infants and very young children, non-English speakers), when there is suspicion of frank neurologic disorder, when confirmation of behavioral findings is needed, or when behavioral findings are inconclusive.

The most common way to diagnose APD is to use a specific group of listening tests. Audiologists often look for these main problem areas in kids with APD:

  • Auditory figure-ground: This is when a child has trouble understanding speech when there is speech babble or ambient noise in the background. Noisy, loosely structured or open-air classrooms can be very frustrating for a child with APD.
  • Auditory closure: This is when a child can’t “fill in the gaps” of speech when it is more challenging. This can happen in a quieter situation but is more common when the speaker’s voice is too fast or is muffled, making it hard for the child to make sense of the sounds and words.
  • Dichotic listening: This is when a child has trouble understanding competing, meaningful speech that happens at the same time. For example, if a teacher is talking on one side of the child and another student is talking on the other side, the child with APD cannot understand the speech of one or both of the speakers.
  • Temporal processing: This is the timing of a child’s processing system, which helps them recognize differences in speech sounds (such as mat versus pat). It also helps them understand pitch and intonation (for example, asking a question instead of giving a command), understand riddles and humor, and make inferences.
  • Binaural interaction: This is the ability to know which side speech or sounds are coming from, and to localize sound in a room. Although less common, this problem happens in children with a history of brain trauma or seizure disorders.

Test Principles of an Audiologic Evaluation of the Central Auditory System

Principles applied when determining the composition of a central auditory test battery includes the following:

  • The test battery process should not be test-driven; rather, it should be motivated by the referring complaint(s) and the relevant information available to the audiologist.
  • A central auditory test battery should include measures that are sensitive to the integrity of the CANS.
  • Tests should examine different central processes, tasks, and the integrity of multiple levels and regions of the CANS.
  • Most available behavioral central auditory tests are more appropriate for administration to children 7 years of age and older due to the challenging nature of the tasks and considerable performance variability.
  • Communication checklists, language tests, and cognitive tests can be used to identify younger children that may be “at risk” for auditory difficulties (Moore et al., 2013). A diagnosis should be withheld until formal testing can be completed.
  • Tests should generally include both nonverbal and verbal stimuli to examine different aspects of auditory processing and different levels of the auditory nervous system.
  • Individuals who are medicated successfully for attention, anxiety, or other disorders that may confound test performance should be tested under the influence of their medication.
  • Neuromaturation, subject state, and cognitive factors may affect the outcomes of many electrophysiologic procedures when used with children younger than 10 years of age. These measures need to be administered and interpreted accordingly.
  • The duration of the test session should be appropriate to the individual’s attention, motivation, and energy level. As with all behavioral tests, it is important to monitor the individual’s level of attention and effort and to take steps to maintain motivation throughout testing.
  • Referral to the appropriate professional(s) should be made when there is a suspected speech or language impairment or intellectual, psychological, or other deficit. In some cases, this referral should precede CAP testing to ensure an accurate interpretation of test results. Comorbid diagnoses may preclude CAP testing (e.g., significant intellectual deficit, severe hearing loss).
  • Test findings should be corroborated by relating them to the individual’s primary symptoms or complaints (e.g., difficulty hearing with the left ear vs. the right ear, difficulty understanding rapid speakers, difficulty hearing in the presence of competing noise).
Interpretation of Central Auditory Diagnostic Test Battery

Norm-based interpretation of test results involves comparing the individual’s performance to normative group data. Patient-based interpretation involves comparing the individual’s performance to his or her baseline performance. Comparison of results observed across disciplines can also be helpful with interpretation.

Examples of suggested diagnostic criteria and interpretations of test results include the following:

  • Performance deficits are noted in one or both ears of at least two standard deviations below the mean on two or more tests in the battery (Chermak & Musiek, 1997).
  • If poor performance is observed on only one test:
    • Diagnosis may be withheld unless performance falls at least three standard deviations below the mean or the finding is accompanied by significant functional difficulty in auditory behaviors that rely on the process being assessed.
    • The failed test—and other tests that assess the same process—should be re-administered to confirm initial findings.
  • Administering and comparing results for several tests that measure the same auditory process can be used to look for patterns in auditory processing abilities and to support the findings of the evaluation.
  • Inconsistencies across tests might signal the presence of a non-auditory confound, even when the CAPD criterion is met. Likewise, pervasive deficits on all tests may signal a cognitive deficit or another non-auditory confound.

Interdisciplinary Contributions to Assessment

Various professionals may be involved in providing essential information during the assessment period.

Speech and Language Assessment

A comprehensive speech and language assessment includes an assessment of spoken and written language; phonemic awareness (e.g., ability to segment and blend sounds in syllables and words); phonological working memory and phonological retrieval; and social communication. See ASHA’s Practice Portal pages on Spoken Language Disorders, Written Language Disorders, Speech Sound Disorders: Articulation and Phonology, and Social Communication Disorders.

Psychoeducational or Cognitive Assessment

These assessments include tests of memory, executive functioning, and attention. An educational psychologist or cognitive psychologist may perform these assessments.

Types of Testing

  1. The SCAN-C[rx] for children and SCAN-A[rx] for adolescents and adults are the most common tools for screening and diagnosing APD in the USA. Both tests are standardized on a large number of subjects and include validation data on subjects with auditory processing disorders. The SCAN test batteries include screening tests: norm-based criterion-referenced scores; diagnostic tests: scaled scores, percentile ranks, and ear advantage scores for all tests except the Gap Detection test. The four tests include four subsets on which the subject scores are derived include: discrimination of monaurally presented single words against background noise (speech in noise), acoustically degraded single words (filtered words), dichotically presented single words and sentences.
  2. Random Gap Detection Test (RGDT) is also a standardized test. It assesses an individual’s gap detection threshold of tones and white noise. The exam includes stimuli at four different frequencies (500, 1000, 2000, and 4000 Hz) and white noise clicks of 50 ms duration. It is a useful test because it provides an index of auditory temporal resolution. In children, an overall gap detection threshold greater than 20 ms means they have failed and may have an auditory processing disorder based on the abnormal perception of sound in the time domain.[rx][rx]
  3. Gaps in Noise Test (GIN) also measures temporal resolution by testing the patient’s gap detection threshold in white noise.[rx]
  4. Pitch Patterns Sequence Test (PPT) and Duration Patterns Sequence Test (DPT) measure auditory pattern identification. The PPS has s series of three tones presented at either of two pitches (high or low). Meanwhile, the DPS has a series of three tones that vary in duration rather than pitch (long or short). Patients are then asked to describe the pattern of pitches presented.[rx]
  5. Masking Level Difference (MLD) at 500 Hz measures overlapping temporal processing, binaural processing, and low redundancy by measuring the difference in the threshold of an auditory stimulus when a masking noise is presented in and out of phase.[rx]
  6. The Staggered Spondaic Word Test (SSW) is one of the oldest tests for APD developed by Jack Katz. Although it has fallen into some disuse by audiologists as it is complicated to score, it is one of the quickest and most sensitive tests to determine APD.

Treatment

There’s no cure for APD, and the treatment is specific to each person. But it usually focuses on the following areas:

  • Classroom support: Electronic devices, like an FM (frequency modulation) system, can help your child hear the teacher more clearly. And their teachers can suggest ways to help them focus their attention, like sitting toward the front of the class and limiting background noise.
  • Making other skills stronger: Things like memory, problem-solving, and other learning skills can help your child deal with APD.
  • Therapy: Speech therapy can help your child recognize sounds and improve conversational skills. And reading support that focuses on specific areas where your child has trouble can be helpful as well.

Treating additional issues related to APD can result in success. For example, treatment for phonological disorders (difficulty in speech) can result in success in terms of both the phonological disorder as well as APD. In one study, speech therapy improved auditory evoked potentials (a measure of brain activity in the auditory portions of the brain).[rx]

While there is evidence that language training is effective in improving APD, there is no current research supporting the following APD treatments:

  • Auditory Integration Training typically involves a child attending two 30-minute sessions per day for ten days.[rx]
  • Lindamood-Bell Learning Processes (particularly, the Visualizing and Verbalizing program)
  • Physical activities that require the frequent crossing of the midline (e.g., occupational therapy)
  • Sound Field Amplification
  • Neuro-Sensory Educational Therapy
  • Neurofeedback

At Home

At home, these strategies can help your child:

  • Reduce background noise whenever possible.
  • Have your child look at you when you speak. This helps give your child visual clues to “fill in the gaps” of missing speech information.
  • Use strategies like “chunking,” which means giving your child simple verbal directions with fewer words, a keyword to remember, and fewer steps.
  • Speak at a slightly slower rate with a clear voice. Louder does not always help. (Again, think Mr. Rogers!)
  • Ask your child to repeat the directions back to you to ensure they understand.
  • For directions to be completed later, writing notes, keeping a chore chart or list, using calendars with visual symbols, and maintaining routines can help.
  • Many kids with APD find using close captions on TV and computer programs helpful.

Encourage kids to advocate for themselves. Telling adults when listening is hard for them can help. But shy kids might need to use agreed-upon visual cards or signals for coaches, parents, and teachers.

Most important, remind your child that there’s nothing to be ashamed of. We all learn in different ways. Be patient. This is hard for your child and takes time. Your child wants to do well and needs patience, love, and understanding while they work toward success.

At School

Teachers and other school staff may not know a lot about APD and how it can affect learning. Sharing this information and talking about it can help build an understanding of the disorder.

APD is not technically considered a learning disability, and kids with APD usually aren’t put in special education programs. Depending on a child’s degree of difficulty in school, they may be eligible for an accommodation plan such as an individualized education program (IEP) or a 504 plan that would outline any special needs for the classroom. Accommodations for APD often fall under the disability category of “Other Health Impairment.”

Other helpful adjustments are:

  • strategic (or preferential) seating so the child is closest to the main person speaking. This reduces sound and sight distractions and improves access to speech.
  • pre-teaching new or unfamiliar words
  • visual aids
  • recorded lessons for later review
  • computer-assisted programs designed for kids with APD

Stay in touch with the school team about your child’s progress. One of the most important things that parents and teachers can do is acknowledge that the APD symptoms your child has are real. APD symptoms and behaviors are not something that a child can control. What your child can do, with the help of caring adults, is recognize the problems from APD and use the strategies recommended for home and school.

A positive, realistic attitude and healthy self-esteem in a child with APD can work wonders. Kids with APD can be as successful as their classmates. With patience, love, and support, they can do anything they work toward.

References

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