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What is Auditory Processing Disorder?

Auditory processing disorder (APD), also known as central auditory processing disorder (CAPD) is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. Individuals with APD usually have normal structure and function 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.

These difficulties arise from dysfunction in the central nervous system (i.e., brain). APD has been referred to as dyslexia for the ears.

APD does not feature in mainstream diagnostic classifications such as the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). APD is not a coherent syndrome with clear diagnostic criteria. Rather, it is a label applied when a person has difficulties in recognizing and interpreting sounds that are not due to peripheral hearing loss.

APD can affect both children and adults, although the actual prevalence is currently unknown. It has been suggested that males are twice as likely to be affected by the disorder as females, but there are no good epidemiological studies.

Symptoms of Auditory Processing Disorder:

The National Institute on Deafness and Other Communication Disorders state that children with Auditory Processing Disorder often:

APD can manifest as:

For APD, fewer words may be perceived than were actually said, as there can be problems detecting the gaps between words, creating the sense that someone is speaking unfamiliar or nonsense words.

Those suffering from APD may have problems relating what has been said with its meaning, despite obvious recognition that a word has been said, as well as repetition of the word. Background noise, such as the sound of a radio, television or a noisy bar can make it difficult to impossible to understand speech, since spoken words may sound distorted either into irrelevant words or words that don't exist, depending on the severity of the auditory processing disorder.

Using a telephone can be problematic for someone with auditory processing disorder, in comparison with someone with normal auditory processing, due to low quality audio, poor signal, intermittent sounds and the chopping of words. Many who have auditory processing disorder subconsciously develop visual coping strategies, such as lip reading, reading body language, and eye contact, to compensate for their auditory deficit, and these coping strategies are not available when using a telephone.

As noted above, the status of APD as a distinct disorder has been queried, especially by speech-language pathologists and psychologists, who note the overlap between clinical profiles of children diagnosed with APD and those with other forms of specific learning disability. Many audiologists, however, would dispute that APD is just an alternative label for dyslexia, SLI, or ADHD, noting that although it often co-occurs with these conditions, it can be found in isolation.

Diagnosis of Auditory Processing Disorder:

APD is a difficult disorder to detect and diagnose. The subjective symptoms that lead to an evaluation for APD include an intermittent inability to process verbal information, leading the person to guess to fill in the processing gaps. There may also be disproportionate problems with decoding speech in noisy environments.

APD has been defined anatomically in terms of the integrity of the auditory areas of the nervous system. However, children with symptoms of APD typically have no evidence of neurological disease and the diagnosis is made on the basis of performance on behavioral auditory tests. Auditory processing is "what we do with what we hear", and in APD there is a mismatch between peripheral hearing ability (which is typically normal) and ability to interpret or discriminate sounds. Thus in those with no signs of neurological impairment, APD is diagnosed on the basis of auditory tests.

There is, however, no consensus as to which tests should be used for diagnosis, as evidenced by the succession of task force reports that have appeared in recent years. The first of these occurred in 1996. This was followed by a conference organized by the American Academy of Audiology. Experts attempting to define diagnostic criteria have to grapple with the problem that a child may do poorly on an auditory test for reasons other than poor auditory perception: for instance, failure could be due to inattention, difficulty in coping with task demands, or limited language ability.

In an attempt to rule out at least some of these factors, the American Academy of Audiology conference explicitly advocated that for APD to be diagnosed, the child must have a modality-specific problem, i.e. affecting auditory but not visual processing. However, an ASHA committee subsequently rejected modality-specificity as a defining characteristic of auditory processing disorders.

The issue of modality-specificity has led to considerable debate among experts in this field. Cacace and McFarland have argued that APD should be defined as a modality-specific perceptual dysfunction that is not due to peripheral hearing loss. They criticise more inclusive conceptualizations of APD as lacking diagnostic specificity. A requirement for modality-specificity could potentially avoid including children whose poor auditory performance is due to general factors such as poor attention or memory. Others, however, have argued that a modality-specific approach is too narrow, and that it would miss children who had genuine perceptual problems affecting both visual and auditory processing.

It is also impractical, as audiologists do not have access to standardized tests that are visual analogs of auditory tests. The debate over this issue remains unresolved. It is clear, however, that a modality-specific approach will diagnose fewer children with APD than a modality-general one, and that the latter approach runs a risk of including children who fail auditory tests for reasons other than poor auditory processing.

Another controversy concerns the fact that most traditional tests of APD use verbal materials. The British Society of Audiology has embraced Moore's (2006) recommendation that tests for APD should assess processing of non-speech sounds. The concern is that if verbal materials are used to test for APD, then children may fail because of limited language ability. An analogy may be drawn with trying to listen to sounds in a foreign language. It is much harder to distinguish between sounds or to remember a sequence of words in a language you do not know well: the problem is not an auditory one, but rather due to lack of expertise in the language.

In recent years there have been additional criticisms of some popular tests for diagnosis of APD. Tests that use tape-recorded American English have been shown to over-identify APD in speakers of other forms of English. Performance on a battery of non-verbal auditory tests devised by the Medical Research Council's Institute of Hearing Research was found to be heavily influenced by non-sensory task demands, and indices of APD had low reliability when this was controlled for.

Depending on how it is defined, APD may share common symptoms with ADD/ADHD, Specific language impairment, Asperger syndrome and other forms of autism. A review showed substantial evidence for atypical processing of auditory information in autistic children. Dawes and Bishop noted how specialists in audiology and speech-language pathology often adopted different approaches to child assessment, and they concluded their review as follows: "We regard it as crucial that these different professional groups work together in carrying out assessment, treatment and management of children and undertaking cross-disciplinary research." In practice, this seems rare.

Auditory Processing Disorder


Brain Mapping - QEEG

Brain Mapping (QEEG) is a safe and non-invasive brain imaging technique. It measures brain waves (EEG) that the brain sends out from at least 19 locations simultaneously.

Careful analysis of these brains waves (EEG) can reveal information on how one is using his/her brain. It can also tell us the maturity of different parts of the brain. It is often used to investigate if there are any hidden seizures.

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Learning Difficulties

Auditory Processing Disorder

Symptoms and Diagnosis

Test and Assessments Interventions Symptoms & Diagnosis

Finding the Causes

Most clinicians do not bother about the causes as diagnosis is based on behavioral symptoms …   

At Spectrum Learning, we have been investigating the possible causes …

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