Questionnaires which address common listening problems can be used to identify individuals who may have auditory processing disorder, and can help in the decision to pursue clinical evaluation. One of the most common listening problems is speech recognition in the presence of background noise. According to the respondents who participated in a study by Neijenhuis, de Wit, and Luinge (2017), symptoms of APD which are characteristic in children with listening difficulties, and are typically problematic with adolescents and adults, include: • Difficulty hearing in noisy environments • Auditory attention problems • Understanding speech more easily in one-on-one situations • Difficulties in noise localization • Difficulties in remembering oral information According to the New Zealand Guidelines on Auditory Processing Disorders (2017), the following checklist of key symptoms of APD or
comorbidities can be used to identify individuals who should be referred for audiological and APD assessment: • Difficulty following spoken directions unless they are brief and simple • Difficulty attending to and remembering spoken information • Slowness in processing spoken information • Difficulty understanding in the presence of other sounds • Overwhelmed by complex or "busy" auditory environments e.g. classrooms, shopping malls • Poor listening skills • Insensitivity to tone of voice or other
nuances of speech • Acquired brain injury • History of frequent or persistent middle ear disease (otitis media, "glue ear"). • Difficulty with language, reading, or spelling • Suspicion or diagnosis of dyslexia • Suspicion or diagnosis of language disorder or delay Finally, the New Zealand guidelines state that behavioral checklists and questionnaires should only be used to provide guidance for referrals, for information gathering (for example, prior to assessment or as outcome measures for interventions), and as measures to describe the functional impact of auditory processing disorder. They are not designed for the purpose of diagnosing auditory processing disorders. The New Zealand guidelines indicate that a number of questionnaires have been developed to identify children who might benefit from evaluation of their problems in listening. Examples of available questionnaires include the Fisher's Auditory Problems Checklist, the Children's Auditory Performance Scale, the Screening Instrument for Targeting Educational Risk, and the Auditory Processing Domains Questionnaire among others. All of the previous questionnaires were designed for children and none are useful for adolescents and adults. The University of Cincinnati Auditory Processing Inventory (UCAPI) was designed for use with adolescents and adults seeking testing for evaluation of problems with listening and/or to be used following diagnosis of an auditory processing disorder to determine the subject's status. Following a model described by Zoppo et al. (2015), a 34-item questionnaire was developed that investigates auditory processing abilities in each of the six common areas of complaint in APD (listening and concentration, understanding speech, following spoken instructions, attention, and other.) The final questionnaire was standardized on normally-achieving young adults ranging from 18 to 27 years of age. Validation data was acquired from subjects with language-learning or auditory processing disorders who were either self-reported or confirmed by diagnostic testing. A UCAPI total score is calculated by combining the totals from the six listening conditions and provides an overall value to categorize listening abilities. Additionally, analysis of the scores from the six listening conditions provides an auditory profile for the subject. Each listening condition can then be utilized by the professional in making recommendation for diagnosing problem of learning through listening and treatment decisions. The UCAPI provides information on listening problems in various populations that can aid examiners in making recommendations for assessment and management. 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, so the diagnosis is made based on how the child performs 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, a committee of the
American Speech-Language-Hearing Association subsequently rejected modality-specificity as a defining characteristic of auditory processing disorders. The American Academy of Audiology has released more current practice guidelines related to the disorder. In 2018, the British Society of Audiology published a "position statement and practice guidance" on auditory processing disorder and updated its definition of APD. According to the Society, APD refers to the inability to process speech and on-speech sounds. Auditory processing disorder can be developmental or acquired. It may result from
ear infections,
head injuries, or
neurodevelopmental delays that affect processing of auditory information. This can include problems with: "...
sound localization and
lateralization (see also
binaural fusion); auditory discrimination; auditory
pattern recognition; temporal aspects of audition, including temporal integration, temporal discrimination (e.g., temporal gap detection), temporal ordering, and
temporal masking; auditory performance in competing acoustic signals (including
dichotic listening); and auditory performance with degraded acoustic signals".
Types of testing • The SCAN-C for children and SCAN-A 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. • 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. This test 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 abnormal perception of sound in the time domain. • Gaps in Noise Test (GIN) also measures temporal resolution by testing the patient's gap detection threshold in white noise. • 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. • Masking Level Difference (MLD) at 500 Hz measures overlapping temporal processing, binaural processing, and low-redundancy by measuring the difference in threshold of an auditory stimulus when a masking noise is presented in and out of phase. • 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.
Modality-specificity and controversies 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 criticize 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. The debate over this issue remains unresolved between modality-specific researchers such as Cacace, and associations such as the
American Speech-Language-Hearing Association (among others). The British Society of Audiology 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. This research undermines the validity of APD as a distinct entity in its own right and suggests that the use of the term
disorder itself is unwarranted. In a recent review of such diagnostic issues, it was recommended that children with suspected auditory processing impairments receive a holistic psychometric assessment including general intellectual ability, auditory memory, and attention, phonological processing, language, and literacy. The authors state that "a clearer understanding of the relative contributions of perceptual and non-sensory, unimodal and supramodal factors to performance on
psychoacoustic tests may well be the key to unraveling the clinical presentation of these individuals." 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. To ensure that APD is correctly diagnosed, the examiners must differentiate APD from other disorders with similar symptoms. Factors that should be taken into account during the diagnosis are: attention,
auditory neuropathy,
fatigue, hearing and sensitivity, intellectual and
developmental age, medications, motivation, motor skills, native language and language experience, response strategies and decision-making style, and
visual acuity. It should also be noted that children under the age of seven cannot be evaluated correctly because their language and auditory processes are still developing. In addition, the presence of APD cannot be evaluated when a child's primary language is not English.
Characteristics The
American Speech-Language-Hearing Association state that children with (central) auditory processing disorder often: • have trouble paying attention to and remembering information presented orally, and may cope better with visually acquired information • have problems carrying out multi-step directions given orally; need to hear only one direction at a time • have poor
listening skills • need more time to process information • have difficulty learning a new language • have difficulty understanding jokes, sarcasm, and learning songs or nursery rhymes • have language difficulties (e.g., they confuse syllable sequences and have problems developing vocabulary and understanding language) • have difficulty with reading, comprehension, spelling, and vocabulary APD can manifest as problems determining the direction of sounds, difficulty perceiving differences between speech sounds and the sequencing of these sounds into meaningful words, confusing similar sounds such as
hat with
bat,
there with
where, etc. 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. In addition, it is common for APD to cause speech errors involving the distortion and substitution of consonant sounds. Those with 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 do not 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.
Subcategories Based on sensitized measures of auditory dysfunction and on psychological assessment, patients can be subdivided into seven subcategories: • middle ear dysfunction • mild cochlear pathology • central/medial olivocochlear efferent system (MOCS) auditory dysfunction • purely psychological problems • multiple auditory pathologies • combined auditory dysfunction and psychological problems • unknown Different subgroups may represent different pathogenic and
etiological factors. Thus, subcategorization provides further understanding of the basis of auditory processing disorder, and hence may guide the rehabilitative management of these patients. This was suggested by Professor
Dafydd Stephens and Fei Zhao at the Welsh Hearing Institute,
Cardiff University. ==Treatment==