APD has been defined and classified in different ways by audiology societies worldwide (Wilson, 2018). Those differences reflect the lack of consensus not only on APD diagnosis and treatment (Dillon et al. 2012; De Bonis, 2017, Wilson, 2018) but also on the nature of this condition (Vermiglio, 2014; Kraus & Anderson, 2016, Keith et al., 2018; Moore, 2018, Wilson, 2018, Dillon & Cameron, 2021). Here, I will use the APD guidelines of the British Society of Audiology (BSA) for several reasons: firstly, because it considers the evolution of APD concept through an evidence-based approach, including the latest research; secondly, it acknowledges the importance of differentiating types of APD based on their probable cause.

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According to the British Society of Audiology (BSA), APD is defined as an inability involving the perception of speech and non-speech sounds. Basically, it is characterized by problems in understanding what we hear, especially in acoustically challenging situations, such as in the presence of background noise or when many people talk simultaneously. It can be categorized into three groups:

1- Developmental APD - It is the most “popular” APD. Those difficulties have no clear explanation, such as a hearing loss or a neurological condition, for instance. The individual has normal hearing sensitivity; however, he struggles to understand speech. This type of APD is common in children, but the symptoms may persist into adulthood.

2- Secondary APD - It is related to a hearing loss, either permanent or temporary, such as in cases of glue ear. Children with a history of recurrent glue ear might have a specific type of APD, called Spatial Processing Disorder (SPD). 

3- Acquired APD – It is related to ageing or any known medical condition, such as neurological brain damage (e.g., stroke and traumatic brain injury). 

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While the cause of both Secondary and Acquired APD is more precise and straightforward, there is no consensus regarding the nature of those listening difficulties presented in Developmental APD (Wilson, 2018; Moore, 2018; Keith et al., 2018, Iliadou et al., 2018, Dillon & Cameron, 2021). The prevalence reported is around 5% (Hindi et al., 2011); however, this number is also controversial given the lack of gold standard criteria for diagnosis. Initially, it was established that those difficulties derived from an impairment in the neural function of the central auditory nervous system. However, nowadays, research has shown it might also involve non-auditory-related brain areas critical for auditory processing, such as language, executive functioning, attention, and memory (Schmithorst et al., 2013; Farah et al., 2014). This is also observed through the vast heterogeneity of symptoms (Ahmmed et al., 2014; Tomlin et al., 2015), including predominantly listening but often subtle cognitive impairments (e.g., working memory).

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The main symptoms include:

• Difficulty hearing in background noise or any other situation that the auditory message is a bit unclear, such as on the phone or when many people talk at the same time

• Frequently ask people to repeat what they told

• Problems to pay attention or memorize auditory instructions

• Frequently mishearing speech

• Difficulty paying attention to an auditory message and ignoring others presented at the same time

• Taking more time to process auditory information

         

APD usually overlaps with other developmental disorders such as dyslexia, ADHD, and speech sound disorder (Murphy & Schochat, 2009; Tomlin et al., 2015; Sharma et al., 2019). Thus, the clinical presentation can also vary depending on the co-occurrence of those conditions. In those cases, the conclusion of the APD diagnosis is much more challenging as it is difficult to separate all those factors to distinguish one problem from another. Thus, a multidisciplinary approach will be essential for a better understanding of the other diagnoses and their impact on the auditory processing (AP) assessment.

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Despite the controversies surrounding APD, there is no doubt about the existence of listening difficulties, a broad term used to designate any reported problem involving understanding speech or recognizing sounds, regardless of their nature (Dillon & Cameron, 2021). There is also no doubt about the importance of investigating and managing them, considering their negative impact on everyday life and, again, regardless of their nature (Barry et al. 2015). It is then essential that, in addition to the basic hearing tests, individuals with the symptoms reported above have a comprehensive evaluation of their functional listening skills that outline their everyday listening difficulties. The investigation of the nature of the problem must be part of the evaluation to conclude whether those listening difficulties are, in fact, categorized as APD or are secondary symptoms of other general conditions. This will be possible through a preliminary broader assessment that gathers information about all the key listening aspects, including those non-auditory-related skills previously mentioned. Through this approach, we acknowledge and embrace those APD controversies but also recognize the importance of providing assessment and treatments to support those individuals. In fact, we move forwards by providing the latest evidence-based assessments and treatments.

 

Click on the link below to read more about APD Assessment, Diagnosis and Management. 

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References:

• Ahmmed AU, Ahmmed AA, Bath JR, Ferguson MA, Plack CJ, Moore DR. (2014). Assessment of children with suspected auditory processing disorder: a factor analysis study. Ear Hear. 35(3):295-305.

• Barry JG, Tomlin D, Moore DR, Dillon H. (2015) Use of Questionnaire-Based Measures in the Assessment of Listening Difficulties in School-Aged Children. Ear Hear. 2015 Nov-Dec;36(6):e300-13

• British Society of Audiology APD SIG. (2018). APD Position Statement and Practice Guidance.

• DeBonis, D.A. (2017). AAA (2010) CAPD clinical practice guidelines: Need for an update. Int J Audiol, 56: 657–663.

• Dillon H., Cameron S., Glyde H., et al. (2012). An opinion on the assessment of people who may have an auditory processing disorder. J Am Acad Audiol. 23, 97–105

• Dillon H, Cameron S. (2021). Separating the Causes of Listening Difficulties in Children. Ear Hear. Jun 16.

• Farah R, Schmithorst VJ, Keith RW, Holland SK. (2014). Altered white matter microstructure underlies listening difficulties in children suspected of auditory processing disorders: a DTI study. Brain Behav.2;4(4):531-43.

• Hind SE, Haines-Bazrafshan R, Benton CL, Brassington W, Towle B, Moore DR. (2011). Prevalence of clinical referrals having hearing thresholds within normal limits. Int J Audiol. 50(10):708-16.

• Iliadou VV; Chermak GD, Bamiou DE et al. (2018). Letter to the Editor: An Affront to Scientific Inquiry Re: Moore, D. R. (2018) Editorial: Auditory Processing Disorder, Ear Hear, 39, 617-620. Ear Hear. 2018 Nov/Dec;39(6):1236-1242.

• Kraus, N., & Anderson S. (2016). Chapter 3 Auditory Processing Disorder: Biological Basis and Treatment Efficacy. In Le Prell CG et al. (eds.): Translational Research in Audiology, Neurotology, and the Hearing Sciences, Springer Handbook of Auditory Research 58, Springer International Publishing, Switzerland

• Keith W.J., Keith R.W., Purdy S.C. (2018) Letter to the Editor: Comments on the Ear and Hearing Ban on Certain Auditory Processing Disorder Articles Re: Moore, D. R. (2018) Editorial: Auditory Processing Disorder, Ear Hear, 39, 617-620. Ear Hear 39(6): 1242-1243.

• Moore D.R. (2018). Editorial: Auditory Processing Disorder. Ear Hear. 39(4): 617-620.

• Murphy CF, Schochat E. (2009) How auditory temporal processing deficits relate to dyslexia. Braz J Med Biol Res. 2009 Jul;42(7):647-54.

• Schmithorst VJ, Farah R, Keith RW. (2013). Left ear advantage in speech-related dichotic listening is not specific to auditory processing disorder in children: A machine-learning fMRI and DTI study. Neuroimage Clin. 2;3:8-17.

• Sharma M, Purdy SC, Humburg P. (2019). Cluster Analyses Reveals Subgroups of Children With Suspected Auditory Processing Disorders. Front Psychol. 15;10:2481.

• Tomlin D, Dillon H, Sharma M, Rance G. (2015) The Impact of Auditory Processing and Cognitive Abilities in Children. Ear Hear. 36(5):527-42

• Wilson, W. J. (2018) Evolving the concept of APD. Int J Audiol, 57, 240–248.

• Vermiglio, A. J. (2014). On the clinical entity in audiology: (Central) auditory processing and speech recognition in noise disorders. J Am Acad Audiol, 25, 904–917.

 

 

 

 

 

 

 

 

 

 

 

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