Auditory Processing Disorder (APD)

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APD is a condition in which the person does not suffer from hearing loss but struggles to understand what is being spoken to them. This may be more prevalent when the person speaking has an accent, it is noisy around them, or the person with APD is emotionally stressed. 

APD is associated with Autism Spectrum Disorders. People with APD may have varying levels of impairment when listening to other people, but usually, they do not have significant hearing loss, and the problem is associated with how the brain interprets the sounds that they hear.

Initially, it was thought that there were three types of auditory processing disorders. 

  • Secondary APD: related to some form of hearing loss, temporary or permanent. 
  • Acquired APD: as a result of normal ageing or a known medical condition.
  • Developmental APD: common in children, with no clear cause. 

It is also possible for APD to be caused by trauma or a stroke.2

Symptoms 

  • Unable to hear in certain environments, for example, when there is a lot of background noise. 
  • Problems with reading and/or spelling. 
  • Problems with temporal processing
  • Problems understanding different accents.
  • Problems comprehending information over the telephone or when you can’t see the other person’s face.4

Diagnosis 

One of the main tests to diagnose APD involves electrodes being placed on the head to measure how the brain reacts to different sounds. 

Monaural low-redundancy speech tests

This test measures auditory closure ability, in which a person is asked to complete or “fill in the gaps” of a distorted part of the sound. This method is completed on each ear independently. Being able to recognise missing sounds, such as words or syllables, is a listening skill that should be apparent once the child reaches their teenage years.6

Other tests that may be used include: 

This is a test that is used to determine how well people’s perceptual skills are when listening. Dichotic stimulation is used, which means that different sounds are presented to the right and left ear at the same time.11 

  •  Screening test for auditory processing disorders (SCAN)

This test determines if a person has a problem with auditory comprehension and needs further evaluation. For example, they can’t understand what it is they are hearing. 

  • Multiple Auditory Processing Assessment (MAPA) This test includes many different listening skills, including completion of sentences and pitch pattern tests.

Causes 

There are several potential causes for APD, such as:

  • Babies who are born prematurely have an increased risk of developing APD. A baby is considered to be born prematurely if they are born before 37 weeks of gestation. 
  • Stroke. A stroke can be either ischemic or hemorrhagic. An ischemic stroke is where the blood supply has been stopped by a clot, causing part of the brain to be starved of oxygen. A hemorrhagic stroke is when a blood vessel in the brain has ruptured, causing excessive bleeding.7
  • Transient ischaemic attack (TIA) This is similar to an ischemic stroke; however, in the case of a TIA, the blood flow is only temporarily blocked. This causes less severe symptoms than an ischemic stroke but still can cause brain damage.7
  • Trauma 
  • ADHD. ADHD is a very common comorbidity with APD.
  • Autism spectrum disorder (ASD) is a group of conditions that have communication and intellectual differences. ASD affects how they communicate with other people. For example, some people with ASD may be non-verbal or have a reduced ability to communicate with words. ASD is a spectrum of different conditions, and symptoms can range from mild to more severe, with different challenges for different people. People with ASD are at a higher risk of having APD.8
  • Non-syndromic cleft lip and/or palate. This is a type of craniofacial (skull and face) abnormality in which the lip does not form normally, and there is a gap where the lip has not fused during the development of the foetus. In a cleft palate, there is a hole in the roof of the mouth.3

The central auditory nervous system involves the cochlear nucleus and the auditory cortex. The maturation of this complex system of auditory processing can take 10-12 years, and as such, it is important to remember that children may not have the same hearing capacity as adults. As people develop, their ability to listen and comprehend information gets better. This is why it is common for young children to struggle with auditory processing. Sometimes, people grow out of this condition, and for others, the problems remain and can have a big impact on their day-to-day lives. This is called auditory processing disorder.5

Treatment 

Treatment for APD will depend on the different types of APD. 

  • Hypersensitivity – This is also called misophobia. People have an aversion to certain sounds, such as chewing gum or the rustling of crisp packets. This can cause the person to experience a painful sensation when they hear the sound. They may also not hear other sounds around them if they are focusing on the sound that they are adverse to. 
  • Decoding – This type of APD is when the person can hear what is being said, but the brain has trouble comprehending what is said to them. 
  • Integration – People who struggle to both read and hear at the same time will have integration APD. The brain has difficulty in multitasking, and as such, the person struggles to hear what is being said when they are also carrying out a different sensory task, like reading or writing. 
  • Prosodic – This is usually associated with a monotone voice. People struggle with the tone and implied meaning of speech. The inflexion can also be something that people struggle with; for example, when people ask a question the pitch goes up at the end of the sentence. People with this type of APD will struggle to tell the difference in the inflexion of what people are saying to them. For example, people may not understand if the speech is happy or excited. They may also mistake a statement for a question and vice versa.  
  • Organisational – Not being able to recall information in the order in which it is given is the main symptom of organisational APD. One of the main impacts of organisational APD is difficulty with hearing in crowds and other noisy environments. 

You cannot cure APD and remove all of the symptoms that are associated with the condition. However, some therapies have been proven to improve symptoms and make it easier for patients to cope with the symptoms. It is also essential to make it easier for parents to communicate with their children to keep them safe and to manage their needs with effective communication.1

To help people with APD, the NHS recommends the following: 

  • Avoid background noise.to help with attention. 
  • Make sure that you can see each other’s faces when communicating. For example, wearing masks can make it harder for people with APD to communicate as they can’t see the different shapes that the mouth makes during speech. 
  • Use basic words to reduce confusion when communicating. Complicated words and idioms can make it hard for people with APD to communicate. For example, using phrases such as “It’s raining cats and dogs”.1

Frequency modulation 

Frequency modulation technology allows the voice of the person speaking to be at a higher volume than the background noise. This makes it easier for people with APD to direct their attention to the person (usually their teacher). 

Normally, a microphone is worn around the neck, and the student will have a receiver which alters the sound that they hear, making what the teacher hears clearer.9

Conclusion

In conclusion, APD is a condition that affects many people with ADHD and also people who have suffered from conditions such as brain damage due to trauma or stroke. It is important to remember that people with APD have normal hearing, but they struggle to decode the information that they hear due to problems with attention and making sense of what they hear. There is no cure for APD, but therapy can help to reduce the symptom severity and also to help train other people in ways that can better aid communication. For example, using pictures and gestures when talking can help people with APD to communicate effectively.1

References

  1. Moore DR. Guest editorial: auditory processing disorder. Ear & Hearing [Internet]. 2018 Jul [cited 2023 Nov 30];39(4):617–20. Available from: https://journals.lww.com/00003446-201807000-00002
  2. Emanuel DC, Ficca KN, Korczak P. Survey of the diagnosis and management of auditory processing disorder. Am J Audiol [Internet]. 2011 Jun [cited 2023 Nov 30];20(1):48–60. Available from: http://pubs.asha.org/doi/10.1044/1059-0889%282011/10-0019%29
  3. Ma X, McPherson B, Ma L. Electrophysiological assessment of auditory processing disorder in children with non-syndromic cleft lip and/or palate. PeerJ [Internet]. 2016 Aug 25 [cited 2023 Nov 30];4:e2383. Available from: https://peerj.com/articles/2383
  4. Hind SE, Haines-Bazrafshan R, Benton CL, Brassington W, Towle B, Moore DR. Prevalence of clinical referrals having hearing thresholds within normal limits. International Journal of Audiology [Internet]. 2011 Oct [cited 2023 Nov 30];50(10):708–16. Available from: http://www.tandfonline.com/doi/full/10.3109/14992027.2011.582049
  5. Bamiou DE. Aetiology and clinical presentations of auditory processing disorders---a review. Archives of Disease in Childhood [Internet]. 2001 Nov 1 [cited 2023 Nov 30];85(5):361–5. Available from: https://adc.bmj.com/lookup/doi/10.1136/adc.85.5.361
  6. Miotti MV, Maggi AL, Villarreal AV, Neustadt N, Hinalaf M. El cierre auditivo según el procesamiento auditivo central y las habilidades psicolingüísticas en adolescentes. Rev Fac Cien Med Univ Nac Cordoba [Internet]. 2019 Nov 19 [cited 2023 Nov 30];76(4):204–2010. Available from: https://revistas.unc.edu.ar/index.php/med/article/view/21963
  7. Gomes F, Hookway C, Weekes CE. Royal College of Physicians Intercollegiate S troke working P arty evidence‐based guidelines for the nutritional support of patients who have had a stroke. J Human Nutrition Diet [Internet]. 2014 Apr [cited 2023 Nov 30];27(2):107–21. Available from: https://onlinelibrary.wiley.com/doi/10.1111/jhn.12185
  8. Haesen B, Boets B, Wagemans J. A review of behavioural and electrophysiological studies on auditory processing and speech perception in autism spectrum disorders. Research in Autism Spectrum Disorders [Internet]. 2011 Apr [cited 2023 Nov 30];5(2):701–14. Available from: https://linkinghub.elsevier.com/retrieve/pii/S175094671000173X
  9. Keith RW. Interpretation of the staggered spondee word (Ssw) test: Ear and Hearing [Internet]. 1983 Nov [cited 2023 Nov 30];4(6):287–92. Available from: http://journals.lww.com/00003446-198311000-00005

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Rachel Siobhan Smith

MSc Biomedical Science, University of Greenwich

Rachel is a Post Graduate student reading Biomedical Science at the University of Greenwich. They have years of experience working in Biomedical laboratories, but also a keen interest in medical communications. Rachel previously worked in a Covid Testing laboratory to help enable the UK, to increase testing capacity during the Covid-19 pandemic.

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