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Auditory Processing Disorder

APD is a generic term for hearing disorders that result from atypical processing of auditory information in the brain. APD results in persistent limitations in the performance of auditory activities with resultant significant consequences for participation.

The symptoms of APD bear many similarities to other types of hearing disorders, but APD differs in that it is not detected by standard audiometric assessments.

The overall prevalence in children in New Zealand (NZ) is estimated at 6.2%, with higher rates in some populations, particularly the elderly. APD affects academic achievement, participation, career opportunities and psychosocial development.

APD should be suspected when there are reports of poor hearing and auditory comprehension in some circumstances despite normal pure tone hearing test results.

Checklists of symptoms and comorbidities provide a simple and effective method of identifying children and adults who should be referred for diagnostic assessment.

APD frequently co-occurs with other learning or
developmental disabilities. It is recommended that children with dyslexia, language disorder, disorders affecting the brain, significant history of middle ear disease, autism spectrum disorder and reading difficulties are referred for APD assessment.

Referral is also recommended for children with attention deficit disorder/attention deficit hyperactivity disorder (ADD/ADHD) if listening concerns persist after treatment.

Taken from New Zealand Guidelines On Auditory Processing Disorder 2019 – Keith, W. J., Purdy, S. C., Baily, M. R., & Kay, F. M. (2019).

New Zealand Guidelines on Auditory Processing Disorder. New Zealand Audiological Society. www.audiology.org.nz

Some causes of APD are listed below:

Hereditary developmental abnormalities
Maturational delay
Antenatal, perinatal and postnatal factors including prematurity and low birth weight, prenatal anoxia, prenatal exposure to cigarette smoke or alcohol, hyperbilirubinemia
Diseases, toxins and neurological conditions affecting the brain including space-occupying
Lesions; Moyamoya disease and other cerebrovascular disorders; multiple sclerosis and other neurodegenerative diseases; bacterial meningitis; herpes simplex encephalitis; Landau Kleffner Syndrome and other seizure disorders;
Lyme disease; metabolic disease; heavy metal exposure; solvent exposure
Traumatic brain injury
Blast injury
Auditory deprivation
Ageing. (Bamiou, Musiek, & Luxon, 2001; AAA, 2010, p. 13; Witton, 2010)

Behavioural Manifestations

Behaviours in children and adults with APD that may be reported and/or observed include, but are not limited to, the following:

Difficulty following multiple or lengthy oral instructions
Difficulty understanding speech in competition, for example, in the presence of competing messages, background noise
Difficulty hearing when a signal is not clear or is degraded’ (for example, soft, rapid or distorted
Speech, accented speech, speech in reverberant environments, phone conversation)
Mishearing auditory information
Slowness in processing and responding to auditory information
Inconsistent or inappropriate responses to spoken requests for information
Frequent requests for repetition and/or rephrasing of information, saying “what” or “huh” often
Listening fatigue
Difficulty or inability to interpret prosody cues that underlie emotion, humour and shades of meaning in speech
Difficulty maintaining attention, poor listening skills, tendency to be easily distracted
Poor auditory memory
Hyperacusis including reduced tolerance for noise and sensitivity to noise difficulty localising the source of a signal and tracking sounds.

(ASHA, 2005; AAA, 2010; Geffner, 2012; Campbell, Bamiou, & Sirimanna, 2012)

Secondary difficulties associated with APD may include:

Speech and language delay/disorder in children including difficulties with phonological and phonemic awareness
Academic difficulties, including reading, spelling and/or learning problems
Psychosocial difficulties
Exhaustion after school from listening effort.

(Campbell et al., 2012; Crandell, 1998; Kreisman, John, Kreisman, Hall, & Crandell, 2012; Esplin & Wright, 2014, p. 10; Lawton, Purdy, & Kalathottukaren, 2017)