Auditory processing disorders
Auditory processing is the term used to describe how we use our hearing to make sense of the world. The human brain uses the input from the senses of hearing, balance, vision, smell, touch and taste to process information. Individuals rely differently on each of these senses.
Auditory processing is defined as “what we do with what we hear”
Our ears are exposed to sounds 24 hours a day. The sounds collected from the environment are transmitted from both ears all the way to the brain. Most sounds coming from the right ear go to the left side of the brain and vice-versa. The brain selects relevant sounds, processes and makes sense of the received information.
Auditory processing is not dependent on normal hearing. Individuals with a hearing loss may have good auditory processing skills provided the sounds are amplified to compensate for the loss by means of properly fitted hearing aids. On the other hand, sound deprivation caused by a non-treated hearing loss may lead to an auditory processing disorder.
Auditory processing disorders may involve a variety of symptoms…
- Difficulties in understanding speech in adverse conditions such as in noisy environments.
- Difficulties in localising sounds.
- Difficulties in following verbal instructions.
- Intolerance to loud sounds.
- Attention deficit.
- Memory deficit.
- Learning difficulties such as spelling, writing and reading problems (dyslexia).
- Hyperactivity and behavioural problems in children.
Who is at risk and what is the cause?
Children may present an auditory processing disorder while the cause may remain unknown.
Adults can also be affected by APD. The incidence tends to increase in the elderly mostly due to auditory deprivation caused by an age-related hearing loss
Risk factors for auditory processing disorders
Recent research points to biochemical disorders leading to an imbalance of neurotransmitters. The risk factors may be genetic as well as environmental such as exposures to toxins in the air, food and water.
Prolonged episodes of ear infection (glue ear, otitis media) are known to cause auditory processing disorders in children due to auditory deprivation (lack of sound stimulation to the brain) caused by transient loss of hearing. In many cases, chronic ear infections are caused by biochemical disorders associated with allergies.
Other causes of APD
- Sound deprivation due to untreated hearing losses.
- Birth distress or prematurity
- Craniofacial or external ear abnormalities
- Head trauma
- Cerebral vascular ischaemia (stroke)
- Brain lesions
- Brain tumours (rare)
How do we test and who can be tested for APD?
Auditory processing skills can be clinically tested by a qualified audiologist. The first step is a comprehensive hearing test to exclude the possibility of a peripheral hearing loss. This assessment involves a pure tone and speech audiogram, tympanometry, acoustic reflexes, otoacoustic emissions and auditory evoked responses.
Subjective assessment for auditory processing is performed using behavioural tests where the individual is required to listen and respond to a series of sounds, words and sentences presented through headphones at different levels of difficulties, such as with competing noises in the opposite ear and/or in the same ear, with distorted and filtered speech etc.
Behavioural tests can be reliably performed on children from seven years of age
Younger children may be objectively assessed using electrophysiological tests provided there is some degree of co-operation. These are measurements of the brain responses to sound performed by placing electrodes on the earlobes and on the scalp. Different sounds are presented via headphones while the child sits quietly watching a movie.
Both subjective and objective test procedures are not invasive and do not cause any physical discomfort.
Why is it important to test for APD?
Everybody is different. This universal rule also applies to sensory processing skills. Different individuals process information using different strategies and this may not necessarily be due to a “processing disorder”. Some situations may not provide an adequate environment for an individual’s “preferential” processing skills.
For example, a child with weak auditory processing skills who relies more on visual processing may not perform well in a school using phonics.
This situation may be improved by training the child to develop stronger auditory processing skills or by modifying the environment, for example by changing to another school with a different teaching method.
A referral to an integrative doctor to address biochemical balance through appropriate diet and supplements may also help these children.
Audiological intervention aims to assess auditory processing to identify the individual’s auditory function, develop and strengthen the weaker skills by means of auditory training, and/or environmental modifications.