Central auditory processing disorder (CAPD)

Hall and Muellar48 have defined central auditory processing disorder as a deficiency in transmitting auditory impulses to the higher brain centres while receptive aphasia (language deficiency) is a deficiency in the interpretation of these impulses after they have been transmitted. Assessment is carried out with a comprehensive test battery of behavioural tests with proven sensitivity to central auditory dysfunction. These include:

• Dichotic word tests

• Dichotic sentence tests

• Speech- competition test

• Auditory sequencing test

Peripheral auditory function will normally be evaluated with pure tone audiometry, word recognition, and aural immittance measures (eg tympanometry) and otoacoustic emissions for cochlear function.48 For young children (up to age 7), the diagnosis of CAPD is difficult due to the level of speech and auditory development.51

Hall and Muellar list the key auditory components of auditory processing as:48

• Auditory discrimination: the ability to distinguish similarities and differences in sounds

• Auditory memory: The ability to retain information via the auditory channel

• Auditory perception: The ability to receive, process and understand sounds

• Auditory vocal association: the ability to draw relationships over what is heard

• Auditory synthesis: The ability to combine smoothly all the sounds or syllables of words to make them whole or to analyse a word into its separate sounds

• Auditory vocal automacity: The ability to predict future linguistic events from past experience

• Auditory figure-ground: The ability to distinguish and process important information by bringing it to the focus of attention while relegating other unimportant sounds to the background

The ASHA* Task Force (convened to define and develop coherent statements on the understanding of this condition), describe a CAPD as an observed deficiency in one or more of a group of mechanisms and processes related to auditory behaviours49 Keith50 states that individuals with a CAPD have difficulties with all types of acoustic distortions of auditory information including reverberation, background noise, rapid speech and competing speech. Any speech signal such as speech presented in less than optimal conditions is difficult for these individuals to understand. Hayes51 states that features of conditions such as autistic spectrum disorder (ASD), central auditory processing disorder (CAPD), attention-deficit/hyperactivity disorder (ADHD) and dispraxia can overlap which make differential diagnosis a challenge with some children. The problem of understanding CAPD becomes more complex when other conditions co-exist involving language delay, learning difficulties, reading disorders etc.50 A child presenting with ASD may also meet the criteria for CAPD. However the difficulties in social interactions and rigidities characteristic of ASD cannot be explained by the criteria of CAPD.51

There appears confusion with criteria for ADHD and CAPD. In the experience of Hall and Muellar48 they stipulate that ADHD and CAPD are independent and unrelated

disorders. However the following characteristics can be shared between children diagnosed with either condition:

• Male to female ratio of 2:1

• Depressed academic performance

• Seems not to listen

• Easily distracted

For young children (up to age 7) the diagnosis of CAPD is difficult with the above audiological procedures.

6.7 Attention-deficit/hyperactivity

disorder

(ADHD)

A 19th century German physician, Heririch Hoffman, is credited with the first person to describe the condition and to prepare a case description of a child showing symptoms of the disorder.52 It was first labelled as brain damage syndrome following an encephalitis outbreak in the USA in 1917 –1918 where a large number of children recovering from the condition showed symptoms of hyperactivity and short attention span. Later work found that all children who exhibited these symptoms did not suffer brain damage so the term was changed to minimal brain dysfunction. Various other terms followed until in 1980 when the American Psychiatric Association described the condition as attention- deficit disorder (ADD) with or without hyperactivity. In 1987, the term was again modified to attention-deficit/hyperactivity disorder (ADHD) along with a revision of the diagnostic criteria. There has been some debate and criticism over the loss of distinction between attention-deficit disorder with or without hyperactivity. In the current Diagnostic and Statistical Manual of Mental Disorders,19 the disorder is described as attention-deficit/hyperactivity disorder. For the purposes of this work the terms attention-deficit disorder (ADD) and attention-deficit/hyperactivity disorder (ADHD) are synonymous.

Diagnosis and treatment of ADHD has proved difficult, complex and subject to much debate in New Zealand. This disorder could be described as among the most invisible

of psychiatric disorders, where there is often no dysmorphic or physical appearance. The New Zealand Ministry of Health has recently produced a set of guidelines for the assessment and treatment of this disorder.53 Diagnosis is made by reference to the ‘DSM-1V Diagnostic Criteria for Attention-Deficit/Hyperactivity Disorder.’19

The aetiology of attention-deficit/hyperactivity disorder (ADHD) is likely to involve neurological and genetic factors with hereditary factors thought to account for most of the variance. The New Zealand Ministry of Health cites studies now receiving considerable support, which suggest an organic neurological problem involving frontal lobes and/or basal ganglia in the brain.54 The Ministry also finds that social factors alone are now not considered an aetiological cause, but may exacerbate pre-existing symptoms and genetic vulnerability.

The symptoms of ADHD have been divided into the following 3 subgroups: 1. Predominantly inattentive type

2. Predominantly hyperactivity type 3. Combined type

Symptoms include persistent hyperactivity, impulsiveness and inattention.53 These are characterised by difficulties in sustaining effort and persistence, organisation skills and disinhibition.54 Inattention items include:53

• Failure to give close attention to details and making of careless mistakes in tasks and activities

• Difficulty in sustaining attention

• Inability to follow through on instructions and failure to complete tasks such as schoolwork, chores, duties etc

• Difficulty in organizing tasks or activities, and forgetfulness in daily activities

• Appearance of not seeming to listen when spoken to directly

• The problem of being easily distracted by extraneous stimuli (e.g. noise) Hyperactivity items include:

• Fidgeting and squirming

• Talking excessively and acting as driven by a motor Impulsiveness items include:

• Difficulty in awaiting their time (turn) for something

• Interrupting and intruding on others

The preschool years are the most difficult in the parents' life and in the management of these children, which can also include sleeping problems, toilet training problems, and delays in speech and motor skills. If these children enter schools they are at a higher risk of low cognitive and academic performance, including reading skills. Overseas research has found persistent disruptive behaviour, in children, experiencing ADHD and other such disorders, and this is a powerful predictor of poor adjustment in adolescence and adult hood.

ADHD in preschool age is a most important target for intervention where a severe and persistent condition exists. One issue, which appears clinically difficult, is the coexistence (comorbidity) of other related conditions. Comorbidity is a significant issue for children with ADHD and it is important to identify other comorbid disorders, which may be present. The New Zealand Ministry of Health53 estimates that 54-67% of ADHD also experience oppositional defiant disorder, which manifests in a range of negativistic, hostile and such anti-social behaviours. Other comorbid disorders identified include a conduct disorder (20 – 56%), specific development disorders such as reading disability (8-39%), speech problems (12-27%) and in adolescence, substance abuse disorder at a rate 2-5 times that of the general population. Autistic spectrum disorders have also been listed as a comorbid condition of ADHD. Adolescents with comorbid oppositional defiant and conduct disorders have a higher risk of adverse outcomes.53

Children experiencing these disorders find it difficult to screen out unimportant information and focus on everything in the environment rather than attending to a single activity.54 Background noise in the classroom becomes a major distraction, affecting their ability to learn and concentrate.55

These children often become noisier as they concentrate more intently and seem to need to self-talk or make other noise to focus on the task at hand. This can often be

misinterpreted in the classroom or learning environment, when a teacher believes the child is becoming noisier because he/she is not working. Allowances are needed for such productive and involuntary noisiness.56

Selikowitz summarises the characteristics of children with ADHD which include:56

• Having greater difficulties with auditory rather than visual attention

• Having attention which quickly fades, with tedious tasks testing their attention the most

• Having performance inconsistency, which is characteristic of an immature or attention ability

• Moving from one thing to another and maybe lacking self-direction or being unable to occupy themselves. They can quickly become bored, disruptive and attention seeking

• Being easily distracted in classroom or similar learning environment

• Having difficulty in changing their level of attention during transitions from one setting to another

• Often becoming noisy when attending appropriately to a task

6.8 Down syndrome

Children with Down syndrome are well known to have specific deficits in language, which are often exacerbated by conductive hearing loss caused by middle ear infections.12 A study reported by Bennetts and Flynn12 reports that 33% of children with Down syndrome have a fluctuating hearing loss and 33% suffer a permanent loss. Like the children with other disabilities mentioned above, children with Down syndrome are especially disadvantaged as their specific deficits in language are further exacerbated by hearing loss.