Dyslexia: what do paediatricians need to know?

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  • Dyslexia: what dopaediatricians need to know?Anne OHare

    ment of dyslexia. This article aims to give the paediatrician

    OCCASIONAL REVIEWAnne OHare MD FRCPCH Honorary Professor in the Section of Child Life &

    Health, University of Edinburgh, 20 Sylvan Place, Edinburgh EH91 UW,

    UK and Consultant Paediatrician at the Royal Hospital for Sick Children,

    Edinburgh, UK. Conflict of interest: none.AbstractForty per cent of a childs waking life is spent in school and one of the

    most intrusive impacts on the success or otherwise of this experience

    is that of reading difficulties. Developmental dyslexia has a high genetic

    contribution affecting 50% of children with dyslexic parents. The paedia-

    trician may be consulted for a child with dyslexia to advocate, interpret

    predisposing factors in the childs developmental and medical history

    and offer scientific interpretation of the vast range of theories and inter-

    ventions proposed for dyslexia. The purpose of this article is to orientate

    the paediatrician to what they need to know, so that they can maximize

    their contribution in the care of children with developmental dyslexia

    within a multidisciplinary team. It will cover the epidemiology and defini-

    tion, the underlying hypotheses and underpinnings as well as the clinical

    diagnosis and examination, the longer-term prospects for affected

    children and the role of interventions.

    Keywords developmental dyslexia; phonological awareness; reading

    interventions; risk factors

    Epidemiology and definition

    Dyslexia is a common condition affecting 10e15% of English

    speaking populations and is recognized more commonly in boys,

    who outnumber girls by 4:1. Dyslexia affects users of all written

    languages, but learning to read and write in English is particu-

    larly challenging because it has an opaque orthography and the

    relationship between letters and sounds is inconsistent and many

    errors are permitted. This is compounded by the later introduc-

    tion of many subject and technical words which are multisyllabic

    and often contain Latin and Greek roots and affixes.

    The most prominent symptom in dyslexia is a relative

    inability to acquire word recognition in early school, resulting in

    problems marrying up the phoneme (speech sound) to the

    grapheme (its encoded or symbolic representation) on the page.

    This symptom should be an educational flag with most children

    being recognized in early school, assessed and offered remedia-

    tion and support within school with no resort to medical

    consultation outwith the usual universal health services.

    However, there are a number of exceptions to this pattern of

    identification and management, whereby paediatricians are

    approached by parents/carers, teachers and colleagues in other

    professions in order to contribute to the diagnosis and manage-PAEDIATRICS AND CHILD HEALTH 20:7 338sufficient background knowledge of dyslexia so that he/she can

    make this contribution effectively.

    The obvious starting point in any paediatric consultation is to

    clarify the details of the presenting complaint but almost inevi-

    tably the child with a possible dyslexia is a challenge because

    there will be important aspects of the history that need to be

    established both from the teachers and the family. It is invaluable

    to establish at the outset of the consultation the route by which

    the child was referred for paediatric assessment. What was the

    referrer hoping to achieve? Was the referral instigated by the

    teacher or by the parents and the paediatrician should open

    discussion in a non-judgemental way which allows teachers and

    parents to air their concerns. The experience of ones child failing

    academically is a difficult one. Parents of such children can all

    too often be met with opposition when what they need is reas-

    surance that the problem is being taken seriously with all parties

    working together.

    Dyslexia is defined in the International Classification of

    Diseases in the following way: Dyslexia or a specific reading

    disability is a difficulty learning to read, despite conventional

    instruction, adequate intelligence and sociocultural opportunity.

    It is dependent upon fundamental cognitive disabilities which are

    frequently of constitutional origin.

    Dyslexia is a difficulty learning to read that is always present

    in the early years. The reading difficulty can however appear to

    recover particularly for reading comprehension in more intel-

    lectually able children in secondary school. Conventional

    instruction is often assumed to have taken place if the child has

    attended school regularly. However, this might be the area that

    the parents feel was inadequate and which might have led to

    them consulting a paediatrician. They may hold views that the

    teaching of reading in school was poor, or that it should have

    been dyslexia-specific as their childs difficulties came to light.

    They may feel that the instruction needed to be more intense or

    delivered on a one-to-one basis and are seeking to enlist the

    paediatrician as an advocate to achieve this.

    Alternatively, the teacher may have put in a huge amount of

    input, but the childs difficulties remain and they are looking to

    the paediatrician for advice as to whether the child has any

    health or developmental predispositions that might have resulted

    in this persistent picture.

    There are also many complex theories around the causes of

    dyslexia and parents and teachers may consult a paediatrician

    because of their scientific training. They hope to get some

    interpretation of the efficacy of these treatments and are looking

    to be guided as to how to best support and manage the childs

    dyslexia.

    The definition of dyslexia also refers to the concept of

    adequate intelligence and this too may represent a significant

    challenge at a consultation. The so-called discrepancy model

    whereby dyslexia is only defined if it is a specific difficulty and

    out of step from the childs intelligence is contentious (Figure 1).

    Nevertheless, the term dyslexia is generally confined to

    a specific reading difficulty. Reading skills do vary along with

    intelligence in the normal population but in addition, dyslexic

    children fall within the normal distribution of reading skills when

    corrected for ability. Therefore, they do not form a hump at the

    lower end of the normal distribution. However, there are

    a number of conditions which illustrate how an ability to decode 2010 Published by Elsevier Ltd.

  • dys

    OCCASIONAL REVIEWin reading is not synonymous with intelligence. Examples of this

    are children with a learning disability who bark at print or

    children with autism spectrum disorders who are hyperlexical

    and in both these situations the child will not have the accom-

    panying comprehension of what they are reading. Therefore,

    whilst adequate intelligence might appear in these examples to

    be irrelevant to the acquisition of reading, a low intelligence can

    impact on the so-called top down skills in reading. The resulting

    poor world knowledge, vocabulary, attention and motivation

    may make successful reading acquisition more elusive for such

    children.

    Therefore it can be helpful to have some knowledge of the

    childs intellectual/learning potential in the formulation of why

    he or she is experiencing difficulty learning to read. However, as

    dyslexia is regarded as a specific difficulty, it is an inappropriate

    term with which to label reading delay for children who have

    more general learning problems. However, the contrary situation

    can also arise whereby a childs intellectual potential is under-

    estimated and dyslexia discounted. Such a child might have

    a developmental phonological speech delay associated with the

    commonly accompanying delay in fine motor skills and the

    surface features of their poor speech and handwriting may lead

    the specific nature of their difficulty to be overlooked.

    The definition of dyslexia also encompasses sociocultural

    opportunities as an exclusionary factor and the paediatrician may

    Figure 1 Discrepancy between the spelling of a child with developmentalbe able to assist here by taking into consideration what is known

    about the context of the family and the childs opportunities.

    Learning to read is a complex behavioural development and

    children who live in crowded homes with poor amenities or who

    have been looked after have lower attainments in their

    academic skills from children with similar socioeconomic back-

    grounds. Also children who are neglected or abused can differ-

    entially experience more difficulties with speech and language

    development than other cognitive domains and this in turn can

    predispose them to reading difficulties. The mediators of poor

    reading for children with reduced sociocultural opportunities are

    highly complex and incorporate lack of parents/carers reading

    to the child, anxiety which can interfere with concentration in

    school, motivation and application to read which is compounded

    by a disinterest in the childs achievements from the parents or

    low expectations from the teacher. Possibly these are the reasons

    why dyslexia can appear to be a middle class diagnosis as it

    PAEDIATRICS AND CHILD HEALTH 20:7 339might appear much more straightforward to exclude aspects such

    as poor sociocultural opportunities and inadequate instruction

    for children from these socioeconomic backgrounds.

    Finally, within the definition of dyslexia, there is the challenge

    of identifying fundamental cognitive disabilities which are

    frequently of constitutional origin. This may be the reason why

    the paediatrician is being consulted and is the most contentious

    area and so will be considered in some detail in the rest of this

    article, with some direction to extended reading. This challenge

    is much more for children with developmental dyslexia and it is

    important to remember that the brain and the environment work

    together to produce the neural networks for reading acquisition

    so although there may be constitutional cognitive disabilities, the

    poor reading difficulties can also be compounded by experiential

    factors.

    Acquired dyslexia is much less common than the develop-

    mental form. It can follow conditions such as dysphasia from

    acquired brain injury or visual difficulties such as onset ocular

    dyspraxia in ataxiaetelangiectasia and disconnection syndromes

    as seen in infarction of the splenium of the corpus callosum from

    ischaemia in the posterior cerebral artery territory following

    raised intracranial pressure. Conditions of acquired dyslexia are

    all individually rare but they should be suggested by the devel-

    opmental trajectory, any evidence of regression and relevant and

    predisposing past medical histories. As there is frequently

    lexia and their competence in visuo-motor figure drawing.a presumption of mainstream education for these children, it is

    critical not to overlook the possibility of acquired dyslexia as

    a cause of poor academic attainment.

    Causes of dyslexia

    There has been enormous progress made in understanding the

    pathogenesis of dyslexia with many contributions from carefully

    delineated neuropsychological and linguistic studies,

    complemented by information from the new techniques such as

    functional brain imaging (fMRI).

    Phonological awareness

    Phonological awareness is appreciating the constituent speech

    sounds of a word and it has the largest body of evidence that it is

    an important deficit in dyslexia. Successful reading depends on

    skills in word identification combined with reading and language

    2010 Published by Elsevier Ltd.

  • comprehension. The child needs to understand that the written

    words are encoded or symbolized representations of the spoken

    words. Temple states that dyslexia appears to involve a problem

    in learning to relate visual input to phonological representations

    (Figure 2).

    Phonological representation allows the child to appreciate the

    constituent speech sounds of a word and then in turn, phonemic

    awareness is the ability to decompose words into these constit-

    uent sounds and map them onto orthographic or the written

    representation. Sight word learning depends on the childs

    appreciation of alphabetic principles, that is to say that letters

    represent sounds. It is possible to learn to talk without this

    conscious appreciation of the individual phonemes but learning

    to read calls upon these skills. In turn, reading builds up the

    childs capacity for both phonemic awareness and orthography

    and phonological representations, so that normal readers

    OCCASIONAL REVIEWdevelop proficiency in language comprehension and fluent word

    identification and in that very process, build up their own

    underlying skills. In contrast, children with dyslexia compound

    their underlying weaknesses in these areas.

    Children with poor phonological awareness have problems in

    acquiring skills in speech sound combinations with rhyme and

    alliteration and syllable recognition and can be identified in

    nursery school. Their poor phonological representations are also

    contributed to by relative deficits in verbal short-term memory

    and verbal working memory. The former can be conceived as the

    skill that would be required to remember a forward digit span,

    whereas the latter refers to a manipulation in the so-called

    mental workspace for a task such as a backward digit span.

    Verbal working memory is not synonymous with verbal intellect

    and it has a wide variability. However, dyslexic children with

    poor verbal working memory capacity struggle with maths as

    well as with literacy. Decreased phonological awareness is also

    accompanied by problems in rapid naming.

    Phonological awareness is now a generally accepted theory of

    dyslexia, although it is still unclear why some children develop

    their phonological skills later in the course of their dyslexia but

    that these skills remain less fluent, particularly in spelling and

    they still experience difficulty with orthographically irregular

    words.

    However, more controversy surrounds a related theory of

    rapid auditory processing which suggests that low level auditory

    Figure 2 Dyslexia appears to involve a problem in learning to relate

    visual input to phonological representations (Temple 2000).PAEDIATRICS AND CHILD HEALTH 20:7 340sensory processing difficulties underpin the poor phonological

    awareness. This hypothesis proposes that there are deficits in

    processing transient acoustic signals that impair the ability to

    discriminate phonemes or speech sounds and which in turn lead

    to the difficulty in establishing stable phonological representa-

    tions. Adaptive computer game interventions that address the

    auditory processing deficits have been developed but with an

    equivocal evidence base. Other researchers have argued that

    these low level auditory deficits (and perhaps also low level

    visual deficits) are actually biological markers of dyslexia but are

    not causative.

    Vision and reading

    The fact that dyslexia was originally known as word blindness

    illustrates the importance assigned to the visual system as

    a potential underpinning of dyslexia. Although the strength of

    evidence in recent years has been cle...

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