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There is increasing awareness of the co-occurrence of reading difficulties with other learning disorders. The work of Fawcett and Nicolson has emphasised the frequency with which reading difficulties are associated with impaired movement and balance but there is also evidence to suggest that other disorders of learning, such as attention deficits, co-occur with dyslexia more often than would be expected by chance (Kaplan et al. 199*). Exploring such associations could be one way of researching causal theories for dyslexia and a better understanding of the overlap of symptoms could assist in treatment and remediation.
This session covered a range of issues. Lois MacDonell from the Highland Psychiatric Research Foundation used the overlap in symptoms from a number of psychiatric and neurodevelopmental disorders to discuss the possible role of fatty acids (phospholipids). Phosopholipid abnormalities, for example, have been implicated in schizophrenia, depression and neurodevelopmental disorders including dyslexia (Stordy, 1995). Using a new technique developed at the Victoria Infirmary, Glasgow the Foundation has undertaken research suggesting that both dyslexics and schizophrenics are deficient in the enzyme, cytosolic phospholipase A2. This enzyme controls the release of one of the major fatty acids (Arachidonic, AA) from the membranes. The Foundation are also investigating the possibility of using simple non-invasive diagnostic tests, such as a niacin skin patch and breath analysis, to identify abnormal fatty acid metabolism.
A lively presentation was given by Ken Jacobson from the University of Massachusettes-Amherst who considered dyslexia and ADHD from a social and environmental perspective. He challenged the prevailing theories for a biological basis for these disorders and proposed instead that reactions to stress may adversely affect the hippocampus and thus impair short-term memory. Jacobson reported observations of behaviour for over 100 mainstream primary school children which he had undertaken in the UK and USA. Measures of hyperactivity and distractibility suggested that at any one time around 30% of the children were displaying ADHD-like behaviours ( this average, however, was based on the incidence of such behaviours being as low as 10% for some children and over 80% for others ). Observations at a specialist school for dyslexia produced the lowest scores for ADHD-like behaviours which he attributed to the approach taken by the school, highlighting the importance of environment. Whilst many may not agree with Ken Jacobson's dismissal of biological factors and the emphasis on environment , it is important that we do not loose sight of the impact of social and environmental factors for children with difficulties.
Dr Andrew Newton, an Associate Specialist in Emergency Medicine and Paediatrics, discussed the overlapping symptomatology of Dyslexia, Dyspraxia and Attention Deficit Hyperactivity Disorder (ADHD) suggesting that co-morbidity may be the rule rather than the exception for specific learning difficulties. He highlighted recent neurological studies which have identified similarities in neurological dysfunction as the possible explanation for the overlap of symptoms. Dr Newton described his study in which the families of 150 children with dyslexia, dyspraxia and ADHD (50 of each) completed questionnaires containing 20 health-related and 50 behaviour-related questions. Six behaviours were found to be common in all three diagnostic groups. These were the tendency to fidget, poor attention to detail, frequent careless mistakes, difficulty organising tasks, difficulty following instructions and the tendency to loose belongings. Questions on previous medical history provided only limited overlap between the three diagnostic groups, although postnatal jaundice and asthma warranted further investigation. He concluded that the identification of all symptoms was necessary to ensure each child received appropriate intervention rather than using symptoms merely to identify a diagnostic category.
The final presentation of the session was by Aryan van der Leij from the University of Amsterdam who concluded that the ability to read non-words made children good readers! His study investigated differences in cognitive functioning for 12 year-old children who displayed either reading, arithmetic or comprehension difficulty or any combination of these three. The functions assessed were perception and motor function, attention, working memory capacity, non-word reading and rapid naming and finally an assessment of reading, spelling and reading comprehension. His key results suggested that those with arithmetic difficulty (dyscalculia) showed problems with working memory and to a lesser extent attention but comprehension difficulty was not associated significantly with any of the functions assessed. Those children with difficulties in reading, arithmetic and comprehension showed problems with all the functions assessed while those with problems in only two areas were indistinguishable from those with problems in a single area. This presentation emphasises the need to recognise children with multiple difficulties as they are at greater risk of failure. Overall the session reminds us that all children need to be treated on the basis of their individual needs rather than as a 'typical example' of a diagnostic category.
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