Current Status of Treatments for Dyslexia: Critical Review

Ann W. Alexander, MD; Anne-Marie Slinger-Constant, MD


J Child Neurol. 2004;19(10):744-758. 

In This Article

Abstract and Introduction

The acquisition of reading is a complex neurobiologic process. Identifying the most effective instruction and remedial intervention methods for children at risk of developing reading problems and for those who are already struggling is equally complex. This article aims to provide the clinician with a review of more current findings on the prevention and remediation of reading problems in children, along with an approach to considering the diagnosis and treatment of a child with dyslexia. The first part of the review describes interventions targeted at preventing reading difficulties in the at-risk younger child. The second part of the review discusses the efficacy of approaches to treat the older, reading-disabled child ("intervention studies"). Factors that impact the response to treatment are also discussed, as are neuroimaging studies that offer insight into how the brain responds to treatment interventions. With appropriate instruction, at-risk readers can become both accurate and fluent readers. In contrast, although intensive, evidence-based remedial interventions can markedly improve reading accuracy in older, reading-disabled children, they have been significantly less effective in closing the fluency gap. Owing to the dynamic course of language development and the changes in language demands over time, even after a child has demonstrated a substantial response to treatment interventions, his or her subsequent progress should be carefully tracked to ensure optimal progress toward the development of functional reading and written language skills.

Over the last 15 to 20 years, there has been a great deal of research focused on finding the most effective methods for treating reading disability (dyslexia). We have had the opportunity to evaluate not only the effect of specific interventions on reading skill but also to devise technologies that make it possible to study the way in which the brain responds to these interventions. This body of knowledge is complex, in part because although all individuals with dyslexia have a similar problem, namely, difficulty reading, they have heterogeneous characteristics, and depending on the child's developmental level, the demands of reading and the required skills are quite different. As Torgesen pointed out, even the definition of a good reader varies.Is it being able to orally decode accurately and fluently? Is it simply being able to get the gist of what is read? Or is it being able to analyze, synthesize, and convert information from multiple sources into a meaningful whole?[1] Torgesen noted that all of these factors have contributed to the challenge of designing intervention studies, interpreting the outcomes of treatment, and answering the following crucial questions:

  1. What types of prevention or intervention treatment will be most effective? The answer depends on what children need to know to read at a given grade level and the reading level expected for their developmental stage (eg, mechanics of word reading, fluency, or text reading and comprehension of reading).

  2. What level of intensity is most effective? There are two types of intensity: one referring to the frequency of the intervention (daily, two to three times per week, once per week) and the other referring to the instructor to student ratio (1:1, small group, classroom).

  3. How many hours are needed to complete the intervention? What is the optimal duration of treatment?

  4. How well are gains and skills maintained after the intervention has ended?

  5. What therapist or teacher skills are needed?

  6. What child characteristics contribute to the success or failure of the intervention (type of language involvement, severity, age, and comorbidity)?

  7. In what educational context can these interventions be implemented?

To address some of these questions, the National Research Council, the research arm of the National Academy of Science, published a report in 1998 summarizing available research findings that could be used to prevent reading difficulties in young children.[2] The report emphasized the importance of early childhood language and literacy experience as the foundation on which systematic phonologic decoding should be taught. To explore how reading research could be more specifically applied to classroom implementation, the National Institute for Child Health and Human Development and the Department of Education convened the National Reading Panel to conduct a meta-analysis of reading research since 1990 in the areas of alphabetics, fluency, comprehension, teacher education, and the effects of computer technology. Only studies meeting rigorous research methodologic criteria were analyzed. Although much of the research in the field did not meet these criteria, and in some instances there were too few studies to conduct a meta-analysis, the National Reading Panel did find robust evidence in the areas of alphabetics (phonologic awareness, reading and spelling skills).[3]

Specifically, direct and systematic phonologic awareness and phonics instruction produced significant effects for at-risk readers (ie, young children in kindergarten or first grade who have had minimal exposure to reading and are deficient in phonologic awareness and letter knowledge—precursors for the acquisition of phonologic decoding), as well as disabled readers (those who have had exposure to adequate reading instruction and have not learned to read). The panel noted that there were differences in the type of instruction and the response of these two groups of children to instruction:

One type of instruction involved the prevention of reading disability in the young, at-risk child.

  1. The younger the child (kindergarten through first grade), the better the outcome.

  2. The at-risk child responds best to small-group instruction (2:1 or 3:1), with phonologic awareness training being combined with letter knowledge and explicit phonics instruction.

  3. Trained teachers achieved good results.

  4. More frequent instruction (4–5 days/week) was more effective.

  5. Gains were maintained in most of the children at long-term follow-up.

  6. The following characteristics of the child were associated with poor outcome in reading and spelling.poor rapid naming, poor verbal ability, and attention or behavior overall. Low socioeconomic status was also associated with poor spelling achievement. Computer programs were helpful aids.

The second type of instruction, remediation, was directed at the older, reading-disabled child (second to sixth grade):

  1. Although the older, reading-disabled children responded with improved word reading to similar intensive, direct, and explicit instruction, they were less responsive, and gains were not as marked.

  2. They did better with one-to-one or small-group instruction.

  3. More intensive work for a longer duration was required.

  4. Spelling and fluency did not respond well, but there was some improvement in reading comprehension.

  5. Gains were maintained in most children at follow-up.

  6. Characteristics that impeded reading and spelling gains included poor attention and behavior control, rapid naming deficits, and weak verbal ability. Low socioeconomic status affected reading gains; trained teachers achieved good results, but they were typically not as robust as the results when working with researchers. Computer instruction served as an effective aid but was not effective by itself.

The skills needed for normal reading development were found to encompass five essential domains:

  1. Phonemic awareness.awareness of the sound structure of spoken language and the basic units of speech (phonemes)

  2. Phonics.knowledge of relationships between letters and sounds and spelling-sound correspondences; allows fluent phonologic decoding

  3. Sight word acquisition.automaticity of reading words by sight without having to decode sound by sound; leads to orthographic decoding fluency

  4. Vocabulary.the storage of word meanings and the ability to fluently access that information

  5. Comprehension of text.the ability to think about and extract the information provided in text while reading, a fluent integration of multiple processes.

Although the National Reading Panel's review of the research literature answered some of the questions about word reading instruction, there were not enough data to draw firm conclusions about the best way to teach fluency, vocabulary, and text comprehension or to train teachers, illustrating the need for more stringent research in the field. Nonetheless, preliminary findings suggested that:

  1. Fluency is better achieved by repeated guided oral reading than by silent reading practice.

  2. Vocabulary instruction should be taught by both direct and indirect methods, with computer programs as adjuncts.

  3. Comprehension is developed by fluent word reading, vocabulary strength, and a combination of strategies for helping the child connect with and think about the text.

The most rigorous methodologic studies resulted in very robust effect sizes for reading gains; however, even the studies with the weakest methodology also yielded significant gains in phonologic awareness. With the impetus to improve the quality of the experimental studies to arrive at more definitive answers to our questions, research has continued to advance our understanding of how children develop skilled reading and to learn more about the factors that hinder that development.[4] More recent findings are summarized below.


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