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Author(s): |
Bruce Shapiro M.D. |
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Reprinted with Permission From: |
International Dyslexia Association (info) |
Printed Date: Winter 1999
Date Posted on this Website: May 22 2002
At present, there is actually very little that pediatricians can do to identify or treat dyslexia at an early age. As I will explain in this essay, current techniques and knowledge in pediatric medicine are simply not advanced enough to support such goals, worthy though they may be. Furthermore, I am not terribly optimistic that more effective approaches will become clinically applicable in the near future, given the stringent requirements that must be met to insure that such interventions would be valid and useful.
From the viewpoint of pediatric medicine, it is especially problematic that dyslexia has historically been seen as both an educational disability, involving weaknesses in cognitive and language processing that impede learning to read, and as a neurological disorder, stemming from constitutional differences that may be genetically transmitted. The definition recently adopted by the IDA, for instance, embodies both of these ideas. Thus, the hallmark of dyslexia - namely, poor reading achievement - is a behavioral symptom that pediatricians are not trained to examine or treat. At present, a means of diagnosing dyslexia in the absence of reading dysfunction does not exist. Research in pediatric medicine aims to determine and understand the underlying biological conditions that contribute to reading difficulties. Although some of these might eventually serve as definitional criteria, the evidence in support of this is lacking so far. Contemporary medical practice, therefore, does not yet incorporate into standard pediatric and neurological examinations techniques for detecting or treating any such anatomical or physiological differences.
Few pediatricians espouse a strictly nurturist view of child development, in which dyslexia is seen as a purely academic problem that arises in response to school experiences. If one adopts this perspective, then early identification efforts would be fruitless because the modifiability of the organism precludes prediction. In that case, early intervention to prevent reading disabilities could be uncoupled from early identification by providing intervention to all children, for instance by ensuring universal access to high quality preschool programs and school instruction. This road toward the prevention of reading disabilities may also be the most sensible one at present, regardless of one's stance on the nature-nurture question.
On the other hand, if one takes the more widespread view of dyslexia as a neurologic disorder, then the possibility of presymptornatic identification certainly exists. Four assumptions would have to be met, however. First early neural dysfunction would have to be linked in a predictive fashion to later differences that are associated with dyslexia. If there is no predictive validity, then early identification cannot proceed. Second, neural dysfunction in childhood must be diffuse. This assumption is necessary to define the proxies for reading dysfunction. Third, the neural dysfunction would have to be clearly delineated from normal function either categorically (i.e., a clear qualitative difference can be detected) or dimensionally (i.e., an extreme degree of severity can be measured along a continuum of level of functioning).
Fourth, strictly speaking, the neural dysfunction chosen ought to be related specifically to dyslexia and not also to other outcome conditions. This is predicated on the traditional (but increasingly controversial) notion that dyslexia differs from other kinds of reading difficulties in its nature and causes. If the goal under consideration is broadened to encompass the preven- tion of all sorts of reading problems, whether or not they are accompanied by general learning difficulties, then this requirement can be relaxed to some extent.
These assumptions are, unfortunately, not well met when we attempt to predict reading outcomes on the basis of current neurological knowledge and assessment techniques. In the standard preschool neurological examination, the child's movement, sensation, and higher cortical functions are evaluated. Performance in these areas does not predict reading disability for the individual child, although it is useful for detecting other important disorders. For example, the child neurologist can reliably assess young children's fine motor functioning, which affects such activities as coloring, drawing, and tying their shoes. Poor fine motor control is associated with academic dysfunction that is mediated through attention or slow output and is also related to global developmental delays; it does not, however, specifically predict dyslexia. In the neonatal neurologic examination, the infant's state, habituation, movement, and basic sensations are tested. Despite its lack of diagnostic precision, this exam, alone and in conjunction with later assessments, is associated with later academic dysfunction. In one study, the number of abnormal examinations rather than any single examination was most closely associated with prognosis. It is also well established that disorders that insult the brain are associated with poor reading achievement. Extreme prematurity, traumatic brain injury, meningitis, coma, and seizures are events that increase the risk of a child's developing a reading disability (as well as other academic and nonacademic problems).
Major research efforts are underway to identify biological markers that will permit a more precise and objective diagnosis of dyslexia on biological rather than just behavioral grounds. The majority of these attempts are focusing on genetic and neuroimaging approaches. If such efforts are successful then the likelihood of diagnosing dyslexia in the absence of reading disability is increased.
Genetic approaches are being pursued because there is now considerable evidence from family and twin studies that dyslexia often has a genetic basis. The degree of risk for familial dyslexia is discussed in Scarborough and Dickman's essay (this issue). Geneticists are also using linkage studies to try to identify the gene(s) associated with dyslexia. Some early results drew attention to chromosome 15, but confirmation of that site has not been forthcoming. The most promising candidate is on chromosome 6. If this research continues to bear fruit, a means of diagnosing dyslexia (or at least agenetic predisposition for its development) using genetic testing could be on the horizon. The possibility would then also exist that such diagnoses could be obtained via chorionic villus sampling in the first trimester of pregnancy.
Neuroimaging techniques can be classed into three broad categories: static scans, volumetrics, and functional imaging. The static scans assess brain structures and myelin. No abnormalities of structure or myelin have been identified that can diagnose dyslexia. Volumetric studies measure the sizes of specified areas of brain (such as the corpus callosum) and the degree of symmetry or asymmetry between corresponding structures in the left and right hemispheres of the brain. Early research along these lines suggested that areas of the cerebrum (particularly the planum temporale) tend to be atypically symmetrical in children and adults with dyslexia, but some doubt has been cast on those findings. Furthermore, even if verified, this difference between dyslexic and nondyslexic brain architecture is far from clear cut, since a fair number of nondisabled readers showed the 'dyslexic' pattern, and vice versa.
Functional neuroimaging techniques are currently the method of choice in studies of dyslexia. These include positron emission tomography (PET) scanning, functional MRI (MRI), computer-assisted EEG analysis, and magnetoencephalography. Instead of a static snapshot of what the brain looks like, these techniques provide a dynamic look at the working brain. Researchers are using these methods to locate and measure changes in activity levels (as indicated by blood flow and metabolic alterations) at various sites, and to compare patterns of brain activation during different kinds of mental tasks (recognizing letters, judging rhymes, evaluating word meanings, etc.). Very promising results have been obtained that suggest that the processing of printed material is accomplished using somewhat different routes by dyslexic than nondyslexic readers. Again, however, this distinction does not permit diagnosis. Also, longitudinal research with novice readers has not been conducted, so the observed differences in older children and adults could be a consequence, rather than a cause, of reading disability. Nevertheless, the rapid pace at which our knowledge of the neurologcal underpinnings of reading processes progressing is impressive, and meaurements that provide even better diferentiation of individual differences are likely to emerge as technology improves.
Despite the appeal of technology, neuroimaging techniques must meet the same criteria that are required of other kinds of testing. Imaging tests must be administered in a standard fashion to all children. It must be demonstrated that the results from the tests can be replicated on multiple administrations (reliability). The test results must relate to current functions. Most importantly, in preschoolers, the test results must be specifically related to later outcomes. These requirements are far from being met at the present time.
Given the current state of affairs regarding the prediction of reading ability on the basis of preschool neurological assessments, it is clear that any efforts will have to rely on other bases for now. One approach could focus on the relationship between reading disability and other, more easily diagnosed, conditions that are associated with it, such as early language impairment or attention deficit disorder (ADHD). This approach is feasible only if the associated disorder: (a) has a very close relationship with dyslexia; (b) can be reliably diagnosed; and (c) is identifiable at much younger ages than is dyslexia. The relationship of delayed language development to reading difficulties, and the consequences of this for the early identification and treatment of dyslexia, are discussed in detail by Fey (this issue). Trying to identify children with dyslexia on the basis of preschool hyperactivity is unlikely to be successful because the transitory nature of ADHD in preschoolers (McGee et al. 1991) may cause many errors in prediction.
Another approach to early identification would be based on behavioral assessments of skills and knowledge that are known to be associated with later differences in reading achievement, and that probably represent strands of preschool development that contribute causally to success in learning to read. Of course, the accuracy of early identification would depend heavily on the reliability of early assessments and on the strength of their predictive relationship with dyslexia. This approach is the one adopted by the other contributors to this theme issue, but it does not lend itself readily to the pediatric setting. Although screening instruments are available for pediatricians to use for the preliminary detection of cognitive and language impairments, referrals to other specialists is the main course of action when a problem is suspected.
What, then, might pediatricians be expected to do, if anything, to assist in the identification and treatment of dyslexia at an early age? For the near future, we cannot offer any genetic or neurological procedures for diagnosing dyslexia in preschool children. We can, however, make two important contributions. First, simply by carrying out our main professional responsibility of dealing with the physical health and development of young children, we insure that preventable and treatable medical problems will not interfere unduly with learning and cognitive development in the preschool years and beyond.
Second, because we are in a position to observe children and talk to their parents at regular intervals during the early years, we can and should serve as a resource for information and referrals. This is more than just a matter of arranging for an ophthalmological exam when a vision problem is suspected, for audiological testing when there are suggestions that hearing is impaired, and so forth. It also means that pediatricians should stay up-to-date in their knowledge about dyslexia in general and about current thinking in the field about the possibilities (or lack thereof) for early identification and treatment. Brochures and suggestions for additional reading (such as this issue of Perspectives, perhaps) should be made available, and parents can also be referred to IDA as a source of information. If there are local programs that provide books to low-income families, the pediatrician should enlist their cooperation. Pediatricians should also encourage all parents to talk at length with their preschool children about interesting things and to provide them with ample opportunities for literacy activities (shared reading, scribbling on paper, etc.). Finally, when a speech or language impairment is suspected, they should refer the child to a speech-language professional for an in-depth examination; research makes it clear that even though some such delays are transient, many are not, so simply saying "he'll probably out- grow it" is no longer justified.
My final point is a cautionary one. All efforts that are undertaken, including those suggested above, must be done in a way that avoids the potentially harmful repercussions of attempting to identify dyslexia at an early age. I am concemed that children who are classified as "at risk" will be viewed differently by their families. Parents may perceive their children as less competent, and might thus lower their expectations for achievement. Labeling may also adversely affect child development in other areas. Children who are misidentified as "at risk," furthermore, may be denied normal child experiences as a result of the misclassification. Prediction errors of the other sort, namely failures to identify preschoolers who do develop dyslexia later, may lead to delayed recognition of the problem when it does emerge, and hence delayed intervention. Finally, if parents are led to believe that early intervention will successfully eliminate a child's risk for reading disabilities, then they may experience a sense of failure (which may extend to the child) if the child nevertheless has difficulties in learning to read. In short, until a framework is in place to deal with these potentially harmful consequences of early identification and intervention, it would be unwise to undertake any such efforts on a large scale.
Instead, at least for now, I feel that the responsibility for detecting and remediating dyslexia should remain in the educational system. An effective curriculum combined with continuous monitoring of each child's progress, such that those who are lagging behind receive assistance immediately, would go a long way toward reducing the prevalence of reading disabilities.
Suggested Readings
DeFries J.C. & Alarcon M. (1996). Genetics of Specific Reading Disability. Mental Retardation and Developmental Disabilities Research Reviews. 2:39-47.
McGee R., Partridge F., Williams S., Silva P.A. 1991. A twelve year follow-up of preschool hyperactive children. Journal of the American Academy of Child and Adolescent Psychiatry. 30:224-232.
Rumsey I. 1996. Developmental Dyslexia: Anatomic and Functional Neuroimaging. Mental Retardation and Developmental Disabilities Research Reviews. 2:28-38.
Shapiro B.K. 1994. Early Detection of Leaming Disability. In A.I. Capute, PJ. Accardo, B.K. Shapiro, Eds. Learning Disabilities Spectmm: ADD, ADHD, & LD. Tlffionium, MD: York Press. p121-138.
Shapiro, B.K., Accardo, P.J., and Capute, A.I. (1998). Specific Reading Disability: A View of the Spectrum. Timonium, MD: York Press. Of particular relevance are chapters by Rumsey and Eden (on functional neuroimaging), Shapiro (on early identification), and Smith (on genetics).
Shapiro B.K., Palmer F.B., Wachtel R.C., Capute A.J., 1984. Issues in the early identification of specific learning disability. Journal of Developmental and Behavioral Pediatrics 5:15-20.
Bruce K. Shapiro, M.D. is an associate Professor of Pediatrics at the Johns Hopkins University School of Medicine in Baltimore, MD, and is the Director of Neurodevelopmental Pediatrics at the Kennedy Krieger Institute. Dr. Shapiro directs the interdisciplinary training program, Leadership Education in Neurodevelopmental Disabilities (LEND}, that is funded by the Maternal and Child Health Bureau of the Health Resources and Services Administration. His research interests are in neurodevelopmental disabilities and his clinical interests focus on school-aged children with academic and behavioral dysfunction.
