Risk Factors (Genetics & Inherited Conditions)
Etiology and Genetics (Genetics & Inherited Conditions)
Dyslexia is a complex learning disability that results from a combination of genetic and environmental factors. The most recent estimates suggest that inherited factors account for up to 80 percent of the determinants involved in the development of dyslexia. The disability has long been known to run in families, and twin studies have confirmed that genetic factors are primarily responsible for the observed family clustering. While there is no single predictable pattern of inheritance, one report suggests that a child with one affected parent has a 40-60 percent risk of developing dyslexia. Another study found that 88 percent of dyslexics had a close relative who also had problems with spelling or reading.
Linkage analyses in families where two or more family members are dyslexic have helped to identify nine chromosomal regions that appear to contain a gene or genes for susceptibility to dyslexia. Four of these are particularly significant, since they are found in multiple large family samples: DYX1, at chromosomal position 15q21; DYX2, at position 6p21-p22; DYX6, at position 18p11; and DYX8, found on chromosome 1 at position 1p34-p36. Other DYX genes for susceptibility are found on chromosomes 2, 3, 11, and X. Molecular genetic studies have not yet revealed the exact locations or the protein products of these susceptibility genes, but this is an area of active current...
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Symptoms (Genetics & Inherited Conditions)
If a child experiences any of the following symptoms, his or her parents should not assume it is due to dyslexia. These symptoms may be caused by other health conditions. If a child experiences any one of them over time, his or her parents should see their physician or pediatrician. Symptoms include difficulty in the following areas: learning to speak, reading and writing at grade level, organizing written and spoken language, learning letters and their sounds, learning number facts, spelling, learning a foreign language, and correctly doing math problems.
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Screening and Diagnosis (Genetics & Inherited Conditions)
The doctor will ask about a parent or a child’s symptoms and medical history and will perform a physical exam, including hearing and vision tests. The patient may then be referred to an expert in learning disabilities, such as a school psychologist or learning specialist, for additional testing to determine if he or she has dyslexia. Tests given by the specialist may include cognitive processing tests to measure thinking ability; intelligence quotient (IQ) tests to measure intellectual functioning; and tests to measure speaking, reading, spelling, and writing skills.
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Treatment and Therapy (Genetics & Inherited Conditions)
Most people with dyslexia need help from a teacher, tutor, or other trained professional. Parents should talk with their doctors or pediatricians and learning specialists about the best plans for them or their children.
Treatment options include remediation, a way of teaching that helps people with dyslexia to learn language skills. Concepts used in remediation include teaching small amounts of information at a time, teaching the same concepts many times (“overteaching”), and using all the senses—hearing, vision, voice, and touch—to enhance learning (multisensory reinforcement).
Compensatory strategies are ways to work around the effects of dyslexia. They include audiotaping classroom lessons, homework assignments, and texts; using flashcards; sitting in the front of the classroom; using a computer with spelling and grammar checks; and receiving more time to complete homework or tests.
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Prevention and Outcomes (Genetics & Inherited Conditions)
There is little that can be done to prevent dyslexia, especially if it runs in a patient’s family. However, early identification and treatment can reduce its effects. The sooner children with dyslexia get special education services, the fewer problems they will have learning to read and write at grade level. Under federal law, free testing and special education services are available for children in the public school system.
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Further Reading (Genetics & Inherited Conditions)
Brunswick, Nicky. Dyslexia: A Beginner’s Guide. Oxford, England: Oneworld, 2009.
EBSCO Publishing. Health Library: Dyslexia. Ipswich, Mass.: Author, 2009. Available through http://www.ebscohost.com.
Hultquist, Alan M. An Introduction to Dyslexia for Parents and Professionals. Philadelphia: Jessica Kingsley, 2006.
Nicolson, Roderick I., and Angela J. Fawcett. Dyslexia, Learning, and the Brain. Cambridge, Mass.: MIT Press, 2008.
Reid, Gavin, ed. The Routledge Companion to Dyslexia. New York: Routledge, 2009.
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Web Sites of Interest (Genetics & Inherited Conditions)
Canadian Dyslexia Association. http://www.dyslexiaassociation.ca
International Dyslexia Association. http://www.interdys.org
KidsHealth from Nemours. http://kidshealth.org/kid
Learning Disabilities Association of Canada. http://www.ldac-taac.ca/index-e.asp
National Center for Learning Disabilities. http://www.ld.org
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Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
Nearly 25 percent of the individuals in the United States and in many other industrialized societies who otherwise possess at least average intelligence cannot read well. Many such people are viewed as suffering from a neurological disorder called dyslexia. This term was first introduced by the German ophthalmologist Rudolf Berlin in the nineteenth century. Berlin defined it as designating all those individuals who possessed average or above-average intelligence quotients (IQs) but who could not read adequately because of their inability to process language symbols. At the same time as Berlin and later, others reported on dyslexic children. These children saw everything perfectly well but acted as if they were blind to all written language. For example, they could see a bird flying but were unable to identify the written word “bird” seen in a sentence.
The problem involved in dyslexia has been defined and redefined many times since its introduction. The modern definition of the disorder, which is close to Berlin’s definition, is based on long-term, extensive studies of dyslexic children. These studies have identified dyslexia as a complex syndrome composed of a large number of associated behavioral dysfunctions that are related to visual-motor brain immaturity and/or brain dysfunction. These problems include a poor memory for details, easy distractibility, poor motor skills, visual letter and word reversal, and the...
(The entire section is 857 words.)
Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
The early diagnosis and treatment of dyslexia is essential to its eventual correction. Many experts agree that if a treatment begins before the third grade, there is an 80 percent probability that the dyslexia can be corrected. If the disorder remains undetected until the fifth grade, however, success at treating dyslexia is cut in half. If treatment does not begin until the seventh grade, the probability of successful treatment drops below 5 percent.
The preliminary identification of a dyslexic child can be made from symptoms that include poor written schoolwork, easy distractibility, clumsiness, poor coordination, poor spatial orientation, confused writing and/or spelling, and poor left-right orientation. Because numerous nondyslexic children also show many of these symptoms, a second step is required for such identification: the use of written tests designed to identify dyslexics. These tests include the Peabody Individual Achievement Test, the Halstead-Reitan Neuropsychological Test Battery, and the SOYBAR Criterion Tests.
Electroencephalograms and CT scans are often performed in the hope of pinning down concrete brain abnormalities in dyslexic patients. There is considerable disagreement, however, over the value of these techniques, beyond finding evidence of tumors or severe brain damage—both of which may indicate that the condition observed is not dyslexia. Most researchers agree that children who seem...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
The identification of dyslexia by German physician Rudolf Berlin and England’s W. A. Morgan began the efforts to solve this unfortunate disorder. In 1917, Scottish eye surgeon James Hinshelwood published a book on dyslexia, which he viewed as being a hereditary problem, and the phenomenon became much better known to many physicians.
Attempts at educating dyslexics were highly individualized until the endeavors of Orton and his coworkers and of Fernald led to more standardized and widely used methods. These procedures, their adaptations, and several others not mentioned here had become the standard treatments for dyslexia by the late twentieth century.
Many famous people—including Hans Christian Andersen, Winston Churchill, Albert Einstein, George Patton, and Woodrow Wilson—had symptoms of dyslexia, which they subsequently overcame. This was fortunate for them, because adults who remain dyslexic are very often at a great disadvantage. In many cases in modern society, such people are among the functionally illiterate and the poor. Job opportunities open to dyslexics of otherwise adequate intelligence are quite limited.
Furthermore, with the development of a more complete understanding of the brain and its many functions, better counseling facilities, and the conceptualization and actualization of both parent-child and parent-counselor interactions, the probability of success in dyslexic training...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Huston, Anne Marshall. Understanding Dyslexia: A Practical Approach for Parents and Teachers. Rev. ed. Lanham, Md.: Madison Books, 1992. Explains dyslexia, describes its three main types, identifies causes and treatments, and covers useful teaching techniques. A bibliography, a useful glossary, appendixes, and teaching materials are valuable additions.
International Dyslexia Association. http://www.inter dys.org. Association Web site includes a bookstore and information on new assistive technologies. Site is divided into sections for children, teens, college students, adults, educators, and parents.
Jordan, Dale R. Overcoming Dyslexia in Children, Adolescents, and Adults. 3d ed. Austin, Tex.: Pro-Ed, 2002. Examines the role of genetics and brain development in relation to learning disabilities and explains the perceptual and emotional nature of dyslexia. Eight “success stories,” strategies for improving academic performance and social skills, and assessment checklists are included.
Levinson, Harold N. Smart but Feeling Dumb: The Challenging New Research on Dyslexia—and How It May Help You. Rev. ed. New York: Warner Books, 2003. Argues that the basis of dyslexia and other disorders is an inner ear dysfunction that can be cured with judicious application of the correct medications. Also discusses adults and families with dyslexia, speech disorders, and attention deficit...
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Introduction (Psychology and Mental Health)
The ability to read quickly and well is essential for success in modern industrialized societies. Several researchers, including Robert E. Valett, have pointed out that an individual must acquire considerable basic cognitive and perceptual-linguistic skills to learn to read. First, it is necessary to learn to focus one’s attention, to concentrate, to follow directions, and to understand the language spoken in daily life. Next, it is essential to develop auditory and visual memory with sequencing ability, word-decoding skills, a facility for structural-contextual language analysis, the ability to interpret the written language, a useful vocabulary that expands as needed, and speed in scanning and interpreting written language. Valett has noted that these skills are taught in all good developmental reading programs.
Yet 20 to 25 percent of the population of the United States and many other industrialized societies, people who otherwise possess at least average intelligence, cannot develop good reading skills. Many such people are viewed as suffering from a neurological disorder called dyslexia, a term that was first introduced by a German ophthalmologist, Rudolph Berlin, in the nineteenth century. Berlin meant it to designate all those individuals who possessed an average or above-average performance intelligence quotient (IQ) but who could not read adequately because of an inability to process language symbols. Others reported...
(The entire section is 328 words.)
Brain Development (Psychology and Mental Health)
Two basic explanations have evolved for dyslexia. Many physicians propose that it is caused by either brain damage or brain dysfunction. Evolution of the problem is attributed to accident, to disease, or to faults in body chemistry. Diagnosis is made by the use of electroencephalograms (EEGs), computed tomography (CT) scans, and other related technology. After such evaluation, medication is often used to diminish hyperactivity and nervousness, and physical training procedures called patterning are used as tools to counter the neurological defects.
In contrast, many special educators and other related researchers believe that the problem is one of dormant, immature, or undeveloped learning centers in the brain. The proponents of this concept encourage the correction of dyslexic problems by emphasized teaching of specific reading skills to appropriate individuals. Although such experts also agree that the use of appropriate medication can be of value, they lend most of their efforts to curing the problem by a process called imprinting, which essentially trains the dyslexic patient through use of often-repeated, exaggerated language drills.
Another interesting point of view is the idea that dyslexia may be at least partly the fault of the written languages of the Western world. Rudolph F. Wagner has pointed out that children in Japan exhibit an incidence of dyslexia that is less than 1 percent. One explanation for this,...
(The entire section is 339 words.)
Auditory Dyslexia and Dysgraphia (Psychology and Mental Health)
The other two problems viewed as dyslexia are auditory dyslexia and dysgraphia. Auditory dyslexia is the inability to perceive individual sounds of spoken language. Despite having normal hearing, auditory dyslexics are deaf to the differences between certain vowel or consonant sounds; what they cannot hear, they cannot write. Dysgraphia is the inability to write legibly. The basis for this problem is a lack of the hand-eye coordination required to write legibly.
Usually, a child who suffers from visual dyslexia also exhibits elements of auditory dyslexia. This complicates the issue of teaching such a student, because only one type of dyslexic symptom can be treated at a time. Also, dyslexia appears to be a sex-linked disorder; three to four times as many boys have it as do girls. In all cases, early diagnosis and treatment of dyslexia are essential to its eventual correction. For example, if treatment begins before the third grade, there is an 80 percent probability that dyslexia can be corrected. When dyslexia remains undiscovered until the fifth grade, this probability is halved. If treatment does not begin until the seventh grade, the probability of successful treatment is only 3 to 5 percent.
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Assessment Methods and Treatment (Psychology and Mental Health)
Preliminary identification of the dyslexic child often can be made from symptoms that include poor written schoolwork, easy distractibility, clumsiness, poor coordination and spatial orientation, confused writing and/or spelling, and poor left-right orientation. Because nondyslexic children can also show many of these symptoms, the second step of such identification is the use of written tests designed to pick out dyslexic children. These include the Peabody Individual Achievement Test, the Halstead-Reitan Neuropsychological Test Battery, and the SOYBAR Criterion Tests. Many more personalized tests are also available.
Once conclusive identification of a dyslexic child has been made, it becomes possible to begin a corrective treatment program. Most such programs are carried out by special-education teachers in school resource rooms, in special classes limited to children with reading disabilities, and in schools that specialize in treating the disorder.
One often-cited method is that of Grace Fernald, which utilizes kinesthetic imprinting, based on a combination of “language experience” and tactile stimulation. In this popular method, the child relates a spontaneous story to the teacher, who transcribes it. Next, each word unknown to the child is written down by the teacher, and the child traces its letters over and over until he or she can write that word without using the model. Each word learned...
(The entire section is 701 words.)
Research (Psychology and Mental Health)
The identification of dyslexia more than one hundred years ago, which resulted from the endeavors of the German physician Berlin and of W. A. Morgan, in England, launched efforts to find a cure for this unfortunate disorder. In 1917, the Scottish eye surgeon James Hinshelwood published a book on dyslexia, which he viewed as being a hereditary problem, and the phenomenon became better known to physicians. Attempts at educating dyslexics, as recommended by Hinshelwood and other physicians, were highly individualized until the endeavors of Orton and coworkers and of Fernald led to more standardized and soon widely used methods.
Furthermore, with the development of a more complete understanding of the brain and its many functions, better counseling facilities, and the conceptualization and actualization of both parent-child and parent-counselor interactions, the prognosis for successful dyslexic training has improved significantly. Also, a number of extensive studies of dyslexic children have been carried out and have identified dyslexia as a complex syndrome composed of numerous associated behavioral dysfunctions related to visual-motor brain immaturity. These include poor memory for details, easy distractibility, poor motor skills, letter and word reversal, and the inability to distinguish between important elements of the spoken language.
A particularly extensive and useful study was carried out by Edith Klasen and described...
(The entire section is 320 words.)
Sources for Further Study (Psychology and Mental Health)
Hoien, Torliev, and Ingvar Lundberg. Dyslexia: From Theory to Intervention. Norwell, Mass.: Kluwer, 2000. Presents European research in the causes and treatment of dyslexia, much of it presented in English for the first time.
Nicolson, Roderick I., and Angela Fawcett. Dyslexia, Learning, and the Brain. Cambridge, Mass.: MIT Press, 2008. Leading dyslexia researchers theorize that the source of this disability may be rooted in the procedural learning system, in the cortical and subcortical regions of the brain.
Reid, Gavin. Dyslexia: A Practitioner’s Handbook. 4th ed. New York: John Wiley & Sons, 2008. A review of dyslexia research and teaching practices for educators. Includes a review of resources for classroom strategies.
Reid, Gavin, and Janice Wearmouth. Dyslexia and Literacy: An Introduction to Theory and Practice. New York: John Wiley & Sons, 2002. Covers recent theoretical and practical approaches to dyslexia in both psychological and pedagogical contexts.
Snowling, Margaret J. Dyslexia: A Cognitive Developmental Perspective. 2d ed. New York: Basil Blackwell, 2000. Covers many aspects of dyslexia, including its identification, associated cognitive defects, the basis for development of language skills, and the importance of phonology. In addition, it contains many references.
West, Thomas G. In the Mind’s Eye: Visual...
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Dyslexia (Encyclopedia of Medicine)
Dyslexia is a learning disability characterized by problems in reading, spelling, writing, speaking, or listening. In many cases, dyslexia appears to be inherited.
The word dyslexia is derived from the Greek word, dys (meaning poor or inadequate) and the word lexis (meaning words or language).
The National Institutes of Health estimates that about 15% of the United States population is affected by learning disabilities, mostly with problems in language and reading. The condition appears in all ages, races, and income levels. Dyslexia is not a disease, but describes rather a different kind of mind that learns in a different way from other people. Many people with the condition are gifted and very productive; dyslexia is not at all linked to low intelligence. In fact, intelligence has nothing to do with dyslexia.
Dyslexic children seem to have trouble learning early reading skills, problems hearing individual sounds in words, analyzing whole words in parts, and blending sounds into words. Letters such as "d" and "b" may be confused.
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Dyslexia (Encyclopedia of Neurological Disorders)
Dyslexia is an unexpected impairment in reading and spelling despite a normal intellect.
Dyslexia was first described by Hinshelwood in 1896. Orton originally hypothesized that dyslexia results from a dysfunction in visual memory and visual perception due to a delayment in maturation. Most dyslexics also display poor writing ability. Dyslexia is a classical primary reading disorder and should be differentiated from secondary disorders such as mental retardation, educational or environmental deprivation, or physical/organic diseases. The disorder results as a combination of genetic and environmental causes, which can induce variations in the behavioral, cognitive, and physiological measures related to reading disability. Dyslexia was previously called congenital word blindness. Dyslexia is a reading disorder, not caused by lowered motivation, inadequate learning opportunity or any overt neurological disability. Reading is a complex process which involves multiple systems to process the information cognitively and physiologically. In simple terms reading typically begins with a visual sensation stimuli and processing the text via the visual pathway in the brain (from the retina in the eye, the impulse goes in the brain to the lateral geniculate nuclei and primary visual cortex, the occipital lobe, located in...
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Dyslexia (Encyclopedia of Science)
Dyslexia is a learning disorder characterized by difficulty reading and writing. Dyslexia is not caused by poverty, psychological problems, lack of education, or laziness. People who are identified as dyslexic generally have normal or above-normal intelligence, normal eyesight, and tend to come from average families. It is not unusual for a student with dyslexia to fail English while earning straight As in science.
There are dozens of symptoms associated with the disorder. Dyslexic people may skip words, reverse the order of letters in a word (writing or reading "was" for "saw"), or drop some letters from a word (reading "run" instead of "running"). They may invent strange spellings for common words, have difficulty remembering and following sequences (like reciting the alphabet in order), and have cramped, illegible handwriting.
Causes of dyslexia
Scientists generally agree that dyslexia results from a neurological problem in the areas of the brain involved in reading. Several regions of the brainll located in the brain's left sideave been identified...
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Dyslexia (Encyclopedia of Psychology)
A reading disability that is not caused by an identifiable physical problem (such as brain damage, visual or auditory problems).
Dyslexia is a specific learning disability characterized by a significant disparity between an individual's general intelligence and his or her language skills, usually reflected in school performance.
Estimates of people with dyslexia range from 2% to the National Institutes of Health figure of 15% of the U.S. population. It is a complicated disorder with no identifiable cause or cure, yet it is highly responsive to treatment in the form of special instruction. The most obvious symptoms of the dyslexic show up in reading and writing, but listening, speaking, and general organizational skills are also affected. The dyslexic may have trouble transferring information across modalities, for example from verbal to written forms. The dyslexic's characteristic reversal of letters, confusion between similar letters such as "b" and "d," omission of words when reading aloud, trouble sounding out words, and difficulty following written instructions were first thought to be the result of vision and perceptual problems.e., a failure of taking in the stimulus. Only a small percentage of dyslexics have vision disorders, however, and it is now generally agreed by physicians, researchers, and educators...
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Dyslexia (Encyclopedia of Children's Health)
Dyslexia is a learning disability characterized by problems in reading, spelling, writing, speaking, or listening. It results from the inability to process graphic symbols. In many cases, dyslexia appears to be inherited.
The word dyslexia is derived from the Greek word, dys (meaning poor or inadequate) and the word lexis (meaning words or language). Dyslexic children seem to have trouble learning early reading skills, problems hearing individual sounds in words, analyzing whole words in parts, and blending sounds into words. Letters such as "d" and "b" may be confused. Often a child with dyslexia has a problem translating language into thought (such as in listening or reading), or translating thought into language (such as in writing or speaking). Dyslexia is also referred to as developmental reading disorder (DRD).
Dyslexia is a problem involving higher (cortical) processing of symbols in the brain. Most children with dyslexia are of normal intelligence; many have above-average intelligence. However, when a child is dyslexic, there is often an unexpected difference between achievement and aptitude. Each child with dyslexia has different strengths and weaknesses, although many have...
(The entire section is 1668 words.)
Dyslexia (Encyclopedia of Alternative Medicine)
Dyslexia is a kind of learning disability noted for spatial reversals and shifts and is sometimes described as a neurological disorder. It manifests as difficulties with reading, writing, spelling and sometimes math. Occasionally, balance, movement, and rhythm are affected. Persons with dyslexia frequently display above average to superior intelligence, gifted creativity and genius. Leonardo da Vinci, Albert Einstein, Walt Disney, and the Olympic multi-Gold Medal diving champion, Greg Louganis, are noted examples of persons with dyslexia.
Genetics is believed to be a deciding factor in whether or not a person develops dyslexia. The condition may appear as early as three months. One report suggested that as many as 55% of Americans are affected. The National Institute of Health (NIH) reports that up to 8% of American elementary school children may have the unique characteristics described originally in 1920 by Dr. Samuel Torrey Orton. Believing it first a condition of "cross lateralization of the brain," by which he meant that functions normally processed on the right side of the brain are processed on the left side in the person with dyslexia, Dr. Orton later modified his description of the condition as being a "mixed hemispheric dominance," by which he meant that the alteration of functions to the opposite side of...
(The entire section is 2070 words.)