dyslexia

More about Dyslexia: Causes and symptoms Diagnosis Treatment Prognosis Resources

Definition

Dyslexia is a learning disability characterized by problems in reading, spelling, writing, speaking, or listening. In many cases, dyslexia appears to be inherited.

Description

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.

When a person is dyslexic, there is often an unexpected difference between achievement and aptitude. However, each person with dyslexia has different strengths and weaknesses, although many have unusual talents in art, athletics, architecture, graphics, drama, music, or engineering. These special talents are often in areas that require the ability to integrate sight, spatial skills, and coordination.

Often, a person 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).

Common characteristics include problems with:

• identifying single words
• understanding sounds in words, sound order, or rhymes
• spelling
• transposing letters in words
• handwriting
• reading comprehension
• delayed spoken language
• confusion with directions, or right/left handedness
• confusion with opposites (up/down, early/late, and so on)
• mathematics

— Beth Kapes

---

n.
A learning disorder marked by impairment of the ability to recognize and comprehend written words.

[New Latin : DYS- + Greek lexis, speech (from legein, to speak).]

Definition

Dyslexia is an unexpected impairment in reading and spelling despite a normal intellect.

Description

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 the back of the head, which functions to process and integrate incoming visual information). Input information from vision is probably integrated with other neuronal systems that include language-specific rules, learned information and symbolic images into components of language thinking related to reading. Reading-related thinking is correlated with high activity in the left-hemisphere cortical regions, and language processing centers in the brain. Additionally, learning to read is also related to the learning process, which is mediated by the cerebellum and on relay feedback mechanisms between related areas of the brain.

Deficits in reading may stem from disruptions of simple sensory impairments to more complex problems involving thinking related to language. There are several subtypes of dyslexias and they can be categorized as either central or peripheral dyslexias (of which there are two, attentional dyslexia and neglect dyslexia), which result from impairment to brain processes that are capable of converting letters on the page into visual word forms. There are two types of peripheral dyslexias called attentional dyslexia, and neglect dyslexia. The attentional dyslexia subtype is a rare disorder of attention control, typically correlated with damage to the left parietal lobe (located on the sides of the head). The attentional dyslexia causes an impairment of reading words in sentences, since the defect causes many words to be visible at the same time. Neglect dyslexia is usually due to brain damage, and causes an impairment of reading because the affected person misidentifies letters in certain spatial regions of either a word or a group of words. The defect for neglect dyslexia subtype is associated with the right parietal lobe. Neglect dyslexia can be further divided into left neglect dyslexia and right neglect dyslexia. In the left neglect dyslexia subtype, the affected person experiences difficulty reading initial letters of the word, which may cause a letter(s) to be substituted, omitted or added. The right neglect dyslexia subtype causes a patient to have letter errors at the end of the word.

Letter-by-letter reading (LBL, pure alexia, or pure word blindness) is another form of peripheral dyslexia causing patients to have very slow reading performance with large effects on word length and response time. There is damage to the prestriate cortex of the occipital cortex and most patients also have a dense right visual field deficit. The damage impairs the word-form system in an abnormal way so that written words seem as random letter strings.

Central dyslexias are typically caused by disruption to neuronal processes correlated with sound analysis and meaning of written words. There are two major subtypes of central dyslexias which either impair semantic reading or nonsemantic reading. Semantic reading dyslexia is also referred to as deep and phonologic dyslexia. Semantic reading is due to extensive damage to the left hemisphere which results in a deficit whereby patients can only assemble the pronunciation of a word by first assessing its meaning. Affected individuals also make visual errors when reading. Nonsemantic reading, due to damage of the left temporal lobe causes patients to have difficulty reading exception words (i.e. shove), but can read correctly words that are common and similar (i.e. love).

Demographics

It is thought that dyslexia is the most common neurobehavioral disorder affecting children. The prevalence (existing cases) ranges from 5-10% of school-aged children (school and clinic identified) in the United States. However, these rates may be significantly more (up to 17.5%) in unselected populations. Research indicates that dyslexia is a chronic and persistent disorder. Evidence concerning gender predilection remains controversial. Dyslexia may also co-occur with another disorder called attention deficit/hyperactivity disorder (ADHD, 40% comorbidity). Dyslexia affects approximately 80% of children identified as manifesting a learning disorder.

Causes and symptoms

Persons affected with dyslexia have dysfunction developing an awareness of spoken and written words and segmenting smaller units of sound that are essential in an alphabetic language like English. Patients lose the ability to link and map printed symbols (letters) to sound.

Dyslexia runs in families. Studies demonstrate concordance rates of 68% for monozygotic twins and 37% for dizygote twins (Colorado Twin Study of Reading Disability). However, the genetic transmission is not simple and does not follow classical knowledge of trait heritability. Findings suggest that several genetic factors determine reading ability and the interactions of some or all factors determine the ultimate ability to read.

Evidence from neurobiological research utilizing high resolution imaging techniques, and brain measurement studies indicate differences in left temporo-parieto-occipital brain regions in dyslexic patients when compared to nonimpaired readers. Furthermore, evidence using functional brain imaging techniques in adult and children with dyslexia demonstrates a failure of normal left hemisphere posterior brain systems during reading with increased brain activation in frontal regions. This data indicates that impairment of posterior reading systems results in a disruption of the smoothly functioning and integrated reading system seen in nonimpaired persons. The impairment of posterior reading systems causes dyslexic persons to shift to ancillary neuronal systems to compensate for the deficit. It is the impairment in the posterior reading systems that prevents the development of skilled reading. Postmortem studies (confirmed in live subjects using MRI imaging) indicate a lack of symmetry in language-associated regions in the brain. The abnormal symmetry is associated with the common linguistic deficits that are characteristic of dyslexia.

The specific signs of dyslexia in both adults and school-aged children are similar. Patients exhibit inaccurate and labored decoding, word recognition, and text reading. They also exhibit difficulties in spelling and remain slow readers. Typical early symptoms can include difficulty playing rhyming games and problems with learning numbers and letters. Children often avoid reading independently and are unusually happy at the opportunity for parents to read to them.

Diagnosis

All cases and ages are diagnosed clinically by a combination of careful medical history, observation and psychological testing. There is no one test that is sufficient to render a definitive diagnosis. Rather, the diagnosis is made based on the results of all the clinical data attained. Dyslexia can be distinguished from other learning disorders by identifying the phonologic deficit. Family history and collateral data obtained from school and test results are essential. Tests to determine attention, memory, intelligence and math and language skills may be administered to establish the diagnosis.

Treatment team

The treatment team can consist of a neurologist, a pediatrician, and special education instructors. A clinical psychologist can perform psychological assessments (psychometric testing) to help establish the diagnosis. School and/or college counselors also comprise part of an effective and integrated treatment team.

Treatment

The management for dyslexic patients is lifelong. Early identification and intervention (remediation) of reading deficits involves specialist education. Intervention programs must systematically and explicitly teach phonics ensuring a clear understanding of how letters are linked to sounds (phonemes) and spelling. Typically individualized teaching is recommended to provide a balanced remedial program providing systematic instruction on phonemic awareness, phonics, vocabulary fluency and comprehension strategies. A well-integrated treatment program also includes opportunities for writing, reading, and discussing literature. A well-executed treatment program considers each component of the reading process to improve phonemic awareness and the ability to manipulate speech sounds.

Treatment for older persons (high school, college, and graduate school) is accommodation rather than remediation. College students require extra time with examination and reading/writing assignments. Other accommodations include recorded books, tape recorders in the classroom, tutorial services, alternatives to multiple choice questions and computer availability with spelling checkers.

Recovery and rehabilitation

Rehabilitation for dyslexics is a lifelong process. Early intervention in younger patients consists of a highly structured, integrated, systematic and explicit treatment program. A balanced treatment program should include the meaning and phonetic approaches to reading to ultimately improve language development (since dyslexia is a language-based disorder.) The program should allow for personalized instruction. Older persons require accommodation in college and at work versus remediation.

Clinical trials

There are two current clinical research trials entitled: Comprehensive Program to Improve Reading and Writing Skills in At-Risk and Dyslexic Children; and Using MRI to Evaluate Instructional Programs for Children with Developmental Dyslexia. Information can be obtained from http://www.ClinicalTrials.com.

Prognosis

Dyslexia is a lifelong disorder, but improvement is possible. Multiple learning disabilities can be expected, since the brain connections for reading, spelling, listening, speaking, and writing are part of the linguistic system. The prognosis can ultimately depend on associated comorbidities (other disorders associated with the primary disorder), early detection and intervention, and an intensive and comprehensive treatment plan.

Special concerns

Early recognition, intervention, and family members are important. Remediation programs must be delivered by highly-trained specialists, and treatment should be individualized.

Resources

BOOKS

Behrman, Richard, E., et al., eds. Nelson Textbook of Pediatrics. 17th ed. Philadelphia: Saunders, 2004.

PERIODICALS

Brow, W. E., A. L. Reiss, and S. Eliez. "Preliminary evidence of widespread morphological variations of the brain in dyslexia." Neurology 56, no. 6 (March 2001).

Bub, Danial. "Alexia and related reading disorders." Neurological clinics 21, no. 2 (May 2003).

Francks, C., and L. Macphie. "The genetic basis of dyslexia." The Lancet Neurology 1, no. 8 (December 2002).

Olitsky, Scott E. "Reading disorders in children." Pediatric Clinics of North America 50, no. 1 (February 2003).

Wood, F., and E. L. Grigorenko. "Emerging Issues in the Genetics of Dyslexia: A Methodological Preview." Journal of Learning Disabilities 34, no. 6 (November-December 2001).

WEBSITES

Dyslexia.http://www.dyslexia.com.

The International Dyslexia Association.http://www.interdys.org.

ORGANIZATIONS

The National Center for Learning Disabilities. 381 Park Avenue South, Suite 1401, New York, NY 10016. (212) 545-7510 or 888-575-7373; Fax: (212) 545-9665. http://www.ncld.org.

The International Dyslexia Association. 8600 LaSalle Road, Baltimore, MD 21286-2044. 410-296-0232 or 800-ABCD123; Fax: 410-321-5069. http://www.interdys.org.

Laith Farid Gulli, MD

Nicole Mallory, MS, PA-C

Robert Ramirez, DO

n

An impairment of the ability to read. Dyslexic persons often reverse letters and words, cannot adequately distinguish the letter sequences in written words, and have difficulty determining left from right.

Definition

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.

Description

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 5–15% 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 brain occurred sometimes, but not all the time.

Since the advent of Magnetic Resonance Imaging (MRIs), scientists have been able to view dyslexia from

SYMPTOMS OF DYSLEXIA
inability to associate symbols with sounds and vice versa
frequent word guessing
confusion with verbal instructions without visual cues
confused handedness
difficulty sequencing items
slow, soft spoken reading
frequent mispronounciation of words when reading
misperception of words, letters, and numbers moving or disappearing on a written page

another vantage point, ironically, a process imitating what happens inside the mind of a dyslexic individual, according to one educator with dyslexia, Ronald D. Davis. He describes the ordinary ability of the person with dyslexia to visualize an object from multiple points of view, a process which has a moving point of view and which is spatially unanchored. When presented with a word that is easily visualized as a known object, like horse, the dyslexic mind easily imagines the horse from multiple perspectives, and, so rapidly—somewhere between 400 to 2,000 times faster than those without dyslexia—visual cues are processed 'almost intuitively,' demonstrating great mastery of the objectified visual world. However, when it comes to processing sound, language, speaking, handwriting and understanding verbalized communication not associated with an object, like the words the or and, a series of non-image disconnections leads to confusion, disorientation, and an inability to adequately make sense of key pieces of visual information. To the person with dyslexia, a simple seven word sentence may look like a three word sentence with four blank spaces here and there.

Causes & Symptoms

Although an exact cause has not been identified, studies have identified differences in the way sound and visual information are processed between persons with and without dyslexia. In the dyslexic individual these differences create what one NIH scientist refers to as a "physiologic signature"—a unique brain pattern—perhaps the result of emphasized activity along dopamine related neuro-pathways. Dopamine is a neurotransmitter, a chemical substance acting in the brain that facilitates certain kinds of messages. According to one author, when dopamine levels are high, the person with dyslexia experiences time as moving very slowly outside themselves, and very fast inside. As if time stands still. This author also notes that when the person with dyslexia experiences episodes of disorientation, when words or sounds do not create a visual picture for them and their mind continues to try and solve the confusion visually, dopamine levels shift and change. This would seem to be consistent with some of the symptoms of dyslexia, such as inaccurate perceptions of time and a lot of day dreaming.

Symptoms may include:

• poor ability to associate symbols with sounds and vice versa
• frequent word guessing when reading, and an inability to retain meaning
• confusion when given verbal instructions unaccompanied by visual cues
• confused sense of spatial orientation, especially by reversing letters and numbers, and losing one's place frequently while reading, or skipping lines
• having the perception that words, letters and numbers move around, disappear, or get bigger or smaller
• overlooking punctuation marks or other details of language
• slow, labored reading and speech may be difficult to understand, words often mispronounced and softly spoken
• confused sense of right and left handedness
• math concepts are difficult to learn, excessive daydreaming, and difficulty with time
• difficulty sequencing items
• difficulty with jigsaw puzzles; walking a chalk line straightly or other fine motor skill tasks.

Other more positive characteristics common with dyslexia include:

• primary ability of the brain to alter and create perceptions
• highly aware of their environment, intelligent, and above average curiosity
• intuitive, insightful, and having the extraordinary ability of thinking in pictures
• multi-dimensional perception (from various viewpoints almost simultaneously)
• vivid imagination
• experiencing thought as reality (confusing what they see with what they think they see), thereby being abundantly creative.

Diagnosis

Diagnosis is difficult in part because symptoms can also result from other conditions and because no two individuals display the same symptoms. As a result, dyslexia can be viewed as a developmental condition, a "self-created condition," rather than as a disease. As each individual baby interprets visual data, and adapts to the environment accordingly, developing their own individual and unique brain patterns. It is that developmental pattern that is consistent among people with dyslexia. When the individual's mind cannot make sense of the data, confusion and disorientation result; incorrect data is incorporated, causing the individual to make mistakes that leads to emotional reactions, primarily frustration. A behavior is adopted that constitutes a learning disability because it disables future learning and, ultimately, affects self esteem.

Sometimes the learning disorder of dyslexia is inaccurately paralleled to Attention Deficit Disorder (ADD) or Attention Deficit Hyperactivity Disorder (ADHD). In a 2003 study, distinguishable differences between the two learning disorders were readily apparent. Comparing 105 boys between the ages of eight and ten, from three different schools and cross divided into three different groups—35 boys diagnosed with ADHD not taking stimulant medication, 35 boys with dyslexia, and 35 boys without learning disabilities—the study found clear and diagnostically useful differences in speech related patterns between all groups. However, since diagnosis of a learning disability may be made between parents and teacher or other school administrators on the basis of symptoms rather than clinical diagnostic testing, careful diagnosis, as always, is advisable.

Treatment

Ronald D. Davis, writing in The Gift of Dyslexia outlines an alternative and complementary treatment consistent with the "moving point of view" model. According to this model, and the reason why letters seem to change shape and float, why lines of print appear to move, and why words appear to be other than they are is that the dyslexic individual sees the world predominantly through his or her "mind's eye," rather than through his or her physiologic eye. In other words, the person with dyslexia more than all others, sees what he or she 'thinks' they see, rather than what their eyeballs see. To further complicate matters, they do this so quickly, they easily become confused when the multiple facets do not produce a solid view. The object of treatment proposed by Ronald Davis, a dyslexic individual himself, is to train the mind's eye to return to a learned, anchored, viewpoint when they realize they are seeing with their mind, and not with their eyeballs. This is accomplished with assessment testing, followed by one-on-one exercises that retrain mental perception pathways. Using the gifts of the dyslexic individual—their imagination and curiosity—these exercises involve creative physical activities, including the use of modeling clay, "koosh" balls, and movement training. Davis founded the Reading Research Council's Dyslexia Correction Center in 1982, and the Davis Dyslexia Association International, which trains educators and therapists, in 1995.

Another alternative treatment option seeks to address unmastered learning skills needed for reading and math. This system, called Audioblox, may be used one-on-one (especially for children) or in groups, and involves a series of mental exercises that address learning, focussing on the "deficits" of dyslexia. Treatment involves the purchase of a kit online that contains a book entitled The Right to Read, a supplementary manual, a computer program on CD to supplement Audioblox training, and teaching materials. The book is in two parts; first, an explanation of theory; second, the program itself, with exercises. The supplementary manual contains specialized programs for areas of deficit, including handwriting, spelling, math, pre-school readiness, and high school or adult learning. The teaching materials include 96 colored blocks, representing each of six colors on each of the six sides of the block; a view blocking screen; colored cards with preprinted patterns; letter cards; a reading book with a story written in the 800 most common English words, and word cards; and, a demonstration video. The kit originates in England; pricing in America ranges approximately between $135 and $150.

Special education recommendations include helping a child stay organized and on task by keeping their desk and workplace free of extraneous, distracting materials; making more frequent, shorter assignments to increase confidence; providing positive, "immediate gratification" feedback; and short conferences or work contracts as needed.

Allopathic Treatment

Allopathic medical treatment for dyslexia includes use of anti-motion drugs, addressing the symptoms of balance and coordination which results from visual perception alterations; stimulant drugs such as Cylert or Ritalin, to address symptoms of low self esteem, restlessness, and distractibility, and 'nootropics' drugs, a class of drugs believed to improve cognitive function. The stimulant drugs may be more effective for learning disorders related to ADHD or ADD than for dyslexia. The drug Piracetam, a nootropic, although reported as a possible treatment for dyslexia, is also reported to have legal issues because it has not been approved for use in the United States by the Food and Drug Administration (FDA). Reported potential side effects of the stimulants include nervousness and insomnia, and are contra-indicated with epilepsy, allergies, blood pressure problems, or with use of monoamine oxidase (MAO) inhibitors. Long-term use of stimulants in children are reported to adversely affect growth, may ironically depress the nervous system or lead to loss of consciousness. By reducing natural levels of stimulants in the brain, they may also cause dependence. The stimulants and nootropics are said to increase the effects of alcohol and amphetamines. Other possible interactions include use of anti-convulsants or anti-epileptics; tricyclic anti-depressants; anti-coagulants, like Coumadin; and "atropine-like drugs" that blocks the neurotransmitter acetylcholine.

Prognosis

If left unaddressed, a person with dyslexia may become "functionally illiterate," able to function limited by their ability to read, spell, have their handwriting understood, or do arithmetic. Recognizing that dyslexia is a developed learning disorder affecting people of extraordinary curiosity, imagination and intelligence—people of genius, often—from a productive or functional point of view, dyslexia may contribute significantly, positively or negatively, to performance levels. From an emotional or psychological point of view, dyslexia affects self esteem, and promotes confusion and frustration, that may contribute to under achievement.

Prevention

No method of preventing dyslexia is currently known. However, existing methods of treatment may prevent or reduce the secondary or indirect losses to individuals, society and culture that might otherwise occur. As the genetic aspects of dyslexia are revealed, genetic chromosomal modifications may prevent the expression of dyslexia in future generations. Wise use of present and future understandings will allow individuals with dyslexic gifts, individuals such as Leonardo daVinci, Albert Einstein, Walt Disney and Greg Louganis, to continue to contribute their genius and talents.

Resources

Books

Clayman, M.D., Charles B., ed. The American Medical Association Guide to Prescription and Over-The-Counter Drugs. New York: Random House, 1988.

Davis, Ronald D., with Edlon M. Braun. The Gift of Dyslexia, Why Some of the Smartest People Can't Read and How They Can Learn. New York: Berkley Publishing Group, 1997.

Pierangelo, Ph.D., Roger and Robert Jacoby. Parents' Complete Special Education Guide. New York: Simon Schuster, 1996.

Thomas, M.D., Clayton L., ed. Taber's Cyclopedic Medical Dictionary, 16th edition. Philadelphia: Davis Co., 1989.

Other

Audioblox U.K. Audioblox Program [Cited May 12, 2004]. .

Audioblox U.K. Dyslexia [Cited May 12, 2004]. .

Breznitz, Zvia. "The Speech and Vocalization Patterns of Boys with ADHD Compared with Boys with Dyslexia and Boys Without Learning Disabilities." Journal of Genetic Psychology. 164.4. December 2003. [Cited May 10, 2004]. .> "Dyslexia" The Dyslexia File, Center for Current Research. [Cited May 12, 2004]. .

Schoon, Chris. Piracetam FAQ Version 0.6. Dated 2/1/03. Last modified, March 14, 2004. [Cited May 10, 2004]. .

[Article by: Katy Nelson, N.D.]

Definition

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.

Description

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 unusual talents in art, athletics, architecture, graphics, drama, music, or engineering. These special talents are often in areas that require the ability to integrate sight, spatial skills, and coordination.

Common characteristics of a child with dyslexia include problems with:

• identifying single words
• understanding sounds in words, sound order, or rhymes
• spelling
• transposing letters in words
• handwriting
• reading comprehension
• the spoken language
• understanding directions
• understanding opposites, such as up/down or early/late

Social and emotional difficulties often accompany this disorder, as children are unable to meet expectations of parents and teachers and feel frustrated at their inability to achieve their goals. They may have a negative self-image and become angry, anxious, and depressed.

Demographics

About 15–20 percent of the population of the United States has a language-based learning disability. Of students with specific learning disabilities receiving special education services, 70–80 percent have deficits in reading. With such a high incidence, there is a question as to whether this is really a difference in learning style rather than a true "disability." The condition affects males more than females, and appears in all ages, races, and income levels.

Causes and Symptoms

The underlying cause of dyslexia is not known, although research suggests the condition is often inherited. In 1999, The Centre for Reading Research in Norway presented the first research to study the largest family with reading problems ever known. By studying the reading and writing abilities of close to 80 family members across four generations, the researchers reported, for the first time, that chromosome 2 can be involved in the inheritability of dyslexia. When a fault occurs on this gene, it leads to difficulties in processing written language. Previous studies have pointed out linkages of other potential dyslexia genes to chromosome 1, chromosome 15 (DYX1 gene), and to chromosome 6 (DYX2 gene). The researchers who pinpointed the localized gene on chromosome 2 (DYX3) hope that this finding will lead to earlier and more precise diagnoses of dyslexia.

Research suggests a possible link with a subtle visual problem that affects the speed with which affected people can read. Anatomical and brain imagery studies show differences in the way the brain of a dyslexic child develops and functions.

Indicators of dyslexia include:

• possible family history of learning disorders
• difficulty learning to recognize written words
• difficulty rhyming
• difficulty determining the meaning (idea content) of a single sentence
• writing or arithmetic learning problems

When to Call the Doctor

The doctor should be called if a child appears to have difficulty learning to read or exhibits any symptoms of dyslexia.

Diagnosis

Anyone who is suspected to have dyslexia should have a comprehensive evaluation, including medical, psychological, behavioral, hearing, vision, and intelligence testing. The test should include all areas of learning and learning processes, not only reading. Other causes of learning disabilities, such as attention deficit hyperactivity disorder (ADHD), affective disorders (e.g. depression or anxiety), central auditory processing dysfunction, pervasive developmental disorders, and physical or sensory impairments, must be ruled out before the diagnosis of dyslexia can be confirmed. A child of any age may be evaluated for dyslexia using an age-appropriate battery of tests.

Test results are used to determine eligibility for special education services in many states as well as eligibility for programs in colleges and universities. They provide a basis for making educational recommendations, and determine the baseline for evaluation of improvement in the child's performance. In the United States, the Individuals with Disabilities Education Act (IDEA), Section 504 of the Rehabilitation Act of 1973 and the Americans with Disabilities Act (ADA) define the rights of children with dyslexia and other learning disabilities. These children are legally entitled to special services to help them overcome and accommodate their learning problems, including education programs to meet their needs. The Acts also protect people with dyslexia against unfair and illegal discrimination.

As further research pinpoints the genes responsible for some cases of dyslexia, there is a possibility that earlier testing will be established to allow for timely interventions to prevent the onset of the condition and treat it when it does occur. Unfortunately, in many schools, a child is not identified as having dyslexia until after repeated failures.

Treatment

Dyslexia is a life-long condition, but with proper intervention, a child can learn to read and/or write well. When a child is diagnosed with dyslexia, the parents should find out from the school or the diagnostician exactly what the problem is, what method of teaching is recommended, and why a particular method is suggested.

The primary focus of treatment is aimed at solving the specific learning problem of each affected child. Most often, this may include modifying teaching methods and the educational environment, since traditional educational methods will not always be effective with a dyslexic child. An Individual Education Plan (IEP) should be created for each child, reflecting his or her specific requirements. Special education services may include specialist help by an instructor specifically trained to teach dyslexic students through individualized tutoring or special day classes. It is important to teach these students using all the senses—hearing, touching, writing, and speaking—through a multi-sensory program.

People with dyslexia need a structured language program, with direct instruction in the letter-sound system. Teachers must provide the rules governing written language. Most experts agree that the teacher should emphasize the association between simple phonetic units with letters or letter groups, rather than an approach that stresses memorizing whole words.

To assist with associated social and emotional difficulties, teachers must use strategies that will help the child find success in academics and personal relationships. Such strategies include rewarding efforts and not just the results, helping the child set realistic goals, and encouraging the child to do volunteer work that requires empathy and a social conscience (for example, a child with dyslexia who does well in science or math could serve as a peer tutor in those subjects or could tutor a younger child with dyslexia). Psychological counseling may also be helpful.

Prognosis

There is a great deal of variation among different people with dyslexia, producing different symptoms and degrees of severity. The prognosis depends on the severity of the disability, but is usually good if the condition is diagnosed early, the intervention used is effective and appropriate for the specific child, and if the child has a strong self-image and supportive family, friends, and teachers. However, difficulties with reading may persist throughout adulthood, which may result in occupational problems in certain careers. However, many successful people, such as Erin Brockovich and Whoopi Goldberg, have dyslexia.

Prevention

Since learning disorders often run in families, affected families should try to recognize learning disability problems early. For families without a previous history of learning disabilities, an intervention can begin as early as preschool or kindergarten if teachers detect early signs.

Parental Concerns

There are many resources available to aid parents in helping their children. For example, the International Dyslexia Association () provides extensive information for parents, teachers, and children. Parents are encouraged to utilize these resources to ensure their child's success in school and in interactions with their peers and later as working adults. They must also guard against feeling that the child is lazy or not trying hard. Instead, they should provide a supportive and loving environment.

Dyslexia may have an impact upon the child's family. Non-dyslexic siblings may be jealous of the attention, time, and money the dyslexic child receives from the parents. Since dyslexia runs in families, one or both parents may have had similar school problems. The child's problems may bring back feelings of frustration and failure for parents, which may interfere with their parenting skills.

See also Language delay; Language disorders.

Resources

Books

Reid, Gavin.Dyslexia—A Complete Guide for Parents. Hoboken, NJ: John Wiley & Sons, 2004.

Shaywitz, Sally. Overcoming Dyslexia: A New and Complete Science-Based Program for Overcoming Reading Problems at Any Level. New York: Knopf, 2003.

Stowe, Cynthia. How to Reach and Teach Children with Dyslexia: A Parent and Teacher Guide to Helping Students of All Ages Academically, Socially, and Emotionally. San Francisco, CA: Jossey-Bass, 2002.

Organizations

International Dyslexia Association. Suite 382, Chester Bldg., 8600 LaSalle Rd., Ste. 382, Baltimore, MD 21286-2044. (800) ABC-D123 or (410) 296-0232.

Learning Disabilities Association. 4156 Library Rd., Pittsburgh, PA 15234-1349. (412) 341-1515; Fax: (412) 344-0224. www.ldanatl.org

[Article by: Judith Sims Beth A. Kapes]

---

For more information on dyslexia, visit Britannica.com.

(dis-lek-see-uh)

Difficulty in reading when experienced by persons with normal vision and normal or above-normal intelligence. A common example of dyslexia is reading words with the letters in reverse order, as in fyl for fly.

At the end of the 19th century (1896), a case study of a boy with congenital word-blindness was reported in the British Medical Journal by W. Pringle Morgan. Percy F was described as a bright, intelligent boy, quick at games, as good as others of his age except for an inability to learn to read. In spite of laborious and persistent training, he could only spell out words of one syllable with great difficulty. This report served as a stimulus for research and debate on word-blindness. Half a century later, the term 'dyslexia' was adopted for the condition. 'Dyslexia' is derived from the Greek 'dys' (difficulty) and 'lexicos' (words). Today, developmental dyslexia is seen as a complex neurological condition occurring in about 4 per cent of the population and is a legally recognized disability.

The criteria for recognizing the existence of a condition are that it should have a distinct aetiology, identifying characteristics, and a prognosis, and should respond to intervention. There has been a lot of controversy about the extent to which dyslexia meets these requirements and in the UK the term 'specific learning difficulties' was preferred for use in legislation ('specific learning disabilities' in the USA). The word 'dyslexia', however, has continued to be used in cognitive research and has entered everyday parlance to such an extent that the legal term in the UK has been changed to 'specific learning difficulties (for example, dyslexia)'. The definition of dyslexia and its subtypes, and programmes for remediation, continue to evolve with developments in research and understanding of the condition.

In the 1980s and 1990s, the dominant theoretical framework for dyslexia research focused on phonological deficits. These include difficulty segmenting words into phonemes, in keeping strings of sounds or letters in short-term memory, in repeating long non-words and in reading and writing short ones, and slowness in naming colours, numbers, letters, or objects in pictures. The association between poor phonological awareness and later reading difficulty has been demonstrated across different languages, ages, and tasks. The emphasis on phonological difficulty is seen in the Orton Society (now the International Dyslexia Association) Research Committee's definition of 1994. In this, dyslexia is seen as a specific language-based disorder of constitutional origin characterized by difficulties in single word coding, usually reflecting insufficient phonological processing abilities. Such difficulties are unexpected in relation to age and other cognitive and academic abilities and are not the result of generalized developmental disability or sensory impairment. Dyslexia is seen not only as a problem with learning to read but also in acquiring proficiency in writing and spelling.

Much remedial help for dyslexic children has focused largely on the provision of multisensory phonic programmes involving the systematic teaching of letter–sound correspondences. Many dyslexic children learn to read fairly accurately but they read slowly. The positive effects of phonological support are largely on reading accuracy with relatively little effect on reading fluency. Research on speed of processing has shown a strong relationship between early letter-naming speed and later reading fluency. A 'double deficit' hypothesis for dyslexia led to the suggestion that effective remedial programmes should contain not only phonologically based instruction but also a systematic and comprehensive support directed at developing reading fluency and comprehension.

Over the last two decades, there has been a growing interest in visual processing problems in relation to text. In 1980, Olive Meares, a teacher in New Zealand, described the difficulties reported by some children of dealing with glare from the printed page when reading. At about the same time, Helen Irlen, in California, was exploring the use of tinted lenses to alleviate a problem which she called scotopic sensitivity syndrome. Irlen centres were set up in several countries to supply tinted lenses using her techniques. This triggered a great deal of interest in visual processing difficulties and poor reading, particularly as only some dyslexic children appear to benefit from using coloured overlays or tinted lenses.

In the early 1970s, Arnold Wilkins was interested in the 4 per cent of people with epilepsy who experience visually induced seizures. He noted that susceptibility to visual discomfort is most pronounced in people who suffer from frequent severe headaches. He went on to argue that reading can provoke 'pattern glare' which can result in eyestrain and headaches, and even visual illusions and seizures. Electric lighting changes in brightness twice during each cycle of the alternating electricity supply and fluorescent lighting pulsates even faster. Wilkins suggested that, although the pulsations from such lights are too fast to be seen as flicker, they affect the firing of the visual neurons in the eye. In 1991, he examined twenty volunteers with a history of reading difficulty who had been selected by the Irlen Centre in London as having benefited from the use of tinted glasses. Seventeen of them had a history of migraine in the family; nearly all of them reported a reduction in headaches when wearing their tinted glasses. To investigate this finding systematically, he built a colorimeter for the intuitive manipulation of colour (hue) and depth of colour (saturation), and developed a Rate of Reading Test to identify the poor readers who would benefit from using coloured overlays on the printed page. There is now good research evidence that some poor readers, particularly those with a family history of migraine, can be helped in this way, and that this is due neither to a placebo nor a Hawthorne effect (Wilkins 1995).

Poor readers sometimes display erratic eye movements which appear to be associated with blurring of print, letters jumping over other letters, and letter reversals. Stein and Fowler (1985) reported a study on the effect of monocular occlusion on reading in dyslexic children. They suggested that the experience of an unstable visual world when reading could be attributed to unstable vergence control of the eyes and that this could be improved by the occlusion of one eye. This was open to the objection, however, that a relationship between vergence control and the experiences reported had not been shown to be causal. In 2000, they attempted to set up a double-blind randomized controlled trial to test this. One hundred and forty-three children were selected as dyslexic with unstable binocular control from a sample of 300 7-to 11-years-olds who had been referred to a learning disabilities clinic. The children were randomly assigned to wear spectacles with pale yellow lenses with or without the left eye occluded for all reading and writing activities for nine months. They were tested without their spectacles every three months by researchers who did not know whether they belonged to the occluded or non-occluded group. At the end of nine months, there was no difference in the number of children who achieved stable binocular control but the occluded group achieved it earlier and had gained an advantage in reading performance which was maintained throughout the study. It was of course impossible for the children, parents, or teachers to be unaware of whether a child was in the occluded or non-occluded group.

Evidence has accumulated about differences in the symmetry of the cerebral hemispheres in dyslexics and controls and on the predominant location of language processing in the left hemisphere. Much detailed research has been done on the visual system and its responses to different types of visual stimuli.

In 1980, Bill Lovegrove and his colleagues suggested that dyslexic readers have low-level impairments of the transient visual system. The transient (magnocellular) visual system carries fast low-contrast information and is responsible for detecting moving stimuli but does so with poor acuity. The sustained (parvocellular) system transmits information more slowly but with high acuity. In 1991, Margaret Livingstone and her co-workers examined the functioning of the magnocellular and parvocellular divisions of the visual system by recording visually evoked potentials in response to high-and low-contrast stimuli in dyslexic and non-dyslexic people. There were no differences between the groups for the high-contrast stimuli but there were for the low. With Albert Galaburda, she and their co-workers went on to carry out a series of histological postmortem studies of the brains of people known to have been dyslexic and to compare them with non-dyslexic controls. They found that whilst the magnocellular and parvocellular layers of the lateral geniculate nucleus were clearly separated in the controls they were more merged together in the brains of the dyslexics. Moreover, the magnocellular neurons in the dyslexics were about 30 per cent smaller than in the controls. Both the magnocellular and parvocellular layers receive neuronal projections from the ganglion cells of the retina at the back of the eye. Ninety per cent of these are parvocells which signal fine detail and colour and the remainder are larger magnocells which signal the timing of visual events. Differences have since been found between dyslexics and controls in the magnocells of the auditory thalamic relay associated with the processing of sounds.

The critical factor behind fluent word reading appears to be the ability to recognize letters, spelling patterns, and whole words effortlessly and automatically. Rod Nicolson and Angela Fawcett (1990) explored the idea of automaticity suggesting that dyslexic children have difficulties in making some cognitive and motor skills automatic in spite of intensive practice. A conscious compensation hypothesis was invoked to explain why in spite of more limited automaticity many dyslexic children are able to perform at apparently normal levels in most areas, most of the time. There is growing evidence that there are differences between dyslexics and controls in motor coordination and balance. Motor skills training can improve performance on motor tasks and it was suggested in the early 1970s that motor skills intervention could help learning-disabled children. A longitudinal evaluation of a balance remediation exercise training programme for dyslexic children and matched controls is currently under way in the UK.

It has been shown recently, using positron emission tomography (PET), that in comparison with controls, dyslexics showed less activation of the cerebellum during a motor learning task. In addition, the metabolism of the cerebellum has been shown to be lower in dyslexics than controls. Research using magnetic resonance imaging (MRI) in the USA has provided evidence of the involvement and integration of seventeen regions in the brain, including the cerebellum, in reading. The cerebellum contains and receives considerable inputs from the magnocells and recent histological study of the cerebellum has confirmed cerebellar differences between dyslexics and controls.

John Stein, Joel Talcott, and Caroline Whitton (2001) suggested that the influence of polyunsaturated fatty acids (PUFAs) on the magnocell membrane may be under the control of a particular enzyme that is higher in dyslexics than controls. They think that the decline of eating fish in modern diets has led to lower levels of PUFAs. Research is under way on supplementing the diets of dyslexic children with particular omega-3 fatty acids found in some fish oils and on a breath test to identify children who may benefit from this. They also suggested that individual differences in magnocellular sensitivity may be under genetic control.

Familial clustering of dyslexia is well documented. Strong support for genetic influences rather than a shared family environment comes from studies which have found twice the rate of dyslexia in monozygotic twins who have almost identical genetic make-up, compared with dizygotic twins who have about half their genes in common. Techniques in molecular genetics have so far identified loci on chromosomes 2, 4, 6, 13, and 18 as being implicated in dyslexia. Several authors have pointed out that some of these genetic markers occur in the same regions as genes involved in some autoimmune diseases which have an increased prevalence in dyslexics. Although considerable advances have been made, understanding the biological basis of dyslexia is still at a relatively early stage, and significant questions remain about its genetic basis and the brain mechanisms involved.

Since the identification of pre-reading correlates of dyslexia, considerable efforts have been made to develop early screening programmes; this is difficult because early childhood development is so variable but a recent study compared the literacy skills of children at genetic risk of dyslexia with those with no such family history. The children at genetic risk were more likely to have slower speech and language development at 4 years of age and literacy problems at age 6. It appears that early childhood screening should be sequential to allow for differences in rates of development and treated as probabilistic. Developments in screening and assessing the difficulties of school children and adults now include work on computerized screening and assessment.

In describing the pattern of difficulties in dyslexia, Tim Miles (1993) pointed out that dyslexia involves more than a language and literacy problem. Certainly there can be considerable individual differences in schoolchildren and adults with dyslexia, not least because many develop individual coping and compensatory strategies. For some, the extent to which their dyslexic difficulties will impair performance at work will be minimal but for others it may result in working in occupations which do not make full use of their real abilities and potential. The stress of coping with dyslexia at school, college or university, and work is well documented (e.g. Miles and Varma 1995). Information on screening, assessment, intervention, and current legislation affecting children and adults is available on the websites of the British Dyslexia Association, the Dyslexia Institute, and the International Dyslexia Association.

(Published 2004)

— Mary N. Haslum

Bibliography
• Bradley, L., and Bryant, P. (1983). 'Categorizing sounds and learning to read'. Nature.
• Livingstone, M. S., Rosen, G. D., Drislane, F. W., and Galaburda, A. M. (1991). 'Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia'. Proceedings of the National Academy of Sciences of the USA, 88.
• Lovegrove, W. J., Martin, F., Blackwood, M., and Badock, D. (1980). 'Specific reading difficulty: differences in contrast sensitivity as a function of spatial frequency'. Science, 210.
• Miles, T. R. (1993). Dyslexia: The Pattern of Difficulties (2nd edn.).
• — —  and Varma, V. (1995). Dyslexia and Stress.
• Morgan, W. P. (1896). 'A case study of congenital word blindness'. British Medical Journal, 2.
• Nicolson, R. I., and Fawcett, A. J. (1990). 'Automaticity: a new framework for dyslexia research'. Cognition, 35/2.
• Orton Society Research Committee (1994). 'Dyslexia'. Perspectives, 20.
• Stein, J. F., and Fowler, S. (1985). 'Effect of monocular occlusion on reading in dyslexic children'. Lancet, 13 July.
• — —  Talcott, J., and Whitton, C. (2001). 'The senorimotor basis of developmental dyslexia'. In Fawcett, A. J. (ed.), Dyslexia Theory and Good Practice.
• Wilkins, A. (1995). Visual Stress.
• Websites:www.bda-dyslexia.org.uk
• www.dyslexia-inst.org.uk
• www.interdys.org

---

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - ordblindhed

Nederlands (Dutch)
dyslexie, leesblindheid

Français (French)
n. - dyslexie

Deutsch (German)
n. - Dyslexie, Lesestörung

Ελληνική (Greek)
n. - δυσλεξία

Italiano (Italian)
dislessia

Português (Portuguese)
n. - dislexia (f) (Med.)

Русский (Russian)
дислексия

Español (Spanish)
n. - dislexia

Svenska (Swedish)
n. - dyslexi, nedsättning av läs- o skrivförmågan beroende på hjärnskada

中文（简体）(Chinese (Simplified))
诵读困难

中文（繁體）(Chinese (Traditional))
n. - 誦讀困難

한국어 (Korean)
n. - 실독증, 읽기 장애, 난독증

日本語 (Japanese)
n. - 失読症

العربيه (Arabic)
‏(الاسم) خلل بسيط في الدماغ يسبب صعوبه في القراءة والكتابه‏

עברית (Hebrew)
n. - ‮קשיי קריאה וכתיבה, דיסלקציה‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.