Dyslexia
Medical Author: David Perlstein, MD, FAAP
Medical Editor: Melissa Conrad Stöppler, MD
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What is dyslexia?
Dyslexia has been around for a long time and has been defined in different ways.
For example, in 1968, the World Federation of Neurologists defined dyslexia as
"a disorder in children who, despite conventional classroom experience, fail to
attain the language skills of reading, writing, and spelling commensurate with
their intellectual abilities." According to the U.S. National Institutes of
Health, dyslexia is a learning disability that can hinder a person's ability to
read, write, spell, and sometimes speak. Dyslexia is the most common learning
disability in children and persists throughout life. The severity of dyslexia
can vary from mild to severe. The sooner dyslexia is treated, the more favorable
the outcome; however, it is never too late for people with dyslexia to learn to
improve their language skills.
Children with dyslexia have difficulty in learning to read despite
traditional instruction, at least average intelligence, and an adequate
opportunity to learn. It is caused by an impairment in the brain's ability to
translate images received from the eyes or ears into understandable language. It
does not result from vision or hearing problems. It is not due to mental
retardation, brain damage, or a lack of intelligence.
Dyslexia can go undetected in the early grades
of schooling. The child can become frustrated by the difficulty
in learning to read, and other problems can arise that disguise
dyslexia. The child may show signs of depression and low self-esteem. Behavior problems at home as well as at school are frequently
seen. The child may become unmotivated and develop a dislike for
school. The child's success in school may be jeopardized if the
problem remains untreated.
What causes dyslexia? What are the different types of dyslexia?
There are several types of dyslexia that can
affect the child's ability to spell as well as read.
"Trauma dyslexia" usually occurs after
some form of brain trauma or injury to the area of the brain that
controls reading and writing. It is rarely seen in today's school-age
population.
A second type of dyslexia is referred to as
"primary dyslexia." This type of dyslexia is a dysfunction
of, rather than damage to, the left side of the brain (cerebral
cortex) and does not change with age. Individuals with this
type are rarely able to read above a fourth-grade level and may
struggle with reading, spelling, and writing as adults. Primary
dyslexia is passed in family lines through their genes (hereditary).
It is found more often in boys than in girls.
A third type of dyslexia is referred to as "secondary"
or "developmental dyslexia" and is felt to be caused
by hormonal development during the early stages of fetal development.
Developmental dyslexia diminishes as the child matures. It is
also more common in boys.
Dyslexia may affect several different functions.
Visual dyslexia is characterized by number and letter reversals
and the inability to write symbols in the correct sequence. Auditory
dyslexia involves difficulty with sounds of letters or groups
of letters. The sounds are perceived as jumbled or not heard
correctly. "Dysgraphia" refers to the child's difficulty
holding and controlling a pencil so that the correct markings can be
made on the paper.
Next: What are the signs and symptoms of dyslexia? »
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