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Learning
disabilities are conditions that cause a discrepancy between potential
and actual levels of academic performance as predicted by the person's
intellectual abilities. Learning disabilities involve impairments
or difficulties in concentration or attention, language development,
or visual and aural information processing. Diagnosis includes intellectual,
educational, speech and language, medical, and psychologic evaluations. Treatment
consists primarily of educational management and sometimes medical,
behavioral, and psychologic therapy.
Specific learning disabilities affect the ability to understand or use spoken or written language, do mathematical calculations, coordinate movements, or focus attention on a task. These disabilities include problems in reading, mathematics, spelling, written expression or handwriting, and understanding or using verbal and nonverbal language (see Table 3: Learning and Developmental Disorders: Common Learning Disorders ). Most learning disabilities are complex or mixed, with deficits in more than one system.
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Table 3
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Common Learning Disorders
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Disorder
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Manifestation
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Dyslexia
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Problems with reading
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Phonologic dyslexia
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Problems with sound analysis and memory
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Surface dyslexia
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Problems with visual recognition of forms and structures of words
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Dysgraphia
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Problems with spelling, written expression, or handwriting
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Dyscalculia
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Problems with mathematics and difficulties with problem-solving
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Ageometria
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Problems due to disturbances in mathematical reasoning
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Anarithmia
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Disturbances in basic concept formation and inability to acquire computational skills
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Dysnomia
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Difficulty recalling words and information from memory on demand
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Although the number of children with learning disabilities is unknown, about 5% of the school-age population in the US receives special educational services for learning disabilities. Among affected children, boys outnumber girls 5:1.
Learning disabilities may be congenital or acquired. No single cause has been defined, but neurologic deficits are evident or presumed. Genetic influences are often implicated. Other possible causes include maternal illness or toxic drug use during pregnancy, complications during pregnancy or delivery (eg, spotting, toxemia, prolonged labor, precipitous delivery), and neonatal problems (eg, prematurity, low birth weight, severe jaundice, perinatal asphyxia, postmaturity, respiratory distress). Potential postnatal factors include exposure to environmental toxins (eg, lead), CNS infections, cancers and their treatments, trauma, malnutrition, and severe social isolation or deprivation.
Symptoms and Signs
Children with learning disabilities typically have at least average intelligence, although such disabilities can occur in those with lower cognitive function as well. Symptoms and signs of severe disabilities tend to manifest at an early age. Mild to moderate learning disabilities are usually not recognized until school age, when the rigors of academic learning are encountered. Affected children may have trouble learning the alphabet and may be delayed in paired associative learning (eg, color-naming, labeling, counting, letter-naming). Speech perception may be limited, language may be learned at a slower rate, and vocabulary may be decreased. Affected children may not understand what is read; may have very messy handwriting or hold a pencil awkwardly; may have trouble organizing or beginning tasks or retelling a story in sequential order; or may confuse math symbols and misread numbers.
Disturbances or delays in expressive language or listening comprehension are predictors of academic problems beyond the preschool years. Memory may be defective, including short- and long-term memory, memory use (eg, rehearsal), and verbal recall or retrieval. Problems may occur in conceptualizing, abstracting, generalizing, reasoning, and organizing and planning information for problem solving. Visual perception and auditory processing problems may occur, including difficulties in spatial cognition and orientation (eg, object localization, spatial memory, awareness of position and place), visual attention and memory, and sound discrimination and analysis.
Some children with learning disabilities may have difficulty following social conventions (eg, taking turns, standing too close to the listener, not understanding jokes); these are often components of mild autism spectrum disorders as well (see Learning and Developmental Disorders: Autism Spectrum Disorders). Short attention span, motor restlessness, fine motor problems (eg, poor printing and copying), and variability in performance and behavior over time are other early signs. Difficulties with impulse control, non-goal–directed behavior and overactivity, discipline problems, aggressiveness, withdrawal and avoidance behavior, excessive shyness, and excessive fear may occur. As noted above, learning disabilities and attention-deficit/hyperactivity disorder (ADHD) often occur together.
Diagnosis
Children with learning disabilities are typically identified when a discrepancy is recognized between their academic potential and their academic performance. Speech and language, intellectual, educational, medical, and psychologic evaluations are necessary for determining deficiencies in skills and cognitive processes. Social and emotional-behavioral evaluations are also necessary for planning treatment and monitoring progress.
Intellectual evaluation typically includes verbal and nonverbal intelligence testing and is usually performed by school personnel. Psychoeducational testing may be helpful in describing the child's preferred manner of processing information (eg, holistically or analytically, visually or aurally). Neuropsychologic assessment is particularly useful in children with known CNS injury or illness to map those areas of the brain that correspond to specific functional strengths and weaknesses. Speech and language evaluations establish integrity of comprehension and language use, phonologic processing, and verbal memory.
Teachers' observations of classroom behavior and academic performance are essential. Reading evaluations measure abilities in word-decoding and recognition, comprehension, and fluency. Writing samples should be obtained to evaluate spelling, syntax, and fluency of ideas. Mathematical ability should be assessed in terms of computation skills, knowledge of operations, and understanding of concepts.
Medical evaluation includes a detailed family history, the child's medical history, a physical examination, and a neurologic or neurodevelopmental examination to look for underlying disorders. Although infrequent, physical abnormalities and neurologic signs may indicate medically treatable causes of learning disabilities. Gross motor coordination problems may indicate neurologic deficits or neurodevelopmental delays. Developmental level is evaluated according to standardized criteria.
Psychologic evaluation identifies ADHD, conduct disorder, anxiety disorders, depression, and poor self-esteem, which frequently accompany and must be differentiated from learning disabilities. Attitude toward school, motivation, peer relationships, and self-confidence is assessed.
Treatment
Treatment centers on educational management but may also involve medical, behavioral, and psychologic therapy. Effective teaching programs may take a remedial, compensatory, or strategic (ie, teaching the child how to learn) approach. A mismatch of instructional method to a child's learning disability and learning preference aggravates the disability.
Some children require specialized instruction in only one area while continuing to attend regular classes. Other children need separate and intense educational programs. Optimally, and as required by US law, affected children should participate as much as possible in inclusive classes with peers who do not have learning disabilities.
Drugs minimally affect academic achievement, intelligence, and general learning ability, although certain drugs (eg, stimulants, such as methylphenidate and several amphetamine preparations—see Learning and Developmental Disorders: Drugs) may enhance attention and concentration, allowing the child to respond more efficiently to instruction. Many popular remedies and therapies (eg, eliminating food additives, using antioxidants or megadoses of vitamins, patterning by sensory stimulation and passive movement, sensory integrative therapy through postural exercises, auditory nerve training, optometric training to remedy visual-perceptual and sensorimotor coordination processes) are unproven.
Dyslexia
Dyslexia
describes a general term for primary reading disorder. Diagnosis
is based on intellectual, educational, speech and language, medical,
and psychologic evaluations. Treatment is primarily educational
management, consisting of instruction in word recognition and component
skills.
No definition of dyslexia is universally accepted; thus incidence is undetermined. An estimated 15% of public school children receive special instruction for reading problems, of which about ½ may have persistent reading disabilities. Dyslexia is identified more often in boys than girls, but gender is not a proven risk factor for developing dyslexia.
Etiology
and Pathophysiology
Phonologic processing problems produce deficits in discrimination, blending, memory, and analysis of sounds. Dyslexia may affect both production and understanding of written language, which is often restricted further by problems with auditory memory, speech production, and naming or word-finding. Underlying weaknesses in verbal language are often present.
Dyslexia tends to run in families. Children with a family history of reading or learning difficulties are at higher risk. Because changes have been identified in the brains of people with dyslexia, experts believe dyslexia results predominantly from cortical dysfunction stemming from congenital neurodevelopmental abnormalities. Lesions affecting the integration or interactions of specific brain functions are suspected. Most researchers concur that dyslexia is left hemisphere–related and linked to dysfunctions in brain areas responsible for language association (Wernicke's motor speech area) and sound and speech production (Broca's area) and in the interconnection of these areas via the fasciculus arcuatus. Dysfunctions or defects in the angular gyrus, the medial occipital area, and the right hemisphere produce word recognition problems.
The inability to learn derivational rules of printed language is often considered part of dyslexia. Affected children may have difficulty determining root words or word stems and determining which letters in words follow others.
Reading problems other than dyslexia are usually caused by difficulties in language comprehension or low cognitive ability. Visual-perceptual problems and abnormal eye movements are not dyslexia. However, these problems can interfere further with word learning.
Symptoms and Signs
Dyslexia may manifest as delayed language production; speech articulation difficulties; and difficulties remembering the names of letters, numbers, and colors. Children with phonologic processing problems often have difficulty blending sounds, rhyming words, identifying the positions of sounds in words, and segmenting words into pronounceable components. They may reverse the order of sounds in words. Delay or hesitation in choosing words, substituting words, or naming letters and pictures is often an early sign. Short-term auditory memory and auditory sequencing difficulties are common.
Fewer than 20% of children with dyslexia have difficulties with the visual demands of reading. However, some confuse letters and words with similar configurations or have difficulty visually selecting or identifying letter patterns and clusters (sound-symbol association) in words. Reversals or visual confusions can occur, most often because of retention or retrieval difficulties that cause affected children to forget or confuse the names of letters and words that have similar structures; subsequently, d becomes b, m becomes w, h becomes n, was becomes saw, on becomes no. Such reversals are normal in children < 8 yr, however.
Diagnosis
Most children with dyslexia are not identified until kindergarten or 1st grade, when they encounter symbolic learning. Children with a history of delayed language acquisition or use, who are not accelerating in word learning by the end of 1st grade, or who are not reading at the level expected for their verbal or intellectual abilities at any grade level should be evaluated. Often, the best diagnostic indicator is the child's inability to respond to traditional or typical reading approaches during 1st grade, although wide variation in reading skills can still be seen at this level. Demonstration of phonologic processing problems is essential for diagnosis.
Children suspected of having dyslexia should undergo reading, speech and language, auditory, cognitive, and psychologic evaluations to identify their functional strengths and weaknesses and their preferred learning styles. Such evaluations can be requested of school staff by the child's teacher or family based on the Individuals with Disabilities Education Act (IDEA), a US special education law. Evaluation findings then guide the most effective instructional approach.
Comprehensive reading evaluations test word recognition and analysis, fluency, reading or listening comprehension, and level of understanding of vocabulary and the reading process.
Speech, language, and auditory evaluations assess spoken language and deficits in processing phonemes (sound elements) of spoken language. Receptive and expressive language functions are also assessed. Cognitive abilities (eg, attention, memory, reasoning) are tested.
Psychologic evaluations address emotional concerns that can exacerbate a reading disability. A complete family history of mental disorders and emotional problems is obtained.
The physician should ensure that the child's vision and hearing are normal, either through office-based screening or referral for formal audiologic or vision testing. Neurologic evaluations may help detect secondary features (eg, neurodevelopmental immaturity or minor neurologic abnormalities) and rule out other disorders (eg, seizures).
Treatment
Although dyslexia is a lifelong problem, many children develop functional reading skills. However, other children never reach adequate literacy.
Treatment consists of educational interventions, including direct and indirect instruction in word recognition and component skills. Direct instruction includes teaching specific phonics skills separate from other reading instruction. Indirect instruction includes integrating phonics skills into reading programs. Instruction may teach reading from a whole-word or whole-language approach or by following a hierarchy of skills from the sound unit to the word to the sentence. Multisensory approaches that include whole-word learning and the integration of visual, auditory, and tactual procedures to teach sounds, words, and sentences are then recommended.
Component skills instruction consists of teaching children to blend sounds to form words, segment words into word parts, and identify the positions of sounds in words. Component skills for reading comprehension include identifying the main idea, answering questions, isolating facts and details, and reading inferentially. Many children benefit from using a computer to help isolate words within text samples or for word processing of written work.
Other treatments (eg, optometric training, perceptual training, auditory integration training) and drug therapies are unproven and not recommended.
Last full review/revision November 2005
Content last modified November 2005
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