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dyslexia (reading disability)
Primary reading disorder.
Etiology:
1) 40% of dyslexic children have an immediate relative with a similar problem
2) symmetry or reversal of asymmetry of planum temporale, with right > left
3) visual evoked potentials indicate altered rapid visual processing
4) bioelectrical mapping shows altered left hemisphere function
5) Misconceptions regarding dyslexia:
a) visual-spatial deficits do not underlie dyslexia
b) backward writing & letter reversals are not characteristic of dyslexia
c) uncertain hand preference is not characteristic of dyslexia
Epidemiology:
- common, affects 5-10% of school-age children
Genetics:
- susceptibility associated with defects in KIAA0319 (DYX2) gene
- chromosomal translocation t(2;15)(q11;q21) involving DYX1C1 may be a cause of dyslexia
History:
1) poor school performance
2) reading skills are below normal
3) writing skills are below normal
4) inability to decipher phonetics of words
5) misinterpreting number sequences
6) frequent errors with simple mathematical tasks
7) social problems with school mates
8) poor school behavior
Physical examination:
1) evaluation may be normal: no significant neurologic or psychiatric findings
2) motor dysfunction may be observed
a) arms extended: may drop or spread
b) head rotation: arms drop or spread
c) unable to hop or stand on one foot
d) slow finger or foot tapping
e) choreiform movements may be observed
3) cerebellar dysfunction may be observed
a) finger-to-nose dysmetria
b) tandem walk dysfunction
c) dysdiadochokinesia
4) sensory dysfunction may be observed
a) inability to imitate gestures
b) finger agnosia
5) cranial nerve dysfunction may be observed
a) head moves with extraocular muscles
b) strabismus
c) inability to hold lateral gaze
d) unable to raise eyebrow (grimace)
e) irregular tongue movements
f) inability to repeat sounds in a sequence at a given rate
Laboratory:
- no biochemical studies
Special laboratory:
neuropsychologic testing
1) initial screening:
a) Wide-Range Achievement Test-revised (WRAT-r)
b) Wechsler Intelligence Scale for Children-revised (WISC-r)
2) additional testing as indicated
a) naming tasks
b) language comprehension
c) repetition tasks
d) auditory discrimination tasks
e) sound-blending tasks
f) articulation tasks
g) segmentation tasks
h) visual-motor tasks
i) sequencing tasks
j) memory tasks
k) visual-perceptive tasks
l) reading tests
m) spelling tests
n) math tests
Radiology:
1) no routine imaging studies
2) positron emission tomography (PET) scan
-> reduced activation of language areas of the brain [2]
Differential diagnosis:
1) mental retardation
2) cerebral palsy
3) delayed maturation
4) psychosocial disorder
a) depression
b) family conflicts
c) child abuse
5) education deprivation
6) emotional deprivation
7) neurologic dysfunction:
a) visual dysfunction
b) auditory dysfunction
8) chronic illness
9) trauma
10) attention-deficit hyperactivity disorder (ADHD)
11) autism
Management:
1) team approach of neurologists, neuropsychologists, educators
2) individualized tutoring
3) exercises to correct the deficit
4) counseling
5) supportive parents
6) resources for patient & family
a) The Orton Dyslexia Society Suite 382 8600 La Salle Road Baltimore, MD 21204-6020 Phone: (800) 2223-123
b) The National Center for Learning Disabilities 99 Park Avenue New York, NY 10016 Phone: (202) 687-7211
c) Learning disablities Association of America, Inc. 4156 Liberty Rd. Pittsburgh, PA 15234 Phone: (412) 341-1515
Specific
alexia
General
learning disorder (learning disability)
Database Correlations
OMIM correlations
References
- Saunders Manual of Medical Practice, Rakel (ed),
WB Saunders, Philadelphia, 1996 pg 1036-37
- Journal Watch 21(9):73, 2001
Paulesu et al, Science 291:2165, 2002
Helmuth, Science 291:2064, 2001
- National Institute of Neurological Disorders and Stroke (NINDS)
NINDS Dyslexia Information Page
https://www.ninds.nih.gov/Disorders/All-Disorders/Dyslexia-Information-Page