dyslexia (reading disability)

Introduction

Primary reading disorder.

Etiology

• 40% of dyslexic children have an immediate relative with a similar problem
• symmetry or reversal of asymmetry of planum temporale, with right > left
• visual evoked potentials indicate altered rapid visual processing
• bioelectrical mapping shows altered left hemisphere function
• Misconceptions regarding dyslexia:
  • visual-spatial deficits do not underlie dyslexia
  • backward writing & letter reversals are not characteristic of dyslexia
  • 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

• poor school performance
• reading skills are below normal
• writing skills are below normal
• inability to decipher phonetics of words
• misinterpreting number sequences
• frequent errors with simple mathematical tasks
• social problems with school mates
• poor school behavior

Physical examination

• evaluation may be normal: no significant neurologic or psychiatric findings
• motor dysfunction may be observed
  • arms extended: may drop or spread
  • head rotation: arms drop or spread
  • unable to hop or stand on one foot
  • slow finger or foot tapping
  • choreiform movements may be observed
• cerebellar dysfunction may be observed
  • finger-to-nose dysmetria
  • tandem walk dysfunction
  • dysdiadochokinesia
• sensory dysfunction may be observed
  • inability to imitate gestures
  • finger agnosia
• cranial nerve dysfunction may be observed
  • head moves with extraocular muscles
  • strabismus
  • inability to hold lateral gaze
  • unable to raise eyebrow (grimace)
  • irregular tongue movements
  • inability to repeat sounds in a sequence at a given rate

Laboratory

• no biochemical studies

Diagnostic procedures

neuropsychologic testing

• initial screening:
  • Wide-Range Achievement Test-revised (WRAT-r)
  • Wechsler Intelligence Scale for Children-revised (WISC-r)
• additional testing as indicated
  • naming tasks
  • language comprehension
  • repetition tasks
  • auditory discrimination tasks
  • sound-blending tasks
  • articulation tasks
  • segmentation tasks
  • visual-motor tasks
  • sequencing tasks
  • memory tasks
  • visual-perceptive tasks
  • reading tests
  • spelling tests
  • math tests

Radiology

• no routine imaging studies
• positron emission tomography (PET) scan
  • reduced activation of language areas of the brain

Differential diagnosis

• mental retardation
• cerebral palsy
• delayed maturation
• psychosocial disorder
  • depression
  • family conflicts
  • child abuse
• education deprivation
• emotional deprivation
• neurologic dysfunction:
  • visual dysfunction
  • auditory dysfunction
• chronic illness
• trauma
• attention-deficit hyperactivity disorder (ADHD)
• autism

Management

• team approach of neurologists, neuropsychologists, educators
• individualized tutoring
• exercises to correct the deficit
• counseling
• supportive parents
• resources for patient & family
  • The Orton Dyslexia Society Suite 382 8600 La Salle Road Baltimore, MD 21204-6020 Phone: (800) 2223-123
  • The National Center for Learning Disabilities 99 Park Avenue New York, NY 10016 Phone: (202) 687-7211
  • Learning disablities Association of America, Inc. 4156 Liberty Rd. Pittsburgh, PA 15234 Phone: (412) 341-1515

More general terms

• learning disorder (learning disability)

More specific terms

• alexia

Patient information

dyslexia patient information

Database

• OMIM: https://mirror.omim.org/entry/600202
• OMIM: https://mirror.omim.org/entry/127700