Learning disability is a disorder of cognitive and psychological processes involved in understanding and using written and spoken language. Reading disorder (dyslexia) is a language-based learning disability that affects reading ability and is considered the most common learning disability.
In DSM-5, among specific learning disorders (SLD), those with reading and writing difficulties are classified as developmental dyslexia. Dyslexia accounts for 80% of SLD. The basic feature is difficulty with accuracy and fluency in reading and writing letters and words.
Language differences: In languages like Japanese, where spelling and pronunciation are consistent, the disorder is less likely to become apparent compared to languages like English.
Current situation in Japan: Awareness is low, and responses are delayed.
Genetic factors: About 40% of siblings, parents, or children of affected individuals have dyslexia.
Sex differences: It is believed there is no sex difference in prevalence.
US data: 40% of early elementary school children have some difficulty learning to read, and 5% are referred for remedial education
QIs dyslexia the same as intellectual disability?
A
Dyslexia and intellectual disability are different. Dyslexia involves normal intellectual development and is caused by a neurological abnormality in the brain’s phonological processing function. There are no issues with the learning environment or the individual’s motivation.
Difficulty in vocalizing written symbols; reading is possible but lacks accuracy and fluency. Symptoms related to reading and writing are common in early childhood, but dyslexia is diagnosed when development appropriate for the school grade is impaired after school entry. Inaccurate reading also leads to difficulty in writing. Children may become fatigued from trying to keep up with peers in learning the same content, which can lead to school refusal.
The main symptoms related to reading and writing are shown below.
Symptoms related to reading
Symptoms related to writing
Lack of interest in letters in early childhood
Errors in special syllables such as geminate consonants, moraic nasals, and diphthongs
Letter-by-letter reading
Errors in homophonic notation, such as confusing “ha” and “wa”
Reading arbitrarily (changing text as one pleases)
Errors with visually similar characters like “me” and “nu”
Skipping over letters, words, or sentences while reading
Adding or omitting strokes in kanji with many strokes
Dyslexia is a neurobiological SLD. It is fundamentally caused by neurological abnormalities in phonological processing and visual information processing, not by vision or hearing problems.
Neural basis: fMRI shows abnormal activity in the basal ganglia and left anterior superior temporal gyrus, areas involved in phonological processing.
Brain functional imaging: Reduced activation in the left occipitotemporal region (visual word form area) is observed, with compensatory development of alternative circuits on the right and anterior sides.
Genetic factors: There is a strong genetic component. Approximately 40% of family members of affected individuals have reading disorders.
Association with ADHD: ADHD is a risk factor for comorbid reading disorders. Children with a family history of ADHD are at higher risk.
It is important to understand that the cause is not the individual’s motivation, personality, or family upbringing.
QIs dyslexia hereditary?
A
There is a strong genetic component. About 40% of siblings, parents, and children of affected individuals have dyslexia. Family history is one of the risk factors.
The diagnosis of dyslexia involves multiple professionals. Ophthalmologists play a key role in ruling out organic eye diseases and referring patients to appropriate facilities.
Role of the Ophthalmologist
Exclusion of organic diseases: Rule out treatable eye conditions such as strabismus, amblyopia, convergence insufficiency, accommodation disorders, and refractive errors.
Refractive correction and eye alignment correction: Perform correction as needed.
Medical interview: Obtain results from the 3-year-old eye health check and school entry health check, family history, and the child’s behavior at school.
Referral to specialized facilities: If dyslexia is suspected, refer to an appropriate facility for testing and diagnosis.
Role of Educational and Psychological Professionals
Within schools: Educational diagnosticians, reading specialists, and school psychologists are responsible for assessment and diagnosis.
Outside schools: Child psychologists, educational diagnostic specialists, and child neuropsychologists are considered optimal for diagnosis.
Formal evaluation: Comprehensively assess cognition, memory, attention, intellectual ability, information processing, psycholinguistic processing, academic skills, social-emotional development, and adaptive behavior.
Dyslexia testing includes general intelligence tests and assessments of reading and writing, but must be conducted at specialized hospitals such as pediatric neurology departments. Local health centers often serve as the point of contact. If ADHD is comorbid, testing itself may be difficult, making diagnosis challenging.
Ophthalmic and auditory screening tests are essential components of evaluation.
There is no fundamental cure. However, early diagnosis and active training interventions can minimize difficulties in school and daily life.
Effective Interventions
Reading aloud instruction and vocabulary instruction: Improvements have been observed in areas that showed abnormal activity on fMRI.
Phonics (phoneme)-based instruction: This is a major intervention method as a specific educational technique.
Management of ADHD: Comorbid ADHD should be treated with appropriate stimulant medication.
Ineffective Interventions
Vision training: It is expensive and has no proven effectiveness for dyslexia.
Colored lenses/overlays: No benefit has been demonstrated in controlled clinical trials.
Eye muscle exercises: No benefit has been demonstrated except for the treatment of convergence insufficiency.
Sena et al. (2024) implemented a phonological remediation program (60 minutes per week, 20 sessions total) for a 9-year-old girl with developmental dyslexia and giftedness. Her reading speed improved from 20 words per minute before intervention to 94.4 words per minute after intervention, and her reading level advanced from the alphabetic stage to the orthographic stage1).
The response of those around the patient is also important as part of treatment.
Understand that the cause is a neurological abnormality
Make it clear that it is not a problem of the patient’s motivation or parenting style
Cooperation between home and school is essential
Recognizing, encouraging, and praising the patient’s efforts leads to great confidence
QIs vision training effective for reading disorders?
A
It is not effective. It has been clearly shown that vision training has no effectiveness for dyslexia. Colored lenses and overlays have also not been shown to be beneficial in controlled clinical trials. Expensive alternative therapies without evidence should be avoided.
QHow should those around a child with a reading disorder interact with them?
A
Understand that the cause is a neurological abnormality, not a problem of the child’s motivation or upbringing. The child is under more stress than imagined, and recognizing and encouraging their efforts can build confidence. Cooperation between home and school is essential.
6. Pathophysiology and Detailed Mechanisms of Onset
It has been confirmed that therapeutic training interventions such as reading aloud instruction and vocabulary instruction lead to improvements in areas where abnormal activity was observed on fMRI.
In the phonological remediation program by Sena et al. (2024), interventions included phoneme and syllable identification and manipulation, rhyme and alliteration, lexical access, visual and auditory working memory, and reading training. After the intervention, phonological awareness scores improved from 49 to 57 for syllables and from 14 to 20 for phonemes, and backward digit span in working memory improved from 4 to 121).
7. Latest Research and Future Perspectives (Research Stage Reports)
Sena et al. (2024) reported the effects of phonological remediation on children with “twice-exceptionality (2E)” who have both giftedness (high ability) and developmental dyslexia. Typically, in children with dyslexia alone, reading level improvement is gradual even after phonological remediation programs, but in this case, the reading level markedly improved from the alphabetic stage to the orthographic level. It is suggested that enhanced executive function due to high ability may have facilitated improvement in working memory tasks (backward digit span 4→12)1).
Research on dyslexia in the Japanese-speaking world is lagging, and improving awareness and developing support systems are future challenges. Because Japanese has regular correspondences between spelling and pronunciation, the disorder is less likely to become apparent and tends to be overlooked.
Sena AMBG, Messias BLC, Bezerra RLM, et al. Phonological remediation effects on a child with giftedness and developmental dyslexia. CoDAS. 2024;36(3):e20230068.
Birch EE, Kelly KR. Pediatric ophthalmology and childhood reading difficulties: Amblyopia and slow reading. J AAPOS. 2017;21(6):442-444. PMID: 28870794.
