Learning disorders or disabilities (Minimum brain dysfunction syndrome) include a large group of low severity-high incidence disorders, all characterized by ‘difficulties in coping with academic skills (learning) due to problems related to attention span, speech, language or motor co-ordination, which can not be explained by intelligence quotient, visual and hearing handicaps or extraneous factors like parental education and family environment’.
Note that these children are not mentally retarded and have normal or even above average IQ.
Incidence: Although frequently under-diagnosed, learning disorders are estimated to be present in —5-15% of school children, more common in boys than girls (6:1).
Pathogenesis: Achievement of academic skills require normal development of certain domains including — 1) attention span, 2) cognitive function, 3) Memory, 4) speech & language, 5) neuromotor coordination, 6) visual-spatial capability, 7) Temporal-sequential order, and 8) personal-social relationship.
Children with learning disorders have abnormalities in either all (generalized) or some of these fields (specific).
Exact etiology is difficult to ascertain in majority of cases. However, certain inherent or environmental factors have been associated with higher risk, as follows:
a) Genetic defects like Duchanne muscular dystrophy, Phenylketonuria, Turner syndrome, Kleinfelter syndrome, Fragile X syndrome etc.
b) Prenatal factors like maternal malnutrition, smoking, alcoholism, Intrauterine infections and placental insufficiency like Toxemia etc.
c) Perinatal complications like birth asphyxia, hypoglycemia, hyperbilirubinemia etc.
d) Postnatal problems like malnutrition, anemia, head injury, lead poisoning, drugs like anti-convulsants, chronic infections and illnesses like epilepsy.
Clinical presentation of these disorders depends on the multiplicity and severity of developmental domains involvement and include —
a) Learning disorders of attention span, characterized by poor attention span, hyperactivity and impulsivity. A severe and clinically distinct form of these manifestations, fulfilling certain criteria, is termed as Attention-deficit disorder.
b) Learning disorders of academic skills like:
a) Dyslexia – inability to read,
b) Dysgraphia – inability to write,
c) Dysorthographia – spelling difficulties,
d) Dyscalculia – problems in mathematics, and
e) Dysnoniia – difficulty in finding correct word for an expression.
c) Learning disorders of neuro-motor coordination (apraxia) are very common, characterized by presence of certain soft neurological signs, which affect the child’s ability to perform specific motor acts like writing or thawing.
d) Disorders of personal—social adjustments i.e. difficulty in reading the facial expressions or establishing inter-personal relationship.
Many of these children also develop secondary behavioral problems like frustration, low self-esteem, anxiety neurosis and ticks.
Learning disorders are one of the leading causes of poor school performance, usually first suspected by teachers. Role of school-counselors is vital for timely referral of these children. Evaluation of these cases involves a multi-disciplinary approach, with—
a) History of similar problem in other siblings, specific learning difficulty, previous school performance, stressful events at school/home and organic illnesses, with inputs from teachers.
b) Clinical examination, including hearing and visual evaluation and search for soft neurological signs.
c) Specific evaluation tests like IQ testing with specific sub-set scores to identify areas of strength, domain- specific developmental tests, Psycho-educational tests and psychiatric evaluation.
d) Relevant investigations for clinical suspected cause.
Management of learning disabilities requiring cooperation from child, parents, peers and school teachers and should involve school counselors, psychologists, psychiatrists, social workers and education consultants. Although these children have problems in coping with routine pace of learning, it is preferable to continue regular schooling with suitable modifications, rather than to shift in special schools. Important principles in management are —
- Explain the nature of learning disorders to child and parents,
- Bypass strategies like calculators for dyscalculia,
- Strengthen non-affected developmental skills,
- Curriculum modification,
- Modification of teaching & evaluation methods.
Prognosis: It persist throughout life, though it is usually possible to achieve adequate academic skills and school performance with appropriate teaching and learning techniques.
Dyslexia is the commonest learning disorders, characterized by persistent, unexpected difficulty in reading in children or adults, who otherwise possess normal intelligence, motivation and opportunities to learn, considered necessary for accurate and fluent learning.
Incidence: Although frequently under-diagnosed, -5- 10% of school-children are estimated to be dyslexic.
Etiology: Proper comprehension of written and oral words requires segmentation of each word into smaller units, before central decoding. Dyslexic children lack this capability of segmentation.
Although the exact etiology is unknown, 25-65% dyslexic learning disorders children have a parent with dyslexia. Some of them have been identified to have under-activation of posterior brain regions and over-activation of anteroinferior frontal regions during the reading process.
Clinical presentation: Despite individual variations in the severity, four cardinal features of dyslexia learning disorders include —
a) Inaccurate and labored approach to decoding, word- recognition and text-reading,
b) Normal listening and comprehension – These children like to listen the stories but do not want to read them,
c) Difficulty to spell correctly,
d) Delayed language development in early life.
Attention-deficit and hyperactivity is common in dyslexic learning disorders children, but not invariably present.
Soft neurological signs
- Synkinetic (mirror) movements on opposite side,
- Dysdiadochokinesis – difficulty in rhythmic movements
- Purposeless rhythmic movements like foot-tapping
- Lack of lateral dominance i.e. handedness
- Difficulties in left-right discrimination
- Finger agnosia – inability to localize a stimulus
- Motor impersistence – inability to sustain a motor action like tongue protruding.
Causes of Scholastic Backwardness
- Mental retardation
- Learning disorders (Dyslexia)
- Attention-deficit hyperactivity disorder
- Visual or hearing impairment
- Systemic: CNS disorders*, hypothyroidism
- Drugs: Anticonvulsants, substance abuse
- Toxins: Lead or Aluminum poisoning
- Family : Lack of encouragement, stress
- School: Inappropriate teaching methods poor student-teacher relationship
- Emotional like Frequent school changes
- Behavioral disorders
- Frequent school absenteeism
- Chronic diseases like Asthma, Epilepsy
Diagnosis depends on presence of family history, classroom observation and specific language tests, as well as exclusion of sensory impairment like visual hearing defects.
Management of dyslexic children is similar to that for other learning disorders, as discussed earlier, with special emphasis on phonological training by speech therapists.