•MR refers to a group of disorders that have in common deficits of adaptive & intellectual function & an age of onset before maturity is reached. During developmental period, before the age of 18)
•It is generally accepted that MR occurs in 2-3% of the general population.
•There are two categories of MR – ‘Under MR’ & ‘More severe MR’. Milder MR is 85%.
ETIOLOGY
1.Unexplained
2.Genetic conditions -
a)Chromosomal disorder –
i.Down’s syndrome
ii.Criduchat symdrome
iii.Fragile - X - syndrome
iv. Pradu – Willi syndrome
b)Inherited metabolic disorder –
i.Galactocaemia
ii.PKU
iii.Hunter symdrome
iv.Huslar syndrome
v.Tulurous sclerosis
3. Problem during pregnancy –
i.Alcohol ingestion
ii.Drug ingestion/ addiction
iii.Malnutrition
iv.Toxoplasmosis
v.Rubella, syphilis, HIV infection
4.Problem at birth - Intracranial haemorrhage (e.g. PVH)
i.Perinatal asphyxia
ii.Prematurity
iii.LBW
5.Problem after birth -
i.Hyperbilirubinaemia
ii.Meningitis, encephalitis
iii.Head injury
iv.Near drowning
v.Lead poisoning
vi.Mercury poisoning
6.Poverty & cultural deprivation -
i.Poor family
ii.Malnutrition
iii.Inadequate medical care
iv.Understimulation
7.Metabolic –
i.Reyes syndrome
ii.Congenital hypothyroidism
iii.Hypoglycemia
Cause of MR can be determined in 60-70% of cases as
Compared to mild MR where 35 - 55% remain idiopathic,
mild cases are usually of polygenic inheritance.
Around 40% cases of severe MR, chromosomal
abnormalities constituted the highest (~ 23.7%) followed by
identifiable syndrome (11.6%) & metabolic cases (5%). In
the group of undifferentiated cases around 33% had
congenital malformations with or without a neurological
deficit. In 33% of cases there was either consanguinity or
positive family history.
APPROACH TO CHILD WITH MR
1.History
2.Physical examination
3.Investigation
History:
History plays a pivotal role in approaching a diagnosis. The history must often
taken from the parents, with particular attention to mother’s pregnancy, labor &
delivery, family’s pedigree; consanguinity of the parents; hereditary disorders.
Also assessment of socio-cultural background, home’s emotional climate & the
parents intellectual functioning.
Physical examination:
Apart from routine physical & systemic examination some features
need special mention & should be very carefully looked for.
Head size, hair, facies, skin, eye abnormalities, hearing defect,
hepato – splenomegaly, short stature, ataxia etc can give clues to diagnosis of
various abnormalities.
Detailed neurological examination is mandatory.
Investigation:
The most commonly used medical diagnostic testing for children
with MR include neuroimaging; metabolic, genetic & chromosomal
blood testing & EEG. These test should not be used as screening
tools for all children with an intellectual disability.
Decisions or diagnostic testing should be based on the
medical/family history. Physical examination, testing by other
disciplines, & the family’s wishes.
1.Thyroid function tests – T3, T4, TSH.
2.Cytogenetic studies.
3.Metabolic studies.
4. Radiological investigations -
i.X-ray skull – Hydrocephalus, craniosynostasis, intracranial calcification.
ii.CT- scan & MRI – For internal hydrocephalus, cortical atrophy or procencephaly.
5.EEG
6.Specific tests – According to the suspected diagnosis should be carried out which may include BM examination, skin biopsy, urine tests for MPS, enzyme assays, serology for
TORCH/HIV.
Psychometric tests:
1)Standardized intelligence test
2)Standardized adaptive skill test
•Methods of intelligence & adaptive behavior testing :
Psychometric test Age – range
1.The Baily scale – II 1-42 mo
2.Denver – II 0 -72 mo
3.Stanford – Binet scale 2-16 yr
4.Griffiths scale for mental Infant – 6yr development
5.WISC – II 11mo – 16 yr
(Wechsler intelligence
scale for children)
DSM – IV : Diagnostic criteria for MR (Diagnostic & statistical manual of MR, 4th edition)
A.Significantly sub average intellectual functioning : an IQ of approximately 70 or below.
B.Concurrent deficits or impairment in present adaptive functioning i.e. the child's effectiveness in meeting the standards expected for his/her age by his or her cultural groups in at least two the following areas :
–Communication
–Self care
–Home living
–Social/interpersonal skills
–Use of community resources.
–Self direction functional Academic skills
–Work
–Leisure
–Health & safety.
C.The onset is before age 18 yrs. A person with intellectual function but no limitation in adaptive skill areas, may not be diagnosed as MR.
Intelligent quotient (IQ):
IQ = Mental age / chronological age X 100
IQ level reflects the degree of severity of intellectual impairment.
IQ score Degree of retardation
55-70 Mild MR
40-55 Moderate MR
25-40 Severe MR
Below 25 Profound MR
71-84 – Borderline MR, is not under the category of MR
but may be a focus of psychiatric attention.
TREATMENT
•Although MR is not treatable many associated impairments are amenable to intervention & therefore benefit from early identification.
•Treatment is based on each individual case & a multi disciplinary approach may be required in many of the cases.
Outline of the treatment of MR
Aspects of therapy :
1.Specific therapy
2.Education
3.Social & recreational therapy
4.Behavior & emotional problems
5.Associated deficits
6.Family education/counseling.
1. Specific therapy:
i.Early detection.
ii.Early intervention – May be causative – Hypothyroidism, PKU, Galactosaemia.
iii.Alleviation – Some inherited metabolic disorder.
2. Education:
i.Physical therapy
ii.Occupational therapy
iii.Speech & language therapy
iv.Psychological counseling
v.Special education classes -
For mild MR – Mainstreamed with unaffected children for art,
music, gym & separated only for academics.
For moderate MR – Self continued classes in special education
school.
For severe MR - Special programme.
3. Social & recreational activities:
Needs opportunity to play with other children outside the school.
Children with MR do better in individual or small group, activities
than in team sports.
4. Behavioral & emotional problems:
Tamper tolerance, food refusal, refusal to go to bed etc, are best
dealt with behavioral psychologist. Behavioral modification
techniques are needed but sometimes medications are also
needed to control behavior. Emotional disorders are generally
death with by a psychiatrist, clinical psychologist or social worker.
5. Associated defects:
Hearing & vision impairment, seizure disorder should be
early identified & treated accordingly.
6. Family education & counseling: Should be taken in account.
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