Intellectual disability - Burton Flashcards
What is the ICD-10 definition of intellectual disability (mental retardation)?
A condition of arrested or incomplete development of the mind, which is especially characterised by impairment of skills manifested during the developmental period, skills which contribute to the overall level of intelligence, i.e. cognitive, language, motor, and social abilities.
What three things does the DSM-IV stipulate are required to diagnose intellectual disability?
- IQ of 70 or less
- Significant limitations in adaptive functioning in at least two areas
- Onset before the age of 18
What are the four subtypes of intellectual disability?
Mild (85% of cases)
Moderate (10%)
Severe and Profound (5%)
What is mild intellectual disability?
Needs only limited assistance and support
Can otherwise become self-sufficient and live independently
IQ 69-50
What is moderate intellectual disability?
Needs variable degrees of assistance or support
Can live in a supervised environment such as a group home, and work in a sheltered workshop
IQ 49-35
What is severe intellectual disability?
CAn master basic self-care and communication skills, but nonetheless needs continuous care
IQ 34-20
What is profound intellectual disability?
Not capable of self-care, needs continuous care.
IQ <20
What is the prevalence of intellectual disability?
2-3%
What are some common specific causes of intellectual disability?
Genetics
Pre-natal
Peri-natal
Post-natal
What are the pre-natal causes of ID?
Pre-eclampsia Placental insufficiency Hydrocephalus Myelomeningocoele Congenital hypothyroidism Infection (rubella, toxoplasmosis, cytomegalovirus, syphilis, HIV Foetal alcohol syndrome
What are the peri-natal causes of ID?
Brain trauma and hypoxia
Intraventricular haemorrhage
Hyperbilirubinaemia
Infections
What are the post-natal causes of ID?
Head injury Brain infections Brain tumours Hypoxia Chronic lead poisoning Neglect and abuse Malnutrition and general poverty
What are the genetic causes of ID?
Trisomy 21 (Down's syndrome) Fragile X syndrome (Martin-Bell syndrome) Other chromosomal abnormalities Single gene disorders (phenylketonuria) Other metabolic disorders Neurofibromatosis Tuberous sclerosis
What is the most common and second most common cause of ID and what is its incidence?
Most common:
Down’s syndrome
1 in 700 births
Second most common:
Fragile X syndrome
1 in 1500 births
What are the causes of Down’s syndrome and what percentage do they cause?
Trisomy 21 (95%) Robertsonian translocations (4%) Mosaicism (1%)
What are the physical abnormalities of Down’s syndrome?
Oblique or almond-shaped palpebral fissures Brushfield spots on the irises Flat nasal bridge Protruding tongue Short neck and shortened limbs Single transverse palmar creases
What risk factors are associated with Down’s syndrome?
Deafness Cataracts Respiratory infections Cardiovascular malformations GI abnormalities Haematological abnormalities Hypothyroidism Epilepsy Early onset Alzheimer's disease
What is the cause of fragile X syndrome?
CGG trinucleotide repeats in the FMR1 gene on the long arm of chromosome X, so commoner in males
What are the physical abnormalities of fragile X syndrome?
Elongated face Large or protruding ears Prognathism (extension of jaw) Macro-orchidism Hypotonia
What do all trinucleotide repeat disorders (Huntington’s, Lesch Nyhan…) have in common?
Anticipation (disease severity increases in successive generations)
What is the most common metabolic disorder?
Phenylketonuria
1 in 10000 births
What is the pathophysiology of phenylketonuria?
Autosomal recessive inheritance of a defect in the phenylalanine hydroxylase enzyme results in a high serum phenylalanine.
What are the physical abnormalities of phenylketonuria?
What is the treatment?
Short stature Hyperactivity Irritability Epilepsy Lack of pigment Eczema
Diet control (avoid protein rich foods; eggs, milk etc)
Mental disorders are all more common in ID than in the normal population: how could schizophrenia present in ID?
Deterioration from previous level of functioning
Behaviour that seems out of character
Indirect evidence of hallucinations and delusions
How could hypomania present in ID?
Giggling
Overactivity
Disinhibition
How could depressions present in ID?
Loss of appetite
Sleep disturbance
Speech and motor retardation
Anhedonia
