#13 Intellectual Disability Flashcards
What are the two components of intelligence?
- General mental capacity
- Task specific intelligence (ability to reason, solve problems, think abstractly, plan)
What does intellectual disability refer to?
A group of disorders where children fail to develop normal cognitive skills including language, activity of daily living, learning and memory
Have many different causes: genetic, environmental, drugs, brain malformation
Can be inherited from parents, or sporadic (de novo, after zygote forms)
What is the traditional view of neurodevelopmental disorders? What is the novel view of NDDs?
More cognitive based
There is genetic overlap between NDD and mental health, it is a continuum with some genes leading to more than one condition and differential manifestation
What percent of the population does ID affect? (HINT: same as percent of children with tics)
3%
How do we investigate individuals with ID?
- Assess the developmental milestones: use scales to monitor the development of children and the acquisition of new skills
- Psychometric testing: test the general mental capacity (ability to reason, solve problems, think abstractly and plan), and test IQ (objective)
- Classify intellectual disability (mild-profound)
- Neuroimaging (MRI yields diagnosis 48.6-65.9% of the time and CT only 30% of the time)
Who was Alfred Binet? What were his contributions to psych?
Psychology, developed testing of various mental functions to help schooling of children, test would give mental age therefore we could place kids in the correct grade and determine most effective peer group
Worked with Charcot and Sorbonne
What are the two components of the IQ test? What is IQ distribution in the population?
Verbal
Non-verbal (visuo-spatial)
IQ is normally distributed in the population and is relative to kids of the same age
How is intellectual disability characterized?
Intellectual quotient less than 70
Mild ID: 50-70
Moderate ID: less than 36-50
Severe ID: less than 20-36
Profound ID: less than 20
How is genetic testing performed for intellectual disability?
DNA analysis can be performed from the chromosome level down to a single base
Genome wide approaches where you do not need to know what gene you are looking for (comparative genomic hybridization using CNV, next generation sequencing)
Gene specific testing where you do need to know the gene you are looking for (Fragile X syndrome, and Rett syndrome)
TRUE OR FALSE: Accumulation of mutations leads to increased phenotypic complexity (due to differing mutational load per person)
TRUE
What is true about heterogeneity of NDDs?
More mutations means more complex phenotype
Shows that parents do not have ID but will have learning disability, and when their child gets another mutation then they develop ID
For example, the chr 16 deletion in parents has more detrimental effects in their kids if it is passed on due to interactions with other mutations
What is Down’s Syndrome?
Most common cause of ID, caused by trisomy of chromosome 21 (in part or entirely), and no known treatment
Indications in kids: decreased tone, dysmorphic facial features
What is a syndrome?
Common association of certain symptoms (past events) in the history of the patient and certain signs (things you can see) upon patient examination
What are the four causes of SEVERE intellectual disability? Which one is most responsible?
Unknown (18%)
Postnatal (12%)
Perinatal (15%)
Prenatal (55%) : chromosomal and other genetic factors (34%), congenital abnormalities and syndromes (12%), and pregnancy factors (8%)
What is fragile X syndrome? How was it initially found?
Most common ID in males, but also effects females
Dysmorphic features, epilepsy, visuospatial memory defects, and autism (60%)
Initially found on karyotype, and involves more than 200 CGG repeats and increased methylation which silences the gene
