Chapter 24 - Neurodevelopmental disorders Flashcards
1
Q
What’s the broad definition of neurodevelopmental disorders?
A
- Multifaceted conditions generally defined by significantly lower-than-average performance in a school subject
- Origin in abnormal brain development
- Encompasses disorders of attention, social behaviour, general cognition, learning, communication, motor skills
2
Q
What are the general stages of brain development?
A
1) Cell birth (neurogenesis; gliogenesis)
2) Neural migration
3) Cell differentiation
4) Neural maturation (dendrite and axon growth)
5) Synaptogenesis
6) Cell death and synaptic pruning
7) Myelogenesis
3
Q
Which brain development stages occur prenatally and which continue well into adulthood?
A
- Cell birth - cell differentiation: Prenatally
- Neural maturation - Myelogenesis: Continues well into adulthood
4
Q
What important development occurs during weeks 4-6?
A
- The neural tube is forming, very sensitive to insults (ex. drinking)
5
Q
Why are gestational weeks 6-8 weeks so important for neural development?
A
- Neurogenesis is in full force and new neurons are developing, and neural migration is about begin
6
Q
How does dendritic growth differ from axonal extension?
A
- Dendritic growth - helps provide surface area for synapses with other cells; occurs very slowly (arborization)
- Axonal extension - to appropriate targets to initiate synapse formation; occurs very quickly (1000X faster)
7
Q
T/F: Most intellectual disability cases are mild.
A
- TRUE
8
Q
Which sex is more diagnosed with intellectual disabilities? What’s a major risk factor?
A
- Males are more commonly diagnosed
- Poverty is a risk factor
9
Q
What’s Cerebral Palsy (CP)?
A
- Group of motor function disorders caused by brain damage or abnormalities either before, during, or after birth
- Diverse causes can include blood clots, infections, and a wide range of traumatic brain injuries
- Considered an intellectual disability
10
Q
What are some of the major symptoms of CP?
A
- Can be mild impairments in a single limb to severe impairments which can affect the entire body
- May be accompanied by other impairments (cognitive, emotional, epilepsy etc.)
- 35-60% of cases are associated with moderate to profound intellectual impairment
11
Q
Is there a difference between incidence of CP in male and females?
A
- No
12
Q
What’s considered a risk factor for CP?
A
- Premature births can increase incidence by 100-fold
13
Q
What’s spastic CP?
A
- Makes up around 50% of cases
- Characterized by hypertonia (excessive muscle tone), worse when limbs are moved quickly
14
Q
What’s athetoid CP?
A
- Makes up around 25% of cases
- Characterized by continuous ongoing movement (uncontrolled)
- Often caused by severe oxygen deprivation at birth, basal ganglia and thalamus are affected
15
Q
What’s rigid CP?
A
- Makes up around 10% of cases
- More continuous, uniform hypertonia, affects whole body
- More severe than spastic
- Brain regions affected: basal ganglia, brain stem, and spinal cord
16
Q
What’s ataxic CP?
A
- Affects around 10% of cases
- Caused by cerebellum damage, may need an aid to walk on their own
- Balance and coordination and voluntary movement most affected
- The least severe form of CP
17
Q
What’s hypoxia?
A
- Diminished oxygen flow during
- May lead to an intellectual disability
18
Q
What’s hydrocephalus?
A
- Abnormal buildup of CSF in the ventricles
- CSF bathes entire brain (cushions, adds buoyancy, provides ions etc.)
- CSF flow is blocked
- Atrophy of surrounding brain tissue leads to ventricle enlargement
19
Q
When does infant hydrocephalus develop?
A
- Usually develops during first 3 months
- Affects around 2/1000 babies
20
Q
Where is CSF produced and where does it move to?
A
- Produced in the choroid plexus
- Moves downward to the fourth ventricle
21
Q
Where may CSF get blocked in hydrocephalus?
A
- The cerebral aqueduct
- The fourth ventricle
- The foramen of Magendie
- Foramen of Luschka
- Foramen of Monro
22
Q
How does CSF circulate throughout the brain?
A
- The subarachnoid space (found between the arachnoid membrane and the pia mater)
23
Q
What’s the most common cause of hydrocephalus?
A
- Most are the result of inflammation of trauma
24
Q
What are the treatments for hydrocephalus?
A
1) Endoscopic third ventriculostomy (drilling a hole in the third ventricle, allows for fluid to leak out)
2) Shunt (permanent, inserted into lateral ventricle, most common solution)
25
What's Fragile-X Syndrome?
- The most common inherited cause of an intellectual disability and autism spectrum disorder
26
Which sex has more learning disabilities with Fragile-X syndrome?
- Most boys have learning disabilities, compared to only 1/3 of affected girls
27
What symptoms are found in Fragile-X syndrome?
- Facial abnormalities and mental disabilities
- Attention deficits, hyperactivity, anxiety, unstable mood and behaviour
28
What causes Fragile-X syndrome?
- Caused by mutations in the FMR1 (fragile X Messenger ribonucleoprotein 1) gene on the X chromosome
- Mutation is a trinucleotide repeat (CGG) expansion
- Leads to loss of the FMRP (Fragile-X mental retardation protein)
- FMRP participates in synapse formation (GABA and glutamate receptors) and functioning
29
What are some structural differences in Fragile-X syndrome?
- Poorly formed and more numerous dendritic spines
- MRI scans show cortical thinning, small caudate nucleus, and an increase in ventricular size
30
What's Fetal Alcohol Spectrum Disorder (FASD)?
- Caused by abuse of alcohol by mothers/fathers preconception, or mothers during pregnancy
- Physical malformation and intellectual impairment
- Varying degrees of learning disability, relatively low intelligence scores, hyperactivity, social problems
31
What may be some theories for the effects of alcohol toxicity on the developing brain?
- Cell death
- Cell signalling defects
- Gene expression changes, including epigenetics
- Vitamin deficiencies
32
What causes Down Syndrome?
- Congenital condition caused by an extra copy of chromosome 21
- Failure of chromosome 21 to separate during meiosis
- 88% of trisomy 21 cases result from nondisjunction during oogenesis
33
T/F: Down syndrome is the least common chromosome abnormality in humans.
- FALSE, it's the most common
34
What are some of the health risks of Down Syndrome?
- 50% may have heart defects which require surgery in early infancy
- Increase risk of developing autoimmune disorders
- Higher risk of sleep apnea
- More prone to obesity
- Increase risk of developing dementia and Alzheimer disease
35
What's language disorder?
- Persistent difficulties in learning and using spoken, written, or sign language
- Understanding or using language, or both
- Impairment usually extends to vocabulary, sentence structure, and discourse
36
What are the general symptoms of a language disorder?
- Short and simple sentences
- Grammatical errors in speech
- Small vocabulary
- Word-finding difficulties
- Persists into adulthood
37
What's the Wernicke-Geschwind model?
- Classical anterior and posterior speech zones are connected by the arcuate fasciculus
38
What may be the cause of a language disorder?
- There's a strong genetic component
- The anterior frontal cortex pathways representing language syntax and meaning it may not fully mature
39
What's speech sound disorder?
- Impaired pronunciation and articulation
- May be due to difficulty with phonological knowledge or ability to coordinate movements necessary for speech
40
What are some speech sound disorder symptoms?
- Dropping, adding, distorting, or swapping word sounds
- Saying only 1 syllable in a word
- Simplifying a word by repeating 2 syllables
- Leaving out a consonant sound
- Changing certain consonant sounds
- Running out of air while speaking
- Hoarse, raspy, or nasally sounding voice
41
What's childhood-onset fluency disorder?
- AKA stuttering
- Fluency and rhythm of speech are interrupted
- 4X more likely in males
- Onset usually during 306 years, but is usually outgrown
41
What's the cause of speech sound disorder?
- The cause is not well understood (often idiopathic)
- There is a genetic component
42
Developmental vs. Acquired childhood-onset fluency disorder?
- Developmental - Number of structures in frontal and temporal cortices (both hemispheres)
- Acquired - May occur after trauma/emotional and/or physical stress, or following neurological injury
43
How does childhood-onset fluency disorder impact brain connectivity?
- May be due to decreased white matter 'integrity' along left dorsal language tract (make it hard for articulation)
- 'Integrity' - axon density, myelination, axonal diameter
44
What's social communication disorder?
- Impaired verbal and nonverbal communication for social purposes
- Difficulties with indirect use of language (i.e., implied sentences, metaphors, humour, aphorisms
- Presence of ASD excludes an SCD diagnosis
45
What are some major symptoms of ASD?
- Impaired social interaction, narrow range of interests, abnormal language/communication skills, fixed and repetitive movements, and in some cases intellectual impairment
46
What is Asperger syndrome called now?
- Often referred to as high-functioning autism
- They have good verbal communication, but difficulty with social communication
- Narrow repetitive play, poor peer relations, need for routine/sameness
- May excel in some aspect of behaviour
- Can develop exceptional memory abilities
47
T/F: ASD is 4X more common in boys
- TRUE
48
What is characteristic of the brain in those with ASD?
- Brain characterized by accelerated rates of neuronal maturation
- Excessive brain volume in the amygdala, temporal and frontal lobes
49
What are some other anatomical correlates of ASD?
- Von Economo neurons may fail to develop normally
- These are large bipolar neurons found in areas of cortex associated with social cognition
- Develop late, around age 4
- May also be brainstem changes, such as a reduced size in posterior pons
50
Where are VENs found in the brain?
- DLPFC
- Frontal insular cortex
- Anterior cingulate cortex
51
ACC vs. Insula in social cognition?
- ACC - empathy, impulse-control, emotion, decision-making
- Insula - empathy, trust, guilt, humor, etc.
52
Why are VENs? important?
- May allow for rapid adjustment to changing social contexts
- They contribute to out theory of mind
53
How may the cerebellum differ in those with ASD?
- Decreased Purkinje cell counts in the cerebellar cortex and cerebellar volume
- Cerebellar atrophy
- Patients with cerebellar agenesis may have symtpoms of ASD
54
What are the three core symptoms of ADHD?
1) Inattention
2) Hyperactivity
3) Impulsivity
*All must be present before age 12
*impulsivity must be present in any diagnosis
55
Which ADHD symptoms are more common in which sexes?
- Inattention is more common in females
- Hyperactivity and impulsivity are more common in males
56
T/F: Boys are 3X more likely than girls to have ADHD.
- FALSE, it's 2X more likely
57
What are the structural differences in those with ADHD?
- Widespread structural (gray matter) and connection (white matter) irregularities
- Affects specifically the frontal-striatal, frontal-parietal networks
- Also reductions in orbitofrontal gray matter and basal ganglia gray matter
58
What's the main cause of ADHD?
- Largely genetic, may also be environmental risk factors (e.g., prenatal smoking, neonatal anoxia, childhood lead exposure)
59
What stimulants are often prescribed for those with ADHD?
- Methylphenidate (Ritalin)
- Amphetamine (Adderall)
*Both work by increasing levels of DA/NE.
60
What can perinatal brain injury result in?
- Can lead to neonatal encephalopathy
- Most commonly due to hypoxia-ischaemia
61
Which brain region may exposure to ACEs effect?
- May compromise frontal lobe development
62
What were some of the outcomes of the case of the Romanian orphans?
- Astounding recovery if adopted before 2 years of age
- By 12 years of age: average brain size was up to 20% smaller, and widespread reduction in cortical white and grey matter
- Unresolved cognitive and behavioural problems
- PFC, HPC, and amygdala likely affected
63
What has prenatal stress been associated with in terms of brain function?
- Increased size of amygdala
- Decreased size of HPC
- Later development of depression and anxiety disorders
64
What did Donald Hebb do?
- Provided enriched environments for rats and discovered they performed better on the Hebbs-William maze than lab-reared controls
- He reared a group of rats in his kitchen
65
What were some differences found in rats that were reared in rat condos?
- Larger, more complex cortices, richer in synapses
66
What's Tooley's Integrative Theory?
- Stress accelerates brain development
- High SES children = slower segregation of connectivity into adult networks
- Positive and rare experiences lead to slower maturation and enhanced plasticity, while repetitive and negative experiences lead to faster maturation and reduced plasticity
