Brain development has some critical stages during pregnancy -> very rapid brain
growths and connectional specificity -> There are already forms of neuronal
networks in the fetal brain
Picture of the brain of a newborn already looks like the adult brain -> this partly true,
not for the function but the structure looks the same as an adult brain (=At birth all
the anatomical structures are already present).
Brain development happens:
- So the development is always hierarchical (so not every part develops at the same time:
cerebellar is in the back -> then posterior which is the back and -> going anterior, anterior is
more front. Anterior develops until late adolescence.
- Additive & Regressive (groeiend en verwijderd)
Additive = adding with what is already there -> more myelination.
Regressive = inverse development so synaptic pruning/ apoptosis = all the synapses that
don’t have a function anymore will be deleted
- In growth spurts -> most processes are not linear. These spurts can lead to too much
overproduction so then pruning will be activated. The spurts are also not happening in the
whole brain (!)
Neurons develop -> Neurons multiply -> Neurons
migrate (and find their location)-> Neurons branch
& form synapses (on their sent location) -> Pruning
& Synapses reorganize -> Myelination
So it is remarkable that in the prenatal period
myelination already starts (!)
The first trimester can be seen as ‘starting a brain’
and the second trimester is more about making
connections. The third semester is making a start in
the locations and myelinate (= increases the processing speed)
When damage in this period happens (prenatal) it mostly conflicts with the structure of the brain, not
the function yet!!!
During the postnatal period there is still the same amount of
neurons but the amount & length of dendrites increases!
-> leads to more synapses (=synaptogenesis) and more white
matter = myelination = more functional starters, not only
structure anymore.
When damage in this period happens (postnatal) it mostly
impacts the function of the brain (interconnections & networks).
Early disruptions to the early brain development
- injury -> postnatal a car accident for example, or too less oxygen in prenatal period
- maternal (mental) health -> depression/ anxiety, infections or sickness
- environmental -> toxins, smoking, drug use
- genetic -> genetic disorders
- etc.
,Is rapid growth a strength or a vulnerability? It could be both!
- Strength -> Immature brains are extremely plastic & recover better
Some children show greater brain improvement after an injury then with no injury
-> the earlier the injury in life, the better (because of plasticity)
Another strength is the theory about an equipotential -> for example when the left hemisphere
is removed the right part can take over (only at young age)
On the other hand are there also theories about innate specialization = it is shown that every
part has a specific purpose and specialization
- Vulnerability -> When there are dramatic developmental processes the brain may be
extremely sensitive to environmental influences early in life (mother smoking for example)
This could be called critical periods -> if you don’t learn a specific skill in this period, you don’t
ever learn it again after this period -> this is shown to be true
Also functional plasticity may only be restricted to certain sensitive periods
-> Maybe it’s somewhere between plasticity / good recovery and vulnerability / poor recovery
This is called the recovery continuum model
The cognitive reserve model = brain insult is interacting
with multiple things -> it depends on the brain reserve
capacity (BRC), the insult location, the age, and ultimately
the cognitive reserve capacity (CRC)
All these things lead to a certain functional plasticity which
leads to a functional outcome
Early brain damage is different from adult brain damage because you need to take into account that
the children are still learning skills -> the time when the damage occured is really important:
- Emerging skills -> just learning how a skill works
- Developing skills -> not fully functional yet, so partially acquired abilities
- Established skills -> the abilities are matured/ fully functioned
->> So with adult brains the skills are established, whilst for children you also have emerging and
developing skills -> this is important to take into account because then you also know the amount of
plasticity still available.
And even by taking this into account ; healthy children also vary in their ability to perform cognitive
tasks
A child could run into trouble at the beginning of acquisition so when time passes they start to deviate
more than normal -> because you only see post-injury
So you don’t see a child talking at an age where it should be able to talk, but you don’t know when this
deficit started because it couldn’t talk before like when it was a baby. Because these skills are still
developing you don’t know when the deficit started -> a longer follow up is important
The difference with children instead of adults are also:
- The type of insult -> usually there is more wider damage, not in one area, so there are less
specific impairments. Children have less specialization so for example if the left hemisphere is
removed the kid could still be fine, but for adults this is not
- The recovery trajectory -> for children it is difficult to prognose, there are so many factors so
much more research is needed to set a prognosis.
- Testing -> you cannot assume that adult tests measure the same skills in children -> for a
child it is different to make straight lines so the rey’s complex figure is a whole different test
for children than for adults
, Factors impacting recovery:
- large and unilateral lesions are better than small & diffuse lesions (strange!)
- diffuse (stukken weg over hele hersenen) is worse than focal (1 groot gebied naast elkaar)
- brain development is complex in children because of the non linear relation
- males more vulnerable -> later in puberty so more immature brains, that’s why they could be
more vulnerable. Another theory is that females have more neural connections so less
vulnerable.
- way better recovery when healthy environment for the child than bad food, bad sleep etc. ->
important for clinical research because this is modifiable (veranderbaar)
So these make it extra important to have long term follow-ups after early brain insult!
1.2 Preterm birth
There are 3 types of prenatal insult -> -preterm birth (PB), Hypoxic-ischaemic encephalography (HIE)
and a prenatal stroke (PS)
All of these three can lead to cerebral palsy (later in text)
Preterm birth <37 weeks
Extreme prematurity <32 weeks
Viable > 24-25 weeks.
-> These babies do survive sometimes but have many complications like sensory overstimulation,
missing out on intra-uterine stimulation (maternal nutrients), less physical contact (for example the
mother's voice, stimulation, moving around the uterus), illness, medical treatments
-> It really depends on when they are born and what they miss out on -> the later the better
Some facts: premature babies have smaller brains (in terms
of gray and white matter), there is an additive effect of
stressors when premature, brain connectivity is less when
premature (still when they are adults), cerebellum is mostly
implicated (achter hoofd, heeft grootste groei in derde
semester) which leads to motor issues & cognitive delays &
epilepsy, about ⅓ of preterm born children has multiple
medium to severe issues in several domains at 19 years of
age.
Long Term implications of preterm birth (even just a few weeks too early):
- psychosocial -> mostly attention issues, ADHD, ASS, conduct disorder
- mental -> lower IQ/ cognitive delays, special education, language problems
- motor -> cerebral palsy, motor delays
- physical -> growth delays, lower immunity, deaf, blind, breathing issues (because in the latest
stage the lungs develop), most important one is epilepsy -> can lead to additional lesions
1.3 Cerebral palsy
= a description of symptoms that come together (so not a disease) -> has to do with cerebral damage
in early life -> mostly during pregnancy, during birth or early postnatal
CP is the most common cause of child-onset lifelong disability! (1,5-2,5 per 1000 births)
Much heterogeneity in severity (how it came the cause) and aetiology (what it looks like in clinical
practice) -> some kids are in a wheelchair and some have nothing
Usually not clear what exactly happened -> most common is preterm birth, other factors are infections
or IUGR (= foetus isn't growing enough).
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