Birth & Infancy Neurodevelopment

• ectoderm (outer)

• mesoderm (middle)

• endoderm (inner)

What are the 3 distinct layers that the cells of the fertilized egg divide into 2 weeks after conception?

skin, sensory organs, nervous system (hence the outer layer)

What does the ectodermal layer go on to form?

skeleton, muscle, bones, CT, cardiovascular system

What does the mesodermal layer go on to form?

GI system, liver, pancreas, respiratory system (internal organs)

What does the endodermal layer go on to form?

• the nervous system starts developing

• neural plate appears

• the 3 distinct cell layers form

What happens on the 16th day?

• neural groove is created and visible

• beginning formation of the neural tube from the neural plate (neurulation)

What happens on the 18th day?

plate → groove → crest (part of the ectoderm that becomes peripheral sensory neurons)

What does the neural plate become?

inferior neuropore

the temporary caudal opening of the neural tube that closes last during neurulation

Spina Bifida

failure of the closing of the inferior neuropore

differentiation

term used to describe when structures start to specialize (cells divide)

neural plate

What contains the cells that specialize and form the entire nervous system?

3

The first ___ months are the most important for brain development.

newborn

At what age does the brain have all the neurons it will ever have? (About 100 billion)

glia (which divide and multiply) and addition of new synapses

Why does the newborn brain continue to grow even though it has all the neurons it will ever have?

be flexible and resilient

By age 2, a child generates up to 15,000 synapses. What does this enormous amount of synapses allow the growing brain to do?

10

At what age does the brain undergo pruning of its weakest synapses?

18

At what age is pruning complete?

pruning

deletion of synapses that are seldom or never used

decline in plasticity, increase in power in the existing synapses (more specialized)

What does the completion of pruning result in? (age 18)

between day 14 and week 20

When is the CNS most susceptible to major malformations?

• functional disturbances and minor malformations

• less serious period after week 20

After week 20, what kind of malformations are more common?

Anencephaly

incomplete formation of the brain due to the cranial end of the neural tube not closing

The forebrain is not formed.

• The brainstem is there, but no cerebral or cerebellar hemispheres form.

Which parts of the brain are formed and which are not formed due to Anencephaly?

in utero or within a week after birth

life expectancy of a baby with Anencephaly

Tethered spinal cord

occurs when the spinal cord adheres to a lower vertebra (instead of floating down lower in CSF) causing nerve damage

symptoms in the dermatomes (skin) and myotomes (muscles)

• abnormal sensation in skin (pain, tingling, loss of sensation)

• muscular weakness, difficulty walking

What does the traction of a tethered spinal cord mean as the child ages?

Arnold Chiari Malformation Type I (less serious)

herniation (bulge) of the cerebellum at the foramen magnum, causing the pons and medulla to deform

• may have none

• If they do occur, they include severe head and neck pain in the teen years

What are the symptoms like for people with Arnold Chiari malformation when it occurs in adolescence or adulthood?

pressure increase on cranial nerves, causing multiple symptoms

What is affected when the Arnold Chiari malformation compromises CSF flow?

Arnold Chiari Malformation Type II (more serious b/c brainstem is involved)

malformation of the brainstem and cerebellum, signs are present at birth

• the medulla and cerebellum extend through the foramen magnum

hydrocephalus, paralyzed sternocleidomastoid, deafness, facial weakness, etc.

What are some things that can be caused by Arnold Chiari Malformation Type II?

myelomeningocele

What is Arnold Chiari Malformation Type II usually associated with?

Occulta, Meningocele, Myelomeningocele, Myeloschisis

4 types of spina bifida

L5, S1, or both

Occulta is a vertebral defect at what vertebrae?

Occulta (10% of people have this)

type of spina bifida where neural function is usually normal, sometimes a tuft of hair, vertebral defect at L5, S1, or both

Meningocele

type of spina bifida where there may be no impairment

• spinal cord is still inside the body, but there is a bulge of the dura mater and subarachnoid space

• the vertebrae are not protecting the space

The neural tissue is protruding, and the spinal cord is bulging outside the body into the subarachnoid space, with protection only from the dura mater.

Explain Myelomeningocele spina bifida

Myeloschisis

spina bifida where the spinal cord is open to the surface of the body, most serious type

spinal muscular atrophy

genetic disorder where motor neurons with cell bodies in the spinal cord degenerate

muscle weakness atrophy and premature death

What does spinal muscular atrophy result in?

Type I (Wernig Hoffman)

What type of spinal muscular atrophy is most severe?

symptoms of Fetal Alcohol Syndrome

impaired CNS, growth deficiencies before and after birth, facial abnormalities

cerebellum, cerebral nuclei, corpus callosum, neural tube, neuroglia

part of the brain that may be malformed due to FAS

small head, low nasal bridge, epicanthal folds, flat midface, small eye openings, short nose, thin upper lip, smooth philtrum (under nose), underdeveloped jaw

physical features of children with FAS

intelligence, memory, language, attention, reaction time, visuospatial abilities, decision making, goal-oriented behavior

possible deficits for FAS children

neuronal proliferation deficits, attention and impulse control (behavioral problems)

common effects of cocaine in utero

Cerebral Palsy

Movement and postural disorder caused by permanent, nonprogressive damage to the developing brain

postnatally (after birth)

When does damage from CP occur?

spastic, dyskinetic, ataxic, hypotonic, mixed

types of Cerebral Palsy

spastic

type of CP: muscles have too much tone, rigid

Dyskinetic, Ataxic

type of CP: inability to coordinate

Hypotonic

type of CP: muscles are floppy

Mixed

type of CP: combination of types

Hemiplegia

CP classification: half of the body is affected (ex. right leg and right arm)

Diplegia

CP classification: two of the same body part affected (ex. both arms or both legs)

Quadriplegia

CP classification: both legs and both arms are affected

prematurity

What is the prime cause of congenital cerebral palsy?

trauma ex. drowning, no oxygen to brain for long period of time

How do people acquire cerebral palsy?

Strabismus

eye alignment deviations, similar to a lazy eye

nystagmus

repetitive, uncontrolled eye movements (side to side is most common)

dysarthria

difficulty articulating words

aphasia

difficulty expressing thoughts or understanding ideas

Stabismus, Nystagmus, Dysarthria, Aphasia

comorbidities of CP

Athetosis

slow, continuous, involuntary muscle movements

Choreoathetosis

fast, jerky, involuntary muscle movements