Download Chapter 3 Neurologic Development in Young Children Prenatal

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Chapter 3
Neurologic Development in Young Children
Prenatal Development: There are developmental differences between the embryonic stage and fetal
stage.
1) Embryonic stage- The embryo refers to the first stage of development of a baby from the
moment of fertilization and occurs between week 3 to 8. The embryo is the first thing noticed when a
woman has a pregnancy test. It is the size of a sesame seed at the time of the first ultrasound. By the
fifth week of development, the embryo will display a heartbeat in the early ultrasounds. As time
progresses, the tiny embryo will develop buds in its form that develop into hands and legs.
Development of neural tube. The neural tube later develops into the brain and the spinal cord.
During this time, the developing embryo gets all its nourishment from the uterine tissue or the amnion.
The placenta also starts developing at this stage. The placenta is the lifeline through which your baby
will get its oxygen and nourishment from your body.
2) Fetal stageThe embryo starts developing into a fetus from the eighth week onwards. Once the embryo
reaches the stage of the fetus, other organs like the liver, brain and kidneys start functioning inside the
tiny body. It is also visible the tiny differentiation of the fingers and the toes and the external genitalia is
visible on an ultrasound. The brain is more susceptible to damage during these 2 stages as well as during
early childhood.
Prenatal Developmental Stages
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Alertness: has periods of sleep and wakefulness
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Motor function:
 muscle tone appears in lower extremities around 32 weeks. By 36 weeks also appears in
upper and lower extremities.
 Develops strength around the neck by 36 weeks.
 Swallowing is shown since the 11th week and sucking around 28 weeks. The cycle of
sucking, swallowing and breathing matures between 32 and 34 weeks.
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Senses:
- can perceive and respond to olfactory stimuli
- by 26 weeks, baby is able to blink and squint in response to light
- by 28 weeks, baby is able to startle in response to auditory stimuli
- mother’s flavors in her diet are transmitted into the amniotic fluid and this renders a unique
taste and odor in the fluid. This tastes have an imprint into child’s future dietary preferences.
- by the third trimester a baby can perceive pain by grimacing, frowning, squeezing their eyes
shut, drop of oxygen level, increase heart rate
Postnatal Brain Development:
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Lack of protein intake can affect brain growth and cause impairment in neurotransmitter
functions. Undernourishment can cause low levels of achievement in school, poor behavior and
low developmental levels.
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Appropriate levels of thyroid hormones affect the level of alertness in newborn and promotes
better feeding.
Abnormal Brain Development
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1) Due to disorders in proliferation of neurons
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2) Abnormal migration of cells
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3) Poor myelination of brain cells
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4) Exposure to teratogens
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Neuron connections
1) Disorders of neuronal proliferation
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Micrencephaly- Small brain. Can be caused by teratogenic factors such as:
chemical agents/ radiation
drugs as thalidomide, alkylating agents, cocaine
alcohol
rubella virus and cytomegalovirus
X-rays
environmental factors, such as the age and general health of the mother
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Macrencephaly- Large brain. It involves excessive neuronal proliferation. It can cause severe
intellectual deficit, seizures, or no neurologic deficit.
 Familial macrencephaly can be autosomal dominant ( one of the parents has a head
circumference greater than 90th percentile.
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Epidermal nevus syndrome- growth disorders in the face or scalp, eye abnormalities, skeletal
abnormalities, abnormal central nervous system, and malignant tumors.
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Tuberous sclerosis- intracerebral tumors, seizures, skin lesions, cardiac tumors, abnormal
neuronal proliferation.
Neuronal Migration brings cells into appropriate spatial relationships. In the nervous system,
migration during development brings different classes of neurons together so that they can interact
appropriately. It occurs as early as the second month of gestation and is controlled by a complex
assortment of chemical guides and signals. When these signals are absent or incorrect, neurons do not
end up where they belong. This can result in structurally abnormal or missing areas of the brain in the
cerebral hemispheres, cerebellum, brainstem, or hippocampus.
2) Disorders of Neuronal Migration
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Lissencephaly: brain stays relatively smooth. Poor neuronal migration inner and outer layers.
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Polymicrogyria- surface of brain has excess gyri.
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Schizencephaly – severe localized abnormality of neuronal migration.
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Agenesis of corpus callosum- the structure that connects the two hemispheres (left and right) of
the brain is partially or completely absent.
3) Disorders of brain cell organization
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Babies born small for gestational age, Rett syndrome, Angelman syndrome, fragile X syndrome,
autism, and down syndrome show cell disorganization.
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Can cause seizures, intellectual disabilities.
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Brain organization can also be affected by the learning environment in early childhood
4) Disorders in brain myelination
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Undermyelination of neurons can cause cerebral palsy, cognitive and behavior disorders. In
premature babies, it can cause poor brain oxygenation.
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Low levels of thyroid hormone- at first weeks of gestation, maternal thyroid hormone crosses
placenta to the fetus to start development of fetal brain. Later in gestation, fetus must produce
its own thyroid hormone.
 When thyroid hormone level is not produce properly, proper brain development does
not occur.
5) Disorders of Brain Development
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Hydrocephalus: It is the buildup of fluid in the cavities (ventricles) deep within the brain. The
excess fluid increases the size of the ventricles and puts pressure on the brain.
The most common treatment for hydrocephalus is the surgical insertion of a drainage system,
called a shunt.
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Holoprosencephaly: It is a disorder caused by the failure of the prosencephalon (the embryonic
forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a
single-lobed brain structure and severe skull and facial defects. Can be associated with a
chromosomal defect, genetic abnormality.
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Dandy-Walker malformation: It is a congenital brain malformation involving the cerebellum and
the fluid-filled spaces around it. Enlargement of the fourth ventricle, a partial or complete
absence of the area of the brain between the two cerebellar hemispheres (cerebellar vermis),
and cyst formation near the lowest part of the skull.
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Neonatal Seizures: result from abnormal electrical activity from the brain. It involves movement
of the arms, legs, prolonged extension of extremities, turning the head to one direction, tonguethrusting, eyelid twitching, jerking of the eyes to one side, stop breathing, drop or rise of heart
rate or blood pressure.
EEG can confirm diagnosis. 50%-60% of neonatal seizures are caused by an insult to the central
nervous system
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Hypoglycemia: low blood sugar can lead to seizures. Sometimes babies from diabetic mothers
develop hypoglycemia as they have been exposed to high sugar levels. Treatment is based on
leveling blood sugar to stop seizures.ponatremi
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Hyponatremia: low sodium levels.
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Hypocalcemia: low calcium levels
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Hypomagnesemia: low magnesium levels. Very rare.
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Narcotic withdrawal: within 24 to 72 hours after birth, infants show signs of withdrawal (
franctic sucking, excessive feeding, irritable, prolonged crying, fevers, sweating, fast heart rate,
vomit, diarrhea and seizures). Treatment includes a dark/quiet environment, minimal external
stimuli, and swaddling.
include opium, morphine, codeine, heroin, methadone, cannabis, coca and cocaine.
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Strokes: cerebral infarctions. Relatively rare in the neonate. It is a disturbance to the blood
supply of the developing brain in the first 28 days of life which results in lack of oxygen to the
brain tissue.
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Intracranial Hemorrhage:
Bleeding within the skull.
It may or not lead to seizures.
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Hyperbilirubinemia: bilirubin is a yellow compound that supports the process in the body's
clearance of waste products that arise from the destruction of aged red blood cells. When the
level is high, it can cause jaundice.
Severe jaundice can cause seizures,
delays and deafness.
TERATOGENS
a) Exposure to infections= causes malformations.
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Cytomegalovirus CMV,
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Toxoplasmosis ( parasite found in uncooked meat, and also found in cat feces)
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Varicella (chicken pox)
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Rubella ( 3 day measles)
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Herpes simplex
b) Metabolic defects= caused by poorly controlled levels of PKU. It is an amino acid disorder.
People have problems breaking down an amino acid called PHE from the food they eat. An enzyme,
called PAH, is either missing or not working properly. The job of this enzyme is to chemically change the
amino acid phenylalanine PHE into other substances. When a child with PKU eats food containing PHE, it
builds up in the blood and causes problems. PHE is found in almost every food, except pure fat and
sugar.
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c) Adverse environmental factors=
 maternal hyperthemia (high body temperature) as a consequence of high fever or use of
hot tub.
 Exposure to lead, mercury or radiation
d) Drugs=
Alcohol, cocaine, anticonvulsans, acne medication.