Transcript Central Nervous System Development

CNS- CENTRAL NERVOUS SYSTEM
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Stages of Brain Development – Summary
1. Cell birth or formation
2. Cell Migration
3. Cell Differentiation
4. Cell Maturation (dendrite and axon growth)
5. Synaptogenesis (formation of synapes)
6. Cell Death and Synaptic Pruning
7. Myelination
Adapted from Kolb, B. & Gibb, R. (2011). Brain plasticity and behaviour in
the developing brain. Journal of the Canadian Academy of Child and
Adolescent Psychiatry; 20 (4): 265-276.
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SYNAPTIC GROWTH
From: http://neurowiki2012.wikispaces.com/
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SYNAPTIC PRUNING
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CNS- CENTRAL NERVOUS SYSTEM
After birth, the long portion of the nerve cell, called the axon,
develops a protective sheath that covers it. This protective
sheath is called myelin. Myelination is usually complete by 18
months of age. The myelin coating helps the nerve impulses
travel faster.
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The “At Risk Infant”
“one who has a high probability of
manifesting developmental delay as
a result of exposure to any number
of medical (and environmental)
factors.”
Adapted from Campbell, S. K., Vander Linden, D. W. & Palisano, R. J. (2006). Physical therapy for children (3rd
ed). St. Louis: Saunders Elsevier.
STAGES OF PRENATAL DEVELOPMENT
Germinal Stage- Lasts approximately 2 weeks
Embryonic stem cells differentiate into:
 Ectoderm (skin, spinal cord, teeth)
 Endoderm (blood vessels, muscle, bone)
 Mesoderm (lungs, digestive, and urinary systems)
Prenatal Development –
Embryonic Stage –From 2 to 8 weeks
 Organs are forming during this stage
 Many birth defects occur during this stage (first 3 months of gestation)
 Exposure to toxins and infectious agents
 Neural tube defects
 Myelomeninigocele (spina bifida) Prenatal diagnosis:
 Alpha-fetoprotein in maternal serum at 14-16 weeks
 Ultrasound imaging
 Amniotic fluid analysis/acetylcholinesterase
STAGES OF PRENATAL DEVELOPMENT
Fetal Stage- 2 months until birth
 Physiological flexion occurs from “packaging”
 Premature infants do not experience this
 Rapid growth
 Gestational diabetes and post term delivery may result in a large body size
 Shoulder dystocia
 Brachial plexus injury (Erb’s palsy)
PRETERM BIRTH
Preterm birth is birth before 37 weeks gestation.
Premature birth is more likely in multiple births (twins, triplets)
Premature birth in singleton births differs by ethnicity: American black women experience a
higher rate of premature births and a higher rate of infant mortality because of
preterm birth.
PRETERM BIRTH
Preterm birth rate has increased slightly since the early 1980’s.
Advances in medical science and the care of babies born prematurely has lowered the
survivable gestational age to 23-24 weeks; most infants born after 25 weeks
gestation survive.
PREMATURITY AND LOW BIRTH WEIGHT
Three major categories of low birth weight:
 Low Birth Weight (LBW): 1501-2500 grams
 Very Low Birth Weight (VLBW): < 1501 grams
 Extremely Low Birth Weight (ELBW): <1000 grams
LOW BIRTH WEIGHT
• Infants in a low birth weight category may be:
– infants born prematurely or
– infants born at term but with reduced weight
• VLBW infants are more likely to experience
– Neurologic sequelae
– Delayed development
– Lower intellectual and language abilities
SMALL FOR GESTATIONAL AGE (SGA)
Infants whose birth weights are below the 10th percentile of published norms
Preterm SGA infants are at greater risk than term SGA infants for developmental
problems. (Both groups are at risk!)
MEDICAL COMPLICATIONS OF PREMATURITY- RDS
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Respiratory Distress Syndrome (RDS) (or hyaline membrane disease): a breathing
disorder affecting newborn infants
• Causes of RDS
– Pulmonary (lung) immaturity
– Deficient surfactant (a substance produced by the lungs that allows the air sacs to stay
open)
• Risk Factors for development of RDS:
– Prematurity, LBW, Low Apgar Scores, Maternal age over 34 years
MEDICAL COMPLICATIONS OF PREMATURITY- RDS
• Prevention
– Prophylactic use of corticosteriods (dexamethasone, betamethasone, hydrocortisone)
• Accelerates lung development prior to preterm birth
• Used when preterm birth is anticipated
http://trialx.com/curebyte/2011/07/02/pictures-forinfant-respiratory-distress-syndrome/
MEDICAL COMPLICATIONS OF PREMATURITY- RDS
Intervention
 Supplemental oxygen, assisted ventilation, surfactant, ECMO, inhaled nitric oxide (iNO)
Goal during intervention is infant survival and to minimize damage to the lungs
Infants who survive severe RDS
 Require frequent hospitalizations for URI
 Increased incidence of neurologic sequelae
MEDICAL COMPLICATIONS OF PREMATURITY- BPD/CLD
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Bronchopulmonary Dysplasia- caused by incomplete or abnormal repair of lung
disease during the neonatal period. Also referred to as Chronic Lung Disease (CLD).
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Boys are at a greater risk-maybe because their lung development is 1 to 2.5 weeks
behind girls.
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Infants with BPD experience an increase in the work of breathing
MEDICAL COMPLICATIONS OF PREMATURITY- BPD/CLD
• Causes of BPD/CLD
– Immature lung tissue
– Trauma to lung tissue from (high pressure) assisted ventilation
– Oxygen toxicity
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Prevention-Prevention of premature birth, antenatal steroids
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Treatment-Surfactant replacement, assisted ventilation for as short a time as possible, iNO
MEDICAL COMPLICATIONS OF
PREMATURITYDEFINITIONS
Hypoxic- Body as a whole or a part of the body is deprived of adequate oxygen supply
Anoxic- A total decrease in the level of oxygen; extreme hypoxia
Asphyxia- lack of oxygen to the body because breathing is not normal
Ischemic- A decrease in the blood supply to a bodily organ, tissue, or part
MEDICAL COMPLICATIONS OF PREMATURITY- PVL
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Periventricular Leukomalacia-ischemic lesion to the brain of a premature infant.
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The area of the brain affected is typically the motor tracks descending from the
brain to the spinal cord.
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The motor tracks typically affected are those controlling the legs.
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Clinical outcome is often “spastic diplegic” cerebral palsy
MEDICAL COMPLICATIONS OF PREMATURITY-IVH
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Intraventricuar Hemorrhage – bleeding into the fluid filled spaces of the brain
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Characteristic of the premature infant less than 32 weeks gestational age and
weight less than 1500 grams (VLBW)
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Occurs in preterm infants with RDS requiring ventilation
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An inverse relationship exists between gestational age and IVH
MEDICAL COMPLICATIONS OF PREMATURITY-IVH
IVH is graded based on severity from least to most severe.
 Grade I IVH: Only a small amount of bleeding. Prognosis is good
 Grade II IVH: Bleeding into the ventricle(s), but the ventricle size remains the same. Minimal to
no damage. Prognosis is good.
 Grade III IVH: Bleeding results in larger size of ventricle(s). May obstruct the normal flow of
CSF.
 Grade IV: Bleeding into the ventricle(s) and brain. Prognosis not as good for Grade III and IV
bleeds.
MEDICAL COMPLICATIONS OF PREMATURITY- IVH
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Grades I through IV based on head ultrasound findings
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Hydrocephalus is a complication of IVH
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Prevention/Treatment
Prevent premature birth
Corticosteriods when preterm birth is expected (reduces likelihood of IVH)
Keep blood pressures stable (avoid highs and lows) and control intracranial pressures
Shunt for hydrocephalus
VENTRICULO-PERITONEAL SHUNT
From : A Teachers Guide to Hydrocephalus (2002). Hydrocephalus Association: San
Francisco, California
www.hydroassoc.org
HYPOXIC ISCHEMIC ENCEPHALOPATHY (HIE)
Cause of neurologic problems in both preterm and full term infants.
HIE occurs with a lack of oxygen/substrate delivery to the brain as a result of decreased
blood flow
In the past, treatment of HIE was only supportive care, but newer interventions are
being studied (i.e. hypothermia).
HYPOXIC-ISCHEMIC ENCEPHALOPATHY
• Conditions resulting in increased risk of HIE:
– Altered placental exchange
• Placental abruption– placenta separates from the wall of the uterus prior to birth
• Previa– placenta partially or totally covers the cervix
• Prolapsed cord– umbilical cord descends into birth canal prematurely; pressure on the cord can decrease
/cut off the infant’s blood supply.
– Reduced blood flow to the placenta
– Maternal cardiac arrest
MEDICAL COMPLICATIONS OF PREMATURITY- ROP
Retinopathy of Prematurity- abnormal growth of the
blood vessels of the retina that occurs in premature
infants.
http://www.nei.nih.gov/rop/photos.asp
http://www.retinahawaii.com/condition
rentinopathy-of-prematurity.html
MEDICAL COMPLICATIONS OF PREMATURITY- ROP
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Risk factors associated with ROP include:
Prematurity
LBW
IVH
Supplemental oxygen
• All premature infants who received supplemental oxygen should be screened for
ROP
• The amount of oxygen that is needed for the brain but will minimize the risk of ROP
has not been established
TEROTOGENS
Teratogen- “anything external to the fetus that causes later structural or functional
disabilities.” (Hooper and Umansky, 2009)
PRENATAL EXPOSURE TO ALCOHOL
Fetal Alcohol Syndrome (FAS) and Fetal Alcohol Effects (FES) (partial FAS)
Newer terminology- Fetal Alcohol Spectrum Disorders: FAS, Partial FAS, Alcohol
Related Birth Defects, Alcohol Related Neurodevelopmental Disorder
PRENATAL EXPOSURE TO ALCOHOL
Alcohol rapidly crosses the placenta and the blood-brain barrier of the fetus. There is a dosedependent relationship between intake and occurrence of features of FAS
At birth, infants may experience withdrawal symptoms: irritability, tremors, apnea, seizures
PRENATAL EXPOSURE TO ALCOHOL
FAS is characterized by:
 Growth deficiency
 Cardiac defects
 Dysmorphic features : facial, genital, and joint abnormalities-Central Nervous System
disturbances
 Microcephaly (small head circumference)
 Intellectual disability (one of leading known causes of mental retardation in the
United States)
PRENATAL EXPOSURE TO ALCOHOL
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Fetal Alcohol Spectrum Disorders - July 15, 2005 - American Family Physician
PRENATAL EXPOSURE TO DRUGS
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Neonatal Abstinence Syndrome (NAS)- use of narcotics during pregnancy leads to
the development of dependency on the drug by the fetus.
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Most commonly used drugs are heroine, methadone, cocaine, and pain
medication.
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Women who use drugs often receive less prenatal care, tend to smoke, consume
alcohol and have poor nutrition.
PRENATAL EXPOSURE TO DRUGS
Symptoms of withdrawal in the infant:
 Hyperactivity, irritability, tremors, seizures, apnea, increased muscle tone, and inability
to sleep
 Hyperactive, disorganized, and ineffective sucking that is poorly coordinated with
swallowing
 Increased and irregular breathing rate, runny and stuffy nose, nasal flaring, chest
retractions, intermittent cyanosis and apnea
 Frequent sneezing, yawning, and shrill crying
PRENATAL EXPOSURE TO DRUGS
Disorganized behavior of infants makes early bonding and attachment difficult.
Long term problems associated with prenatal drug exposure include:
 Growth retardation
 Intellectual disability and learning difficulties (↓ attention and visual processing)
 Difficulty with adaptive and social functioning
PRENATAL EXPOSURE TO DRUGS- CONFOUNDING
FACTORS
The effect of a specific substance on a fetus or the development of an infant is difficult
to determine because of confounding factors:
 Mothers who abuse one substance are likely to abuse others.
 Often have poor nutrition and inadequate prenatal care.
 Children are often born into an environment not conducive to normal development.
PRENATAL EXPOSURE TO DRUGS
Compared functioning at age 5 years in a prenatal drug exposed group of children
with that of a non-drug exposed group of children from the same environment.
Children in the drug exposed group scored significantly lower on measures of
expressive and total language, school readiness, impulse control, and visual
attention/sequencing.
Both groups scored below expectations on measures of intelligence, language, school
readiness, visual motor, impulse control and sustained attention when compared
to normative data.
Pulsifer, M.B., Butz, A.M., Foran, M.O., & Belcher, H.M.E. ( 2008). Prenatal drug exposure: Effects on cognitive functioning at 5
years of age. Clinical Pediatrics, 47, 58-65. doi: 10.1177/0009922807305872
MATERNAL INFECTIONS
STORCH Screen- Syphilis, Toxoplasmosis, Other (HIV, Hepatitis B ), Rubella, Cytomegalovirus,
Herpes
These viral infections constitute a relatively small portion of perinatal infections but can result
in significant developmental problems.
Primary infection during pregnancy with certain virus’ may also infect the fetus.
CARDIOVASCULAR COMPLICATIONS
PDA- Patent Ductus Arteriosus- most common cardiovascular defect in LBW infants and
premature infants with RDS.
Medications may be given to help the PDA close. Surgery may be necessary.
CONGENITAL HEART DEFECT
Atrial Septal Defect- ASD: Lack of closure between the two upper chambers of the heart.
Surgical closure within first 5 years.
Ventricular Septal Defect- VSD: Lack of closure between the two lower chambers of the heart.
Most common CHD.
Both of these CHD’s are common in children with Down syndrome.
ADDITIONAL REFERENCES
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Accardo, P. J. (2008). Capute & Accardo’s neurodevelopmental disabilities in
infancy and childhood volume II: The spectrum of neurodevelopmental
disabilities (3rd ed). Baltimore: Paul H. Brooks Publishing.
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Batshaw, M. L. (2002). Children with disabilities (5th ed). Baltimore: Paul H.
Brooks Publishing.
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Campbell, S. K., Vander Linden, D. W. & Palisano, R. J. (2006). Physical therapy for
children (3rd ed). St. Louis: Saunders Elsevier.
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Campbell, S. K., Palisano, R. J., & Orlin, M. N. (2012). Physical therapy for children
(4th ed). St. Louis: Saunders Elsevier.