CENTRAL NERVOUS SYSTEM DEVELOPMENT ECSE 641 SPRING 2014.

Central N

ervous S

ystem

Development

ECSE 641

Spring 2

014

1. Centra

l Nervo

us Syst

em

Development

2. Risk

s of D

evelopment –

Prenatal,

Natal, Postn

atal

CNS- Central Nervous System

• 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.

3

Synaptic Growth

From: http://neurowiki2012.wikispaces.com/

4

Synaptic Pruning

5

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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Factors

Affecting Deve

lopment

Virgin

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wealth

Uni

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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 BirthPreterm 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

• 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


• 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-for-infant-respiratory-distress-syndrome/


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

• Bronchopulmonary Dysplasia- caused by incomplete or abnormal repair of lung disease during the neonatal period. Also referred to as Chronic Lung Disease (CLD).

• Boys are at a greater risk-maybe because their lung development is 1 to 2.5 weeks behind girls.

• 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

• Prevention-Prevention of premature birth, antenatal steroids

• Treatment-Surfactant replacement, assisted ventilation for as short a time as possible, iNO

Medical Complications of Prematurity-Definitions

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

• Periventricular Leukomalacia-ischemic lesion to the brain of a premature infant.

• The area of the brain affected is typically the motor tracks descending from the brain to the spinal cord.

• The motor tracks typically affected are those controlling the legs.

• Clinical outcome is often “spastic diplegic” cerebral palsy

Medical Complications of Prematurity-IVH

• Intraventricuar Hemorrhage – bleeding into the fluid filled spaces of the brain

• Characteristic of the premature infant less than 32 weeks gestational age and weight less than 1500 grams (VLBW)

• Occurs in preterm infants with RDS requiring ventilation

• 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

• Grades I through IV based on head ultrasound findings

• Hydrocephalus is a complication of IVH

• 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

• 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


Alcohol rapidly crosses the placenta and the blood-brain barrier of the fetus. There is a dose-dependent relationship between intake and occurrence of features of FAS

At birth, infants may experience withdrawal symptoms: irritability, tremors, apnea, seizures


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)


• Fetal Alcohol Spectrum Disorders - July 15, 2005 - American Family Physician

Prenatal Exposure to Drugs

• Neonatal Abstinence Syndrome (NAS)- use of narcotics during pregnancy leads to the development of dependency on the drug by the fetus.

• Most commonly used drugs are heroine, methadone, cocaine, and pain medication.

• Women who use drugs often receive less prenatal care, tend to smoke, consume alcohol and have poor nutrition.


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


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.


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• 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.

• Batshaw, M. L. (2002). Children with disabilities (5th ed). Baltimore: Paul H. Brooks Publishing.

• Campbell, S. K., Vander Linden, D. W. & Palisano, R. J. (2006). Physical therapy for children (3rd ed). St. Louis: Saunders Elsevier.

• Campbell, S. K., Palisano, R. J., & Orlin, M. N. (2012). Physical therapy for children (4th ed). St. Louis: Saunders Elsevier.

CENTRAL NERVOUS SYSTEM DEVELOPMENT ECSE 641 SPRING 2014.

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Transcript of CENTRAL NERVOUS SYSTEM DEVELOPMENT ECSE 641 SPRING 2014.