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Flashcards in Neurology of the Newborn Deck (167)
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What are the 3 layers of cells in early embryologic development?

endoderm, mesoderm and ectoderm


What will the endoderm form?

the epithelium


What will the mesoderm form?

muscle and connective tissue


What will the ectoderm form?

skin and the nervous system


How does the CNS initially appear?

the ectoderm thickens and flattens to form the neural plate; one of the first systems to develop


When does the neural plate appear in embryologic development?

at the beginning of the 3rd week of life


How does the neural groove form?

the lateral edges of the neural plate elevate to form the neural folds, and subsequently creating a neural groove


What does fusion of the neural folds create?

the neural tube


When does the formation of the neural fold occur in embryologic development?

beginning of the 4th week of life; fusion occurs at the level of the 4th cervical vertebrae


In what direction does neural tube fusion occur?

proceeds from cephalad and caudal directions


What are neuropores?

fusion delayed at the cranial and caudal ends leaves openings at either pole


What do the neuropores create?

open communication between neutral tube and the amniotic cavity


When is the cranial neuropore expected to close?

on day 25 after conception


When is the caudal neuropore expected to close?

on day 27 or 2-3days after


What is the physiologic cause of a neural tube defect?

failure of the neural tube to close between 25-28 days after conception


What diagnosis accounts for most the CNS congenital anomalies?



How prevalent are NTD in the US?

second most common congenital anomaly (after CHD)


What are the risk factors for NTDs?

1) folic acid deficiency
2) maternal diabetes (poor glycemic control in the first trimester is a high risk factor)
3) Maternal exposure to certain medications (anticonvulsants and folic acid antagonists)
4) previous infants with NTDs


If a family had a child with a NTD, what is their risk for subsequent pregnancies?

with 1 child with a NTD, the risk is 2-4%; if > 1 child with a NTD, the risk is > 10%


What medications are associated with an increased risk for NTDs?

phenytoin, phenobarb, carbamazepine and trimetoprima


What is the greatest measure of NTD prevention?

folic acid supplementation before conception (1-3mo) and during the first month of pregnancy can prevent up to 70% of NTD cases.


What is the recommended doseage of folic acid?

0.4mg for normal women; mother's at increased risk should take 4mg throughout their pregnancy


What are the different forms of NTDs?

1) Anencephaly
2) Encephalocele
3) Myelomeningocele


What is Anencephaly?

the most severe form of NTD, not compatable with life.
failure of the cephalic end of the neural tube to close and results in degredation of the forebrain


What is the extent of structural damage with an Anencephaly diagnosis?

absence of scalp, skull and brain tissue, may be able to visualize the brain stem, exposed hemorrhagic fibrotic tissue; may have brain stem sparing


How is Anencephaly diagnosed?

will have elevated maternal alpha fetoprotein; US 14-15 weeks GA


What is the rate of spontaneous abortion in infants with Anencephaly?

65%; most families elect to abort child


Why do infants with Anencephaly typically continue on into post term maturation?

pituitary and adrenal functions are important in triggering labor; these structures are typically underdeveloped and labor may subsequently occur spontaneously


What is the survival expectancy of infants with Anencephaly?

75% will be stillborn, other infants typically die within a few hours, days or a few weeks


What is the clinical presentation of infants with Anencephaly?

unconscious with varying degrees of brain stem function