Flashcards in Neurology of the Newborn Deck (167)
What are the 3 layers of cells in early embryologic development?
endoderm, mesoderm and ectoderm
What will the endoderm form?
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?
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