1 - Neural Tube Defects Flashcards
overview of neural tube defects and affects of folate on pregnancy
the neural tube forms from what layer of the developing embryo?
ectoderm
what is the neural tube filled with?
fluid
the neural tube is made of a layer of what?
highly proliferative neuronal stem/progenitor cells
the neural tube splits into what 4 things?
- prosencephalon
- mesencephalon
- rhobencephalon
- spinal cord
what are the 3 primary brain vesicles?
prosencephalon
mesencephalon
rhombencephalon
what secondary brain vesicles does the prosencephalon split into?
telencephalon
diencephalon
what secondary brain vesicles does the mesencephalon split into?
stays as the mesencephalon
what secondary brain vesicles does the rhombencephalon split into?
metencephalon
myelencephalon
what is the forebrain comprised of?
- telencephalon - cerebral cortex + basal nuclei
- diencephalon - retina of eye, thalamus, hypothalamus
what is the midbrain comprised of?
mesencephalon
what is the hindbrain comprised of?
- metencephalon - pons, cerebellum
- myelencephalon - medulla
what is the telencephalon?
cerebral cortex
basal nuclei
what is the diencehalon?
retina of eye
thalamus
hypothalamus
what is the mesencephalon?
midbrain
superior colliculus
inferior colliculus
what is the metencephalon?
pons
cerebellum
what is the myelencephalon?
medulla
what splits the brain and spinal cord?
foramen magnum
what does the spinal cord split into?
alar plate - dorsal horn (sensory)
basal plate - ventral horn (motor)
what tissue is left out when the neural tube forms?
neural crest
the neural crest migrates to form what?
- dorsal root ganglia
- enteric plexi
- chromaffin cells of medulla
- melanocytes of skin
what is the result of neural tube closure failing?
neural tube defects
what are the benefits of foetal surgery in spina bifida?
- decreased hydrocephalus and rate of shunting
- frequent reversal of Chiari II malformation
- protects myelomeningocele - protects spinal cord from toxic effects of amniotic fluid
what is the international recommendation of folic acid/day?
400μg/day 3 months before pregnancy and 3 months into pregnancy
why is folate needed 3 months before and into pregnancy?
- neural tube forms in first 4 weeks
- implantation occurs around 2-3 weeks
- folate supply is from the yolk sac until placental support starts
- so egg needs enough folate on release
how do some countries increase daily folate intake?
fortify foods such as cereal
spina bifida occulta is often undetected - what is a common sign in females?
a patch of hair on the back along the spinal cord
what are ‘sunset eyes’ with reference to spina bifida?
- 50% babies also have hydrocephalus
- increased pressure on optic nerves
- lens at the front of the eye is heavy - eyes droop down
closing spina bifida after birth can result in what?
hydrocephaly
how does closing spina bifida after birth result in hydrocephaly?
- CSF exit is blocked
- sometimes due to Chiari malformation
what % of babies with spina bifida also have hydrocephalus?
around 50%
how is hydrocephalus treated?
- shunt inserted into lateral ventricle
- lifelong procedure
folic acid supplements prevent how many NTDs?
up to 70%
folic acid + ? may reduce NTD incidence further?
inositol
what else does folic acid benefit, in addition to NTDs?
congenital heart defects, cardiovascular problems and cancer risk
does folic acid benefit both spina bifida risk and hydrocehaly risk?
no - it has little effect on hydrocephaly, likely bc it is the artificial form of folate
later development of the cerebral cortex does not respond to folic acid, but instead responds to what?
folinic acid
