1 - Neural Tube Defects

Question 1

the neural tube forms from what layer of the developing embryo?

Answer 1

ectoderm

Question 2

what is the neural tube filled with?

Answer 2

fluid

Question 3

the neural tube is made of a layer of what?

Answer 3

highly proliferative neuronal stem/progenitor cells

Question 4

the neural tube splits into what 4 things?

Answer 4

• prosencephalon
• mesencephalon
• rhobencephalon
• spinal cord

Question 5

what are the 3 primary brain vesicles?

Answer 5

prosencephalon
mesencephalon
rhombencephalon

Question 6

what secondary brain vesicles does the prosencephalon split into?

Answer 6

telencephalon
diencephalon

Question 7

what secondary brain vesicles does the mesencephalon split into?

Answer 7

stays as the mesencephalon

Question 8

what secondary brain vesicles does the rhombencephalon split into?

Answer 8

metencephalon
myelencephalon

Question 9

what is the forebrain comprised of?

Answer 9

• telencephalon - cerebral cortex + basal nuclei
• diencephalon - retina of eye, thalamus, hypothalamus

Question 10

what is the midbrain comprised of?

Answer 10

mesencephalon

Question 11

what is the hindbrain comprised of?

Answer 11

• metencephalon - pons, cerebellum
• myelencephalon - medulla

Question 12

what is the telencephalon?

Answer 12

cerebral cortex
basal nuclei

Question 13

what is the diencehalon?

Answer 13

retina of eye
thalamus
hypothalamus

Question 14

what is the mesencephalon?

Answer 14

midbrain
superior colliculus
inferior colliculus

Question 15

what is the metencephalon?

Answer 15

pons
cerebellum

Question 16

what is the myelencephalon?

Answer 16

medulla

Question 17

what splits the brain and spinal cord?

Answer 17

foramen magnum

Question 18

what does the spinal cord split into?

Answer 18

alar plate - dorsal horn (sensory)
basal plate - ventral horn (motor)

Question 19

what tissue is left out when the neural tube forms?

Answer 19

neural crest

Question 20

the neural crest migrates to form what?

Answer 20

• dorsal root ganglia
• enteric plexi
• chromaffin cells of medulla
• melanocytes of skin

Question 21

what is the result of neural tube closure failing?

Answer 21

neural tube defects

Question 22

what are the benefits of foetal surgery in spina bifida?

Answer 22

• decreased hydrocephalus and rate of shunting
• frequent reversal of Chiari II malformation
• protects myelomeningocele - protects spinal cord from toxic effects of amniotic fluid

Question 23

what is the international recommendation of folic acid/day?

Answer 23

400μg/day 3 months before pregnancy and 3 months into pregnancy

Question 24

why is folate needed 3 months before and into pregnancy?

Answer 24

• 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

Question 25

how do some countries increase daily folate intake?

Answer 25

fortify foods such as cereal

Question 26

spina bifida occulta is often undetected - what is a common sign in females?

Answer 26

a patch of hair on the back along the spinal cord

Question 27

what are ‘sunset eyes’ with reference to spina bifida?

Answer 27

• 50% babies also have hydrocephalus
• increased pressure on optic nerves
• lens at the front of the eye is heavy - eyes droop down

Question 28

closing spina bifida after birth can result in what?

Answer 28

hydrocephaly

Question 29

how does closing spina bifida after birth result in hydrocephaly?

Answer 29

• CSF exit is blocked
• sometimes due to Chiari malformation

Question 30

what % of babies with spina bifida also have hydrocephalus?

Answer 30

around 50%

Question 31

how is hydrocephalus treated?

Answer 31

• shunt inserted into lateral ventricle
• lifelong procedure

Question 32

folic acid supplements prevent how many NTDs?

Answer 32

up to 70%

Question 33

folic acid + ? may reduce NTD incidence further?

Answer 33

inositol

Question 34

what else does folic acid benefit, in addition to NTDs?

Answer 34

congenital heart defects, cardiovascular problems and cancer risk

Question 35

does folic acid benefit both spina bifida risk and hydrocehaly risk?

Answer 35

no - it has little effect on hydrocephaly, likely bc it is the artificial form of folate

Question 37

later development of the cerebral cortex does not respond to folic acid, but instead responds to what?

Answer 37

folinic acid