Case 1 - Spina Bifida

Question 1

what is spina bifida

Answer 1

neural tube defect that results from a defect in the closure of the neural tube. anatomically, this results in the loss of the posterior wall of the spinal canal and the spinous process of the affected vertebrae. it ca occur anywhere along the spine

Question 2

where does SB occur most

Answer 2

the lumbar region of the spine

Question 3

why is folic acid important to take during pregnancy

Answer 3

it is vital for the closing of the posterior and anterior neurospores

Question 4

what is the dose of folic acid for a pregnant woman

Answer 4

0.4mg. women who have already had a baby with SB should tale 4mg 1-3 months before pregnancy

Question 5

what is SB occulta

Answer 5

it is the loss of the spinous process but with no obvious bulge.
there may be excess hair on the affected area of the skin.

Question 6

what percentage of the population does SB occulta affect

Answer 6

10%

Question 7

why is there hair on the skin of the affected site

Answer 7

excess CSF leaks out which has growth factors in it

Question 8

what are the 3 types of SB cystica

Answer 8

• meningocele
• myelomeningocele
• rachischsis

Question 9

what is the meningocele

Answer 9

a bulge of the meninges is visible, but the spinal cord remains in its normal anatomical location

Question 10

what is a myelomeningocele

Answer 10

a bulge of the meninges is visible, and the spinal cord lies outside of the normal location, inside the bulge.

Question 11

what is a myelomeningocele often associated with

Answer 11

an Arnold Chiari type 2 malformation

Question 12

what is rachischsis

Answer 12

very severe form of SB where the spine may be completely open and is often associated with anencephaly

Question 13

what is anencephaly

Answer 13

when the neural tube doesn’t close at the top therefore large part of the brain is missing

Question 14

what is syringomyelia

Answer 14

dilation of the fluid filled cavity that runs down the centre of the spinal cord

Question 15

epidemiology of myelomeningoceles

Answer 15

affects 1/2000 pregnancies

Question 16

how is SB diagnosed

Answer 16

by testing the maternal serum alpha fetoprotein (MSAFP). this is the foetal alternative to albumin.

Question 17

how is theMSAFP tested

Answer 17

at 16-18 weeks, a so maple of the mother’s blood is tested for MSAFP. this is made naturally by the foetus and the placenta. during pregnancy, a small amount of AFP normally crosses into the mothers blood stream.abnormally hight levels of AFP may indicate that the foetus has SB or another neural tube defect. it is not specific to SB.

Question 18

what are normal levels of MSAFP

Answer 18

10ng/ml - 150ng/ml

Question 19

what level with SB

Answer 19

2.5MoM

Question 20

when is the ultrasound for SB carried out

Answer 20

18-20 week scan

Question 21

how does valproate lead to SB

Answer 21

VPA exposure prevents morphological and biomechanical conversion of the caudal extreme of the PNP during late spinal closure. closure 5 facilitates neural fold apposition when completion of closure is imminent, such that its disruption in VPA-exposed embryos may lead to distal SB. closure defect in the anterior neural tube and embryonic folate metabolism is disrupted.

Teratogenic effect due to embryonic exposure to valproate action as inhibitor of histone deacetylases, disturbing the balance of protein acetylation and deacetylation, leading to neurulation failure

Question 22

what is the lemon sign

Answer 22

refers to the shape of the foetal skull at ultra-sonogrpagy when the frontal bones lose their normal convex contour and appear flattened or inwardly scalloped.

Question 23

how does a lemon sign occur

Answer 23

decrease in the intraspinal pressure with SB foetus causes the brain to shift downwards. this shift decreases the intracranial pressure which is reflected into the foetal cranium. the frontal bones are the most vulnerable to the deceased intracranial pressure and respond by flattening inward. as the foetus matures, the lemon sign disappears as the frontal bones are stronger and can withstand the pressure.

Question 24

epidemiology of lemon sign

Answer 24

sign of Arnold Chiari Malformation type II and 90-98% of SB children have it

Question 25

what is an Arnold Chiari Malformation

Answer 25

condition in which the brain tissue extends into the spinal canal. it occurs when part of the skull is misshapen or smaller than typical, pressing on the brain and forcing it downward.

Question 26

what is ACM type I

Answer 26

develops as the skull and brain are growing. as a result, signs and symptoms do not occur until late childhood or adulthood

Question 27

what is ACM type II

Answer 27

• the paediatric formation and presents art birth
• a greater amount of tissue extends into the spinal canal
• related to myelomeningocele as the backbone and spinal canal do not close properly
• the cerebellum, and brain stem tissue extend into the foramen magnum - the hole for the spinal cord

Question 28

what gene causes the genetic type of ACM type II

Answer 28

FUZ gene

Question 29

what is ACM type 3

Answer 29

the most severe type of condition
- a portion of the cerebellum, or the brainstem extends through the opening in the back of the skull
- higher mortality rate and causes neurological problems

Question 30

what test is performed to differentiate between a meningocele and myelomeningocele

Answer 30

transillumination test