M5.1: Fetal Spinal Pathology Flashcards
Describe the 3 ossification centres of the spine
What do the 2 neural processes form
The central part is formed by the centrum
The 2 lateral neural processes form:
Peduncles Transverse processes Laminae Spinous process Posterolateral part of the vertebral body
When does ossification of the laminae occur
18 wks
When in wks could you possibly miss a small spinal bifida
Before 18 wks
Risks of and NTD increases with which factors
Valproic acid (medication for seizures) Maternal diabetes (type 1) Folic acid deficiency History of spinal defects -previous preg -family history
What is spinal bifida
NTD in the structure of the spinal canal that can lead to the herniation of its contents including possibly meninges, CSF and neural tissue
Describe spina bifida occulta
- involves only the deeper layers
- May only see a skin dimple or a path of hair on the back
- closed defect, not easily seen
think of a ‘cult’
Describe spina bifida aperta
- involves all layers from dura to skin
- open defect
- accounts for majority of cases
Aperta means open
What are the 2 types of spina bifida aperta
- meningocele- includes meninges and CSF
- completely cystic - Myelomeningocele- includes meninges, CSF and neural tissue/nerves
- not completely cystic
which type of spinal bifida aperta is more severe
Myelomeningocele
fetuses w/ a meningocele display what US appearances when scanning the head
Arnold Chiari type 2- lemon sign, banana sign, no cistena magna
When is the quad screen done
16 wks
When would AFP be elevated w/ an NTD?
When the defect is not covered by skin
where is AFP produced by the fetus
does it cross the placenta
liver
yes…. its important to consider gestational age and values will vary
What are the other causes of elevated MSAFP
Abdo wall defects (Omphalocele or Gastroschisis) multiple preg Fetal death Urinary obstruction Cystic hygroma Incorrect dates
NTD are associated w/ what syndromes
Meckel gruber syndrome
T18
Triploidy
What is spinal dysraphism
Abnormal closure of the spine/failure of fusion of vertebral arches
What is rachischisis
Another name for spinal dysraphism
What are the radiological landmarks for the spine
T-12; most distal rib
L5: superior margin of the iliac wing/crest
S4: most caudal ossification center in the 2nd trim
how are the legs effected by NTDs and why
Legs - Club foot and Hip dislocation (not seen on US)
Caused by an imbalance of muscular activity due to nerve involvement of the neural tube defect
How does a spinal NTD appear on US
- splayed laminae
- protruding mass or cyst
- also look for Arnold chiari and ventriculomegally
how do NTDs usually effect amniotic fluid levels
polyhydramnios
assessment of the spine is best done in which plane
TRX
What is the prognosis of spinal dysraphism
Depends on the location and extent of the neural tissue involved … more superior in the spine the greater the disability
What is iniencephaly
case of dysraphism involving the back of the cranium and c-spine…
… there are segmentation errors of the upper spine which shorten the neck and head into a dorsiflexed position (called the star gazing position)
