Module 5.1: Fetal Spinal Pathology Flashcards
What does each vertebra develop?
Three ossification centres:
- One centrum
- Two neural processes
What is the centrum?
The central ossification centre of the vertebral body
What do the neural processes of the vertebra form?
- Pedicles
- Transverse processes
- Laminae
- Spinous processes (between the two neural processes)
Where do the neural processes form?
Posterolateral to the vertebral body
When is ossification complete?
18 weeks
At what time could a spina bifida likely be missed on US?
Before ossification at 18 weeks
How common are neural tube defects?
1/1000 births
What factors increase the risk of neural tube defects?
- Valproic acid (seizure medication)
- Maternal diabetes
- Folic acid deficiency
- History of spinal defects (Prev. Pregnancy or family history)
What is spina bifida?
Herniation of spinal canal contents
What may tissues may be herniated from spina bifida?
- Meninges
- CSF
- Neural tissue
What is Spina Bifida Occulta?
A closed defect where only the deeper layers are effected and only a dimple or patch of hair may be seen on the skin.
How common is Spina Bifida Occulta?
15-20% of spina bifida cases
What is Spina Bifida Aperta?
An open defect involving all the layers from dura to the skin.
How common is Spina Bifida Aperta?
80-85 % of SB cases
What are the two types of Spina Bifida Aperta?
- Meningocele
2. Myelomeningocele
What is meningocele?
SB where only the meninges and CSF herniate.
What is myelomeningocele?
SB where the meninges, CSF and neural tissue herniate.
What is MS AFP?
Maternal Serum Alpha Fetal-Protein
“Quad screen” maternal blood test that measures the level of AFP in the blood to screen for abnormalities
When is the quad-screen done?
16 weeks
What is AFP?
AFP is a normal protein that is produced by the fetal liver, it crosses over the placenta and can be detected in the maternal blood. The level increases with gestational age.
What conditions can cause AFP to be elevated? (7)
- NTD aperta
- Abdominal wall defects
- Urinary obstruction
- Cystic hygroma
- Fetal death
- Multifetal pregnancy
- Incorrect dates
Where are the NTD landmarks?
T-12 (Distal rib)
L-5 (superior margin of iliac wing)
S-4 (caudal ossification center in 2nd trimester)
Where is the most caudal ossification center?
S-4
Where is the most distal rib?
T-12
What sonographic features can indicate a spinal defect?
- Splayed laminae
- Protruding mass or cyst
- Arnold Chiari II
- Ventriculomegaly
- Obliterated cisterna magna
- Banana sign cerebellum
- Lemon sign (SB)
What is Spinal Dysraphism?
The incomplete fusion of the spine
How is the spine best assessed?
Trans
How does the location of a meningocele affect the prognosis?
The more superior in the spine the greater the disability
What is Iniencephaly?
A special case of dysraphism involving the back of the cranium and c-spine where segmentation errors of the upper spine shortens the neck and the head becomes dorsiflexed.
What does Inien refer to?
The nape of the neck
What is Iniencephaly also know as?
Star gazing position
What is scoliosis?
Lateral curvature of the spine
What is exaggerated curvature of the spine in the sagittal plane called?
Kyphosis
What are Scoliosis and Kyphosis associated with?
- Amniotic band syndrome
- Skeletal dysplasia
- VACTERAL
- Caudal regression syndrome
What is caudal regression syndrome?
A range of anomalies of the spine ranging from an absence of part of the sacrum to absence of the lumbar spine.
What increases the risk of caudal regression?
Maternal diabetes
What is mermaid syndrome called?
Sirenomelia
What are the characteristics of sirenomelia?
- Absence of sacrum
- Fusion of legs
- Rectal atresia
- Renal dysgenesis or agenesis
- Oligohydramnios
What is the prognosis of sirenomelia?
Death in infancy
What is the most severe form of caudal regression?
Sirenomelia
What does VACTERAL stand for?
Verebral (dysraphism) Anal (atresia) Cardiovascular Tracheo-Esophageal (fistula) Renal Limb (radial ray)
What is VACTERAL often associated with? (4)
- Caudal regression (sirenomelia)
- Spina Bifida
- Congenital scoliosis
- Hemi vertebrae
What is a sacrococcygeal teratoma?
An external tumour containing elements of many tissues usually located at the base of the coccyx
How common are teratomas?
1/35000 births (rare)
Where can teratomas arise from?
- Sacrum or coccyx
- Brain
- Gonads
What are the four types of Sacrococcygeal Teratomas and how common are they?
Type 1: External mass predominant (47%)
Type 2: External mass with internal components (34%)
Type 3: Predominant Internal Mass with smaller external portion (5%)
Type 4: Presacral mass, internal only (10%)
How do Sacrococcygeal Teratomas appear on US?
Mass in rump or buttocks area
Why is the echo texture of a Sacrococcygeal Teratomas important?
solid/mixed = malignant tendancy
Cystic = benign
How often are Sacrococcygeal Teratomas malignant or benign?
85% = malignant 15% = benign
What conditions may Sacrococcygeal Teratomas cause?
- Hydronephrosis due to compressed ureters
- Displacement of pelvis structures
- AV shunting = heart failure
When would a cesarean section be warranted in the case of a Sacrococcygeal Teratoma?
If the Sacrococcygeal Teratoma was greater than 4.5 cm.
What is the DDX of a Sacrococcygeal Teratoma?
- Rectal duplication
- Anterior myelomeningocele
- Sarcoma