Fetal Spine Flashcards
What is spina bifida?
a neural tube defect that occurs when the embryonic neural tube fails to close (failure of vertebral column to close during neurulation)
Where does normal fusion of the neural tube begin?
in the dorsal aspect of the mid portion of the embryo and proceeds in both cranial and caudal directions
*what are the most common neural defects?
anencephaly and spina bifida
What is the initial stage of central nervous system development?
neural tube
What can 80% of spina bifida be detected with?
alpha-fetoprotein screening in combo w/ sonography
How is AFP screening used to detect spina bifida?
-it exits the fetus through an opening in the neural tube if one is present, such as with open spina bifida, thus allowing for a greater amount to pass into the maternal circulation
*Is closed spina bifida associated with elevated MSAFP?
NO
What is spina bifida also referred to as?
meningocele and meningomyelocele (myelomeningocele)
What type of disabilities may spina bifida cause?
physical and intellectual disabilities that range from mild to severe
What does the severity of spina bifida depend on?
- the size and location of the opening in the spine
- whether or not spinal cord nerves are affected
*what is the most common location for spina bifida?
the lumbosacral region of the spine
Where can spina bifida be found on the body?
anywhere along the spine
What are the 2 subtypes of spina bifida?
- spina bifida occulta (mild form)-hidden
- spina bifida aperta-open
What is spina bifida occulta?
- mild form
- a defect in the posterior bony nerual arch of the spinal canal, with preservation of overlying tissue and skin (closed defect)
- although the vertebrae fail to close, there is no herniation of the spinal contents outside of the spinal column, and normal fetal head and brain
- no change in MSAFP levels
- skin dimple or tuft of hair commonly noted at defect after birth
- difficult to identify sonographically
*What is the most common form of spina bifida and the type more frequently recognized in utero?
spina bifida aperta
What is spina bifida aperta?
- visible defect along the spine w/ attendant skin, subcutaneous, bony, and neural tissue abnormalities (open lesion)
- the opening in the defective neural tube permits herniation of meninges, forming a cystic sac projecting posteriorly from the spinal canal
- associated cord and meninges abnormalities
Differentiate meningocele and myelomeningocele.
meningocele: meninges herniation only
myelomeningocele: meninges and neural tissue (nerve roots) herniation through defect
what are meningocele and myelomeningocele masses referred to as?
spina bifida cystica
Are open lesions covered by skin?
No, they result in a mass that can be seen with sonography
What significance is the location of the spina bifida?
-the higher the location of spina bifida, the greater the neurologic impairment
What is spina bifida rachischisis?
- the entire spinal canal is splayed open posteriorly from the neck to the sacrum
- associated with anencephaly
What are the sonographic findings of spina bifida aperta (cystica)?
1) splaying of the laminae in the area of the defect
2) cystic mass (meningocele) or complex mass (myelomeningocele) protruding from the spine
3) Lemon sign: lemon shaped cranium w/ flattened frontal bones
4) Banana sign: banana shaped cerebellum (cerebellum will be displaced inferiorly or posteriorly)
5) obliterated cisterna magna
6) colpocephaly, the frontal horns will be small and slit-like, while the occipital horns will be enlarged
7) hydrocephaly
What group of abnormalities associated with cranial findings is spina bifida often initially recognized as?
Arnold-Chiari II malformation
What causes the malformations of the cranium and intracranial contents in spina bifida?
the pressure of a large mass in the distal spine pulling on the spinal cord
What is the sensitivity of the cranial findings at detecting spina bifida? What happens after suggested findings?
- greater than 99%
- once cranial findings are suggestive, a thorough analysis of the spine should be performed
*What happens to the posterior ossification elements or laminae in the presence of spina bifida?
they will often appear splayed in the transverse plane
What is a differential diagnosis of the masses associated with spina bifida aperta?
- sacrococcygeal teratoma
- a fetus with this will most likely have a normal head and intracranial anatomy while the intracranial anatomy of a fetus with spina bifida is often altered
What is Caudal Regression Syndrome (sacral agenesis)?
-a broad term used for a rare complex disorder characterized by abnormal development of or agenesis of the lower (caudal) spine
What abnormalities may occur with caudal regression syndrome
-a wide range of abnormalities may potentially occur in infants with caudal regression syndrome including agenesis of the sacrum and coccyx and abnormalities in the lumbar spine
What are (some) associated complications of caudal regression syndrome?
- clubfoot
- urinary/bowel incontinence
- anomalies of GI Tract
- anomalies of kidneys
- anomalies of heart
- neurologic disorger
- myelomeningocele
- lower limb anomalies
What is the severity of the complications associated with caudal regression syndrome?
- severity varies greatly
- some individuals can walk unassisted, while others may need assistance devices such as crutches, braces, or wheelchairs.
- others will not survive long after birth due to the severe associated complications
What are the sonographic findings of caudal regression syndrome?
- absent sacrum (sacral agenesis) and possibly part of the lumbar vertebra
- possible abnormalities in the lower extremities like clubfeet
- *uncontrolled maternal diabetes has a strong association with caudal regression syndrome
What has a strong association with uncontrolled maternal diabetes?
- caudal regression syndrome
- and sirenomelia
What is sirenomelia?
- mermaid syndrome, because of the fusion of the lower extremities that occurs with this disorder
- very rare congenital developmental disorder characterized by anomalies of the lower spine and lower limbs
- affected infants are born with partial or complete fusion of the legs
What additional conditions may occur with sirenomelia?
imperforate anus, spina bifida, urinary system and cardiac malformations
*What often occurs with sirenomelia and what does that mean?
-bilateral renal agenesis often accompanies this condition, so it is almost always lethal
What other defects/conditions may be seen in fetuses with sirenomelia?
- oligohydramnios and many other defects, including cardiac anomalies, genital absence, and a two-vessel cord
- uncontrolled maternal diabetes seems to play role in the development of this disorder
What are the sonographic findings of sirenomelia?
- fusion of the lower extremities
- bilateral renal agenesis
- oligohydramnios (possibly anhydramnios)
What is sacrococcygeal teratoma (SCT)?
- a germ cell tumor
- contains elements of the 3 different germ cell layers: endoderm, mesoderm, and ectoderm
*What is the most common congenital neoplasm and whom is more frequently found in?
sacrococcygeal teratoma; more frequently found in females
How will a sacrococcygeal teratoma appear?
-tumor will appear as a complex or solid mass extending posteriorly and inferiorly form the distal fetal spine
What is the potential of SCT?
- has potential to grow inside of the pelvis and may cause destruction of the sacrum and pelvic bones
- large ones have malignant potential
What are the sonographic findings of SCT?
- complex mass extending off of the distal fetal spine
- mass can be highly vascular
- hydronephrosis may be present (when mass invades pelvis)
- fetal hydrops may be present
What is scoliosis?
- a lateral curvature of the spine
- can curve in one of three ways
What are the 3 types of curves in scoliosis?
- Levoscoliosis: spine curves to the left side as a single curve and is C-shaped
- Dextroscoliosis: spine curves to the right as a single curve shaped like a backward C
- Thoracic Dextroscoliosis and Lumbar Levoscoliosis: spine has two curves and is S shaped
What is the cause of scoliosis and how common is it?
- idiopathic in most cases (rarely causes pain and usually so minor it does not require treatment)
- occurs in about 2% of the population
What is Kyphosis?
the forward curvature of the spine by 30-60 degrees
What is kyphoscoliosis?
when scoliosis and kyphosis abnormalities exist together
What are the types of scoliosis categorized by age at which the curve is detected?
-congenital scoliosis: develops in utero
-infantile scoliosis: from birth to 3 y.o.
-juvenile scoliosis: from 4-9 y.o.
adolescent scoliosis: from 10-18 y.o.
degenerative scoliosis: occurs later in life as the spine degenerates
What comprises about 80% of all cases of idiopathic scoliosis?
adolescent scoliosis
What are the two classifications of kyphosis?
- failure of formation: portion of one or more vertebral bodies fails to form. Typically occurs in the thoracolumbar spine and results in a kyphosis that usually worsens with growth. Usually visible at birth as a lump or bump on the infant’s spine.
- failure of segmentation: occurs as 2 or more vertebrae fails to separate. this type is more likely to be diagnosed later, after the child is walking, and has a slower rate of worsening.
What is Limb Body Wall Complex?
- LBWC, also referred to a body stalk anomaly, is a rare group of fetal defects
- a uniformly lethal anatomic abnormalities involving the anterior abdominal wall of the fetus
What are the causes of LBWC?
-vascular occlusion, amnion rupture, or embryonic dygenesis
What are the most common sonographic findings of LBWC?
- a short or absent umbilical cord, ventral wall defects, limb defects, craniofacial defects (exencephaly or encephalocele), and scoliosis
- fetus will appear closely connected with the placental and will have marked scoliosis
LBWC can be detected with what, when and why?
-b/c of the opening in the ventral wall, elevated levels of MSAFP can be detected in the 2nd trimester
What has a very similar sonographic finding as LBWC and can be seen simultaneously?
amniotic band syndrome
