Ch 12 Spine Flashcards
Are congenital spine anomalies common?
Yes - will see them in practice
How does the spine look in TRV by the 16th week of gestation?
Looks like 3 echogenic ossification centers, surrounding the neural canal
(2 lie posterior to spinal canal within laminae + 1 is anterior within vertebral body)
How does the TRV spine look at the cervical, thoracic, lumbar + sacral level?
C: posterior ossification centers have a quadrangular shape
T/L: inverted triangle shape with base towards dorsum of fetus
S: posterior ossification centers have a wider placement than upper vertebrae
What is the classic spinal image?
Taken in SAG - often shows its entirety as a parallel structure ending in pointed sacrum
(parallel lines = represent 2 ossification centers: the vertebral body + posterior arch)
The SAG spine images the neural tube in 1st trimester + what during the other trimesters?
Spinal cord
In the 2nd/3rd trimesters, ____ images at the 2nd + 3rd lumbar spine levels?
The conus medullaris
List 3 things that determine if the spine is normal?
-Intact neural canal
-Intact dorsal skin contour
-Normal location + shape of spinal ossification centers
(imaging the conus medullaris in SAG can increase confidence that spine is normal)
How many planes do we image the spine in at minimum?
-SAG
-TRV (axial)
(imaging in coronal is good to do as well tho)
What is the spine protocol we follow?
SAG + TRV: C, T, L + S spine
Coronal: S spine
Is there always a bit of AFP in amniotic fluid?
Yes - if there are elevated levels that is abnormal
The spine can be screened by what 2 things?
-U/s
-Biochemical testing
MSAFP levels occur through diffusion across what?
The placenta + amnion
What types of defects result in higher AFP levels entering the amniotic fluid?
Structural defects - like anencephaly or spina bifida
What prevents AFP from escaping fetal circulation + results in a normal amniotic AFP level?
Skin covered or closed neural tube defects (NTDs)
What forms the neural tube during the 3rd week of embryonic life?
Infolding of the slipper-shaped ectoderm of the neural plate
What fuses to form the neural tube?
The neural groove - it begins midembryo + is completed at cranial + caudal neuropore
(is a 2 day process)
What factors can cause closure failure of the neural tube at either end of it, demonstrating the connection b/w spina bifida + caudal defects?
A disruption to the 2 day process by infections, drugs or genetic factors
What is spina bifida?
-NTD from incomplete closure of the bony elements of the spine (the lamina + spinous processes) posteriorly
List the 2 types of spina bifida defects?
Ventral: involves vertebral body splitting + development of a neurogenic origin cystic structure
Dorsal (m/c): has subdivisions of open (not covered by skin) + closed (covered by skin) forms
Where do ventral spina bifida lesions occur?
At lower cervical + upper thoracic spine (are uncommon)
What is spina bifida occulta?
-Split vertebrae closed + covered by skin
-M/c at sacrolumbar level
-Not noticeable on surface, except for small tuft of hair or dermal lesion over affected area
-Incidental finding
What is spina bifida aperta?
-Open + not covered by skin (exposing neural canal)
-Full thickness defect of skin, tissues + vertebral arches
-This lesion occurs in 85% of all spina bifida cases
Differentiate a meningocele vs a myelomeningocele?
Meningocele: lesion has thin meningeal membrane that does NOT contain neural tissue
Myelomeningocele: neural tissue inside the protruding sac
Is closed spina bifida aperta inconsequential?
Yes - b/c skin is covered it has minimal neural involvement
(15% of time this occurs)
85% of spina bifida aperta is open or closed?
Open: 2 subdivisions
-Meningocele (sac w/o spinal cord)
-Myelominingocele (sac with spinal cord)
What causes a NTD?
Genetics, nutritional factors, environmental factors, or a combo of things
Are males or females m/c to have spina bifida?
Females
NTDs have a high concordance rate in MZ or DZ twins?
MZ
How to sonographically assess for spina bifida?
-Best seen in SAG
-Use TRV to rule out smaller defects
-Look for banana + lemon sign in head (it distorts the shape of brain + cerebellum)
What is the only definitive way to make a diagnosis of spina bifida?
Viewing of a meningomyelocele
How does spina bifida look in TRV?
-Vertebral segments has a “U” or “V” shape
-Splays (widens) the posterior ossification centers
What causes displacement of cranial structures into the foramen magnum + superior cervical canal with spina bifida?
CSF leakage
If the cranium appears normal, does this exclude a myelomeningocele?
Yes
The differentiation b/w open + closed forms of spina bifida are best shown by what?
Sonographic demonstration of abnormal or normal cranial anatomy
What head anomaly occurs in the 2nd trimester when spina bifida aperta is present?
Hydrocephalus (70% of time)
Spina bifida shows what type of lower extremity deformities?
-Bilateral clubfeet
-Rocker bottom feet (curved bottom of feet)
-Hip deformities
What is kyphoscoliosis?
Combo of abnormal lateral + anterior curvature of spine
How is scoliosis + kyphosis best imaged?
Scoliosis: coronal
Kyphosis: SAG
What is scoliosis?
Lateral displacement of anterior ossification centers
Is scoliosis an isolated finding?
It can be isolated or seen with other findings
During the 1st trimester, what 2 sonographic features indicate caudal regression syndrome?
-Short CRL
-Abnormal YS
What is caudal regression syndrome?
-Rare congenital anomaly affecting the caudal spine, spinal cord, hindgut, urogenital system + lower limbs
-Ranges from agenesis of coccyx to absence of sacral, lumbar + lower thoracic vertebrae
This factor increases the risk of caudal regression syndrome 250x?
Maternal diabetes
SAG + TRV views of the spine with caudal regression syndrome uncover what?
-Absence of vertebrae
-Fused iliac wings
-Decreased femur head distance
-Short femurs
-Clubfeet
What is the m/c location for teratomas to develop?
Caudal end (sacrococcygeal)
What is the m/c neoplasm in the newborn?
Sacrococcygeal teratomas (m/c in females)
Where can teratomas develop?
Gonads, umbilical cord, placenta, anywhere in neural tube + caudal end
What is a sacrococcygeal teratoma?
Rare germ cell tumor that forms on fetus’s tailbone/coccyx (usually benign)
(male fetuses have increased chance of developing malignant form)
Most sacrococcygeal teratomas are what type?
Type 1 or 2
How do sacrococcygeal teratomas appear on u/s?
-Protrusion b/w anus + coccyx (some can develop in presacral space of pelvis)
-Solid or complex with cystic parts
-Choroid plexus secretes CSF within tumor, resulting in a cystic component
Fetus’s are at risk for developing what 2 things if they have a sacrococcygeal teratoma?
-Congestive heart failure
-Hydrops
Perinatal mortality + morbidity are related to what type of failure if they have a sacrococcygeal teratoma?
Related to high output cardiac failure - due to arteriovenous shunting within tumor, hydrops, polyhydramnios + preterm delivery
What is fetal hydrops?
Condition in which large amounts of fluid build up in a baby’s tissues and organs, causing extensive swelling (edema)
T/F: Skin covered NTD lesions prevent a rise in MSAFP levels.
True
The posterior elements of the spine seen on u/s are called what?
Laminae
What are the 3 dots we see of the spine in TRV?
-2 posterior laminae
-1 anterior body
What are the 2 types of spina bifida called?
Occulta (closed) + aperta (open)
