Fetal Spine + Musculoskeletal System CH 26
Osteogenesis imperfecta?
"brittle bone disease" Def = a group of disorders in which bones break easily, caused by decreased mineralization and poor ossification of the bones
What lab value helps detect spina bifida?
- maternal serum screening aka triple screen (hCG, estriol, MSAFP) - specifically MSAFP = when open spina bifida or anencephaly is present MSAFP exits the fetus through the opening in the neural tube and allows a greater amount to pass into maternal circulation
Thanatophoric dysplasia?
- most common lethal skeletal dysplasia - limbs are extremely short - folds of extra skin in arms + legs
Heterozygous achondroplasia?
- most common nonlethal skeletal dysplasia - dwarfism - rhizomelia = proximal portions of limbs are much shorter than distal portions (humerus + femur) - autosomal dominant disorder (only from one parent)
Sono findings: Thanatophoric dysplasia?
1. "cloverleaf skull" = frontal bossing + lateral protrusion 2. hydrocephalus = high volumes of CSF in ventricular system 3. depressed nasal bridge 4. "bell-shaped" chest = narrow thorax, distended abd 5. polyhydramnios 6. redundant soft tissue = extra skin in arms + legs 7. "telephone receiver-shaped" long bones = bowing (curving)
What are the four most common skeletal dysplasias?
1. Achondroplasia (most non-lethal) 2. Achondrogenesis 3. Osteogenesis imperfecta 4. Thanatophoric dysplasia (most lethal)
What are the two types of achondroplasia?
1. Heterozygous achondorplasia 2. Homozygous achondroplasia
Clinical findings: Spina bifida occulta?
1. In utero = normal lab values 2. Postnatal = sacral dimple, hemangioma, lipoma, or excessive hair is identified directly over the distal spine (lumbosacral region)
Sono findings: Spina bifida aperta?
1. Splaying of the laminae in the area of the defect = laminae are pointing outwards (inward is normal) 2. Mass: cystic = meningocele or; complex = myelomeningocele 3. "Lemon sign" = lemon shaped cranium with flattened frontal bones 4."Banana sign" = banana shaped cerebellum (curved) 5. Obliterated cisterna magna 6. Colpocephaly = small frontal horns, large occipital horns 7. Hydrocephalus = accumulation of CSF in ventricular system
Sono appearance: Kyphosis?
1. abnormal posterior curvature of the spine
Sono findings: Radial ray defect?
1. absent or hypoplastic radius 2. various defects in other body systems: cardiac and VACTERL association
Sono findings: Caudal regression syndrome?
1. absent sacrum and coccyx 2. possible absence of part of the lumbar vertebra 2. possible abnormalities in the lower extremities (e.g. clubfeet)
Sono findings: Amniotic band syndrome?
1. amputation of fetal parts or severe edema in the affected area 2. thin, linear bands may be seen 3. facial clefting
What are the five sections of the spine?
1. cervical (7) # of vertebrae 2. thoracic (12) 3. lumbar (5) 4. sacrum (5) 5. coccyx
Sono findings: Sacrococcygeal teratoma?
1. complex mass extending off the distal fetal spine 2. hypervascular 3. hydronephrosis may be present when mass invades pelvis = can obstruct 4. fetal hydrops may be present 5. cardiomegaly (high-output CHF)
Sono findings: Osteogenesis imperfecta?
1. demineralization of the skull = decreased posterior shadowing; transducer pressure can alter the shape of the skull 2. multiple fractures 3. bell-shaped chest = narrow thorax, distended abdomen
Clinical findings: Spina bifida aperta?
1. elevated MSAFP = due to opening in tube AFP slips out and into maternal circulation
Clinical findings: LBWC?
1. elevated MSAFP = through opening of ventral wall
Sono findings: Sirenomelia?
1. fusion of the lower extremities 2. bilateral renal agenesis 3. oligohydramnios (possibly anhydramnios) -due to no renals which normally produce amniotic fluid
Sono appearance: Scoliosis?
1. lateral curvature of spine 2. S shaped spine
Sono findings: Achondroplasia?
1. macrocrania 2. frontal bossing 3. flattened nasal bridge 4. micromelia = shortening of an entire limb 5. trident hand = separation btwn third + fourth digits
Sono findings: Clubfoot?
1. metatarsals and toes lie in the same plan as the tibia and fibula
Which 3 scanning planes is the spine visualized?
1. sagittal (SAG) 2. transverse (TRV) 3. coronal (COR)
Sono findings: Achondrogenesis?
1. severely shortened limbs (micromelia) 2. absent mineralization of the skull, spine, pelvis, and limbs 3. large skull 4. narrow chest and distended abdomen 5. polyhydramnios = excessive amniotic fluid
Sono findings: LBWC?
1. short or absent umbilical cord 2. marked scoliosis 3. various other anomalies including craniofacial and limb defects
Clinical findings: Caudal regression syndrome?
1. uncontrolled maternal pregestational diabetes
Clinical findings: Sirenomelia?
1. uncontrolled pregrestational maternal diabetes
Possible causes of limb-body wall complex?
1. vascular occlusion 2. amnion rupture 3. embryonic dysgenesis = abnormal organ development
Fetal vertebra consists of?
3 echogenic ossification centers: - one centrum = will eventually form the vertebral body - two neural processes = will become the lamina, pedicle, transverse process, spinous process, and articular process
When does the axial skeleton begin to form in utero?
6 - 8 weeks gestation
Associated cranial findings with spina bifida aperta?
Arnold chiari II malformation: - spina bifida aperta (spinal cord herniation) pulls downward and distorts brain structures causing: 1. "lemon" sign of cranium 2. "banana" sign of cerebellum 3. obliterated cisterna magna 4. colpocephaly = frontal horn small, occipital horns large
Achondroplasia?
Def = a short-limb disorder that prevents cartilage from turning into bone, especially in the long bones of the arms + legs - aka short-limb dwarfism - normal torso, short limbs
Sacrococcygeal teratoma (SCT)?
Def = a teratoma found in the sacral-coccygeal area of the fetus - germ cell tumor = endoderm, mesoderm, ectoderm - most common congenital neoplasm - more frequently found in females
Caudal regression syndrome?
Def = agenesis of the sacrum and coccyx - Causes: pregestational diabetes (mother who had diabetes prior to pregnancy) *aka sacral agenesis*
Scoliosis?
Def = an abnormal lateral curvature of the spine - S shaped appearance - normally at thoracic and upper lumbar spine
Kyphosis?
Def = an abnormal posterior curvature of the spine
Radial ray defect?
Def = an uncommon abnormality in which there is absense (aplasia) or underdevelopment (hypoplasia) of the radius - present in trisomy 13, trisomy 18, and possibly VACTERL association
appendicular skeleton?
Def = bones of the extremities and pelvic girdle - develops in 6 - 8 weeks gestation (same as axial skeleton)
Spina bifida occulta?
Def = closed spinal lesions that are completely covered by skin and can be difficult to identify sonographically; aka closed spina bifida - skin surface abnormality = sacral dimple, tuft of hair, hemangioma, or lipoma
Sirenomelia?
Def = disorder in which lower extremities fuse together like a mermaid tail; aka "mermaid" syndrome - usually lethal due to bilateral renal agenesis
skeletal dysplasia?
Def = large group of developmental abnormalities of the skeletal system
Spina bifida aperta?
Def = most common form of spina bifida; results in open lesions that are typically not covered by skin and a mass that protrudes from the spine; aka open spina bifida or spina bifida cystica - mass = myelocele (spinal cord) meningocele (meninges) or meningomyelocele (myelomeningocele) = both
uterine synechiae?
Def = uterine adhesions - Sono: linear, thin membranes with a broad base crossing the amniotic sac - can resemble amniotic band
Most common congenital neoplasm?
SCT = sacrococcygeal teratoma
Types of osteogenesis imperfecta?
Type I, III, and IV are typically diagnosed after birth Type II = fatal, most severe form
Limb-body wall complex (LBWC)?
a condition characterized by multiple, severe congenital abnormalities in a fetus, most commonly involving the ventral (anterior) wall and limb defects
Arnold-Chiari II malformation?
a group of cranial abnormalities associated with spina bifida aperta
rockerbottom foot?
abnormal curved shape sole of the foot
Dysplasia?
abnormal development of a structure
phocomelia?
absent long bones with the hands and feet arising from the shoulders and hips
Which other syndrome has similar sonographic findings to limb-body wall complex?
amniotic band syndrome (can exist simultaneously with LBWC)
VACTERL association?
an acronym for a combination of abnormalities that represent: Vertebral anomalies, Anorectal atresia, Cardiac anomalies, Tracheoesophageal fistula, Renal anomalies, and Limb anomalies
two most common neural tube defects?
anencephaly and spina bifida
When can measurements of the long bones be taken?
as early as 12 weeks gestation
axial skeleton?
bones of the cranium and spine
Kyphoscoliosis?
condition in which scoliosis and kyphosis exist together
meningomyelocele aka myelomeningocele?
contain meninges and nerve roots
clinodactyly?
deviation of a finger (e.g. absence of the middle fifth phalanx)
sandal gap?
exaggerated distance between the first and second toe
Long bones?
femur, tibia, fibula, humerus, radius, & ulna
folate?
folic acid dietary supplement of 0.4 mg a day in pregnancy significantly reduces the likelihood of fetus developing spina bifida
syndactyly?
fusion of digits (e.g. webbed toes)
polydactyly?
having more than the normal number of digits
most common nonlethal skeletal dysplasia?
heterozygous achondroplasia
trident hand?
increased space between third finger and fourth finger
splaying of laminae?
laminae are pointing outwards rather than inwards
macrocrania?
large skull, small face
arthrogryposis?
limitation of fetal limb motion as a result of joint contractures; most often affecting the hands and feet
What is the most common location for spina bifida?
lumbosacral region
Clubfoot?
malformation of the bones of the foot in which the foot is most often inverted and rotated medially, and the metatarsals and toes lie in the same plane as the tibia and fibula *aka talipes equinovarus*
spina bifida?
neural tube defect that occurs when the embryonic neural tube fails to close - aka: spinal dysraphism, meningocele, meningomyelocele
How is rhizomelia detected in utero?
notable difference in BPD & FL measurements (will show two completely different gestational ages)
Homozygous achondroplasia?
occurs when both parents are dwarfs, usually fatal within the first 2 years of life
Besides spina bifida aperta, what else might cause elevated MSAFP?
omphalocele, gastroschisis, multiple gestations, fetal death
meningocele?
only contains meninges (protective layers of brain & spinal cord)
myelocele?
only contains spinal cord
As a pregnancy progresses why do the skull and skeletal bones become more echogenic?
ossification of the bones = growth & accumulation of minerals
upper extremities bones?
phalanges (fingers) metacarpals carpals radius ulna humerus clavicle scapula
lower extremities bones?
phalanges (toes) metatarsals tarsals tibia fibula femur
frontal bossing?
prominent, protruding forehead
Achondrogenesis?
rare, lethal condition resulting in abnormal development of the bones and cartilage (deficient ossification) - absent mineralization of the skeletal bones
mesomelia?
shortening of middle segment of a limb (radius, ulna, tibia, fibula)
acromelia?
shortening of the distal segment of a limb (hands + feet)
rhizomelia?
shortening of the prox segment of a limb (humerus or femur)
Most common form of spina bifida?
spina bifida aperta (open)
Which spina bifida is associated with Arnold-chiari II malformation?
spina bifida aperta (open)
Amniotic band syndrome or sequence?
strands of the amnion wrap around fetal parts which could lead to amputation or clefts - more commonly digits, limbs, or skull
Most common lethal skeletal dysplasia?
thanatophoric dysplasia
True or False: the higher the spina bifida location the greater the neurologic impairment.
true
Which part of the fetal vertebra contains the spinal cord?
vertebral column
Sonographic determination of shortening of a limb?
when long bones measure more than four standard deviations below the norm for gestational age
Which structures in utero produce AFP?
yolk sac, fetal gi tract, and fetal liver