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