The Fetal Spine and Musculoskeletal System

Axial skeleton begins to form between & weeks. It consists the bones of the ____ & _____

6 & 8 weeks, cranium & spine

As bones ossify it allows sonographers to readily visualize these structures as echogenic reflections that produce

acoustic shadowing

The spine consists of five sections:

cervical, thoracic, lumbar, sacrum, and coccyx.

Each fetal vertebra consists of three echogenic ossification centers:

one centrum and two neural processes

The echogenic laminae are normally angled inward, whereas with spina bifida, the defective laminae will be angled

outward, or splayed

Among the list of neural tube defects are

cephaloceles, anencephaly, and spina bifida. Anencephaly and spina bifida are the most common neural defects,

because of the skin covering, which conidition is not associated with elevated MSAFP?

closed spina bifida

folic acid significantly reduces the likelihood of her fetus developing spina bifida and other neural tube defects, how many mg a day?

0.4 mg. For high-risk, as high as 4 mg may be prescribed

what is spina bifida

AKA spinal dysraphism, meningocele, and meningomyelocele (myelomeningocele). spina bifida is a neural tube defect that occurs when the embryonic neural tube fails to close.

Spina bifida occulta characteristics:

Closed defect

Skin surface abnormality noted on postnatal physical examination can be a sacral dimple, tuft of hair, hemangioma, or lipoma

Spina bifida aperta (most common version of spina bifida) characteristics

Typically, an open defect

May also be referred to as spina bifida cystica

Mass is referred to as a meningocele or meningomyelocele (myelomeningocele) depending upon contents

cross sectional of normal vertebra and spinal cord

cross sectional of spina bifida occulta

cross sectional of spina bifida aperta

Keep in mind that spina bifida is associated with two yellow fruits

banana sign and lemon sign

With open spina bifida, the exposure of the delicate spinal nerves to the amniotic fluid during fetal life is thought to be one of the causes of

neurologic impairment

Open fetal surgery can be performed on the fetus with spina bifida when a mass is identified on the spine, even as early as

16 weeks

meningocele

myelomeningocele

Clinical Findings of Open Spina Bifida Aperta (Open)

Elevated MSAFP

Sonographic Findings of Spina Bifida Aperta (Open)

Splaying of the laminae in the area of the defect

Cystic mass (meningocele) or complex mass (myelomeningocele) protruding from the spine

Lemon sign—lemon-shaped cranium with flattened frontal bones

Banana sign—banana-shaped cerebellum

Obliterated cisterna magna

Colpocephaly

Hydrocephalus

Clinical Findings of Spina Bifida Occulta

In utero—normal laboratory values

Postnatal—sacral dimple, hemangioma, lipoma, or excessive hair is identified directly over the distal spine

Sonographic Appearance of Scoliosis

Lateral curvature of the spine

S-shaped spine

Sonographic Appearance of Kyphosis

Abnormal posterior curvature of the spine

Although these abnormalities may be the only anomaly noted during a fetal sonogram, distortion of the spine can be seen with

hemivertebrae, myelomeningoceles, amniotic band syndrome, and limb–body wall complex (LBWC)

Scoliosis and kyphosis are also often associated with additional anomalies in other systems, as seen in

VACTERL association/ VATER association

LIMB–BODY WALL COMPLEX (LBWC)

AKA body stalk anomaly or short umbilical cord syndrome, is a rare group of fetal defects

There are three postulated causes for this fatal condition LBWC :

vascular occlusion, amnion rupture, or embryonic dysgenesis

Clinical Findings of Limb–Body Wall Complex

Elevated MSAFP

Sonographic Findings of Limb–Body Wall Complex

Short or absent umbilical cord

Marked scoliosis

Various other anomalies including craniofacial and limb defects

Dysplasia denotes the

abnormal development of a structure.

Skeletal dysplasias exist as a large group of

abnormalities of the skeletal system

The four most common skeletal dysplasias are as

achondroplasia, achondrogenesis, osteogenesis imperfecta, and thanatophoric dysplasia

What is the most common nonlethal skeletal dysplasia

Heterozygous achondroplasia

Heterozygous achondroplasia is

a type of dwarfism in which the proximal portions of the limbs, the humeri and femurs, are much shorter than the distal portion of the limbs, a condition known as rhizomelia.

Heterozygous achondroplasia is an autosomal dominant disorder, although, many times, it is the result of a

spontaneous genetic mutation

Rhizomelia is typically detected when a notable difference in the gestational age measurements between the

biparietal diameter and the femur length is discovered, typically in the mid to late second trimester.

Homozygous achondroplasia, which can occur when both parents are dwarfs, is usually

fatal within the first 2 years of life.

Sonographic Findings of Achondroplasia

Macrocrania

Frontal bossing

Flattened nasal bridge

Micromelia (resulting from rhizomelia)

Trident hand

what is Achondrogenesis

“not producing cartilage”; it is a rare, lethal condition, resulting in absent mineralization of the skeletal bones

Sonographic Findings of Achondrogenesis

Severely shortened limbs (micromelia)

Absent mineralization of the skull, spine, pelvis, and limbs

Large skull

Narrow chest and distended abdomen

Polyhydramnios

Osteogenesis Imperfecta

3D findings of achondrogenesis

what is Osteogenesis imperfecta,

brittle bone disease, is a group of disorders that results in multiple fractures that can occur in utero

There is 4 types of osteogenesis imperfecta, type 1, 3, and 4 are typically diagnosed after birth. Type 2 is the most severe type and results in

multiple fractures in utero, skull demineralization (recognized by a lack of posterior shadowing), bell-shaped chest, and decreased fetal movement.

One distinctive finding of osteogenesis imperfecta type 2 is

when transducer pressure is applied to the skull, the shape of the “soft” skull can be distorted

sonographic findings of osteogenesis imperfecta

Demineralization of the skull (transducer pressure can alter the shape of the skull)

Multiple fractures

Bell-shaped chest

what is Thanatophoric Dysplasia

“death-bearing”; most common lethal skeletal dysplasia. Fetuses typically die shortly after birth, succumbing most often to respiratory distress as a result of pulmonary hypoplasia.

Sonographic Findings of Thanatophoric Dysplasia

Cloverleaf skull

Hydrocephalus

Depressed nasal bridge

Bell-shaped chest (narrow thorax)

Polyhydramnios

Redundant soft tissue

Telephone receiver–shaped long bones

what is Caudal regression syndrome

aka sacral agenesis; Uncontrolled maternal pregestational diabetes has a strong association with caudal regression syndrome.

Clinical Findings of Caudal Regression Syndrome

Uncontrolled maternal pregestational diabetes

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

what is Sirenomelia

aka mermaid syndrome because of the fusion of the lower extremities

Clinical Findings of Sirenomelia

Uncontrolled pregestational maternal diabetes

Sonographic Findings of Sirenomelia

Fusion of the lower extremities

Bilateral renal agenesis therefore leading to

Oligohydramnios (possibly anhydramnios)

what is SACROCOCCYGEAL TERATOMA

a germ cell tumor which contains the three different germ cell layers: endoderm, mesoderm, and ectoderm. SCT has been cited as the most common congenital neoplasm and is more frequently found in females

Large SCTs have

malignant potential

Sonographic Findings of Sacrococcygeal Teratoma

Complex mass extending from the distal fetal spine

Mass can be highly vascular

Hydronephrosis may be present (when mass invades the pelvis)

Fetal hydrops may be present

Cardiomegaly

types of sct

Similar to the axial skeleton, the appendicular skeleton begins to form between the

sixth and eighth menstrual weeks

The appendicular skeleton includes the bones of the

upper extremities, lower extremities, and pelvic girdle.

The sonographic determination of the shortening of a limb is made when the

long bones measure more than four standard deviations below the norm for gestational age

Various limb abnormalities and their description

sandal gap

syndactyly

what is Radial ray defect

uncommon and described as the absence (aplasia) or underdevelopment (hypoplasia) of the radius. This abnormality can be seen in the presence of trisomy 13, trisomy 18, and several other syndromes.

Sonographic Findings of Radial Ray Defect

Absent or hypoplastic radius

Various defects in other body systems: cardiac and VACTERL association

what is Clubfoot,

aka talipes or talipes equinovarus;malformation of the bones of the foot. The foot is most often inverted and rotated medially

. If an abnormal foot shape is suspected, a foot length measurement can be obtained by measuring from the skin edge of the heel (calcaneus) to the distal end of the longest toe. Foot length has been used for gestational dating as well, and it has been shown to be nearly equivalent to the

resulting in a femur-to-foot ratio of approximately 1.0 after 14 weeks’ gestation

Sonographic Findings of Clubfoot

Metatarsals and toes lie in the same plane as the tibia and fibula

Limb reduction can be caused by

amniotic band syndrome, also referred to as amniotic band sequence. Sticky bands result from the rupture of the amnion.

amniotic bands should not be confused with

uterine synechiae; which may be recognized as linear, thin membranes with a broad base crossing the amniotic sac

Sonographic Findings of Amniotic Band Syndrome

Amputation of fetal parts or severe edema in the affected area

Thin, linear bands may be seen

Facial clefting