U/S OB chapter 6&8

Neurulation

Neurulation

the process by which the neural tube is formed (begins 21-23 days after conception)

after closure the rostral neuropore evolves into 3 primary vesicles

prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

visualization of the rhombencephalon as early as

8 menstrual weeks

ossification centers; appears as 3 echogenic foci

1 centrally located in the vertebral body

2 laterally located between the laminae and pedicles in the posterior vertebral element

hydrocephalus

congenital enlargement of the ventricular system (DWM agenesis of the corpus colusum; meningomyelocele)

hydrocephalus is aka

ventriculomegaly

hydrocephalus Sono signs

increased lateral ventricle atrial diameter (>10mm) and the presence of a “dangling choroid”

dolichocephally

a head larger than average relative to it’s width

brachycephaly

a skull shorter than average

hydranencephaly

the near or total absence of the cerebral hemispheres in the presence of a normally developed meninges and skull

holoprosencephaly

is a malformation sequence in which the forebrain fails to develop normally (presents of a single primitive ventricle)

3 types

alobar

semilobar

lobar

dandy-walker malformation

is a cystic abnormality of the posterior fossa characterized by the absence or severe dysgenesis of the cerebellar vermis with opportunistic filling of the space with CSP

vein of Galen aneurysm/malformation

is a arteriovenous malformation originating in the median prosencephalic vein in the mid portion of the fetal brain

Agenesis of the corpus callosum(ACC)

a teratogenic insult early (8-12 weeks) can result in complete ACC or in partial dysgenesis of its normal architecture (colpocephaly, absence of the CSP)

microcephaly

is a condition characterized by an abnormally small and underdeveloped brain and skull

cebocephaly

common ventricle hypotelerism and a nose with a single nostril

anencephaly

most common open neural tube defect and results from the incomplete closure of the cranial portion of the neural tube

exencephaly (acranial)

a rare congenital anomaly characterized by partial or complete absence of the calvaria with complete but abnormal development of the brain tissue

cephalocele/encephalocele

incomplete closure of the rostral end of the neural tube may also result in focal defects of the bony calvaria through which intracranial contents

cephalocele

protruding lesion consists of only meninges (mekelgruber syndrome)

encephalocele

if brain tissue accompanies the herniated meninges

spina bifida

is a neural tube defect resulting from the failure of the vertebral column to close during neurulation (yellow fruits)

lemon sign

overlapping of the frontal bones, creating a lemon-shaped fetal head

banana sign

effacement of the cisterna magna due to downward displacement of the cerelebellum

myelocele

meninges are present

myelomeningocele

meninges and neural tissue are present

rashischisis

rare, severe form where the entire spinal canal is splayed open posteriorly from the neck to the sacrum

rhizomelia

shortening of the proximal segment of an extremity

mesomelia

shortening of the distal segment of an extremity

micromelia

shortening of both proximal and distal segments of extremity

amelia

absence of an extremity

meromelia

partial absence of a limb

polydactyly

presence of more than 5 digits on a single hand or foot

syndactyly

soft tissue or bony fusion of digits

osteochondrodysplasia aka

skeletal dysplasias or short limb dysplasias

fetuses with notable short limbs before 20 menstrual weeks are usually lethal at birth

osteochondrodysplasias

achondrogenesis

rare, lethal form of short-limb dysplasia in which there is virtually no ossification of the vertebral bodies

achondrogenesis type I

parenti-fraccaro achondrogenesis

achondrogenesis type II

langer-saldino achondrogenesis

achonfroplasia

is a genetic disorder that affects normal growth and development of the skeletal system (most common cause of short-limb dwarfism; may not be evident until after 22 weeks)

thanatophoric dysplasia

extreme rhizomelia, bowed long bones, a hypoplastic thorax with normal trunk length, a large head

short rib-polysactyly syndrome (SRPS)

short limbs, excessive number of digits, and an extremely narrowed thorax

campomelic dysplasia

rare, bowing of the distal tibia and/or short fibula

chondroectodermal dysplasia

disproportionate and irregular shortened extremities, polydactyly, and narrowed thorax (ellis-van creveid syndrome-amish)

diastrophicdiastrophy dysplasia

associated with micromelia and hitch hiker thumb

osteogenesis imperfecta (OI)

hypomineralization of bone, resulting in abnormal fragility of skeletal structures (type 2 is more severe)

hypophosphatasia

deficiency of serum alkaline phosphatase that causes fetal long bone shortening with deep cupping of the metaphyses, short ribs with fragmentation, and skull may be markedly underossified

talipes equinovarus

inversion of the foot and flexion of the sole, the foot is deviated from the normal position

rocker bottom foot

dorsal and lateral dislocation of the talonavicular joint and a prominent calcaneus mimicking the appearance of the rocker of a rocking chair

craniosynostosis

premature closure of cranial sutures