Fetal head and brain

cranial ossification should be complete by

12 weeks gestation

the falx cerebri is located within

interhemispheric fissue

corpus callosum

completely formed 18 weeks, provides a pathway for communication between the hemispheres

cavum septum pellucidum

closed cavity anterior to the thalamus, non communicative with ventricular system

thalamus

hypoechoic regions located on both sides of the 3rd venticle

cerebellum

width measured in trv plane at level of CM and thalamus

cerebellum is disorted when

spina bifida and arnold-chiari malformation

cisterna magna

<10 mm normal, <2mm = sus arnold-chiari II malformation

choroid plexus

produces CSF, within the lateral ventricles

lateral ventricles

axial view of cranium, visualized when ventricular walls are perpendicular to beam, measure atrium (inner to inner), <10mm normal

3rd ventricle

located midline btwn two lobes of the thalamus, communicates anteriorly with lateral ventricles at foramen of monro, communicates caudally with aqueduct of sylvius

4th ventricle

anterior to cerebellum, connnected to 3rd venticle by aqueduct of sylvius

lateral apertures

foramen of luschka

median apertures

foramen of magendie

CSF flow

lateral ventricle > foramen of monro > 3rd ventricle > aqueduct of aylvius > 4th ventricle > median/lateral aperture > subarachnoid space > arachnoid villi reabsorbs CSF into venous system

craniosynostosis

causes fetal cranium to become abnormally shaped, clover-leaf skull (kleeblattschadel)

brachycephaly

shortened AP diameter (OFD), elongated BPD, most commonly normal variant, associated with trisomy 21

dolichocephaly

elongated AP diameter (OFD), shorted BPD

head shape - lemon

spina bifida and arnold chiari II malformation

head shape - strawberry

trisomy 18

head shape - cloverleaf/klebetesatel

thanatophoric dysplasia

head shape - microcephaly

TORCH infections trisomy 13, trisomy 18, Meckel-gruber syndrome, fetal alchohol syndrome

agenesis of corpus callosum and CSP

absent CSP is common, CC fully developed at 18 weeks gestation

colpocephaly - sono

small frontal horns and enlarged occipital horns, teardrop appearance

sunburst sign - sono

perpendicular or radial arrangement of the sulci/gyri, often appears to have "spokes wheel" pattern

agenesis of corpus callosum and CSP - sono

colpocephaly, sunburst sign, absent pericallosal artery, dilated 3rd ventricle

colpocephaly

small frontal horns and enlarged posterior horn of the lateral ventricle

mega cisterna magna

>10 mm CM with intact cerebellar vermis, normal cerebellum seen with MCM but not with DWM

neural tube defects

close by 6 weeks gestation, increased MSAFP, folic acid (folate) has been proven to reduce the risk of developing NTD

open NTD

anencephaly, myelomeningocele, rachischisis

closed NTD

skin covered defects of spinal cord, spina bifida occulta, spinal cord tethering

NTD - acrania

absence of cranial vault

NTD - anencephaly

absence of the upper cranial vault and cerebral hemispheres

NTD - encephalocele

protruding cerebral tissue

NTD - hydrocephalus

fluid build up in the head

NTD - iniencephaly

short cervical spine

NTD - schizencephaly

clefting of cerebral tissue

NTD - spina bifida

failure of neural tube to close by 6 weeks gestation

NTD - chiari malformations

group of cranial abnormalites associated with spina bifida

acrania - exencephaly

"mickey mouse", absence of superior cranium

anencephaly

little to no brain tissue, absence of the upper cranial vault and cerebral tissue, "frog face", exophthalmos

exencephaly

normal amount of brain tissue although disorganized

anencephaly and spine bifida are the most common

neural tube defect

arnoid-chiari II malformation

group of cranial abnormalities associated with spina bifida, CM <2mm, hydrocephalus, type II strong association with open spina bifida defects

banana sign

curved cerebellum, leads to obliteration of cisterna magna

arnold-chiarii II malformation

CM is completely obliterated, lateral ventricles will also be distorted in shape (colpocephaly)

sonographic signs of arnold chiari II malformation

lemon sign, banana sign, obliterated cisterna magna, colpocephaly, enlarged massa intermedia

ventriculomegaly

dilation of lateral ventricles only, <10 mm normal, most common cranial abnormality

aqueductal stenosis

most common cause of hydrocephalus in utero, 4th ventricle is normal

hydrocephalus

queductal stenosis #1 reason, abn drainage or overproduction of CSF, ventriculomegaly first sign

hydranencephaly

destruction of cerebral tissue during fetal development, causes ICA/MCA occlusion, maternal infections, carbon monoxide exposure, brainstem normal, entire cerebrum is replaced by large sac containing CSF

hydranencephaly can be excluded if

a normal circle of willis is identified

hydrocephalus and holoprosencephaly will have a ____________ while hydranencephaly will be ___________________

rim of brain tissue mainatined, no brain tissue present

hydranencephaly - sono

fluid filled cranium extended to skull bones, absent/partial absence of falx cerebri, maintained brain stem and cerebellum, little to no identifiable cerebral cortex, no circle of willis

holoprosencephaly

midline brain anomaly with single ventricle and missing falx, seen with trisomy 13 (patau)

cyclopia

fusion of the orbits w/ or w/o proboscis

hypotelorism

closely set eyes

proboscis

false nose situated above the orbits

anophthalmia

absence of one or both eyes

cebocephaly

close set eyes and nose with single nostril

ethmocephaly

close set eyes and a proboscis

holoprosencephaly - sono

horseshoe shaped monoventricle, fused, echogenic thalami, absence of CSP/interhemispheric fissure/falx cerebri/corpus callosum/third ventricle

holoprosencephaly - lobar

ventricles are separated, anterior horns = fused, normal thalamus, incomplete anterior falx cerebri/absent CSP, cerebral hemispheres developed, no facial anomalies

holoprosencephaly - semilobar

cerebral hemispheres/ventricles (occipital horns) separated, incomplete thalamus fusion, absent CSP/corpus callosum, rudimentary falx cerebri/cerebral lobes, mild facial anomalies

holoprosencephaly - alobar

single C-shaped ventricle, no ventricular separation, fused thalamus lobes, absent flax cerebri/3rd ventricle/CSP/corpus callosum, irregular cerebral tissues, severe facial anomalies

dandy walker malformation

cystic dilation of 4th ventricle that protrudes into posterior fossa, splaying of cerebellar hemispheres, partial/complete absence of vermis, CM >10mm

schizencephaly

fluid filled clefts within the brain

schixencephaly - sono

fluid filled clefts within the cerebrum, agenesis of CSP and corpus callosum (50% of time), ventriculomegaly

porencephaly

rare condition in which a cyst communicates with the ventricular system

what types of cysts will not communicate with the ventricular system

arachnoid

lissencephaly

"smooth brain", agyria and the absence of sulci and gyri within the brain

choroid plexus cysts

normal anatomic variant if no other abnormalities detected, regress by 26 weeks, most commonly seen with trisomy 18 (edwards)

macrocephaly

HC >98%

microcephaly

seen with fetal alcohol syndrome, meckel gruber syndrome, intrauterine infections, trisomy 13/18

encephalocele

meninges and brain tissue herniation through a defect in the skull, most common location is posterior or occipital, leads to CSF obstruction of flow

encephalocele - associated with

part of meckel gruber syndrome, polycystic kidneys or ARPKD, polydactyly, microcephaly

encephalocele - sono

complex cystic mass connected to the cranium, abn appearance of intracranial structure

encephalocele - meningocele

meninges only

encephalocele - encephalocele

brain tissue only

encephalocele - encephalomengingocele

both meninges and brain tissue

encephalocele - encephalomeningocystocele

meninges, brain tissue, and lateral ventricle

meningocele

herniation of meninges ONLY, through opening in skull, increased MSAFP

teratoma

usually along midline of body, sacrum

the most common intracranial tumor found in utero is

teratoma

fetal intracranial hemorrhage (intraventricular)

common complication in premature infants, blood appears as hyperechoic fluid collection

hemmorrage can spread to ________, often leading to non-communicating ____________ as the clot ________________

lateral ventricle, hydrocephalus, obstructs flow of CSF

fetal intracranial hemorrhage - grade I

confined to germinal matrix, sub epenymal

fetal intracranial hemorrhage - grade II

extension into the lateral ventricles, intact brain parenchyma <15mm

fetal intracranial hemorrhage - grade III

further etension into the lateral ventricles, intact brain parenchyma >15mm

fetal intracranial hemorrhage - grade IV

periventricular lesions and brain parenchyma involvement

most common infection in utero

cytomegalovirus

intracranial ossification

usually related to intrauterine infections, cytomegalocirus, TORCH

vein of galen aneurysm

AV malformation in fetal brain

vein of galen aneurysm - sono

large, anechoic midline mass with turbulent venous and arterial flow within cranium, hydrops, cardiomegaly

most common findings with T21

brachycephaly, frontal bossing

most common findings with T18

micrognathia = poly bc dysphagia

hypotelorism is most commonly seen with

midface hypoplasia and median clef lip/palate