fetal head and brain Chapter 24
subdivision within the middle of the lip
(median) cleft lip
what are the 3 main types of holoprosencephaly?
-alobar -semilobar -lobar
2 main subtypes of acrania:
-anencephaly -exencephaly
Alobar holoprosencephaly is diagnosed when there is absence of the:
-corpus callosum -cavum septum pellucidum -third ventricle -interhemispheric fissure -falx cerebri
In the presence of spina bifida, there are several notable changes that occur within the brain and skull.
-lemon sign -banana sign
anencephaly and spina bifida occur ___ per ________ pregnancies
1 out of 1,000
(ventriculomegaly) atrial diameter measures greater than ___ mm
10
Present when only the cisterna magna is enlarged, measuring more than ______ in depth.
10mm
Pathway for communication between the hemispheres and is completely formed by
18 weeks
choroid plexus cysts regress by the?
3rd trimester
___of folic acid significantly reduces the chances of a neural tube defect
4mg
Their nonexistence has been linked to as many as 50 to 200 different syndromes and anomalies
AGENESIS OF THE CORPUS CALLOSUM AND CAVUM SEPTUM PELLUCIDUM
There can be partial or complete absence of the corpus callosum
AGENESIS OF THE CORPUS CALLOSUM AND CAVUM SEPTUM PELLUCIDUM
absence of one or both eyes
Anophthalmia
Usually caused by narrowing of the cerebral aqueduct (AKA Aqueduct of Sylvius), between 3rd & 4th ventricle.
Aqueductal stenosis
is the most common cause of hydrocephalus in utero.
Aqueductal stenosis
_______________ is a group of cranial abnormalities associated with the neural tube defect spina bifida.
Arnold-Chiari 2 or Chiari 2 malformation
Most often, if the corpus callosum is absent, the _______ will be absent as well.
CSP
small frontal horns and enlarged occipital horns (teardrop-shaped lateral ventricles.)
Colpocephaly
Sono findings: -Enlargement of the cisterna magna greater than 10mm in the AP dimension -Communication of the enlarged cisterna magna with a dilated fourth ventricle -Agenesis or hypoplasia of the cerebellar vermis -Varying degrees of ventriculomegaly.
DWM
_____ is thought to be caused by a developmental abnormality in the roof of the fourth ventricle.
DWM
acrania aka
Exencephaly -anenecephaly
A fatal condition where the entire cerebrum is replaced by a large sac containing CSF.
Hydranencephaly
The brainstem and basal ganglia are maintained and surrounded by CSF
Hydranencephaly
The falx cerebri may be partially or completely absent.
Hydranencephaly
There will be NO cerebral cortex identified
Hydranencephaly
severe cases of ventriculomegaly caused by an obstruction of CSF.
Hydrocephalus
SONO FINDINGS: -Enlargement of the cisterna magna greater than 10mm in the AP dimension -Normal cerebellum and fourth ventricle
Mega Cisterna Magna
A rare condition in which a cyst communicates with the ventricular system.
PORENCEPHALY
is associated with the development of fluid-filled clefts within the cerebrum.
Schizencephaly
radial arrangement of the sulci.
Sunburst sign
maternal serum is screening for?
TORCH
sono findings: calcifications around ventricles
TORCH
TORCH infections
Toxoplasmosis Other Rubella Cytomegalovirus Herpes
SONO APPEARANCE: Atrium of lat ventricle >10mm >15mm moderate/marked Dangling choroid sign
VENTRICULOMEGALY/ HYDROCEPHALUS
_____________ has been cited as the most common cranial abnormality.
Ventriculomegaly
the abnormal enlargement of the ventricles.
Ventriculomegaly
Defined as the absence of the cranial vault above the bony orbits
acrania
Elevated and dilated third ventricle.
agenesis of the CC and CSP
Partial or complete absence of the corpus callosum & absence of the CSP (after 18 weeks)
agenesis of the CC and CSP
most severe holoprosencephaly, often results in neonatal death
alobar
Sono Appearance: -Horseshoe-shaped monoventricle -Fused echogenic thalami -Absence of cavum septum pellucidum, interhemispheric fissure, falx cerebri, corpus callosum, & third ventricle -Normal cerebellum and brainstem
alobar holoprosencephaly
There will be evidence of a horseshoe-shaped monoventricle and the lobes of the thalamus will be fused and echogenic in appearance.
alobar holoprosencephaly
there are no cerebral hemispheres present.
anencephaly
what are the most common neural tube defects?
anencephaly and spina bifida
_______________ will not communicate with the ventricular system
arachnoid cysts
cerebellum will become displaced inferiorly and posteriorly and appear curved
banana sign
the cisterna magna is completely obliterated with which sign of spina bifida?
banana sign
the _________ located inferior to the corpus callosum, and the corpus callosum develop at the same time.
cavum septum pellucidum
close-set eyes w/ one single nostril within the nose
cebocephaly
__________ are common findings in Meckel-Gruber syndrome and a have varying sonographic appearances based on their content?
cephaloceles
are protrusions of intracranial contents through a defect in the skull
cephaloceles
______________ are cysts located within the choroid plexus of the lateral ventricles
choroid plexus
Sono Findings: -Anechoic, round, smooth-walled cyst located within the choroid plexus of the lateral ventricle. -Measure greater than 2mm
choroid plexus cysts
Found within the choroid plexus and increases the production of cerebrospinal fluid?
choroid plexus papillomas
leads to ventriculomegaly
choroid plexus papillomas
Frontal horns will be small and slitlike, while the occipital horns will be enlarged, a condition known as?
colpocephaly
obstruction lies outside the ventricular system.
communicating
2 Types of Hydrocephalus:
communicating and non-communicating
is a bridge of tissue located within the midline of the brain that connects the two cerebral hemispheres.
corpus callosum
-will appear as a solid echogenic mass -may also be present with agenesis of the corpus callosum
corpus callosum lipomas
orbits are fused containing a single eye
cyclopia
___________________ involves posterior fossa abnormalities that involve the cystic dilatation of the cistern magna and fourth ventricle.
dandy-walker complex
mega cisterna magna may be confused with?
dandy-walker malformation
______________ is actually a type of classification of dandy-walker complex
dandy-walker malformation (DWM)
the most common location of spina bifida is within the?
distal lumbosacral region
involves a normal amount of cerebral tissue
exencephaly
holoprosencephaly may be detected with EV as early as the?
first trimester
___________ is normal with mega cisterna magna and enlarged with DWM.
fourth ventricle
The lateral ventricle _______________ from the transducer will be the easiest to visualize.
furthest away
A midline brain anomaly that is associated with brain aberrations (not normal) and atypical facial structures.
holoprosencephaly
Trisomy 13, or Patau syndrome, is present in 50 to 70% of fetuses diagnosed with
holoprosencephaly
Bilateral occlusion of the ICA's causing destruction of the cerebral hemispheres can cause?
hydranencephaly
Brain may have a normal appearance in 1st trimester, then reflect this condition in the 2nd or 3rd trimester.
hydranencephaly
Intrauterine infections such as cytomegalovirus and toxoplasmosis can cause?
hydranencephaly
Sono Findings: -Fluid-filled cranium -Absent or partial absence of the falx cerebri -Maintained brain stem and basal ganglia -No identifiable cerebral cortex
hydranencephaly
___________ is typically a fatal condition, with death occurring in the first year of life.
hydranencephaly
Prevents the CSF flow from the 3rd to 4th ventricle.
hydrocephalus
With ___________________ (usually caused by aqueductal stenosis)...dilation of all of ventricular system EXCEPT 4th ventricular remains normal
hydrocephalus
Reduced distance between the orbits
hypotelorism
frontal bones become flattened and will yield a lemon shape to the cranium
lemon sign
Agyria + the absence of sulci within the brain is not typically diagnosed until the third trimester or postnatally and almost always carries a poor prognosis.
lissencephaly
SONO FINDINGS: Lack of sulci and gyri within the cerebrum
lissencephaly
means smooth brain
lissencephaly
there are no gyri within the cerebral cortex
lissencephaly
consistent with life holoprosencephaly
lobar
the enlargement of the cisterna magna without the involvement of the fourth ventricle
mega cisterna magna
protrusion of meninges
meningocele
Hydrocephalus can be described as:
mild, moderate, or severe.
protrusion of meninges and spinal cord
myelomeningocele
________ occur when the embryonic neural tube fails to close.
neural tube defects
the obstruction level is within the ventricular system.
non-communicating
the most common location of a cephalocele?
occipital region
Arachnoid cysts can be confused with __________?
porencephaly
SONO FINDINGS: -Cystic mass that communicates with the lateral ventricle -Most often unilateral
porencephaly
They can occur after the fetus has experienced hemorrhage within one or both of the cerebral hemispheres.
porencephaly
a false nose situated above the orbits
proboscis
Sono Appearance: A cerebrum containing clefts filled with anechoic, cerebrospinal fluid.
schizencephaly
Screening for neural tube defects is achieved by a combination of
sonography, amniocentesis, and/or maternal serum screening.
___________ may result in a mass that protrudes from the spine
spina bifida
lateral venrtricles will also be distorted in shape with what condition?
spina bifida
________ contains tissues such as hair, sebum, and fat
teratoma
appear as complex masses that distort the normal brain structures
teratoma
the most common intracranial tumor?
teratoma
choroid plexus cyst they are associated with an increased risk of?
trisomy 18
Schizencephaly etiology?
unknown
With _________________...any part of ventricular system can be dilated
ventriculomegaly