Ch. 21 OBGYN - Fetal Head
Holoprosencephaly
"face predicts the brain"
Choroid Plexus Cyst
-Round or ovoid anechoic structure found within the Choroid Plexus. -Resolve by 22-26 wks. -Isolated
Lobar holoprosencephaly
-The least severe form of the holoprosencephaly
Choriod Plexus Cyst
-common benign cyts -located in the choroid of the lateral ventricle -contains CSF and debris trapped within neuroepithelial folds -typically go away on their own but will be monitored
Circle of Willis
A circle of arteries at the base of the brain that supply blood to the brain
anencephaly
Acrania (exencephaly) usually progresses to ________
trisomy 13 and 18, diabetes, infections, and alcohol abuse
Agenesis of the Corpus Callosum can be associated with what?
Dandy-Walker malformation
Agenesis or hypoplasia of cerebellar vermis with resulting dilation on fourth ventricle and enlargement of posterior fossa.
can detect acetylcholinesterase, which is elevated in amniotic fluid in the presence of NTD
Amniocentesis can detect what? How is this helpful?
Spina bifida, talipes, omphalocele, heart defects, hydronephrosis
Anencephaly is associated with what?
Severe hydrocephaly
Aqueductal stenosis causes
3 main cerebral arteries (ant. middle and post.)
Both sides of the Circle of Willis contains the _________
ventricles
CSF filled structures surrounded by solid brain parenchyma
the fourth ventricle
CSF produced in the ventricular system drains into the cisterna magna from which ventricle?
acrania (exencephaly)
Chef's hat
Dandy-Walker malformation
Congenital failure of cerebellar vermis to develop
Agenesis of corpus callosum Aqueductal stenosis Microcephaly Macrocephaly Encephalocele
DWM is associated with what other intracranial anomalies
Lateral ventricles --> interventricular foramen/foramen of monro ---> third ventricle --> cerebral aqueduct/aqueduct of slyvius --> fourth ventricle
Describe the flow of CSF through the ventricles.
Hydranencephaly
Destruction of cerebral hemispheres by occlusion of bilateral internal carotid arteries. brain tissue destroyed and replaced with CSP. GRAVE PROGNOSIS
glomus
Echogenic structures seen tucked within the atrium of each lateral ventricle
Meckel-Gruber syndrome
Encephalocele (cephalocele) is associated with what syndrome?
Meckel-Gruber syndrome
Encephaloceles are associated with what syndrome?
Encephalocele (cephalocele)
Herniation of brain and meninges through a cranial defect.
via the cerebral aqueduct or aqueduct of Sylvius
How do the 4th and 3rd ventricles communicate?
top to bottom (outer to outer) = cerebellum midline width for cisterna magna
How do you measure the cerebellum and cisterna magna?
enlargement
Hydrocephalus occurs when ventriculomegaly coupled with _______ of fetal head
an amniocentesis
If MSAFP is elevated, but the cause isn't identified by U/S, what should be done?
amniotic band
If encephalocele (cephalocele) is asymmetric or atypical location (not along suture) __________syndrome must be considered
subnormal, mental retardation
Infants with DWM have a subnormal _______
females AND multiples
Is Anencephaly more common in males or females?
male 2:1
Is agenesis of the corpus callosum more common in males or females?
males
Is the Vein of Galen Aneurysm more common in males or females?
circle of willis ultrasound
MCA is normally dopplered for fetal distress
holoprosencephaly
Midline facial abnormalities are commonly associated with what intracranial anomaly?
Encephalocele (cephalocele)
NTD in which the meninges alone, or with brain, herniate through a defect in calvarium
folic acid
Neural tube defects are linked to ______ intake early in pregnancy.
Lobar holoprosencephaly
Normal separation of thalami, hemispheres, and ventricles. Corpus callosum may be normal, hypoplastic, or absent Absent cavum septum pellucidum and olfactory tracts
Semi-lobar holoprosencephaly
Partial separation of ventricles & hemispheres with occipital lobe present. Incompletely fused thalami. no falx fissure
Vein of Galen Aneurysm
RARE, arteriovenous malformation (AVM) where the vein is enlarged and communicates with normal appearing arteries.
Schiz = split Schizencephaly
The brain appears "split" into anterior and posterior parts
vermis, hemispheres
The center portion of the cerebellum is called the ______, the lateral portions are called the ______.
roof
The corpus callosum forms the _____ of each ventrical cavity.
midline
The corpus callosum is what kind of structure?
3rd ventricle
The foramen of Monroe drains CSF to the Aqueduct of Sylvius by way of what?
midline
The third ventricle is a ______ structure.
arachnoid cysts - they have no flow
Vein of Gale Aneurysm may often be confused with what? How do you tell the difference on U/S?
acrania
What anomaly can progress into anencephaly?
absent cranial vault and cerebral hemispheres, "frog face" coronally
What are the main sonographic findings of anencephaly?
monoventricle, fused thalami, absence of falx cerebri
What are the sonographic signs of Alobar holoprosencephaly?
Alobar, semi-lobar, lobar
What are the three types of holoprosencephaly?
porencephalic cyst
What can be considered a differential diagnosis for a Vein of Galen aneurysm?
congenital infection (cytomegalovirus and toxoplasmosis) or ischemia
What causes hydranencephaly?
incomplete closure of the neural tube by 6 weeks
What do many congenital malformations of CNS result from?
medially - thalamus laterally - caudate nucleus
What forms the inferior walls of each ventricle cavity?
choriod plexus
What intracranial anatomy can be seen as echogenic structures in each of the lateral ventricles?
Cerebellum and Cisterna Magna
What is labeled C and CM?
brainstem, midbrain, skull base, facial structures (face and orbits)
What is present still with anencephaly?
abnormal migration of neurons
What is schizencephaly though to result from?
Anencephaly
What is the MOST COMMON NTD?
choriod plexus
What is the PRIMARY source of cerebral spinal fluid?
rich capillary network, inclusions of pia mater, and choroid epithelial cells
What is the choriod plexus composed of?
Corpus Callosum
What is the correct label for the asterisks?
absence of the CSP
What is the hallmark finding in agenesis of the corpus callosum?
between 3mm-10mm
What is the normal length for cisterna magna?
10mm or less
What is the normal measurement for the atrium of the lateral ventricles?
embolization
What is the primary treatment for the Vein of Galen Aneurysm?
poor and varies with associated anomalies. survivors are profoundly mentally retarded
What is the prognosis for Aqueductal Stenosis?
poor! severe - fetus dies at birth or shortly after least severe - survival possible with severe mental retardation
What is the prognosis for holoprosencephaly?
depends on degree - most are mentally retarded
What is the prognosis for microcephaly?
poor especially with hydrops or cardiac failure. If children are older then prognosis is generally good.
What is the prognosis for the Vein of Galen Aneurysm?
4th ventricle
What is the solid arrow pointing to?
dura matter
What layer serves as a landmark for the midline falx?
inferior aspects of the thalamus and hypothalamus
What makes up the lateral walls of the third ventricle?
cervical spina bifida, and occipital encephalocele
What other defects are present with iniencephaly?
method of communication between the two cerebral hemispheres - aids in learning and memory
What purpose does the corpus callosum serve?
Two anterior internal carotid arteries Two posterior vertebral arteries
What supplies the brain with oxygenated blood?
Dura matter (tough outer layer), Aracnoid matter (middle), Pia matter (inner layer covering brain and spinal cord)
What three layers cover the brain? What are their positions?
CSF is escaping and causes elevated AFI and MSAFP
When a neural tube defect occurs, what is getting released and what is elevated?
later in second trimester
When can Dandy- Walker be diagnosed?
as early as 12 weeks
When can acrania (exencephaly) be identified on U/S?
12 weeks gestations and is not complete until 20 weeks
When does the corpus callosum develop and finish developing?
by 18-20 weeks
When should the CSP be visualized?
midline, most commonly occipital but may be front of meninges only
Where could encephalocele (cephalocele) be found?
within each cerebral hemisphere beneath the corpus callosum
Where do the lateral ventricles lie?
along the anterior portion of the cerebellum - typically can't see in US unless it's dilated
Where does the 4th ventricle lie?
between the medial walls of the frontal horns and bodies of the two lateral ventricles
Where does the CSP lie?
posteroinferior portion of the intracranial cavity
Where does the cerebellum lie?
in the area of the Slyvian fissure
Where is schizencephaly usually located?
located between the cerebellum and dorsal surface of the medulla oblongata. Posterior to cerebellum on US
Where is the cisterna magna located?
the posterior one (A-P)
Which choriod plexus should be measure? How?
anencephaly
Which is the most common neural tube defect?
anterior (rostral)
Which neuropore of the neurotube is the first to close?
third and fourth ventricles
Which ventricles does the Aqueduct of Slyvius connect?
Sylvian fissure
a deep fissure that demarcates the temporal lobe
Schizencephaly
a rare condition characterized by abnormal openings or clefts in the cerebral cortex
Iniencephaly
a rare neural tube defect in which the occiput is fused to the cervical region
Porencephalic Cysts
also known as porencephaly
Vein of Galen Aneurysm
also known as vein of galen malformation
microcephaly
an abnormally small head (more than 3SD below mean)
Porencephalic cyst
cyst arising from the ventricle that develops as a consequence of parenchymal hemorrhage (brain tissue absorbed but leaves a lesion)
Ventriculomegaly (Hydrocephalus)
dilation of the ventricular system within the brain that occurs with obstruction of CSF flow.
polyhydramnios
excessive amniotic fluid
Anencephaly
failure of neural tube to close by 24 days gestation causing congenital deformity in which the cranial vault is absent, with a complete or partial forebrain. LETHAL ANAMOLY (505)
by 12 weeks (15 at latest)
fetal cranium should be identifiable when?
Schizencephaly
fluid filled cleft in cerebral cortex extending from ventricle to calvarium
Schizencephaly
has been linked with assaults during pregnancy
cocaine abuse
hydranencephaly is associated with....
Cavum septi pellucidi
interhemisperic space in the intracranial space, containing cerebral spinal fluid
Holoprosencephaly
is malformation sequence that results from failure of the forebrain (prosencephalon) to differentiate into two cerebral hemispheres and lateral ventricles between fourth and eighth gestational weeks.
Holoprosencephaly
malformation associated with facial anomalies like cyclopia, hypotelorism, clefts, etc. MIDLINE FACIAL ABNORMALITIES
Teratogens (infecitons, abuse, poisoning)
microcephaly is linked what what?
amniocentesis
needle puncture of the amniotic sac to withdraw amniotic fluid for analysis
communicating hydrocephalus
obstruction outside of the ventricular system
noncommunicating hydrocephalus
obstruction within the ventricular system (children)
Hydranencephaly
sonographically: Absence of normal brain tissue with almost complete replacement by cerebrospinal fluid -Absent or partially absent falx -Presence of midbrain, thalami, cerebellum -Choroid plexus may be identified. -Macrocephaly may occur -Polyhydramnios
Agenesis of the Corpus Callosum
sonographically: Complete or partial absence of corpus callosum Elevation and dilation of third ventricle Widely separated lateral ventricular frontal horns with medial indentation of medial walls Dilated occipital horns (colpocephaly), giving lateral ventricles teardrop shape Absence of cavum septum pellucidum (in complete absence of CC)
Vein of Galen Aneurysm
sonographically: cystic space that may be irregular in shape and located midline and posterosuperior to the third ventricle. Turbulent flow with Doppler.
Porencephalic Cysts
sonographically: cysts within brain parenchyma without mass effect
Ventriculomegaly (Hydrocephalus)
sonographically: excess fluid in lateral ventricles (>10mm), dangling choriod plexus, hydrocephalus >15mm
Iniencephaly
sonographically: hyperextension, other defect
Dandy-Walker malformation
sonographically: posterior fossa cyst, splaying of cerebellar hemispheres, enlarged cisterna magna, ventriculomegaly
menigocele
sonographically: purely cystic extracranial mass - just CSF
microcephaly
sonographically: small BPD, small HC
Encephalomeningocele
sonographically: solid and cystic extracranial mass with CFS and brain components
encephalocele
sonographically: solid mass attached with cranium (has brain components)
Aqueductal Stenosis
sonographically: ventricular enlargement of lateral ventricles, third ventricular dilation, flexion and adduction of thumb (x linked)
aqueductal stenosis
the abnormal narrowing of the cerebral aqueduct causing ventriculomegaly.
Alobar holoprosencephaly
the most severe form of holoprosencephaly
Vein of Galen Aneurysm
usually an isolated anomaly but can be associated with congenital heart defects, hydrops, and nuerologic damage (mass effect or hemorrhage)
Acrania (Exencephaly)
• Complete or partial absence of cranium with the development of normal brain tissue • Brain is exposed to amniotic fluid/trauma (causing is to be malformed)
