Download Sonographic Evaluation of the Fetal Central

Transventricular
Transthalamic
Transcerebellar
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Transventricular
Plane
• the anterior and posterior portion of the lateral ventricles
• the cavum septi pellucidi (CSP): a fluid filled cavity between two thin membranes
• late gestation: membranes usually fuse and become the septum pellucidum
• CSP becomes visible around 16 weeks and undergoes obliteration near term
• Failure to demonstrate the CSP prior to 16 weeks or later than 37 weeks is a
normal finding
• the posterior portion of the lateral ventricles: a complex formed by the atrium that
continues posteriorly into the occipital horn
• atrium, characterized by the presence of the glomus of the choroid plexus
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Transcerebellar
Plane
• This plane is obtained at a slightly lower level than of the transventricular plane
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The frontal horns of the lateral ventricles,
CSP,
thalami,
cerebellum and cisterna magna
• the cerebellar hemispheres, more echogenic cerebellar vermis in the middle
• cisterna magna: a fluid filled space posterior to the cerebellum
• in the second half of gestation the depth of the cisterna magna is stable: 2–10 mm
• vermis has not completely covered the 4th ventricle prior to 20 weeks’ gestation. false
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impression of a defect of the vermis in early gestation
Transthalamic
Plane
The anatomic landmarks:
• the frontal horns of the lateral ventricles,
• the cavum septi pellucidi,
• the thalami and the hippocampal gyruses.
• does not add significant anatomic information
• easier to identify and in late gestation: more
reproducible measurements
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Transfrontal plane
• midline interhemispheric fissure (IHF),
• the anterior horns of the lateral ventricles,
• sphenoidal bone, occular orbits,
• rostral part of the genu of the corpus callosum - IHF
association
Superior sagittal sinus (1),
interhemispheric fissure (3),
frontal horns of the lateral ventricles (4),
genu (5) of the corpus callosum
Orbits (O)
Coronal
views of
the fetal
head
Transarcuadate plane
• CC genu/ anterior part – IHF association ,
• Cavum Septi Pellucidi(CVP),
• the lateral ventricles
parietal bones and anterior fontanel (2),
frontal horns of the lateral ventricles (4),
body (6) of the corpus callosum,
cavum septi pellucidi (7),
caudate nucleus (8)
Orbits (O)
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Transthalamic plane
• Thalamus,
• III. Ventricule,
• Atrium of lateral ventricule
frontal horns of the lateral
ventricles (4),
body (6) of the corpus callosum,
cavum septi pellucidi (7),
hippocampus (9),
cerebellar vermis (10),
Sylvian fissure (SF),
Coronal
views of
the fetal
head
Transcerebellar plane
• Occipital horns of lateral ventricules,
• Interhemispheric fissur,
• Cerebellar hemispheres,
• Vermis
cerebellar vermis (10),
Occipital horns (OH),
cerebellar hemispheres (C),
cisterna magna (CM)
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Midsagittal plane
Fetal
Head
Sagittal
plane
Corpus callosum,
Cavum septi pellicidi,
Brain stem, pons, vermis,
Posterior fossa,
Anterior cerebral artery
(with Doppler)
Pericallosal artery (with
Doppler),
Vein of Galen (with Doppler)
Parasagittal plane
The entire lateral ventricle,
The choroid plexus,
The periventricular tissue,
Cortex
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Acrania
• Absent calvarium above
orbits
• Exposed brain with no
cranium
• Affects membranous flat
bones ( frontal, parietal,
temporal and occipital )
• Skull base intact
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Anencephaly
• No calvarium with absence of
neural tissue above orbits
• Protuberant eyes
• Always fatal, and termination
of pregnancy should be offered
• A part of the cerebral
hemispheres sometimes visible
in the 1st trimester
“exencephaly”
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Cephalocele
• Cranial defects, along bony sutures, in which there is a herniation of the brain
or the meninges, or both.
• Occipital, parietal, or frontal, most common: occipital
• If the cephalocele sac contains brain tissue: encephalocele
• If only cerebrospinal fluid (CSF) is present: meningocele.
• Incidence: 1 in 3500 to 1 in 5000 live births
• Usually isolated, but in a small percentage: a part of a chromosomal or
nonchromosomal syndrome.
• Hydrocephaly in 80% of occipital encephaloceles, microcephaly (20%)
• Approximately 65% of fetuses have at least one major malformation and 35% have
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isolated cephalocele
Cephalocele
• Autosomal recessive syndromes that feature a cephalocele :
• Meckel (cephalocele, renal cystic dysplasia, and postaxial polydactyly);
• Walker-Warburg or HARD ± E (hydrocephaly, agyria, retinal dysplasia, with or without
encephalocele);
• Knobloch (vitreoretinal degeneration and occipital encephalocele)
• Detailed anatomic survey, fetal echocardiography
• Genetic counseling, CVS, and/or AS; microarray if chromosomes are normal
• Prognosis: High mortality rate
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Choroid plexus
cysts
• Well-demarcated, anechoic, fluid-filled structures
within the choroid plexus of the lateral ventricles of
the brain
• Unilateral or bilateral
• Usually small , <10 mm in diameter
• They regress, spontaneously during the third trimester.
• Isolated finding + maternal serum: low risk… AS
unlikely to find any abnormality
• Associated anomalies are those seen with trisomy 18
• congenital heart disease, clenched hands, single
umbilical artery, intrauterine growth restriction, and
rocker bottom feet.
• if associated with other findings (e.g., VSD, clenched
hands) or the maternal serum screen shows increased
risk, offer genetic counseling and amniocentesis.
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Arachnoid cysts
• Collections of cerebrospinal fluid
on the brain surface
• Usually benign, congenital,
space-occupying lesions
• Mostly sporadic
• Commonest over cerebral convexities
• One third in the posterior fossa
• Remaining brain sonographically normal in majority
• Avascular lesion: color Doppler reveals no blood flow in the walls
• congenital (primary) or
secondary (acquired) (inflammation, hemorrhage, or trauma)
• Ventriculomegaly or hydrocephaly—secondarily to pressure
• Anatomic survey, fetal echocardiography, genetic counseling andkaryotype
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Holoprosencephaly
• failure of the forebrain to properly divide along the
midline
• partial or complete failure of division of the
prosencephalon into two separate hemispheres between
the 18th and 28th day after conception
• three “classic forms” arealobar, semilobar, and lobar
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Alobar Holoprosencephaly
• complete lack of division of the forebrain with
absent midline structures
• fusion of the thalami and cerebral hemispheres
• a single primitive ventricle (monoventricle )
• the interhemispheric fissure, falx cerebri, 3rd
ventricle and corpus callosum are totally absent
• associated with a spectrum of facial abnormalities :
• cyclopia (single midline eye), arrhinia (absent
nose), synophthalmia, or microphthalmia, severe
hypotelorism, midline cleft lip and palate, flat nasal
bridge, and single or barely separated nostrils
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Alobar
Holoprosencephaly
• isolated HPE often normal karyotype
• 25%-45% of newborns with HPE
have a karyotype abnormality
(trisomy 13, trisomy 18, triploidies)
• karyotype all fetuses,
• termination offered
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Semilobar
Holoprosencephaly
“Partial cleavage of prosencephalon at posterior”
• absence of the interhemispheric separation
• but posteriorly there is some separation
• the anterior horns are fused
• the septi pellucidi and the anterior part of the corpus
callosum are absent
• partial separation of the thalami
• a rudimentary third ventricle and facial anomalies
• the two cerebral hemispheres are partially separated
posteriorly but there is still a single
ventricular cavity
• degree of developmental disability typically correlates
with the severity of the brain malformation
• karyotype all fetuses, termination offered
Single
ventricule
Some cleavage of thalami
Occipital
horns
Single
ventricule
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Lobar Holoprosencephaly
“lack of separation of the ventral neocortex and agenesis
of the corpus callosum”
Frontal lobes fused
• frontal lobes fused
• absence of the septum pellucidum
• the interhemispheric fissure is well developed posteriorly
and anteriorly
• a variable degree of fusion of the cingulate gyrus and
of the lateral ventricles
• No diagnosis before 18th weeks gestation, as CSP is
not visible properly
occipital lobes
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Schizencephaly
• Gray matter lined cleft extending
from brain surface to ventricle
• CSP absent in 70%
• defect of brain parenchyma
extending from inner table of skull to
underlying ventricle
• probably a neuronal migration
disorder
• prognosis is poor, and termination of
pregnancy should be offered
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Corpus Callosum Agenesis
• Largest midline commissure of the brain
connecting the neocortex of the cerebral
hemispheres
• CC sonographically visible at 18-20 wks
• CC forms in midline lamina between 8-20 wks
• Develops from anterior to posterior
• CC agenesis: partial/ complete …
• In partial agenesis, the anterior parts are
developed, but the posterior aspects are absent.
• Colpocephaly
• Absent cavum septi pellucidi
• Absent corpus callosum
• Absent or abnormal pericallosal artery
• Teardrop-shaped, parallel lateral ventricles on
the axial section
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Corpus Callosum Agenesis
• Karyotype recommended even if isolated finding
• CNS anomalies in up to 85% of cases, non-CNS anomalies in up to 65% of cases
• worse prognosis in the presence of additional anomalies.
• in cases of isolated ACC, it appears to carry a better prognosis n( eurodevelopmental delay in about
25% of cases at 3 years).
• in 10%-17%, ACC is an isolated finding, and these individuals are asymptomatic.
• individuals with ACC and other CNS anomalies are more likely to have neurologic symptoms.
• neuromotor skills are impaired in almost all individuals with ACC (severe spastic or spastic-dystonia,
hypotonia).
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Dandy-Walker
Malformation
• marked cystic dilatation of the fourth ventricle, which may fill much of the
posterior fossa
• hypogenesis or agenesis of the cerebellar vermis
• superior displacement of the tentorium
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Dandy-Walker Malformation
• enlargement of the posterior fossa
• 70% to 80% of the cases, some degree of
ventriculomegaly or hydrocephaly is present, with
progressive postnatal ventriculomegaly
• large cistern magna that communicates with the fourth
ventricle
• cerebellar hemispheres splayed apart with varying
degrees of dysplasia
• elevated tentorium
• absent or hypoplastic vermis
• cephalad rotation of the vermian remnant
• cannot make the diagnosis in the early 2nd
trimester, normal development can resemble disease, must
repeat US later than 18 wks.
• development of vermis: 16-20 wks
• vermian disgenesis: dx at 20-22 wks
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Dandy-Walker
Malformation
• frequency of associated malformations: 50% to 70%.
• CNS anomalies most common: hydrocephaly, CCA or disgenesis, holoprosencephaly,
cephaloceles
• congenital heart disease, craniofacial, renal, limbs, abdominal wall, diaphragmatic
hernia, and ambiguous genitalia.
• IUGR
• Chromosomal anomalies such as trisomy 9, 21, 18, and 13;triploidy; 6p and 3q22q24 deletion
• nonchromosomal syndromes such as Meckel, Walker-Warburg, and Cornelia de Lange
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DWM management_prognosis
Anatomic survey
Fetal neuroscan
Fetal echocardiography
Genetic counseling, karyotype, test
for 3q24 deletion, microarray
studies
• Consider MRI to rule out
associated anomalies
• Offer termination of pregnancy
• Serial scans to monitor
ventriculomegaly
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• Motor deficits; delayed motor
development, hypotonia, and ataxia; about
half have mental retardation
• IU fetal demise in about 14%
• 80% develop hydrocephaly by 3 months
• Overall infant mortality:10%-66%
• infection, uncontrolled hydrocephaly,
and shunt complications
• One third of survivors with DWM can
develop normally
Favorable neurodevelopmental outcome:
no associated CNS or extra-CNS anomalies and a normal lobulated vermis
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Vein of Galen aneurysm
• The vein of Galen is located under the cerebral hemispheres;
it drains the anterior and central regions of the brain
into the sinuses of the posterior cerebral fossa.
• Aneurysmal malformation with an AV shunting of blood.
• High-output heart failure (decreased resistance and high blood flow)
• Cardiomegaly in 64%, enlarged neck vessels in 32%
• Ventriculomegaly in 24%
• Hydrops in severe cases,
• Mass effects, causing progressive neurologic impairment
• Cerebral ischemic changes
• The cardiac and brain status dictates the long-term outcome.
2D and/or 3D color or power Doppler imaging:
• Postnatal: endovascular treatment
high-velocity turbulent flow 29
“Calipers positioned at the
level of the glomus of the
choroid plexus, touching the
inner edge of the ventricle
wall at its widest part and
aligned perpendicular to the
long axis of the ventricle”
Ventriculomegaly
• Mid-trimester average 7 mm ± 2mm
• Ventriculomegaly > 10 mm
• 10-12= mild ventriculomegaly
• 12.1-14.9 = moderate ventriculomegaly
• > 15 mm = Hydrocephaly
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Pilu G, Hobbins JC. Prenat Diagn 2002;22:321-30.
Ventriculomegaly
VM is 1 : 1000 to 2 : 1000 births
<12mm VM: 62% regresses at 24.wks
Associated structural and/or chromosomal malformation in about 41%
chromosomal aneuploidy 11%; Trisomy 21 was most common ,
followed by trisomies 18 and 13
• Structural anomalies (with normal karyotype); 43%
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– brain anomalies, most common: Chiari II, CCA, microcephaly
– heart, diaphragmatic hernia, omphalocele, and limb reduction
– cong. inf.; 0.8% (cytomegalovirus, toxoplasmosis)
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Ventriculomegaly
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Anatomic survey
Fetal neuroscan; additional anomalies.
Fetal echocardiography
Genetic counseling and amniocentesis;
– esp. if the mild VM is not an isolated
finding or
– if maternal aneuploidy screening suggests
risk
• MRI of the brain; additional anomalies
• Send amniotic fluid for Toxo, CMV PCR
• Serial ultrasound to monitor the
progression of the VM
In cases of mild VM :
associated anomalies
influence the prognosis
In utero progression of
VM= ↑ neurologic
sequelae
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Mega cisterna magna
Cisterna Magna>10 mm
From cerebellar vermis posterior to the inner
edge of occipital bone
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Enlarged posterior fossa cerebral spinal fluid (CSF) space
Fourth ventricle is normal
Cerebellar hemispheres normally formed
Cerebellar vermis is complete and normal
Usually an incidental finding
Part of multiple findings seen with trisomy 18
If isolated likely has no adverse clinical outcome
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• Cisterna Magna > 10 mm
• Intact vermis without rotation
• Mega cisterna magna,
normal outcome >90% cases
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• Normal cisterna magna,
hourglass shape of 4th ventricle opening
• Intact vermis rotated <45°
• Usually Blake’s pouch cyst,
normal outcome >90% of cases
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• Large V-shaped cisterna magna
• Normal/small vermis
rotated >45° rotate
• Usually Dandy-Walker
malformation, abnormal outcome
50% of cases
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Thank you
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