VENTRICULOMEGALY

DEFINITION

• Enlargement of lateral ventricles of the developing fetal

brain measuring 10 mm or greater
• Mild VM 10-12 mm
• Moderate VM 12.1-14.9 mm
• Severe VM ≥15 mm
• May be unilateral or bilateral
 INCIDENCE

• Overall incidence of VM is 1:1000 to 2:1000 births

• Reported incidence of mild VM
• 1.4/1000 births in low risk population
• 22/1000 births in the high risk population
• In a study of mild to moderate VM between 18-24 week
• 7.8/10.000 births
Standardized Technique of Measurement

• Midline structure should be equidistant from the proximal and distal

calvarium margins
• The cavum septi pellucidi should be visualized as the anterior landmark
and the ambient cistern as the posterior landmark
• The measurement should be performed opposite the internal
parietooccipital sulcus
• The measurement should be perpendicular to the inner and outer border
of the ventricle
• The measurement should be done on the inner edges of the ventricular
walls
• Axial views of
the fetal head
• Transventricular
plane
• The arrows
indicate the
glomus of the
choroid plexus
• CSP: cavum
septum pellucidi
 Imaging

• Imaging studies of the fetus that assess atrial diameter (AD)

are used to diagnose fetal VM.
• AD has several favorable attributes that support its
diagnostic use. In fetal VM, the occipital horn of the lateral
ventricle is the first area to dilate, and the atrium dilates to a
greater extent than do other ventricle regions, such as the
frontal horns.
 Imaging

• By convention, AD is measured in an axial plane at the level

of the atria of the lateral ventricles, and measurements are
made from the inner walls of the atria at the level of the
glomus of the choroid plexus.
• Measurements are perpendicular to the long axis of the
lateral ventricle.
• Measurement of the
atrium of the lateral
ventricles.
• The calipers should be
positioned at the level of
the glomus of the choroid
plexus, inside the echoes
generated by the
ventricular walls; the
arrows indicate parieto-
occipital fissures
• Diagram to illustrate
correct caliper
placement for
ventricular
measurement
 History and Genetic Testing

• The radiographic findings should be interpreted in the

context of the maternal medical history, including maternal
illness or drug exposure.
• Family history is reviewed to determine the presence of L1
cell adhesion molecule mutations, which alters neuronal
migration and differentiation and can cause hydrocephalus.
 History and Genetic Testing

• DNA testing for L1 spectrum mutations is recommended in

male patients with isolated severe VM or in those with a
positive family history.
• For all patients, fetal karyotype and chromosomal
microarray should be offered. In patients with isolated mild
VM, 4.7% had an abnormal karyotype
 Fetal MRI
• Fetal MRI is especially useful for detecting small foci of brain
hemorrhage, depicting corpus callosum anomalies, and assessing
cortical development.
• Furthermore, certain abnormalities, such as cortical malformations,
porencephaly, migrational abnormalities, and white matter pathologies
may be better detected on fetal MRI than US.
• MRI allows for complete visualization of the ventricles and brain
parenchyma without artifacts fromsurrounding skull ossification or fetal
position.
 Fetal MRI

• The major limitations of fetal MRI are poor image quality due
to fetal motion, cost, and availability.
• FetalbrainMRI is usually performed at 20 to 24 weeks of
gestation, as developmental milestones are more evident at
these times and discontinuation of pregnancy may still be an
option.
 Etiology of VM
• VM represents a common endpoint of various pathological processes
• It may be secondary to brain destruction (congenital infection or a
vascular mechanism), malformations, hydrocephalus, or a combination
of two processes (i.e., hydrocephalus and malformation)
• It may also be related to a brain neoplasm or to a genetic abnormality
not associated with a brain malformation

• In utero, hydrocephalus may be present even with a normal HC

 Etiology of VM
• Progressive, severe fetal ventricular enlargement together with
decreased or absent pericerebral space and parenchymal thinning can
be presumed to be indicative of hydrocephalus.
• The mean ventricular size measurement is not reliable as a means of
distinguishing between the different causes of VM
• VM tends to be unilateral in cases of destruction and bilateral in cases
of malformation
• In isolated VM, we have to distinguish between mild and moderate-to-
severe VM
 Associated Anomalies
• Chromosomal aneuploidy
• Trisomi 21,18,13
• Arnold Chiari malformation (Chiari II)
• Aqueductal stenosis
• Dandy Walker Malformation
• Congenital infection
• CMV
• Toxoplasmosis
 Ventriculomegaly associated with CNS
malformations
• In the Chiari II malformation, VM is associated:
• a small posterior fossa
• a small dysmorphic cerebellum
• an effaced cisterna magna
• a spinal defect with myelomeningocele

• For a conclusive diagnosis, the latter defect must be detected.

 Ventriculomegaly associated with CNS
malformations
• Sonographic sign of the DWM:
• VM with the presence of an enlarged posterior fossa, and complete or
partial agenesis or hypoplasia of the cerebellar vermis

• Agenesis of the CC:

• The “teardrop” appearance of the lateral ventricles with parallel bodies,
which are shifted laterally, and upward displacement of the third ventricle
suggest
• The presence must be confirmed on coronal and sagittal views.
• (a) Chiari II malformation: dilatation of the lateral cerebral ventricles and
“lemon sign” are clearly seen
• (b) Dandy–Walker malformation with ventriculomegaly: cystic dilatation of the
fourth ventricle, cleft between the cerebellar hemispheres (arrow), and
enlarged posterior fossa can be seen; cavum septi pellucidi (CSP) third
ventricle (arrowhead); LV: lateral ventricle.
• (c) Agenesis of corpus callosum; axial transventricular scan showing the
teardrop configuration of the lateral ventricle due to mild enlargement of its
posterior part (colpocephaly). Note also the absence of the CSP.
 Ventriculomegaly associated with cerebral
destruction
• VM associated with destructive lesions can be unilateral or bilateral
• The most common causes are hypoxia, infection, or vascular lesions
• When VM is associated with hyperechogenic foci located in the brain
and periventricular cysts, a fetal infection should be suspected
• If multiple nodular subependymal calcifications, which sometimes
group together to form periventricular hyperechogenic bands, are
present, cytomegalovirus (CMV) infection should be suspected
• (a) Cytomegalovirus infection: a periventricular hyperechogenic band
is clearly seen (arrow)
• (b) Axial scan of the fetal brain, showing hyperechoic clots within the
frontal horn of the proximal lateral ventricle (arrow) and in the third
ventricle (arrow).
 Ventriculomegaly associated with cerebral
destruction
• Free-floating particles, consisting of exudate and shed ependymal cells, may
be detected within the cerebral ventricles, which are often dilated, because
this particulate matter frequently obstructs ventricular foramina, leading to
secondary obstructive hydrocephalus
• In such cases, a differential diagnosis with intraventricular hemorrhage
should be made
• Maternal serology for CMV and other infectious agents and the findings at
earlier US examinations often resolve the differential diagnostic issue.
 Isolated ventriculomegaly

• The diagnosis is made when there is no other associated

sonographically detectable anomaly or markers of aneuploidy at the
time of the initial presentation
• Isolated mild VM may also be unilateral
• It should be noted that ventricular asymmetry, defined as a difference
in atrial size greater than 2 mm, without dilatation may be observed in
normal fetuses
 Severe ventriculomegaly

• Especially if associated with decreased or absence of pericerebral space

and paren- chymal thinning, severe VM is usually referred to as
hydrocephalus, and is defined by an atrial width of more than 15 mm
 Severe ventriculomegaly

• Hydrocephalus may result either from:

• Overproduction of CSF
• Obstruction to CSF flow
• Impaired resorption through the pacchionian granulations
• Depending on whether CSF flow obstruction is intraventricular or
extraventricular, obstructive hydrocephalus is categorized into
noncommunicating and communicating
 Severe ventriculomegaly

• In the fetus, VM is more frequently the result of a noncommunicating

hydrocephalus (as in aqueductal stenosis)
• The typical sonographic pattern of aqueductal stenosis:
 Triventricular hydrocephalus with enlargement of the third and the lateral
ventricles
• Noncommunicating hydrocephalus also includes the bilateral and
unilateral obstruction of foramina of Monro.
 Severe ventriculomegaly

• Hydrocephalus can also be related to abnormal differentiation of the

diencephalon, mesencephalon, and rhombencephalon, which leads to
obstruction of CSF flow.
• For these reasons, when facing severe isolated VM, whose
sonographic features are suggestive of an obstructive mechanism,
close examination of the third ventricle, thalami, sylvian aqueduct, and
cerebellum may reveal pathological differentiation of the diencephalon,
mesencephalon, or rhombencephalon, often in combination.
 Severe ventriculomegaly

• In Severe VM, the rate of association with other cerebral

anomalies (holoprosencephaly, CC agenesis, and DWM)
and extracerebral anomalies (myelomeningocele) ranges
from 45% to 80%.
 Diagnostic

• The finding of mild VM represent an uncommon but clinically relevant

sonographic finding. An accurate diagnostic workup should include:
• Rulling out associate neural and extraneural anomalies
• Ruling out for congenital infections
• Ruling out for feto-neonatal alloimmune Thrombocytopenia
• Rulling out for chromosomal abnormalities
 Rulling Out Associated Neural and
Extraneural Anomalies
• Mild MV associated with neural and extraneural anomalies (10-71%)
• Neural tube defect
• Dandy Walker malformation
• Dysgenesis corpus callosum
• Velum interpositum cyst
• Cortical malformation
• Mild VM also be the first sign of brain anomalies recognizable only in 3rd trimester or
even after delivery
• Ultrasonography recognized only 12.8%
• Using MRI evaluating fetus with mild MV adds important information 6-10% of the cases
 Rulling Out for Congenital Infection
• Up to 5% mild VM caused by Toxoplasmosis and CMV infections
• In fetus proven with CMV infection
• The most common ultrasound finding was VM (18% of cases)
• Futher sign periventricular calcification or small subependymal cyst
• Extraneural sign: liver calcification, ascites, hepatosplenomegaly, echogenic bowel,
placentomegaly and growth restriction
• MRI provide more information: abnormal gyration, cerebellar hyphoplasia and abnormal
white matter

• Maternal serum toxoplasmosis and CMV screening test should be

done in all patient with mild VM
 Rulling Out for Feto-Neonatal Alloimune
Thrombocytopenia
• Feto-neonatal alloimmune thromobocytopenia is a rare condition, but
can complicated in 10% to 30% of cases with ICH and
ventriculomegaly.

• Ventriculomegaly is rarely isolated, but it is usually associated with

hyperechogenicity of the ventricular echogenic material, as a sign of
the hemorrhage.
Rulling Out for Chromosomal Abnormalities

• Mild ventriculomegaly has been considered as one of the several so-

called “soft markers” of abnormal fetal karyotype.
• Mainly is trisomy 21
• The percentage of associated abnormal karyotype ranges from 0 to
28,6% with an average value of 2,8%. The wide variation of results
may depend by the prevalence of trisomies in the studied population,
which in turn depends on previously applied screening programs.
Clinical Diagnostic Flowchart Mild VM
 Prognosis, survival, and quality of life

• Outcome of prenatally detected VM is worse than that of VM detected

in the neonatal period
• spontaneous abortion, in utero fetal demise, stillbirth, and neonatal
death in 60% of cases
• Mortality rate is much lower if the lesion is isolated
• Factors indicating a less favorable prognosis are early detection and
progressive increase of the VM
 Prognosis, survival, and quality of life

• Important factor influencing prognosis is the cause of the VM

• Survival rate of about 80%, with 60% of these having normal
neurologic development
• Neurodevelopmental delay in infants with a prenatal diagnosis of
isolated mild VM is about 11%
 Conclusion

• Fetal mild VM is an uncommon but clinically relevant sonographic

finding.
• It is important to assess the cause and extent of VM (biventricular,
triventricular, etc.), its degree (mild, moderate, or severe), and whether
it is associated with any cerebral or/and extracerebral anomaly
• Diagnostic and prognostic workup is mandatory in managing
pregnancy with ventriculomegaly
Thank You