1. Fetal brain anomalies
(ventriculomegaly, ACC, Dandy-Walker malformations)
Kh. Batnasan
United Family Intermed Hospital, Mongolia
Korea University Hospital
31 Mar 2015
2. Fetal ventriculomegaly
• Ventriculomegaly – Enlargement of
the lateral cerebral ventricles
• Nonspecific marker of abnormal
brain development
• Measurement: Internal width of
the atrium of the lateral ventricle
at the level of glomus of the
choroid plexus
4. Definition
Subtle difference
Ventriculomegaly – obstruction of normal CSF bulk flow
due to global cerebral tissue loss after hypoxic-ischemic
injury (eg., congenital anomalies, TORCH infections…)
Hydrocephalus – impaired, obstructed or altered CSF bulk
flow
5. Fetal ventriculomegaly
• Normal range = 5-10 mm (from
15 weeks)
• Mild VM = 10-15 mm
• Severe VM = >15 mm
(dangling choroid plexus)
6. Mild ventriculomegaly
• ≥10 mm
• Bilateral or unilateral
(Distal and proximal ventricles are should be measured)
• Associated with:
• Brain malformations
• Genetic syndromes
• Infections
• Prevalence: (extremely variable) 0.15 – 0.7%
• Hannon et al., (2012) - 7.9 per 10,000 singleton births
8. Mild VM – diagnostic work up
• ruling out for associated anomalies
• ruling out for congenital infections
• ruling out for feto-neonatal alloimmune thrombocytopenia
• ruling out for chromosomal abnormalities
• monitoring the development of mild VM in the progressing
pregnancy.
9. Mild VM - ruling out for associated anomalies
• May be associated with neural and extraneural anomalies
• May be first sign of brain anomaly in 3rd trimester or after
delivery
• Association range: 10-71% (average – 40%)
• Need an accurate and systematic evaluation of the fetal brain
• Fetal brain MRI – advocated in the case of mild VM
(following neurosonogramm)
• Appropriate time – 3rd trimester
• Helpful in the case of cortical anomalies
10. Mild VM - ruling out for congenital infections
May be seen:
• small periventricular calcifications
• small subependimal cysts
• extraneural abnormal findings:
• liver calcifications
• ascites
• hepatosplenomegaly
• echogenic bowel
• placentomegaly
• growth restriction
• Recommended tests for TORCH infections
(CMV, toxoplasmosis)
11. Mild VM - Ruling out for feto-neonatal alloimmune
thrombocytopenia
• Very rare
• Hyperechogenicity of the ventricular walls
• Intraventricular echogenic blood clots
12. Mild VM - Ruling out for chromosomal anomalies
Melchiorre K et al., UltrasoundObstet Gynecol 2009;34:212-24.
13. Mild VM - Ruling out for chromosomal anomalies
• Devaseelan P. et al., (2010) – 5%
• Pagani G. (2014) – 4.7%
• “soft marker”
• Counseling about chromosomal analysis
14. Mild ventriculomegaly - Outcome
• Kutuk MS. et al., (2013)
64% normal development
36% mild neurodevelopmental
delay
• Xie AL. et al., (2011) –
85% resolved;
>12 mm VM is likely poor
prognosis
15.
16. Severe VM
Prognosis:
• Survival or neurodevelopmental outcome is poor
• Related to the underlying condition (hydrocephalus, cerebral
atrophy or additional anomalies…)
Prevalence:
• 3.6 per 10,000 singleton births
(Hannon et al., 2012)
17. Severe VM
• Associated anomalies – 49.8%
• Chromosomal anomalies: 3.2 – 8.3%
• Structural anomalies – 42.7%
• Neonatal mortality – 16.2%
• Fetal brain MRI – additional tool to diagnose an associated
anomalies
Hannon et al., Obstet Gynecol 2012
20. Agenesis of corpus callosum
Corpus callosum
• The largest connective structure
• Transfer information between right and left hemispheris
• By 18-20 weeks’ gestation – final shape
• CC has 4 segments: 1. rostrum 2. genu 3. body 4. splenum
21. Agenesis of corpus callosum
• Developmental absence of the corpus
callosum: Agenesis (ACC)
• Partial ACC
• Complete ACC
• Each of these may be:
• Isolated: ACC with no other abnormalities
• Complex: ACC with other abnormalities
22. • Incidence – difficult to estimate (asymptomatic individuals)
• There are no large studies
• 1.4 per 10.000 live births (California Birth Defect Monitoring
Program)
• Prevalence of associated brain abnormalities - 45,8%
(posterior fossa, interhemispheric cysts and neuronal
migration disorders)
• The overall rate of chromosomal abnormality - 17,8%
(consider - chromosomal analysis, CGH)
23. Sonographic criteria
Corpus callosum:
• Approach: mid-sagittal or mid-coronal plane of the brain
• Multiplanar sonography or TVS – useful
• Mid-sagittal view – thin anechoic space
• Mid-sagittal view – pericallosal artery as a marker (especially in resolution-related
difficulties )
• 3D/4D reconstruction
25. ACC – Sonographic criteria
• Measurement of CC size – recommended by some authors
Achiron R, Achiron A..Ultrasound Obstet Gynecol 2001; 18: 343–347.
26. ACC – key points on indirect features 1
Absence of the cavum septi pellucidi (CSP)
• Not specific to ACC (holoprosencephaly, hydrocephalus, septo-
optic dysplasia, schizencephaly, encephalocele, porencephaly and
hydranencephaly)
• In partial ACC - CSP is usually present
27.
28. ACC – key points on indirect features 2
Abnormalities of the ventricles
• Colpocephaly - dilatation of the atria and occipital horns
of the lateral ventricles
• Result of the absence of CC posterior portion, which allows
expansion of the occipital horns.
• Usually not associated with progressive ventriculomegaly
29. ACC – key points on indirect features 2
• Lateral displacement of
LV on coronal views
• Upward displacement of
the third ventricle, which
reaches the level of the
lateral ventricles
30. ACC – key points on indirect features 3
Abnormal course of the pericallosal artery
• Complete ACC: the semicircular loop of the pericallosal artery is lost
• Partial ACC: the pericallosal artery follows the anterior part of the CC
but then loses its normal course where the CC disappears posteriorly;
31. ACC – key points on indirect features 4
Widening of the interhemispheric
fissure
• Increased separation of the
hemispheres
• 3 parallel echogenic lines (the
middle - falx cerebri)
• The lateral ones representing the
medial borders of the separated
hemispheres
32. ACC – Prognosis
• Depends on coexistence of other abnormalities
• Association with cortical disorders – poor prognosis
• Normal or borderline intellectual development – in case of
isolated
• Pediatric data suggest – more than 90% mental retardation or
severe abnormalities
35. Cranial posterior fossa
• The part of the intracranial cavity
• Located between the foramen magnum and tentorium cerebelli
• It contains the brainstem and cerebellum
36. Malformation of the posterior fossa
T. Chapman et al., Clinical imaging 39 (2015) 1-8
37. Definition
• Dandy-Walker malformation
• Dandy-Walker variant
1. Marked cystic dilatation of the 4th
ventricle
2. Hypogenesis or agenesis of the cerebellar
vermis
3. Superior displacement of the tentorium
and lateral sinuses
• Dandy-Walker complex (or continuum)
• DWS malformation
• Megacisterna magna (Benign enlargement of
subarachnoid spaces of PF)
• DWS variant
• Blake’s pouch cyst (posterior ballooning of the
superior medullary velum into the cisterna magna)
38. Dandy – Walker malformation
1. Marked cystic dilatation of the 4th ventricle (may fill much of posterior fossa)
2. Hypogenesis or agenesis of the cerebellar vermis
3. Superior displacement of the tentorium and lateral sinuses
46. DWM – Prognosis
• Largely dependent on type of condition, and associated
anomalies
• Strongly related to other intracranial anomalies (degree of
hydrocephalus, cortical malformations, and corpus callosal dysgenesis) and
extracranial and chromosomal anomalies
• Severe cerebellar hypoplasia and vermian agenesis - poor
intellectual outcome
47. DWM – Prognosis
• Isolated megacisterna magna and BPC without hydrocephalus
- normal developmental outcome
• Isolated inferior vermian agenesis - variable prognosis
48. DWM – Prognosis
• Blake’s pouch cysts and megacisterna magna underwent
spontaneous resolution in utero in one third of cases and
over 90% of survivors without associated anomalies had
normal developmental outcome at 1–5 years.
• Isolated Dandy–Walker malformation and vermian hypoplasia
were associated with normal developmental outcome in only
50% of cases.
Gandolfi Coleoni et al., Ultrasound Obstet Gynecol; 2012;39; 625-631
Editor's Notes
As some of cases with ACC, individuals are asymptomatic. That’s why estimation of incidence is difficult
Similar number with NTD – more frequent CNS anomaly
2D is superior than 3D
However, there is no appropriate threshold, some authors recommend to measure size of CC.
Only if there is gross alterations, absence or presence of CC might be identified.
This means diagnostics of ACC are usually challenging.
There are
However, long-term studies indicate a progressive decrease in intellectual capacity throughout the years, most of them have difficulties in school
These measurements are said to increase reliability of identifying of DWM and differentiate vermian hypoplasia.
