Error of Dorsal Induction Results in defect of closure of neural tube which leads to various anomalies like anencephaly, encephalocoele, spinal dysraphism and chiari malformations.

1. Fetal brain Usg.
Presented by: Dr Vrishit Saraswat

2. Topics for today
• Errors of Dorsal Induction
Acrania
Anencephaly
Cephalocoele
Encephalocoele
Spina Bifida

3. • Errors of Ventral Induction
mainly includes various
types of Holoprosencephaly ;i.e
1. Alobar
2. Semi-Lobar
3. Lobar

4. Error of Dorsal Induction
• Results in defect of closure of neural tube
which leads to various anomalies like
anencephaly, encephalocoele, spinal
dysraphism and chiari malformations.

5. Acrania
• Absence of cranial vault bones.
• Acrania can also occur with normal underlying
brain, so this term should not be used when
diagnosis is anencephaly or execncephaly.

7. Anencephaly
• Incidence : 1in 1000 births
Absent Cranial Vault Absent Cerebral Hemi Absent
diancephalon
Replaced by
amorphous
vascular-
neural mass
k/a area
Cerebro-
vasculosa

9. Brain superior to orbits is absent

10. Facial structures & orbits are present

11. • Anencephaly is always associated with
polyhydroamnios
• Outcome is fatal
• Termination of pregnancy is adviced at any
gestational age.

12. Cephalocoele & Encephalocoele
• Cephalocoele is herniation of intracranial
structures through a defect in cranial vault.
• Meningocoele – when meninges filled with
CSF fluid herniatethrough cranium & when
this meningocoele contains brain tissue, then
it is known as Encephalocoele.
• Encephalocoele herniate mostly through
midline and that too mostly in occipital
region(75%)

17. • Encephaocoele can herniate and extend in any
direction , i.e. in to nasal cavity , mouth,
sphenoid area, where their identifivation can
be difficult.
• Diffrential diagnosis
1. Cystic Hygroma
2.Hemangioma
3. Scalp Oedema/ cephalohematoma
4. Epidermal or Dermoid cyst.
• Prognosis is poor, mortality in upto 40% cases.

18. Meckel Gruber Syndrome
• Rare but lethal AR condition.
• The detection of either Cystic Kidney or
encephalocoele should lead to a search for
other components of this syndrome.
Encephalocoele
Cystic Renal Dysplasia
Polydactyly

19. Spina Bifida & Chiari II Malformation
• Spina bifida is classified as either
Open Closed
Covered with Skin Not covered with skin

20. • Virtually all fetuses with open variant have
cerebral changes typically of Chiari II
malformation .
• 80% of all diagnosed spina bifida are open
types
• Open spina bifida causes various changes in
head while closed variants, no matter how
big, will not cause any changes in fetal head.

21. • Head changes in Open Spina Bifida
1. Ventriculomegaly……….........
2. Lemon Sign……………………….
3. Banana Sign………………………

22. Closed Spina Bifida

23. Open Spina Bifida

24. B/L Frontal Bone Indentation

25. Banana Sign
Normal Cerebellum & CM
Banana shaped Cerebellum with
obliterated CM

26. Chiari Malformation II

27. MRI Chiari Malformation II

28. • The banana sign and effacement of cisterna
magna are due to fluid leakage allowing
cerebellum to compress into lower posterior
fossa.
• Cerebellum hemispheres wraps around lateral
aspect of brain stem and so asumes C-shape
{Banana Shape} in transcerebellar plane.
• These sonographic findings constitute Chiari II
malformation.

29. Errors of Ventral Induction
Holoprosencephaly
• Errors in induction of ventral portions of brain
and midline facial structures.
• Holoprosencephaly is a complex brain
malformation resulting from various degree of
incomplete clevage of Prosencephalon
• Most common anomaly of brain development
1 in 250 births.

30. • Prechordial Mesoderm (i.e mesoderm anterior to
notochord) which participates in midface
development ,which later induces forebrain
development.
• Due to any environmental or genetic insult this
above process fails causing Holoprosencephaly.
• From above pathogenesis , it is also clear that
severity of facial dysmorphism corelates with
cerebral anomaly

31. • Holoprosencephaly is a part of many different
syndromes, chromosomal & gene abnormality.
• Associations
1. DM type I
2. Vit A
3. Anti-convulsants
4. Alcohol
5. Velocardiofacial Syndrome
6. Smith Cemle-Opitz Syndrome
7. Tri 13 ***(70%)
8. Tri 18……………..

32. Types Of Holoprosencephaly
3 Types
Alobar
Cerebrum appears as single entity.
Semilobar
Partial attempt to form 2 hemispheres.
Lobar
2 hemispheres are formed but midline structure
is abnormal.

33. Usg Features
• Alobar and Semi-lobar types show absence of
falx and absent or non fused thalami.
• Alobar has 3 sub variants
1. Pan cake -Thin plate of cerebrum with large
dorsal Cyst
2. Cup - somewhat more tissue of cerebrum
with dorsal cyst
3. Ball – single mono-ventricle surrounded by
brain tissue of varied thickness.

34. • Lobar Holoprosencephaly – this subtype is
difficult to diagnose, b/c
both hemispheres are present
falx is present
• But midline structures like CC , Speti Pellucidi &
thalamus not found.
• Absence of Septi pellucidi will cause frontal Horn
of Lat. Ventricle to appear close to eachother
giving a square shaped and fused apperance.
• Diffrential Diagnosis- Septo-optic dysplasia

37. Lobar Holoprosencephaly

38. Alobar – Pancake variant

39. Alobar-Cup Variant

40. Alobar – Ball variant

41. • A new variant , also called as 4th type .
• Also known as middle interhemispheric form/
syntelemcephaly , in which seperation of
anterior and posterior parts of hemisphere
with partial formation of corpus callosum