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.
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.
6.
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
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%)
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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………………………
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
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