description of fetal CNS anomalies

1. CNS ANOMALIES
Dr. Ahmed Mohamed Abbas, MD;
OB-GYN
Saturday 11-1 Assiut Police Hospital
Lecturer of OB-GYN, Faculty of
Medicine – Assiut University

2. Contents
• Normal Planes for CNS examination
• Common CNS anomalies
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Normal Planes for CNS examination
 Trans-ventricular plane
 Trans-thalamic plane
 Trans-cerebellar plane

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5. The Trans-ventricular plane

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The Trans-ventricular plane
 Is obtained by a transverse section at the level of the
Cavum septum pellucidum
 It shows; the lateral borders of the anterior horns, the
medial and lateral borders of the posterior horns of the
lateral ventricles, and the choroid plexus.
 It is the plane used for measurement of BPD, HC.

7. The Trans-ventricular plane

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10. The Trans-cerebellar Plane

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The Trans-cerebellar plane
 Allows the examination of the midbrain and posterior
fossa
 It is the plane used for measurement of the
Transcerebellar diameter (TCD) and Cisterna Magna
(CM)

12. The Trans-cerebellar Plane
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14. Contents
• Normal Planes for CNS examination
• Common CNS anomalies
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16. Structures that are noted in a basic ultrasound
examination of the fetal CNS
 Skull shape
 Lateral ventricles
 Cavum septum pellucidum
 Thalami & cerebral hemispheres
 Cerebellum
 Cisterna magna
 Spine
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17. Calipers are placed at the inner edge of the ventricle wall at its widest
part and aligned perpendicular to the long axis of the ventricle
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18. The depth of the CM measured between the cerebellar vermis and
the internal side of the occipital bone is usually 2–10 mm.
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19. Common CNS Anomalies
 Anencephaly.
 Hydrocephalus.
 Cephalocele.
 Iniencephaly.
 Arnold-Chiarii malformation.
 Dandy walker malformation.
 Corpus callosum agenesis.
 Holoprosencephaly.
 Hydrancephaly.
 Porencephaly.
 Arachnoid cyst.
 Choroid plexus cyst.
 Lissencephaly.
 Vein of Galen aneurysm. DR. AHMED ABBAS
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20. SKULL BONES
 Absent:
Anencephaly – Acrania
 Defect:
Cephalocele – Iniencephaly
 Abnormal shape:
Arnold-Chiari Malformation (SB)
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21. Acrania (Exencephaly)
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 Absent calvarium
 Lethal
 Not NTD

22. Anencephaly
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 Absent calvarium +
cerebral hemispheres
 Lethal
 NTD

23. Cephalocele
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 Defect calvarium + Herniation of meninges or cerebral hemispheres
 Lethal (40%) - Handicapped
 NTD

24. Occipital heamangioma
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25. Cystic Hygroma
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26. Scalp edema
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27. Iniencephaly (Apertus – Clasus)
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 Cervical SP + occipital
bone defect +
Retroflexed head
 Lethal
 NTD

28. Iniencephaly
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29. Arnold-Chiari Malformation (SB)
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 Only seen in open SB
 As a consequence of SB, herniation of posterior fossa
contents through the foramen magnum
1. Frontal bossing: Lemon sign
2. Obliteration of the CM and splaying of the cerebellum:
Banana sign
3. Ventriculomegaly: due to obstruction of the upper
spinal canal.

30. Arnold-Chiari Malformation (SB)
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31. Arnold-Chiari Malformation (SB)
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32. Arnold-Chiari Malformation (SB)
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33. Spina Bifida
 Meningocele (the sac contains meninges and CSF).
 Meningomyelocele (the sac contains elements of spinal
cord &or nerves)
 Myeloschisis (the neural tube defect is not covered and
open to exterior).
 Craniorachischisis (both cranial & spinal neural elements
are exposed).
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34. Ventricles
Enlarged lateral ventricles
 Ventriculomegaly
 Hydrocephalus
 Hydranencephaly
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35. Ventriculomegaly
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• Obstructive hydrocephalus: (the
most common type).
• Chromosomal and genetic
• Congenital infection (TORCH).
• Spina bifida (Arnold Chiari
malformation).
• Dandy-Walker malformation
• Overproduction of CSF (choroid
plexus papilloma)

36. Ventriculomegaly (Not lethal
– Not NTD)
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37. Hemimegalencephaly
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Asymmetry of the cerebral hemispheres with dilatation of the lateral
ventricle on the affected side and a shift of the midline.

38. Cavum septum pellucidum
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Presence of 3 lines in the middle line: Ant. horn medial wall on either side and
Falx cerebri in middle

39. Corpus callosum agenesis (Coplpocephaly)
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40. Corpus callosum agenesis
 Poor prognosis with associated anomalies
 50-100% of isolated cases have normal neurologic
development at 3-11 years
 Progressive decline in intellect over the years
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41. Cavum septum pellucidum agenesis
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42. D.D.
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43. Thalami & Cerebral hemispheres
HOLOPROSENCEPHALY
Incomplete cleavage of the forebrain
 Alobar, the most severe, in which there is complete absence of the
interhemispheric fissure leading to a single ventricle, fused
thalami .
 Semi-lobar, in which the two cerebral hemispheres are partially
separated posteriorly, but there remains a single ventricular cavity.
 Lobar, where the interhemispheric fissure may be well developed
anteriorly and posteriorly, but there still exists a degree of fusion
of some structures, such as the lateral ventricles.
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44. HOLOPROSENCEPHALY
 Monoventricle (alobar and semi-lobar types) or
partial segmentation of the ventricles (lobar type).
 Fused thalami.
 No midline brain structures (falx cerebri, cavum
septi pellucidi, corpus callosum).
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45. HOLOPROSENCEPHALY (lethal – Not
NTD)
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46. HOLOPROSENCEPHALY (lethal – Not
NTD)
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47. Destructive Cerebral lesions
 Hydranencephaly may result from marked vascular
occlusion in the distribution of supraclinoid portion of
the internal carotid arteries.
 Porencephaly may be caused by infarction of the
cerebral arteries or hemorrhage into the brain
parenchyma.
 Schizencephaly may be due to bilateral occlusion of
the middle cerebral arteries.
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48. Hydranencephaly
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49. Porencephaly
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50. Schizencephaly
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51. Cerebellum & Posterior fossa
 Dandy-Walker malformation
Absent cerebellar vermis.
Cystic dilation of the fourth ventricle.
Enlargement of the cisterna magna
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52. Cerebellum & Posterior fossa
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53. Open 4th Ventricle D.D.
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54. Choroid Plexus Cyst
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• In more than 90% of
cases they resolve by 26
weeks
•Single or multiple cystic
areas in one or both
choroid plexuses.
• No pathological
significance.
• Associated with an
increased risk for trisomy
18, 21.

55. Arachnoid Cyst
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• Fluid-filled cyst
contained within the
arachnoid space
• Not associated with loss
of brain tissue
• Spontaneous remission

56. Aneurysm of vein of Gallen
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57. Lissencephaly
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58. Lissencephaly
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59. Microcephaly
Microcephaly with associated malformations
 Genetic: Down syndrome, trisomy 13 , trisomy 18
 Congenital infections: TORCH
 Exposure to drugs or chemical agents
Microcephaly without associated malformations:
 Genetic.
 Environmental: Prenatal exposure to radiation, Fetal starvation,
Hypoxia or perinatal trauma
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60. Conclusions
In a low risk pregnancy at mid-gestation, if:
 The trans-ventricular plane and the trans-cerebellar
plane are satisfactorily obtained,
 The head measurements (HC , BPD) are within normal
limits for gestational age,
 The atrial width is less than 10.0 mm
 The cisterna magna width is between 2–10 mm,
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Fetal CNS is
Normal

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