1. The document discusses various congenital brain malformations including cephaloceles, holoprosencephaly, Dandy-Walker malformation, corpus callosum abnormalities, focal cortical dysplasias, tuberous sclerosis, lissencephaly, heterotopias, polymicrogyria, schizencephaly, and myelination disorders. 2. Key imaging features of these conditions are described including characteristics seen on MRI and CT such as ventricular abnormalities, cortical malformations, white matter changes, and patterns of abnormal myelination. 3. The document emphasizes differential diagnosis of similar appearing conditions and notes that serial imaging may be needed to distinguish delayed myelination from hypomyelination.

1. ImagIng of CongenItalImagIng of CongenItal
BraIn malformatIonsBraIn malformatIons

2. Embrology

5. NeurulationNeurulation

6. Ventral induction

7. MantlMantl
ee
ProliferationProliferation
MigrationMigration
OrganizationOrganization

8. Myelination
PNS CNS

9. Normal myelination
At birth 1 year6 month 2 years

13. CephalocelesCephaloceles
Cephalocoele refers to the outward herniation of
CNS contents through a defect in the cranium.
The vast majority are midline.
There are two main subtypes:
• encephalocoele: herniation of meninges and CSF
and brain parenchyma
• cranial meningocoele: herniation of meninges
and CSF only

15. Location
• occipital cephalocoele: most common, up to 75%
• parietal cephalocoele: up to 37%
• frontal cephalocoele/
fronto-ethmoidal cephalocoele: ~10%, this type is
most common in Asia
• petrous apex cephalocoele : rare
• intra sphenoidal cephalocoele: rare

18. Occipital Meningoencephalocele

19. Parietal Meningoencephalocele

20. Atretic occipital cephalocele

21. Chiari malformation type I

23. Posterior fossa decompression

26. Chiari malformation type III

28. Prosencephalon
Mesencephalon
Rhomboencephalon

30. Holoprosencephaly (HPE) is a rare congenital
brain malformation resulting from incomplete
separation of the two hemispheres.
Other entities include:
•syntelencephaly (or
middle interhemispheric variant (MIH))
•septo-optic dysplasia
•central incisor syndrome
•non-specific midline dysplasia
•frontonasal dysplasia
•agnathia-otocephaly

31. Classification of holoprosencephaly

32. Two selected images from an MRI of the brain demonstrate
fusion of the frontal horns of the lateral ventricles with
abnormal genu and rostrum of the corpus callosum and partial
fusion of the cingulate gyrus anteriorly. The anterior cerebral
artery is azygous and displaced anteriorly.

33. Axial non-contrast CT of the brain (with thick slice sagittal
reformat) demonstrates fused frontal lobes with absent anterior
part of the falx cerebri. There is also absence of the septum
pellucidum with fusion of the lateral ventricles with rudimentary
occipital and temporal horns, with a prominent dorsal cyst.

34. Non-contrast CT demonstrates a thin rim of cerebral tissue
anteriorly, without midline cleft. There is a large CSF density
space posteriorly. There is no evidence of falx cerebri. The
cerebellum is malformed with abnormal appearance of the
fourth ventricle. Brainstem is visualized.

35. Classification of holoprosencephaly

36. Syntelencephaly
MRI of this child demonstrates dysmorphic lateral ventricles with absent
septum pellucidum. Abnormal bridging grey matter is shown between the
hemispheres along the level of the body of the corpus callosum with
resultant thinning and irregular shape of the body of corpus callosum. The
genu and splenium of the corpus callosum are relatively enlarged.

37. Septo-optic dysplasia
Selected images from the MRI of a child demonstrates absence
of the septum pellucidum and an optic chiasm that is markedly
reduced in size. Also note the azygous anterior cerebral artery.

39. DWM DWV Persistent
Blake’s pouch
Mega cisterna
magna
Anterior membranous area anomaly Posterior membranous area anomaly
Retro-cerebellar cyst
Vermis Hypo-plastic
Rotated upwards
Hypo-plastic No or mild
hypoplasia
No or mild
hypoplasia
4th
ventricle Markedly dilated Dilated Dilated Normal
Posterior fossa Expanded Normal size Normal size Normal size
hydrocephalus 75 % of cases 25% of cases Present No

41. Dandy-Walker MalformationDandy-Walker Malformation

42. Dandy-Walker Variant

43. Mega Cistern Magna

44. Posterior Fossa Arachnoid Cyst

45. Corpus callosum genesis

46. Corpus callosum develpment

47. Corpus Callosum genesis
• Genu  body  splenium  rostrum

48. Corpus Callosum Agenesis
Absent cingulate gyrus
High riding 3rd ventricle
Parallel lateral ventricles
Colpocephaly
frontal horns small & pointed
Radiating medial surface gyri

49. Partial corpus Callosum Agenesis

50. • Associations
• Associated anomalies can be frequent and broad which
includes:
• non-aneuploidy syndrome
– Aicardi syndrome
– Apert syndrome
– Bickers Adams Edwards syndrome
– Coffin-Siris syndrome
– fetal alcohol syndrome
– Fryns syndrome
– Gorlin syndrome
– hydrolethalus syndrome
– Lowe syndrome
– Zellweger syndrome

51. Corpus Callosum Agenesis
Interhemispheric cyst

52. Corpus Callosum Agenesis
Pericallosal lipoma

56. Focal cortical dysplasia

57. Focal cortical dysplasias (FCD) represent a heterogeneous group
of disorders of cortical formation, which may demonstrate both
architectural and proliferative features. They are one of the
most common causes of epilepsy and can be associated with
hippocampal sclerosis and cortical glioneuronal neoplasms.
MRI findings:
•cortical thickening
•blurring of white matter–grey matter junction with abnormal
architecture of subcortical layer
•T2/FLAIR signal hyperintensity of white matter with or without the
transmantle sign
•T2/FLAIR signal hyperintensity of grey matter
•abnormal sulcal or gyral pattern
•segmental and/or lobar hypoplasia/atrophy

58. Also, each type of focal cortical dysplasia can exhibit more or less of
these features. The types below refer to the Blumcke classification
of focal cortical dysplasia (2011).
Type I
•location
o type Ia: usually confined to temporal lobes
if associated with hippocampal atrophy (as is common), it is
now classified as type IIIa in the Blumcke classification
o type Ib: more frequently seen outside of the temporal lobes
•structure
o blurring of grey/white matter junction (less marked than
with Type II FCD)
o prominent segmental or lobar atrophy/hypoplasia with loss
of regional white matter volume
•signal
o white matter
moderately increased T2/FLAIR signal
decreased T1 signal

59. Type II
•location
– commonly found in frontal lobes
– less likely to be in the temporal lobes compared to
Type I FCD
•structure
– abnormal gyri and sulci
– marked blurring of grey/white matter junction
– cortical thickening

60. • signal
– white matter
• moderately increased T2/FLAIR signal, typically brighter
than adjacent cortex
• decreased T1 signal
• focal signal abnormality may extend from cortex to
ventricle (transmantle sign): not seen in type I
– grey matter
• some increase in T2 signal
– despite increase in T2 signal, cortex remains hypointense to
much brighter adjacent white matter 4
– more evident than in type I

61. Type III
•Type III focal cortical dysplasia (according to the
Blumcke classification) as associated with
adjacent other abnormalities (e.g. IIIa
- hippocampal atrophy; IIIb - glioneural tumour
(e.g. DNET or ganglioneuroma); IIIc - vascular
malformation; IIId - early childhood insult (e.g.
gliosis)) and as such imaging appearances will be
dominated by the associated abnormality rather
than the dysplasia itself.

63. Focal cortical dysplasia

64. Focal cortical dysplasia

65. Tuberous sclerosis
• Cortical tubers.
• White matte lesions.
• Subependymal nodules.
• SGCA.

66. Neurological
•cortical/subcortical tubers: 50% are in the frontal lobe; high T2
and low T1 with only 10% of tubers showing enhancement;
frequently calcify after two years of age
•subependymal hamartomas
– 88% are associated with calcification, although
calcification absent in early childhood
– visible within the first six months of age
Also known as tuberous sclerosis complex or Bourneville
disease, is a neurocutaneous disorder (phakomatosis)
characterised by the development of multiple benign tumours of
the embryonic ectoderm (e.g. skin, eyes, and nervous system).

67. – variable signal, frequently high T1 and iso to high T2
– enhancement is variable and is not a useful feature in
distinguishing them from subependymal giant cell
astrocytomas (SGCA); only serial growth is reliable
•subependymal giant cell astrocytomas (SGCA)
– peak occurrence 8-18 years
– tend to be large and demonstrate growth 9-10
– tend to have intense enhancement
•white matter abnormalities
– variable appearance, with nodular, ill-defined, cystic and
band-like lesions seen
– radial bands are thought to be relatively specific for TS 12
•retinal phakomas

69. Type 1 lissencephaly
(agyria / pachygyria complex)

70. Type 2 (cobblestone) lissencephaly

71. Grey matter heterotopia

72. Heterotopias
• Normal neurons at abnormal sites
• Result from arrested neuronal migration from
periventricular germinal zone to the cortex.
• Heterotopias are isointense to normal gray
matter in all pulse sequences and do not
enhance on administration of IV contrast.

73. Hetertopia
• Isointense to grey matter on all pulse
sequences
 No enhancement.
 No associated mass effect.

75. Band hetertopia

76. Sucortical curvilinear nodular
hetertopia

77. Subcortical focal nodular heterotopia

78. Subependymal diffuse nodular
heterotopia

79. subependymal focal nodular
hetertopia

81. Polymicrogyria

82. Polymicrogyria

84. Schizencephaly
• CSF cleft , lined by grey matter, between the
ependymal surface of the ventricle to the pial
surface of the cerebral hemisphere.

85. Vascular theory of Schizencephaly

88. Myelination disorders

91. Dys-myelination Vs hypo-myelination

92. Dys-myelination
Hypo-
myelination

93. Delayed myelination Vs hypomyelination
• Repeat MRI after 6 months.
• Delayed myelination  myelination progression.
• Hypomyelination  no myelination progression.
• DD in these 2 conditions is quite different.

94. Delayed myelination
• Delayed myelination is a non specific finding
associated with global developmental delay.
Causes:
• Chromosomal abnormalities (e.g. trisomy 21).
• Metabolic disorders (e.g. phenylketonuria).
• Acquired causes (e.g. HIE).

95. Special features

96. DD of leukodystrophies