This document discusses the normal development of the brain from embryology through maturation. It then reviews various congenital brain lesions that can occur due to disruptions during different stages of development including dorsal induction, ventral induction, neuronal proliferation and migration, and myelination. Specific lesions discussed include holoprosencephaly, septo-optic dysplasia, schizencephaly, corpus callosum agenesis, arachnoid cysts, and more. Imaging findings for each condition are also provided.

1. Imaging of Congenital Brain Lesions
Dr. Milan Silwal
Resident, MDRD, Radiology

2. Notochord induces overlying ectoderm to
differentiate into neuroectoderm and form
neural plate.
Neural plate gives rise to neural tube and
neural crest cells.
Notochord becomes nucleus pulposus of
intervertebral disc in adults.
Alar plate (dorsal): sensory
Basal plate (ventral): motor
Embryology
Fig. Formation and closure of the neural
tube. The neural plate (red) forms, folds,
and fuses in the midline. The neural and
cutaneous ectoderm then separate.
Notochord (green) and neural crest (blue)

3. • Telencephalon – cerebral hemispheres
• Diencephalon – thalamus, epithalamus,
hypothalamus
• Mesencephalon – midbrain
• Metencephalon – cerebellum, pons
• Myelencephalon – medulla
 Neuroectoderm—CNS neurons,
ependymal cells, oligodendroglia,
astrocytes.
 Neural crest—PNS neurons, Schwann
cells.
 Mesoderm —Microglia (like
Macrophages)
Fig. The neural tube
closes in a
bidirectional zipper-
like manner, starting in
the middle and
proceeding toward
both ends.
Fig. Development of
primary vesicles. The
prosencephalon (green)
gives rise to the forebrain,
the mesencephalon
(purple) to the midbrain,
and the rhombencephalon
(light blue) to the
hindbrain.
Fig. prosencephalon gives rise
to telencephalon (green) and
diencephalon (red).
Mesencephalon (purple)
elongates while
rhombencephalon gives rise to
metencephalon (yellow) and
myelencephalon (light blue).

4. Stages of CNS development
 Dorsal induction (3 to 4 weeks of gestation)
 Ventral induction (5 to 8 weeks of gestation)
 Neuronal proliferation/differentiation/histogenesis (8 to 18
weeks of gestation), migration (12 to 22 weeks of gestation)
 Myelination (5 months fetal age to years postnatal age).
 The cortex goes through stages of cell proliferation, cell
migration, and cortical organization in utero at 2 to 4
months, 3 to 5 months, and at 5 months to 2 years post
gestation, respectively

5. Myelination
• White matter when myelinated, is bright on a T1-weighted image
(T1WI) and dark on a T2WI
• Has differentT1 and T2 myelination milestones
6 months
Post natal
• Brain stem
• Internal capsules and optic radiation
1 year
• Forceps major and minor
1 ½ years
• Gyral convolutions as in adults

6. The progression of myelination is predictable and abides by a few
simple general rules; myelination progresses from:
• central to peripheral
• caudal to rostral
• dorsal to ventral
• sensory then motor

8. Dorsal induction (4 wks)
Neural plate forms the neural tube, which
eventually gives rise to the spinal cord and
brain. These inductive events are referred to as
dorsal induction.
Primary Neurulation: formation of the neural
tube from approximately the L 1 or L2 level,
which corresponds to the caudal end of the
notochord upward to the cranial end of the
embryo
Secondary Neurulation - formation of neural
tube below the caudal end of notochord.

9. Ventral Induction (5-10 weeks)
• Ventral induction refers to the inductive events occurring ventrally in the
rostral end of the embryo, resulting in the formation of the face and brain.
Holoprosencephaly
Septo-optic dysplasia
Hypoplasia/aplasia of the cerebellar hemispheres
Hypoplasia/aplasia of the vermis cerebelli
including Joubert syndrome
Dandy-Walker syndrome and Dandy- Walker
variant
Cerebral hemihypoplasia/aplasia
Pituitary anomalies
Lobar hypoplasia/aplasia
Craniosynostosis

10. Neuronal Proliferation and Dysgenesis
Disorders:
Macroencephaly
Microencephaly
Neurocutaneous syndromes
 Aqueductal stenosis

11. Neuronal Migration
Cortical neurons form in embryonic Germinal matrix (adjacent
to lateral ventricles); migrate centrifugally out to surface of
brain to form cerebral cortex.
Disorders:
Lissencephaly
Pachygyria
Polymicrogyria
Heterotopia
Schizencephaly

12. Arachnoid Cyst
 Most common congenital cystic abnormality in the
brain
 Due to congenital splitting of arachnoid membrane.
 Commonest locations
• Middle (50-60%) and posterior cranial fossae
• Suprasellar region and behind third ventricle
 Intraventricular cysts are rare but favor lateral and
third ventricles.
 Usually unilocular; septated cysts may occur.
 Posterior fossa or quadrigeminal cistern cysts- mass
effect: obstructive hydrocephalus; hypoplasia of
cerebral tissue.

13. Imaging
CT
 CSF density HU 0 to +20
 Effaces adjacent sulci
 May or may not remodel
bone
 No enhancement
 D/D: Dilated
subarachnoid space ( if
intrathecal contrast given
it will fill the arachnoid
space first and then fills
the cyst) arachnoid cyst
shows delayed
enhancement
 No calcification, fat
MRI
 Extraaxial mass
 CSF signal intensity
 FLAIR: dark
 DWI: dark
Fig. Arachnoid cyst (arrows)
involving pineal region and
quadrigeminal cistern and
compressing back of third
ventricle, producing marked
hydrocephalus.

14. Meningoencephalocele
• Chiari III malformations - occipital region.
• Also a/w holoprosencephaly and aqueductal stenosis,
agenesis of the corpus callosum, colobomas, and cleft
lips.
• occipital, parietal or frontal meningoencepahaloceles
are diagnosed clinically
• nasofrontal or sphenoethmoidal encephaloceles may
be clinically occult.
• MR: bony defect with continuity of brain parenchyma
below the defect
• The protruded brain can have heterotopic or
disorganized brain tissue.

15. Hydranencephaly
• Result of major destructive process – prenatal
or perinatal: massive intracerebral cavitation.
• Affects anterior parts of hemisphere,
suggesting major involvement of areas
supplied by ICA.
• Falx present: distinguish from severe
holoprosencephaly.
• PCA territory preserved (posterior part of
temporal lobe, occipital lobe, thalamus and
infratentorial structure).
• D/D: Gross hydrocephalus (usually affects
occipital region, with preserved thin rim of
cortical tissue; infant’s head enlarged).
Fig. Autopsy case of hydranencephaly demonstrates
striking transillumination indicating that most of the
cranium is water-filled.
Fig. Hydranencephaly

16. Holoprocencephaly (HPE)
single ("holo") ventricle involving the embryonic prosencephalon ("pros") of the brain ("encephaly")
• fetal forebrain fails to bifurcate into two
hemispheres.
• As ventral induction is closely related to
facial development, HPE is also associated
with a number of characteristic facial
anomalies.
• 3 main subtypes, in order of decreasing
severity are:
1. Alobar Holoprosencephaly
2. Semilobar Holoprosencephaly
3. Lobar Holoprosencephaly

17. Alobar holoprosencephaly
 Monoventricle
 Fused thalami
 Absent corpus callosum, falx, sepum pellucidum and
olfactory bulbs
 Middle and anterior cerebral arteries may be replaced by
tangled branches of internal carotid and basilar vessels;
or azygous ACA
 Severe facial malformations – hypotelorism, cyclopia,
anophthalmia, cleft lip/palate
Fig. NECT scan shows holoprosencephaly. Small rim of cortex
surrounds "horseshoe" central monoventricle. Thalami are
fused; More cephalad scan in the same patient shows a large
dorsal cyst/central monoventricle with thin rim of surrounding
brain. No falx or interhemispheric fissure is present.

18. Semilobar holoprosencephaly
• Basic structure of the cerebral lobes present but fused most
commonly anteriorly
• Absence of septum pellucidum
• Monoventricle with partially developed occipital and
temporal horns
• Rudimentary falx cerebri: absent anteriorly
• Incompletely formed interhemispheric fissure
• Partial or complete fusion of the thalami
• Absent olfactory tracts and bulbs
• Agenesis or hypoplasia of the corpus callosum

19. Lobar holoprosencephaly
• cerebral hemispheres are present.
• fusion of the frontal horns of the lateral ventricles.
• wide communication of this fused segment with the
third ventricles
• fusion of the fornices
• absence of septum pellucidum.
• normal or hypoplasia of the corpus callosum.
• Anterior cerebral artery may be displaced anteriorly
to lie directly underneath the frontal bones (snake
under the skull sign)

20. Septo-optic Dysplasia (De Morsier Syndrome)
 A minor form of holoprosencephaly
 Septum pellucidum is either absent (64%) or partially
absent (36%), causing a squared-off appearance to the
frontal horns of the lateral ventricles
 Anterior optic pathways hypoplasia (Small hypoplastic
optic nerves and a small optic chiasm – poor vision and
nystagmus
 Hormonal abnormalities (60%) - diminished levels of
growth hormone related to the hypothalamo-pituitary
axis abnormality.
 Schizencephaly and neuronal migrational disorders may
accompany septo-optic dysplasia in 50% of cases.
Fig. Septo-optic dysplasia. Coronal T1-weighted image
shows absence of the septum pellucidum with small
optic tracts (arrows) – squaring of frontal horns.

21. Porencephaly
disorder that results in cystic
degeneration
and encephalomalacia and the
formation of porencephalic cysts
 Congenital type:
– Localized ageneis of cortical mantle
resulting in formation of a cavity or a
lateral slit through which lateral
ventricle communicates with
convexity.
– Lined by ependyma and laterally by
a thin pia-arachnoid layer.
 Acquired type (false porencephaly):
– Secondary to any destructive
process: trauma or infarction.

22. Schizencephaly
clefts, often bilateral extend from
ventricles to convexity of operculoinsular
reigons.
Heterotopias with ectopic gray matter
lining the cleft.
The lips of the cleft may be apposed
(closed-lipped) or gaping (open lipped).
Associated with focal cortical dysplasia
(polymicrogyria), grey matter heterotopias,
agenesis of the septum pellucidum (80% to
90%), and pachygyria.

23. Corpus callosum agenesis
Partial agenesis:
• usually involves the posterior
part and anterior part may
remain normal.
Fig. Normal corpus callosum
Fig. partial agenesis of corpus callosum

24. Complete agenesis:
– Complete corpus callosum and cingulate gyrus
agenesis
High riding third ventricle above insertion of
absent corpus callosum.
Sunray appearance – radial configuration of
medial cerebral sulci extending through absent
callosal body region.
Probst’s bundles: longitudinal symmetrical
bundles along medial surface of hemispheres.
Frontal horns and bodies laterally displaced
and smaller. (Moose head appearance on
coronal image)
Atria and occipital horn: large and rounded
Fig. Probst bundle in agenesis of corpus callosum. Coronal T1-
weighted image shows the Probst bundle (P) causing lateral
displacement of the frontal horns of the lateral ventricles.
Cingulate gyri (C) are malformed. B, The shape of the ventricles
suggests agenesis of the corpus callosum with colpocephaly (c)
Probst bundles account for the inward bowing of the lateral
wall of the lateral ventricle. Evagination of the cingulate sulcus
(arrows) accounts for the high signal intensity medial to the
lateral ventricles

25. Hypoplastic fornix;
hypoplastic hypothalamus
Absent septum pellucidum

26. ABNORMALITIES OF NEURONAL MIGRATION
Lissencephaly (agyria): smooth brain
• Most severe form of migrational defect –
absence of sulci and convolutions in the
cortex. {Normal before 7th month of fetal
life.}
• Localized or generalized
• Characteristic nodule of calcification in the
septum pellucidum near foramen of Monro
– seen of X ray or CT

27. Cobblestone lissencephaly
or cobblestone cortical malformation (CCM) - type 2
• distinct from "classic” lissencephaly (type 1).
• Overmigration of neuroblasts => an extracortical layer
of aberrant gray matter nodules—the "cobblestones"—
on the brain surfaces.
• Uneven, nodular, "pebbly“ brain surface that resembles
a cobblestone street.
• Associated with ocular anomalies and occur as a part of
a congenital muscular dystrophy (CMD) syndrome.
Fig. axial CT showing Cobblestone lissencephaly
Fig. Cobblestone

28. Pachygyria (incomplete lissencephaly) – thick gyri
Convolutions and cortex: abnormally
wide and thick.
Congenital abnormality that occurs
relatively late in gestation, at 12 to 24
weeks, because of neuroblastic migration
not proceeding completely to the
superficial layers of the cortex
Fig. Pachygyria. Bilateral symmetric pachygyric
brain is seen in the parietal lobes on this FLAIR
image. The white matter does not arborize in
these regions.

29. Polymicrogyria
Small, disorganized cortical convolutions usually in
the cortex subjacent to the sylvian fissures.
The cortex appears thickened. The white matter
thickness is normal.

30. Pachygyria
• Short broad flat gyri
• Thick cortex (8mm)
• Less bumpier
Polymicrogyria
• Multiple small undulating gyri
• Less thick cortex (5-7 mm)
• More bumpier
• a/w anomalous venous drainage

31. Heterotopias
Gray matter that is located in the
wrong place
Seizures, weakness, spasticity,
hyperreflexia, or developmental delay
2 varieties: nodular and band types.
Islands of T2 high signal intensity and
nonenhancing tissue suggestive of
gray matter in a white matter location
in subcortical, subependymal/
periventricular region.
Fig. Subcortical heterotopia. Axial T2-weighted
image delineates gray matter signal intensity
within the centrum semiovale and corona radiata
on the left side (arrowheads). Note the distortion
of the left lateral ventricle at the interface with
heterotopic gray matter.

32. Megalencephaly
 Enlargement of all or part of the cerebral hemisphere.
 Seizures, hemiplegia, developmental delay, and abnormal skull
configuration
 Often polymicrogyria (associated with increased hemispheric
size) or agyria (associated with less severe hemispheric
enlargement) on the affected side.
 MR demonstrates a distorted, thickened cortex with
ipsilateral ventricular dilation. This unique feature, that of
ventricular dilation on the side of the enlarged hemisphere,
separates congenital hemimegalencephaly from other
infiltrative lesions.
 Heterotopias, Myelination abnormalities

33. Intra-cranial Lipoma
 Most commonly occur in midline.
 Above Normal corpus callosum or 40% associated partial or
complete agenesis.
 Other common locations: pineal and suprasellar regions.
 Do not cause mass effect, and vessels course through these
lesions unperturbed.
 X ray: marginal calcification of lipoma; larger lesions –
increased lucency between the brackets.
 Fatty density with typical location – identified in CT/MRI.
 Adjacent calcification best seen in CT (minimal or absent in
smaller lesions.)

34. Fig. Lipoma of the Corpus Callosum. Sagittal midline T1 WI (A) reveals a hyperintense
midline lipoma curving around the corpus callosum (arrows). When fat saturation is
applied (B), the high signal disappears, paralleling the signal loss of suboccipital fat
and confirming the fatty nature of the lesion (arrows). Note the subtle associated
hypogenesis of the splenium of the corpus callosum(arrowhead).
A B

35. Dandy walker Malformations/continuum
Components:
Complete or partial agenesis of
the vermis
Cystic dilation of the 4th ventricle
Enlarged posterior fossa, with
upward displacement of the
transverse sinuses, tentorium, and
torcula-lambdoid inversion
(elevation of the torcular above
the lambdoid suture)
INFRATENTORIAL ABNORMALITIES

36. Cerebellum
– Hypolastic vermis with counterclockwise
rotated
– Lies behind quadrigeminal plate
– Abnormal or dysplastic foliation
– Rarely completely absent vermis
– Hypoplastic and splayed cerebellar
hemispheres against petrous bones
Brain stem
– Thin brain stem due to hypoplastic pons
– Butterfly midbrain; non decussation of
cerebellar peduncles

37. Classic Dandy Walker malformation (DWM)
Enlarged posterior fossa
Thinning and scalloping of occipital bone and petrous
bone
Straight sinus and torcula are elevated above lambdoid
suture- torcula lambdoid inversion
Absent falx cerebelli

38. Associations
CNS malformations
Corpus callosum agenesis-
25%
Heteropias, schizencephaly
Gyral anomalies
Cephalocele
Spina bifida
Brainstem dysgenesis
Corpus callosum dysgenesis
+/-interhemispheric dorsal
cyst
Non CNS Malformations
Cystic kidneys
Cong heart ds
Facial cleft
Polydactyly

39. Dandy Walker Variants
Less severe forms of the Dandy-Walker complex - better
development of the vermis and the fourth ventricle; posterior
fossa cyst is smaller. Neither significant enlargement of the
posterior fossa nor torcular-lambdoid inversion is present
Although the 4th ventricle is enlarged not large enough to produce
enlargement of posterior fossa.

40. Dandy Walker Variants…
• Vermian Hypoplasia (VH)
– Old term = Dandy-Walker variant
– Superior rotation of vermis
– PF normal size
• Blake Pouch Cyst (BPC)
– Ependyma-lined protrusion from fourth ventricle
– Normal size and morphology of vermis
– Elevated vermis

41. • Mega Cisterna Magna (MCM)
– Enlarged retrocerebellar CSF (> 10 mm)
– No mass effect on vermis or cerebellum
– Normal vermis
– Fluid crossed by veins, falx cerebelli
– May scallop, remodel occiput**
** All categories in DWC may "scallop" inner
occipital bone
• Arachnoid Cyst
– Not truly in the Dandy-Walker Continuum
– Cerebellopontine angle > retrovermian
– No communication with 4th ventricle
– No crossing veins or falx cerebelli
– Causes mass effect

42. Joubert syndrome
 Autosomal recessive disorder, dysgenetic vermis that
appears split/segmented & dysorganized.
 Dysgenesis of inferior portion of brain stem
 Fourth ventricle roof appear superiorly convex in sagittal
images.
 The imaging findings in Joubert syndrome are virtually
pathognomonic. Molar tooth appearance results from a
lack of normal decussation of superior cerebellar
peduncular fiber tracts which in turn leads to
enlargement of the peduncles, which also follow a more
horizontal course.

43. Joubert syndrome…
Hypoplasia of the vermis brings the two cerebellar
hemispheres in virtual contact with each other
and a nodulus is not seen => “bat wing”
appearance the fourth ventricle develops a from
middle cerebellar peduncle, superior cerebellar
peduncle, and pyramidal decussation
maldevelopment.
The absence of crossing fibers => reduction in the
anteroposterior diameter of the midbrain and
deepening of the interpeduncular cistern

44. Rhombencephalosynapsis
rare entity, cerebellar hemispheric
separation is lost and there is fusion
across midline of the cerebellum.
Fusion/apposition of dentate nuclei &
variable fusion of colliculi
absence of the anterior vermis, fusion
of the dentate nuclei and middle
cerebellar peduncles, and a deficiency
of the posterior vermis.
Agenesis of the septum pellucidum
may coexist.

45. Chiari Malformations
(Segmentation Defects)
Chiari I Malformation
Inferiorly displaced "pointed" tonsils with "crowded"
posterior fossa, effaced retrocerebellar CSF spaces at
foramen magnum/upper cervical level
With/without varying degrees of elongation of medulla
oblongata and fourth ventricle.

46. CT Findings
 Bone CT
- Often normal; abnormal cases → short clivus, CVJ
segmentation/fusion anomalies
MR Findings
 T1WI : Pointed (not rounded) tonsils ≥ 5 mm below foramen magnum
– "Tight" foramen magnum with small/absent cisterns
– 4th ventricle elongation, hindbrain anomalies
 T2WI
- Oblique tonsillar folia (sergeant's stripes like)

47. Chiari 1.5
• Cerebellar tonsillar herniation complicated by other
abnormalities (e.g., caudally displaced brainstem and fourth
ventricle and/or cervicomedullary "kink").
• Differs from classic CM1 in that caudal descent of the
brainstem is present, and tonsillar herniation is typically more
severe.
• Differs from CM2, as myelomeningocele is absent.

48. Chiari II Malformation
 Virtually always with a neural tube closure defect (NTD),
usually lumbar myelomenigocele
 NECT: Crowded posterior fossa, widened tentorial incisura,
tectal beaking, and inferior vermian displacement
Bone CT: Small PF, Low-lying tentorium/torcular inserts near
foramen magnum
Large, funnel-shaped foramen magnum with "notched"
opisthion, "Scalloped" posterior petrous pyramids, clivus
 Posterior C1 arch anomalies (66%), enlarged cervical canal
 Lacunar skull: Focal calvarial thinning with scooped-out
appearance
 Mostly resolved by 6 months, some scalloping of inner table
often persists into adulthood
Fig. fetus with Chiari 2 malformation (→)
with the spinal cord tethered into a
myelomeningocele (=>).

49. MR Findings
T1WI: Cascade of cerebellum/brainstem downward displacement
– Uvula/nodulus/pyramid of vermis → sclerotic peg
– Cervicomedullary kink (70%)
– Towering cerebellum → compresses midbrain, associated beaked tectum
– 4th ventricle elongated with no posterior point
 Open spinal dysraphism, MMC ~ 100% (lumbar > >cervical)
 Hydrosyringomyelia (20-90%)
T2WI: Hyperintensity, associated with posterior fossa cysts.

51. Prenatal USG scan
 Grayscale ultrasound
Fetal obstetrical ultrasound (US) pivotal for early
diagnosis
– MMC may be identified as early as 10 weeks
– Characteristic brain findings (lemon and banana
signs) seen as early as 12 weeks
Lemon sign
Banana sign
Effacement of cisterna magna
Lumbar menigomyelocele

52. Chiari III Malformation
 CT Findings :
 NECT
-Midline posterior cephalocele containing cerebellum
-Small posterior cranial fossa ― scalloped clivus, lacunar skull
 Bone CT
- Opisthion, upper cervical osseous dysraphic bone defect
 CTA
- Basilar artery "pulled" into defect along with brainstem into
cephalocele sac

53. MR Findings
 T1WI
-High cervical cephalocele sac containing meninges and cerebellum ― brainstem,
upper cervical cord
- Cisterns, 4th ventricle, dural sinuses may extend into cephalocele (50%)
 T2WI
-Tissues in cephalocele sac may be bright (gliosis), strandlike (necrotic), or
hypointense (hemorrhagic)

54. Chiari IV malformation
– Severe cerebellar hypoplasia without displacement of the
cerebellum through the foramen magnum
Chiari V malformation
– Absent cerebellum
– Herniation of the occipital lobe through the foramen magnum
 Chiari 0 malformation
- syrinx without cerebellar tonsillar, or brain stem descent

55. PHAKOMATOSES
Neurofibromatosis
Sturge Weber Syndrome
Tuberous Sclerosis Complex
Von Hippel Lindau disease
Ataxia Telangiectasia
L’hermitte Duclos disease
Meningiomatosis
Basal cell nevus syndrome
Encephalocraniocutaneous lipomatosis
Neurocutaneous melanosis
Aicardi Syndrome
Li-Fraumeni syndrome
Schanomatosis
Group of diseases of having in common lesions of skin, retina and nervous system.
Also known as neuroectodermal dysplasias

56. Neurofibromatosis (NF)
NF1 (von Recklinghausen disease)
Mutation in NF1 gene : negative regulator of RAS on
chromosome 17.
100% penetrance, variable expression. At least 2 of
the following
o ≥ 6 Cafe-au-lait spots
o Axillary and inguinal frecklings.
o Lisch’s nodules (pigmented iris hamartomas)
o ≥ 2 neurofibromas or ≥1 plexiform neurofibromas
o Optic pathway glioma
o Distinctive bone lesions (pseudoarthroses, cortical thinning
and sphenoid wing dysplasia)
o Positive family history
Fig. Extensive facial
plexiform
neurofibroma
Fig. multiple café au lait
spots (L) and cutaneous
neurofibromas in NF1.
Fig. Multiple Lisch nodules in a
patient with NF1. Multiple café
au lait spots (L) and cutaneous
neurofibromas (R)

57. NF 1 imaging
Scalp/Skull, Meninges, and Orbit
Dermal neurofibromas
Solitary/multifocal scalp nodules
Increases with age
Localized, well-circumscribed
Plexiform neurofibroma
Pathognomonic of NF1 (30-50% of cases)
Large, bulky infiltrative lesions
Scalp, face/neck, spine
Orbit lesions may extend into cavernous sinus
Sphenoid wing dysplasia
Hypoplasia → enlarged orbital fissure
Enlarged middle fossa ± arachnoid cyst
Temporal lobe may protrude into orbit
Dural ectasia
Tortuous optic nerve sheath
Patulous Meckel caves
Enlarged IACs
Brain
Hyperintense T2/FLAIR WM foci
Wax in first decade, then wane
Rare in adults
Astrocytomas
Most common: pilocytic
Optic pathway, hypothalamus > brainstem
Malignant astrocytoma (anaplastic astrocytoma,
glioblastoma multiforme) less common
Arteries
Progressive ICA stenosis → moyamoya
Fusiform ectasias, arteriovenous fistulas
Vertebral > carotid

58. Fig. NF1 "Unidentified Bright Objects." Axial
FLAIR image demonstrates patchy areas of
T2 hyperintensity (arrows).
Fig. Plexiform neurofibroma involving
cervical nerve roots is depicted in the
graphic (L) and on a coronal STIR scan (R).
Fig. 3D bone CT in a patient with NF1 and sphenoid
dysplasia shows enlarged left orbit and widened superior
orbital fissure
Fig. Sagittal (L) and coronal (R) T2WIs show NF1 with
extreme dural ectasia causing posterior vertebral
scalloping and extensive meningoceles

59. Neurofibromatosis 2
o Mutation in Chr-22
o B/L acoustic schwannoma, Meningioma, ependymoma, Juvenile cataracts
Definite NF2
• Bilateral vestibular schwannomas (VSs)
• First-degree relative with NF2 and unilateral VS diagnosed before 30 years of age
• Or first-degree relative with NF2 and 2 of the following
Meningioma
Glioma
Schwannoma
Juvenile posterior subcapsular lenticular opacities or cataracts

60. Neurofibromatosis Type 2, Cranial Nerve schwannoma, Axial fat saturation Tl WI (A) and coronal T2WI (B)
reveal numerous cranial nerve and spinal cord tumors. The vestibular or acoustic schwannomas (white
arrows) often bilateral in NF-2, and are a hallmark of this disorder. Numerous additional cranial nerve
schwannomas are often present and must be carefully looked for; as this will help confirm the diagnosis1is of
NF-2. Fifth cranial nerve schwannomas expand the cavernous sinuses (open arrows in A). Intramedullary glial
cord tumors(white arrowheads in B) are frequent, but may be slow growing and asymptomatic.

61. Neurofibromatosis type 1 Neurofibromatosis type 2
Common (90% of all neurofibromatosis cases)
Chromosome 17 mutations
Almost always diagnosed by age 10
Cutaneous/eye lesions common (> 95%)
oCafé au lait spots
oLisch nodules
oCutaneous neurofibromas (often multiple)
oPlexiform neurofibromas (pathognomonic)
CNS lesions less common (15-20%)
oT2/FLAIR hyperintensities (myelin vacuolization;
lesions wax, then wane)
oAstrocytomas (optic pathway gliomas—usually
pilocytic—other gliomas)
oSphenoid wing, dural dysplasias
oMoyamoya
oNeurofibromas of spinal nerve roots
Much less common (10% of all neurofibromatosis
cases)
Chromosome 22 mutations
Usually diagnosed in second to fourth decades
Cutaneous, eye lesions less prominent
oMild/few café au lait spots
oJuvenile subcapsular opacities
CNS lesions in 100%
oBilateral vestibular schwannomas (almost all)
oNonvestibular schwannomas (50%)
oMeningiomas (50%)
oCord ependymomas (often multiple)
oSchwannomas of spinal nerve roots

62. Von Hippel-Lindau disease (Retinocerebellar angiomatosis)
Rare, familial disease (Autosomal dominant)
Multiple hemangioblastomas in the retina and
cerebellum; also in spinal cord but rarely in
cerebrum prone to sudden spontaneous
hemorrhage.
Associated with visceral tumors and cysts (renal
cell carcinoma, pheochromocytoma, renal, hepatic
and pancreatic cysts, and angiomas of the liver
and kidney).
Fig. HBs in VHL. Spinal cord tumor has
associated cyst causing myelopathy;
Smaller cerebellar HB.

64. Fig. Von Hippel-Lindau Syndrome. T2-weighted images (Left and right ) and postcontrast TI -weighted images
(middle images) The large cystic lesion(*) with a contrast enhancing mural nodule is classic for cerebellar
hemangioblastoma. Often a vascular flow void may be noted associated with the nodule. The syndrome of Von
Hippel-Lindau also includes retinal angiomas; spinal hemangioblastoma.

65. Sturge Weber Syndrome
(encephalotrigeminal angiomatosis)
Nevus flammeus (Port wine stain) on face
and scalp in trigeminal distribution.
Leptomeningeal angiomatosis (pial
angiomas predominantly in parieto-occipital
area on ipsilateral side).
Cortical gliosis and calcification.
– Xray end on calcification: classic Tram line
appearance.
Ipsilateral choroid plexus larger.
Fig. SWS shows pial angiomatosis , deep medullary
collaterals, enlarged choroid plexus, and atrophy of the
right cerebral hemisphere.
Fig. classic CN V₁-V₂ nevus flammeus
characteristic of SWS

66. Fig. NECT in an 8y girl with SWS shows striking cortical atrophy and
extensive calcifications in the cortex and subcortical WM throughout most
of the left cerebral hemisphere. More cephalad NECT in the same patient
shows the typical serpentine gyral calcifications.
Fig. Axial T2WI - Extensive curvilinear hypointensity in the GMWM
interface. Coronal T2* GRE - "blooming" of the extensive
cortical/subcortical calcifications
Fig. T1 C+ FS shows serpentine enhancement covering gyri, filling sulci; enlargement,
enhancement of ipsilateral choroid plexus. Coronal T1 C+ shows pial angioma and enlarged
choroid plexus

67. Tuberous Sclerosis (Bourneville disease or Epiloia)
Complex autosomal dominant disorder.
Characterized by hamartomas within multiple organ
systems including brain, lungs, skin, kidneys, and heart.
Brain MRI may be useful to confirm a presumptive
clinical diagnosis of tuberous sclerosis.
Epilepsy - most common neurologic: symptom,
developing in up to 90% of patients.

68. Tuberous sclerosis
Definite TSC
2 major features or 1 major + 2 minor
Probable TSC
1 major + 1 minor feature
Possible TSC
1 major or ≥ 2 minor features

69. Fig. Tuberous Sclerosis T1WI (A). postcontrast T1WI (B), CT image (C) and postcontrast TIWI (D). Numerous
subcortical tubers (red arrows in A) and subependymal hamartomas (white arrows in A) are evident on
precontrast Tl WI. The subependymal hamartoma enhance mildly (arrows in B). Enhancement of these
benign lesions is common and does not reflect malignancy. Hamartomas (arrow in C) and subcortical tubers
(arrowhead in C) may calcify, best appreciated on CT. Hamartomas on MRI may be most conspicuous on
gradient echo and T2-weighted imaging, as the lesions are low signal intensity in contrast to the high signal
intensity CSF within the ventricles. Enhancing hamartomas in the region of the foramen of Monro (arrowhead
in D) may slowly enlarge, leading to hydrocephalus and are termed subependymal giant cell tumor "SEGA."

70. Ataxia Telangiectasia
• Autosomal recessive condition with
• Gross Cerebellar atrophy and dilated
4th ventricle
– Cerebellar ataxia followed by rapid
deterioration with choreoathetosis
• Telangiectasia
– mucocutaneous
– Cerebral – may cause hemorrhage

71. L’hermitte-Duclos disease
(dysplastic cerebellar gangliocytoma)
• Rare slow growing cerebellar malformation
in young adults (20-40 years).
• Can be associated with Cowden syndrome
(COLD syndrome) – benign skin tumors, GI
polyps, goitre and breast cancer.
• CT: low density cerebellar area with
thickened folia and no enhancement after
contrast. Calcification may be present.
• MRI: low T1WI, high T2WI, thickened folia –
tigroid appearance.

72. Meningiomatosis
• Benign hamartomatous cortical, subcortical WM lesion with
leptomeningeal vascular malformation

73. Neurocutaneous melanosis
• Giant and multiple melanotic nevi (GCMN) of skin with
melanotic lesions of CNS.
– 1o leptomeningeal melanocytic neoplasms (LMNs)
– Leptomeningeal melanocytosis (LMs)
– Leptomeningeal melanoma (LMn)

74. Encephalocraniocutaneous lipoma
• Rare
• Ipsilateral scalp, brain and eye abnormalities (u/l cerebral
atrophy ipsilateral to scalp lipoma)
– Scalp lipoma
– IC lipomas in 67%
– Spinal lipoma/lipomatosis
– Polymicrogyria

75. Aicardi Syndrome
• Classic triad of: callosal dysgenesis, infantile spasms and
chorioretinal lacunae
• Other complex features:
– Heterotopia
– Intracranial cysts
– Ocular coloboma
– Choroid plexus papilloma
– Hemispheric asymmetry
– Hypoplastic/dysplastic cerebellar hemisphere or vermis.

76. Li-Fraumeni Syndrome
• Autosomal dominant familial cancer syndrome (75% loss of fxn
of TP53)
• Astrocytoma: Cerebrum>cerebellum>spine
• Choroid plexus papilloma: LV>4V
• Lifetime increased risk of: OS, soft tissue sarcoma, leukemia,
breast cancers, brain tumors, melanoma, adrenal cortical
tumours

77. Schanomatosis
• Multiple schwannomas of PNS without involvement of
vestibular nerves.

78. Basal cell nevus syndrome
• Basal cell epithelioma (BCE)/Basal cell carcinoma (BCC),
odontogenic keratocysts, palmoplantar keratocysts,
palmoplantar pits, dural calcifications +/- medulloblastoma

79. Summary:
• Congenital CNS anomalies are not uncommon.
• In setting of seizure, delayed development or dysmorphic child
(low set ears, abnormal facie, hypotelorism)- likelihood of brain
malformations is even higher.
• MRI is the investigation of choice for evaluation of congenital
CNS lesions.
• Brain anomaly imaging checklist helps both to analyze in
orderly manner and not to overlook the subtle structural
abnormalities.

80. References:
Osborn’s Brain Imaging, Pathology, and Anatomy; 2/e, Osborn
AG et al.
Congenital central nervous system anomalies, Larry B. Poe et
al, radiographics
Various internet sources

81. Thank you !