Diagnostic Imaging of Congenital Central Nervous System Diseases

Mohamed Zaitoun
Assistant Lecturer-Diagnostic Radiology
Department , Zagazig University Hospitals
Egypt
FINR (Fellowship of Interventional
Neuroradiology)-Switzerland
zaitoun82@gmail.com

Knowing as much as
possible about your enemy
precedes successful battle
and learning about the
disease process precedes
successful management

Congenital Diseases
a) Neural Tube Closure Defects
b) Disorders of Diverticulation and Cleavage
c) Neuronal Migration and Sulcation
Abnormalities
d) Posterior Fossa Malformations
e) Neurocutaneous syndromes (Phakomatoses)

a) Neural Tube Closure Defects :
1-Anencephaly (most common anomaly)
2-Chiari Malformations
3-Cephalocele

1-Anencephaly (Most common anomaly) :
a) Definition
b) Incidence
c) Radiographic Features

a) Definition :
-Absence of cortical tissue (although brainstem
and cerebellum may be variably present) as
well as absence of the cranial vault
b) Incidence :
-1:1000 , more in females , F:M = 4:1

c) Radiographic Features :
-By Antenatal Ultrasound & Fetal MRI
-No tissue above the orbits and absent calvarium
-Less than expected value for crown rump length
(CRL)
-Frog eye or Mickey mouse appearance may be
seen when seen in the coronal plane due to
absent cranial bone / brain and bulging orbits
-May show evidence of polyhydramnios from
impaired swallowing

Fetal MR images demonstrating absent cranial bone / brain and
bulging orbits , in addition , polyhydramnios is seen

2-Chiari Malformations :
a) Overview of Chiari Malformations
b) Chiari I Malformation
c) Chiari II Malformation

a) Overview of Chiari Malformations :
1-Chiari I Malformation :
-Most common
-Peg like cerebellar tonsils displaced into the
upper cervical canal through the foramen
magnum

2-Chiari II Malformation :
-Displacement of the medulla, fourth ventricle
and cerebellum through the foramen magnum
-Usually with associated with a lumbosacral
spinal myelomeningocele
3-Chiari III Malformation :
-Features similar to Chiari II but with an
occipital and / or high cervical encephalocele

4-Chiari IV malformation :
-Severe cerebellar hypoplasia without
displacement of the cerebellum through the
foramen magnum
-Probably a variation of cerebellar hypoplasia

b) Chiari I Malformation :
1-Definition
2-Incidence
3-Associations
4-Radiographic features

1-Definition :
-Downward displacement of cerebellar tonsils
below foramen magnum > 5 mm
2-Incidence :
-Adult disease : 20 years
-More in females
-Most common type of Chiari
-Chiari I malformations often remain
asymptomatic until adulthood, manifests with
headache

3-Associations :
a) Cervical cord syrinx is present in 20-56%
b) Hydrocephalus in up to 30 %
c) Basilar invagination (craniocervical
junction abnormality where the tip of the
odontoid process projects above the foramen
magnum ) , 30%
d) Klippel-Feil anomaly : fusion of 2 or more
cervical vertebrae , 10%
e) Atlantooccipital fusion , 5%
f) Sprengel deformity

4-Radiographic features :
a) Peg-like Tonsillar herniation (the tonsils are pointed ,
rather than rounded and referred to as peg-like) ,
ectopia is 3 to 5 mm, herniation is >5 mm, is age
dependent
b) Syringohydromyelia , more common
c) No brain anomalies
d) Hydrocephalus , less common
**N.B. :
If the only finding is isolated inferior displacement of
the tonsils, the term (borderline tonsillar ectopia) is
generally preferred

(a) Borderline tonsillar ectopia , sagittal T1 shows cerebellar tonsils extending
inferiorly below the foramen magnum (yellow arrow) , there is no hydrocephalus
or cervical spine syringomyelia , (b) Chiari I in a different patient , Sagittal T2 shows
inferior extension of the cerebellar tonsils (yellow arrows) , the presence of
syringomyelia (red arrow) allows more confident diagnosis of Chiari I

Cerebellar tonsils (arrow) herniating through the foramen
magnum (yellow line)

c) Chiari II Malformation :
1-Definition
2-Incidence
3-Associations

1-Definition :
-Herniation of the medulla, fourth ventricle and
cerebellum through the foramen magnum
with resultant beaking of the tectum
-Myelomeningocele is universally present,
typically lumbar
-Hydrocephalus is present in 80-90 % of patients
2-Incidence :
-Most common in newborns

3-Associations :
a) Myelomeningocele, 90%
b) Obstructive hydrocephalus, 90%
c) Dysgenesis of corpus callosum
d) Syringohydromyelia, 50%
e) Abnormal cortical gyration
f) Chiari II is not associated with Klippel-Feil
anomaly or Chiari I

a) Antenatal Ultrasound :
-Lemon Sign, indentation of the frontal bone giving
the head a shape similar to that of a lemon
-Banana Sign, It describes the way the cerebellum
is wrapped tightly around the brain stem as a
result of downward migration of posterior fossa
content, the cisterns magna gets obliterated

b) MRI :
(i) Posterior Fossa
(ii) Supratentorial
(iii) Osseous Abnormalities
(iv) Spinal Cord

(i) Posterior Fossa :
1-Small posterior fossa
2-Elongated brainstem that extends into the cervical
spinal canal
3-Downward herniation of the cerebellar tonsils into
cervical spinal canal
4-Small fourth ventricle, elongated & inferiorly
displaced
5-Aqueductal stenosios
6-Tectal beaking
7-Large massa intermedia
8-Thin corpus callosum
9-Cerebellum wraps around pons (heart shape)

a - Elongated brainstem
that extends into the
cervical spinal canal
b - Downward herniation
of the cerebellar tonsils
into cervical spinal canal
c - Small fourth ventricle
d - Aqueductal stenosios
e - Tectal beaking
f - Large massa intermedia
g - Thin corpus callosum

(ii) Supratentorial :
1-Hypoplastic or fenestrated falx causes
interdigitation of gyri (gyral interlocking)
2-Small crowded gyri (stenogyria), 50%
3-Hydrocephalus almost always present before
shunting
4-Batwing configuration of frontal horns (caused
by impressions by caudate nucleus)
5-Small biconcave 3rd ventricle (hourglass shape
due to large massa intermedia)

Fenestrated Falx with interdigitated gyri

The caudate heads and thalami are enlarged producing
impressions on the frontal horns and on the third ventricle

(iii) Osseous Abnormalities :
1-Scalloped clivus and petrous ridge (pressure
effect)
2-Enlarged foramen magnum

The foramen magnum is enlarged and filled with cerebellar tissue

(iv) Spinal Cord :
1-Myelomeningocele, 90%
2-Cervicomedullary kink at foramen magnum
(pressure effect)
3-Syringohydromyelia and diastematomyelia

3-Cephalocele :
a) Definition
b) Incidence
c) Associations
d) Location
e) Types

a) Definition :
-Outward herniation of CNS content through a
defect in the cranium, the vast majority are
midline
b) Incidence :
-More in females

c) Associations :
-Associated with other malformation (Chiari,
callosal agenesis)
d) Location :
-Occipital, 80%
-Fronto-ethmoidal
-Parietal, 10%

e) Types :
1-Encephalocoele : herniation of meninges + CSF
+ brain tissue
2-Craial Meningocoele : herniation of meninges
+ CSF only

1-Encephalocele :
-Intracranial tissue that herniates through a defect in
the cranium results in an encephalocele
-Types :
a) Occipital Encephalocele
b) Fronto-Ethmoidal Encephalocele
-There are often significant associated intracranial
anomalies, occipital encephaloceles may be
associated with Chiari or Dandy-Walker
malformations and callosal or migrational anomalies,
Frontoethmoidal lesions are not typically associated
with these types of anomalies

-Fronto-ethmoidal encephaloceles are
subdivided into naso-frontal, naso-ethmoidal
and naso-orbital types :
1-Nasofrontal (40%) which exits the cranium
between the nasal and frontal bones
2-Nasoethmoidal (40%) which exits between the
nasal bones and nasal cartilages
3-Nasoorbital (20%) which exits through a
defect in the maxilla frontal process

2 year old male with bilateral naso-orbital encephaloceles and fronto-nasal
encephalocele , axial T1 of the brain at the level of the orbits depicts the
bilateral naso-orbital encephaloceles (solid arrows) as well as the midline
fronto-nasal encephalocele (dashed arrow)

2-Cranial Meningocoele :
Contain only meninges with CSF

b) Disorders of Diverticulation & Cleavage :
(D&C)
1-Dysgenesis of the Corpus Callosum
2-Holoprosencephaly
3-Septooptic Dysplasia
4-Cerebral Hemiatrophy
5-Interhemispheric Lipoma

1-Dysgenesis of the Corpus Callosum :
a) Types
b) Incidence
c) Association
d) Clinical Picture
e) Radiographic Features

a) Types :
-May be complete (agenesis) or partial (the
splenium and rostrum are absent, SR)
b) Incidence :
-Relatively common congenital abnormality
-More in males

Rostrum (r) , genu (g) , body (b) and splenium (s) , Anterior commissure is
denoted by arrow and hippocampal commissure is denoted by arrowhead

Complete Agenesis Partial
Agenesis

Partial agenesis , genu and anterior body present but posterior
body , splenium and rostrum absent

c) Association :
-Associated CNS anomalies occur in 60%
1-DW malformation
2-Lipoma (calcified in 10%)
3-Chiari II
4-Encephalocele
5-Migration anomalies
d) Clinical Picture :
-The most common clinical manifestations of agenesis of the
corpus callosum are refractile seizures &/or developmental
delay

Quadrigeminal plate lipoma , (a) Axial T1 shows a hyperintense lipoma at the
LT quadrigeminal plate (arrow) , (b) Sagittal T1 shows marked thinning of
the posterior body (red arrow) & splenium of the CC , the 3rd
ventricle is
enlarged & high riding , the lipoma (yellow arrow) is reidentified

e) Radiographic Features :
1-Ventricles :
-Ventricles run parallel and widely separated
(with intervening Probst bundles) giving
a racing car appearance on axial imaging
-Colpocephaly (dilatation of the trigones and
occipital horns) gives a characteristic longhorn
/ moose head / viking helmet appearance on
coronal imaging (may result from decreased
white matter volume posteriorly)

-Dilated high riding 3rd
ventricle communicating
with the interhemispheric cistern or
projecting superiorly as a dorsal cyst
2-Cortex :
-Absence of corpus callosum
-Abnormal callosal bundles (bundles of Probst)
causing medial impressions on the lateral
ventricles which are axons that normally
constitute the corpus callosum but instead
pursue an aberrant course parallel to the
interhemispheric fissure

Coronal T1 shows absence of the normal corpus callosum , the lateral
ventricles form a bull's-horn appearance and are indented medially by the
Probst bundle (arrows)

Probst bundles , T1 shows lateral callosal bundles of Probst (arrows)
indenting superomedial margins of lateral ventricles

Callosal agenesis and Probst bundle fibres callosal agenesis and
Probst bundle fibers

FLAIR shows high riding 3rd
ventricle communicating with the
interhemispheric fissure (thin arrow) and crescent shaped frontal horns
indented medially by white matter tracts of Probst's bundles (thick arrow)

2-Holoprosencephaly :
a) Definition
b) Association
c) Types
d) Clinical Picture
e) Radiographic Findings
f) Differential Diagnosis

a) Definition :
-Failure of primitive brain to cleave into left and
right cerebral hemispheres
b) Association :
-50% of patients with holoprosencephaly have
trisomy 13
-Associated with azygos configuration of ACA
(single ACA)

c) Types :
From most severe to least severe
1-Alobar
2-Semilibar
3-Lobar

Alobar Semilobar Lobar
1-Falx Absent Presented
posteriorly
Present with most
anteroinferior
aspect absent
2-Lateral Ventricle U-shaped
monoventricle
Partially fused
anteriorly
Near normal
3-Third V Absent Rudimentary Near normal
4-Cerebral
Hemispheres
One brain Partial formation Near normal
5-Thalamus Fused Variable fusion Near normal
6-Facial Anomalies Severe Less severe None or mild
7-Septum
Pellucidum
Absent Absent Absent

d) Clinical Picture :
-Facial abnormalities usually correlate with
severity of brain abnormalities but not vice
versa
-Hypotelorism (eyes too close together)
-Cleft lip &/or palate
-Cyclopia (single eye)

e) Radiographic Findings :
-Presence of a septum pellucidum excludes the
diagnosis of holoprosencephaly

Septum pellucidum Absent septum pellucidum

1-Alobar Form :
-No cleavage into two hemispheres : cup-shaped
brain
-Single U-shaped monoventricle almost always
communicates with a large dorsal cyst
-Absent third ventricle
-Thalamic fusion
-Absent falx , corpus callosum , fornix , optic
tracts and olfactory bulbs
-Midbrain , brainstem and cerebellum are
structurally normal

(a) T1 , (b) T2 show severe alobar holoprosencephaly , there is continual
frontal lobe across the midline , a midline monoventricle communicates
with a dominant dorsal cyst

Fused thalami (Arrows) , monoventricle with absence of septum
pellucidum and absence of interhemispheric fissure and falx

2-Semilobar Form :
-Partial cleavage into hemispheres (posterior
cerebral hemispheres) , partially fused
anteriorly
-Partial occipital and temporal horns

(a) , (b) T2 , (c) T1 show semilobar holoprosencephaly , there is partial
separation of the posterior cerebral cortex with complete fusion of the
frontal lobes , there is large midline posterior interhemispheric cyst

Single large ventricle , absence of septum pellucidum and rudimentary
interhemispheric fissure (Arrow)

3-Lobar Form :
-Complete cleavage into two hemispheres
except for fusion in the most rostral aspect of
the frontal neocortex
-Lateral ventricles are normal or slightly dilated ,
frontal horns may be squared
-Absent septum pellucidum

f) Differential Diagnosis :
*Alobar Type :
a) Semilobar Holoprosencephaly :
-Partial separation into hemispheres
-Rudimentary occipital and temporal horns
b) Hydranencephaly :
-Thalami are often visible and are not fused
-Not associated with midline facial abnormalities
-No cortex present or sometimes small islands of
tissue

c) Severe Hydrocephalus :
-Falx usually present but may be absent due to
severe long standing hydrocephalus
-Bilateral choroid plexus
-Thalami not fused
-Not associated with midline facial abnormalities
*Semilobar Holoprosencephaly :
-From alobar & lobar types

*Lobar Holoprosencephaly :
a) Semilobar Holoprosencephaly :
-Fusion of the anterior aspects of the
hemispheres
-Falx and interhemispheric fissure incomplete
-Partial fusion of the thalami

b) Septooptic dysplasia :
-Can appear very similar
-Fusion of the frontal lobes and of the fornicies
is not a feature
-Optic nerve hypoplasia & hypothalamic /
pituitary dysfunction

3-Septooptic dysplasia :
a) Definition
b) Radiographic features

a) Definition :
-Absence of septum pellucidum and optic nerve
hypoplasia (mild form of lobar
holoprosencephaly)
-70% have hypothalamic / pituitary dysfunction
-Associated with schizencephaly (50 % of cases)

b) Radiographic features :
-Absence of septum pellucidum
-Squared frontal horns of lateral ventricles
-Hypoplasia of optic nerve and chiasm
-Hypoplastic pituitary stalk

A: Absence of septum pellucidum
B : Non-visualization of bilateral optic nerves

4-Cerebral Hemiatrophy (Dyke-Davidoff) :
a) Etiology
b) Radiographic features

a) Etiology :
-Intrauterine and perinatal ICA infarction leads
to hemiatrophy of a cerebral hemisphere

b) Radiographic features :
-Atrophy of a hemisphere causes midline shift
-Compensatory ipsilateral skull thickening (key
finding)
-Ipsilateral paranasal and mastoid sinus
enlargement

Atrophy of the right hemisphere , the right
frontal sinus is larger than the left , diploic
spaces on the right seem to be widened

Ipsilateral diploic calvarial expansion

5-Interhemispheric Lipoma :
a) Site
b) Association
d) Differential Diagnosis

a) Site :
-Collection of primitive fat within or adjacent to
corpus callosum

b) Association :
1-Absence of corpus callosum, 50%
2-Midline dysraphism
3-Agenesis of cerebellar vermis
4-Encephalocele, myelomeningocele & spina
bifida

-CT : pure fat (-50 to -100 HU, no associated
hair/debris) is pathognomonic
-T1 hyperintense
-Most common location is splenium and genu
-Curvilinear calcifications are common

There is
concurrent partial
posterior
commissural
agenesis (empty
arrow , a) as well
as a small
interhemispheric
cyst (arrow , a)

d) Differential Diagnosis :
1-Intracranial dermoid cyst
2-Intracranial teratoma
3-Fatty falx cerebri

c) Neuronal Migration and Sulcation
Abnormalities :
1-Lissencephaly-Pachygyria
2-Schizencephaly
3-Polymicrogyria
4-Cortical Heterotopia
5-Focal Cortical Dysplasia
6-Hemimegalencephaly

1-Lissencephaly-Pachygyria :
a) Type I (classic) lissencephaly
b) Type II (cobblestone complex) lissencephaly

a) Type I (classic) Lissencephaly :
1-Definition
2-Etiology
3-Clinical Picture
5-Band Heterotopia

1-Definition :
-Characterized by absence or decreased cortical
convolutions causing a smooth thickened
cortical surface
-Patients with classic lissencephaly may have a
smooth brain surface in the complete form or
more commonly they have a smooth surface
with some few broad gyri with shallow sulci
(pachygyria) along the inferior frontal and
temporal lobes in the incomplete form
(agyria/pachygyria complex)
-Named 4-Layer Lissencephaly as there is a four
layered cortex histologically

(a) Complete form , arrows indicate underdeveloped perisylvian region that
creates characteristic figure eight appearance , (b) Incomplete form , T2
shows a smooth brain surface with no sulci on the anterior region (agyria)
& few shallow sulci posteriorly with thick & broad gyri (pachygyria)

2-Etiology :
-This anomaly results from arrest of the migration
process
-May be caused by CMV, in which case
calcifications are often present
3-Clinical Picture :
-Patients present with seizures and developmental
delay in the complete form or complex seizures,
hypotonia, microcephaly (50%) and facial
dysmorphism (30%) in the incomplete form

-Cerebral configuration is oval or hourglass (figure of 8) with
shallow Sylvian fissures
-Complete agyria in the complete form or parieto-occipital
agyria with frontotemporal pachygyria (broad gyri) in the
incomplete form
-The cortex is markedly thickened measuring 12-20mm (rather
than the normal 3-4mm), the subcortical white matter is thin
with a lack of the normal gray-white matter interdigitation
-There is a circumferential band of high signal intensity on T2
most prominent in the parieto-occipital cortex corresponding
to a sparse cell zone with increased water content (separates
the outer cortical layer from the inner thicker cortical layer)

(a) T1 , (b) T2 shows classical type I lissencephaly with a complete smooth
cortex and hour glass or figure of 8 configuration to the cerebral
hemispheres

Complete lissencephaly , axial T2 shows complete absence of sulci with a
thick cortex , a shallow Sylvian fissure and a circumferential band of high
signal intensity in the parietooccipital cortex

Prominent cell sparse zones are seen in areas of agyria (arrows)

5-Band Heterotopia :
a) Definition
b) Incidence
c) Clinical Picture
d) Radiographic Features

a) Definition :
-Bilateral thick layers of arrested neurons
located approximately half-way between the
ventricles and the cortical plate resembling a
doubling of the cortex, more severe in the
frontal lobes

b) Incidence :
-The majority of patients with double cortex
syndrome are female on account of the
genetic abnormality often being located on
the X chromosome
c) Clinical Picture :
-Seizures and delayed development are the
most common presentations, usually evident
in the first decade

d) Radiographic Features :
-On MR imaging, it shows the characteristic 3-
layer cake (continuous double cortex) with the
cortex and bilateral symmetric circumferential
subcortical layer of band heterotopia
separated from each other by a thin white
matter band
-The cortex may be relatively normal or
pachygyric

(a) Axial T1 & (b) axial T2 show a large band of isointense tissue (dots,
a,b) is interposed between the ventricles and the cortex , between
the band heterotopia and the cortex is a thin layer of myelinated
white matter (arrows, a,b) , there is poor, irregular sulcation of the
cerebral cortex

b) Type II (Cobblestone Complex)
lissencephaly:
1-Definition
2-Etiology
3-Clinical Picture

1-Definition :
-Cobblestone lissencephaly is characterized by a
reduction in normal sulcation and nodular
brain surface
2-Etiology :
-Unlike type I lissencephaly which is the result of
neuronal undermigration, type II is due to
over migration

3-Clinical Picture :
-Ocular anomalies and congenital muscular
disorders
-It includes a spectrum of anomalies with
Walker-Warburg syndrome (WWS) being the
most severe form , Fukuyama congenital
muscular dystrophy (FCMD) the mildest form
and muscle-eye-brain (MEB) disease the
intermediate form

-Multi-nodular surface of the cortex
(cobblestone) most pronounced anteriorly
-Lack of normal sulcation
-Small sylvian fissure
-Hour glass or figure-8 appearance of the brain
on axial imaging

(a) T1 , (b) T2 shows cobblestone (type II) lissencephaly with a gently
lobulated external cortex & a finely undulating or serrated interface at the
grey-white junction

Cobblestone lissencephaly , (a) & (b) , axial and coronal T2 show an irregular nodular
cortex with hypomyelination of the white matter

(a) lissencephaly in a boy , (b) pachygyria in a boy and
(c) double cortex in a girl

2-Schizencephaly :
a) Definition
b) Associations
c) Types & Radiographic Features

a) Definition :
-Cleft extending through the whole hemisphere
from the ependymal lining of the lateral
ventricle to the pia covering the brain forming
an abnormal communication between the
ventricles & the extra-axial subarachnoid
space
-The cleft may be unilateral or bilateral and is
constantly lined by polymicrogyric cortex

b) Associations :
-Frequent association with cortical
malformations (grey matter heterotopia) with
up to 30 % of patients with schizencephaly
also having cortical malformations
-Associated with septo-optic dysplasia (agenesis
of the septum pellucidum & optic nerve
hypoplasia)

Schizencephaly (closed-lip) with PMG , T1 shows indentation in the
ependymal surface , called “nipple” (red arrow) lined by polymicrogyria
(green arrow)

Schizencephaly with septo-optic dysplasia , (a) T1 shows
complete absence of the septum pellucidum & open lip
schizencephaly with dysplastic gray matter along the cortical
surface , (b) T1 shows optic nerve & chiasma atrophy

c) Types & Radiographic Features :
-Frontal involvement is the most common
1-Open Lip :
-The walls of the cleft may be widely separated , in
this case , the cleft is occupied by CSF
2-Closed Lip :
-When the walls abut one another (fused lips)
-The cleft may not be easily visible, however, a
dimple may be seen in the wall of the lateral
ventricle where the cleft communicates

Open lips schizencephaly , the cleft is bilateral and involves the full thickness
of the brain , the margins of the cleft are composed of polymicrogyric
cortex , here is no septum pellucidum

Open lip schizencephaly , T2 shows a cleft in the LT temporoparietal cortex
(arrows) extending from the cortical surface to the LT lateral ventricle ,
the cleft is lined by dysplastic appearing gray matter

Fused lips schizencephaly , both CT and MR adequately depict the presence
of cortex bordering the cleft , a dimple along the lateral wall of the right
lateral ventricle is visible in the coronal section (arrow, b) and corresponds
to the opening of the schizencephalic cleft , the opening on the brain
surface is best seen in the CT image in this particular case (a)

Closed lip schizencephaly , the gray matter-lined cleft in the right posterior
frontal lobe communicating with the right lateral ventricle (arrow) , in
addition , there is agenesis of the septum pellucidum

1-Focal Cortical Dysplasia :
-Sometimes may have a cleft on the cortical
surface that does not extend completely to
the ventricular surface
2-Heterotopic grey matter :
-Closed lip schizencephaly can mimic a band of
grey matter heterotopia

-Assessing the ventricular outline will often
demonstrate a slight cleft whereas
periventricular grey matter will usually bulge
into the ventricle
3-Porencephaly :
-A zone of encephalomalacia that extends from
the cortical surface to the ventricular surface
but is lined by gliotic white matter not grey
matter

(a) Prosencephalic cyst , note the absence of grey matter lining
the defect , (b) Open lip schizencephaly , note the grey matter
lining

**N.B. :
-There are several entities that can cause an
interruption or cleft in the cortex, but only
schizencephalic cleft is lined by gray matter,
other cortical clefts include :
1-Porencephaly (where there is replacement of
cortex by a cystic structure)
2-Encephalomalacia
3-Surgical resection cavity

3-Polymicrogyria (PMG) :
a) Definition
b) Clinical Picture

a) Definition :
-A developmental malformation characterized by
an excessive number of small convolutions (gyri)
on the surface of the brain with increased cortical
thickness
-Either the whole surface (generalized) or parts of
the surface (focal) can be affected
-The insult occurs after the end of neuronal
migration that is in the phase of cortical
organization
-May be caused by in-utero infection (especially
CMV), in-utero ischemia or genetic causes

b) Clinical Picture :
-The most frequent cause of partial epilepsy in
the pediatric age
-Developmental delay & quadriparesis

b) Radiographic Features :
-Appears as an area of increased cortical
thickness composed of multiple small gyri
-The gray white matter junction is generally
irregular
-The abnormal cortex itself is isointense to
normal gray matter whereas the underlying
white matter may show T2 prolongation
-Bilateral perisylvian polymicrogyria is the most
common distribution

T2 shows bilateral perisylvian & bifrontal polymicrogyria (arrows point to the
perisylvian PMG) , the affected regions have an irregular junction of the
abnormal cortex & the white matter

Bilateral Perisylvian Polymicrogyria

Polymicrogyria , 8-month-old infant with CMV infection , (a) Axial T1 (b) axial T2
(c) coronal T2 show shallow Sylvian fissure is visible in T1 (empty arrow, a) , T2
is better suited to depict the cortical anomaly by detecting bilateral thickening
of the brain cortex (arrows, b,c) , a few broad shallow sulci are visible in the
anomalous area

T2 shows PMG with normal cortical thickness that is associated
with the high signal intensity of the white matter

4-Cortical Heterotopia :
a) Definition
b) Association
c) Clinical Picture
d) Types

a) Definition :
-Interruption of normal neuronal migration from
near the ventricle to the cortex thus resulting
in (normal neurons in abnormal locations)

b) Association :
1-Agenesis of the corpus callosum
2-Pachygyria
3-Schizencephaly
4-Polymicrogyria
5-Chiari II malformation
6-Cephalocoeles

-Epilepsy and possible delayed milestones
and/or mental retardation
d) Types :
1-Subependymal Heterotopia : most common
2-Subcortical Heterotopia

1-Subependymal Heterotopia :
a) Incidence
b) Location
c) Types
d) Radiographic Features

a) Incidence :
-More Common than subcortical Heterotopia
b) Location :
-Subependymal (periventricular) heterotopias
(PVH) are located in close proximity to the
ventricular wall , commonly seen in the region
of the trigone and occipital horns of the
lateral ventricles
-PVH are usually bilateral with predilection for
the right cerebral hemisphere due to later
migration of the right-sided neuroblasts

c) Types :
-Can be subdivided into :
1-Unilateral focal
2-Bilateral focal
3-Bilateral diffuse

d) Radiographic Features :
-They appear as round or oval nodules
-Isointense to the normal gray matter on all
pulse sequences and do not enhance after
contrast injection
-They may lie in the wall of the ventricle and
project into the ventricular lumen or lie within
the periventricular white matter
-Mild ventricular dilation might be seen

28 month old child with Chiari II malformation , (a) T1 , (b) T2 , there is a
subependymal heterotopic nodule in the lateral wall of right frontal horn
(white arrow, a,b) , the nodule is isointense with gray matter both in T1
and T2 , notice abnormal configuration of the lateral ventricles in this
Chiari II patient and the presence of a shunt catheter (black arrow, b)

2-Subcortical Heterotopia :
a) Location
b) Types
c) Differential Diagnosis

a) Location :
-Located within the subcortical or deep white
matter and are always seen contiguous to the
overlying cortex or the underlying ventricular
system
-The affected hemisphere may decrease in size as a
result of the decreased volume of the neurons
-The overlying cortex appears thin with shallow
sulci

b) Types :
1-Nodular form : extend from the ventricle into
the white matter
2-Curvilinear form : extend from the cortex into
the underlying white matter
3-Mixed form

1-Nodular SCH :
-Appear as nodules that extend from the
ventricular surface outward into the white
matter without continuity with the cerebral
cortex

Axial T2 (a) & Coronal T1 (b) in a 1-month-old patient shows multiple
nodular heterotopia (arrows) lining the frontal horn of the right
lateral ventricle and extending into the center of the frontal white
matter , the right hemisphere is reduced in size , the overlying cortex
is thin and has a reduced number of sulci , the sulci present are
abnormally shallow , the corpus callosum is agenetic

T1 shows multiple nodules isointense to gray matter in
subcortical location in the LT cerebral hemisphere

2-Curvilinear SCH :
-Consist of swirling heterogeneous curvilinear
masses of gray matter that have an
appearance that closely resembles
convolutions of the cortex extending from the
cortical surface into the white matter

Curvilinear SCH , axial T2 shows curvilinear heterotopias in the right cerebral
hemisphere that are associated with its decrease in size

3-Mixed :
-Nodules are seen in the deep part of the brain
adjacent to the lateral ventricle and the
curvilinear convolutions are seen in the
superficial part

(a) T2 shows nodular heterotopia (white arrows) in the periventricular white
matter bilaterally , no cortical connection is seen at this level , (b) T2
shows that the heterotopia (white arrows) are contiguous with the cortex
bilaterally

c) Differential Diagnosis :
-MR spectroscopy can differentiate heterotopia
from low-grade glioma
-The metabolites appear to be similar to those
of normal brain in heterotopia whereas loss of
N-acetylaspartate and increase of choline
were observed in low-grade gliomas

5-Focal Cortical Dysplasia :
a) Definition
b) Clinical Picture
c) Types
d) Radiological Findings
e) Differential Diagnosis

a) Definition :
-Is a heterogeneous group of lesions
characterized by the presence of abnormal
neurons and glial cells within a localized
region of the cerebral cortex
-Patients usually present with intractable
seizures

c) Types :
1-FCD type I (non-Taylor dysplasia) : Ia & Ib
2-FCD type II (Taylor dysplasia) :
IIa : No ballon cells
IIb : Ballon cells present

d) Radiological Findings :
-Localized area of cortical thickening with an
indistinct gray-white matter junction
-A subcortical focus of abnormal signal intensity
extending from the gray-white matter
junction to the superolateral margin of the
lateral ventricle , these foci show low signal
intensity on T1 and high signal intensity on T2
(Transmantle sign)

(a) There is cortical thickening and blurring of the grey/white
matter junction on T1WI , (b) FLAIR shows the subcortical
hyperintensity

Axial T1 , T2 & FLAIR of a 15 year old boy with epilepsy,
notice thickening and hyperintensity of the cortex of
the left superior frontal gyrus , the FLAIR also show
high signal in the subcortical white matter

(a) T1 shows an area of mild cortical thickening with blurring of the white-
gray matter interface in the LT frontal lobe , (b) FLAIR shows hyperintense
signal in the underlying white matter (arrow)

Coronal FLAIR and axial T2 show T2-hyperintense cortical thickening and high
signal in cortex and subcortical region , notice subcortical hyperintensity
extending to the right ventricle indicating transmantle sign (blue arrow)

e) Differential Diagnosis :
-FCD should be differentiated from gliomas
-A frontal location is in favor of FCD whereas a temporal
location is suggestive of neoplasm
-High signal intensity on T2 is less distinct in FCD than in
tumors because the main portion of cortical dysplasia
lesions is located within the gray matter and is
infrequently associated with edema or gliosis
-Gliomas are associated with some degree of mass effect
and might show a degree of enhancement after
contrast injection

6-Hemimegalencephaly :
a) Definition
b) Clinical Picture
c) Radiological Findings

a) Definition :
-Is a rare congenital disorder of cortical
formation with hamartomatous overgrowth
all or a part of a cerebral hemisphere
-This results from either increased proliferation
or decreased apoptosis (or both) of
developing neuron
-Affected newborns suffer from untreatable
epilepsy

c) Radiological Findings :
-Enlargement of a whole hemisphere
-The cortex is affected by diffuse migration
anomalies, while the white matter is gliotic
and dysmyelinated
-The ipsilateral ventricle is frequently dilated
and the frontal horn is stretched
-The homolateral cerebellar hemisphere is
usually enlarged as well

Coronal T2 show an enlarged left cerebral hemisphere , a dilated
left lateral ventricle and a thickened cerebral cortex

d) Posterior Fossa Malformations :
1-DW Malformation
2-DW Variant
3-Mega Cisterna Magna
4-Persisting Blake’s Pouch
5-Chiari I
6-Syndromes Associated With Vermian-
Cerebllar Hypoplasia

1-Dandy Walker Malformation :
a) Definition
b) Incidence
c) Radiographic findings

a) Definition :
-The definition of DWM classically includes
partial or complete vermian agenesis
associated with hypoplastic cerebellar
hemispheres, cystic dilatation of the fourth
ventricle and expansion of the posterior fossa
associated with high insertion of the
tentorium, torcular Herophili and transverse
sinuses

b) Association :
1-Agenesis of corpus callosum , 25%
2-Lipoma of corpus callosum
3-Malformation of cerebral gyri
4-Holoprosencephaly , 25%
5-Cerebellar heterotopia , 25%
6-GM heterotopia
7-Occipital cephalocele
8-Tuber cinereum hamartoma
9-Syringomyelia
10-Cleft palate
11-Polydactyly
12-Cardiac abnormalities

-Patients usually manifest in the first year of life
with symptoms of hydrocephalus and
associated neurological symptoms
-In 80% of cases, the diagnosis is made by the
first year of life

d) Radiographic findings :
-Absent or abnormal inferior cerebellar vermis (key
finding) and cephalad rotation of the vermian
remnant
-Cystic dilatation of the fourth ventricle extending
posteriorly (which communicates with a
retrocerebellar cyst)
-Enlarged posterior fossa with torcular-lambdoid
inversion, i.e. torcular herophili lying above the
level of the lambdoid suture due to abnormally
high tentorium, (the torcular herophili is the
confluence of the transverse sinus & the straight
sinus)
-Hydrocephalus

T1 shows a large posterior fossa cyst elevating the torcular herophili and
sinus rectus (short arrow) , the hypoplastic vermis is everted over the
posterior fossa cyst (long arrow) , the cerebellar hemispheres and
brainstem (b) are hypoplastic, thinned occipital squama is seen
(arrowheads)

T2 shows enlarged posterior fossa and communication of the anterior fourth
ventricle with its large retrocerebellar portion , bilateral temporal horns
are dilated due to obstructive hydrocephalus

T1 shows the posterior fossa is larger than normal due to the presence of a cyst-like
fourth ventricle (4V) (a,b) , whose inferior tip protrudes into the foramen magnum
(white arrow, a) , the vermis (v) is hypoplastic and rotated in a counterclockwise
fashion (a) , the tentorium is elevated (empty arrow, a) so that the torcular comes
to lie cranial to the lambda (so-called torcular-lambdoid inversion) , notice the
scalloped profile of the occipital squama in the sagittal section (a) , in the axial
plane , the hypoplastic cerebellar hemispheres (h) are winged outward (b) , the
pons is hypoplastic (a) , the third ventricle appears to communicate with a dilated
interhemispheric fissure (c) , associated malformations in this particular case
include agenesis of the corpus callosum with the classical spokewheel-like
arrangement of the mesial cortical sulci (a) and a right parietal cephalocele
(arrowhead, c)

(a) Normal Torcula , (b) Torcular-lambdoid inversion , large
posterior fossa cyst elevating the torcular herophili and sinus
rectus (short arrow)

(a) T1 shows agenesis of the corpus callosum , a hypoplastic brainstem (b),
elevation of the torcular herophili (lambdoid-torcular inversion, large
arrow), a large fourth ventricle, and a markedly hypoplastic vermis that is
rotated superiorly (small arrow) , (b) T1 shows an elevated , anteriorly
displaced torcular herophili (arrow) and a superiorly displaced posterior
fossa cyst

Axial CT scan showing the sinus confluence (large arrow) and sinus
transversus (small arrows) displaced superiorly in Dandy-Walker
malformation (lambdoid-torcular inversion)

1-Mega cisterna magna
2-Epidermoid cyst
3-Arachnoid cyst (see brain tumors , cystic
lesions)
4-Blake’s pouch cyst
5-Vermian hypoplasia (Joubert anomaly)

2-Dandy Walker Variant (DWV) :
a) Definition
b) Incidence

a) Definition :
-The definition of DWV classically includes key
features of DWM such as a rotated hypoplastic
vermis and a cystic dilatation of the fourth
ventricle (the 4th ventricle is not as dilated as in
the DW malformation) with an essentially
normal posterior fossa
-The main difference between DWM & DWV being
in the degree of dilatation of the fourth ventricle
and therefore of the posterior fossa

b) Incidence :
-The incidence of DWV is actually higher than
that of the full-blown DWM representing at
least one-third of all cerebellar malformations

-4th ventricle communicates dorsally with
enlarged cisterna magna (keyhole deformity)
-Hydrocephalus not common

3-Mega Cisterna Magna :
a) Definition
b) Incidence

a) Definition :
-Refers to adult patients with significantly
enlarged CSF retrocerebellar cisterns in the
posterior fossa with normal cerebellar
morphology

b) Incidence :
-MCM is a fairly common condition, accounting
for approximately 54% of cystlike posterior
fossa malformation

- Expansion of the cisterna magna typically seen
as prominent retrocerebellar CSF appearing
space which freely communicates with the
ventricular system and with the perimedullary
subarachnoid spaces with a normal vermis
and normal cerebellar hemispheres
-The fourth ventricle has normal shape and size

4-Persisting Blake’s Pouch :
a) Definition
b) Radiological Findings

a) Definition :
-The persistent Blake’s Pouch Cyst is a cystic
malformation of the posterior fossa thought
to derive from persistence and expansion of
the normally transient Blake pouch that arises
from the area membranacea inferior (AMI)
and that normally regresses during the fifth to
eighth gestational weeks

b) Radiological Findings :
-Retrocerebellar cyst formation with CSF signal
intensity , hypointense on T1 and
hyperintense on T2 without abnormal
enhancement
-The cysts are well marginated , have a smooth
wall and are nearly always unilocular and
located in midline

-The persistent Blake`s pouch cyst is in
communication with the fourth ventricle and
separated from the subarachnoid space
-Size of The posterior fossa is normal in size
-Because the foramen of Magendie never
opens , CSF obstruction with tetraventricular
hydrocephalus results

-Persisting Blake’s
pouch , 5-month-old
infant
-The Blake’s pouch
(asterisk) widely
communicates with a
dilated fourth
ventricle
-There is marked
tetraventricular
hydrocephalus

6-Syndromes Associated With Vermian-
Cerebllar Hypoplasia :
1-Joubert Syndrome
2-Walker-Warburg Syndrome
3-Muscle-Eye-Brain Syndrome
4-Rhombencephalosynapsis
5-Tectocerebellar dysraphism

1-Joubert Syndrome :
a) Definition
b) Clinical Picture

a) Definition :
-Vermian aplasia or molar tooth midbrain-
hindbrain malformation
-Presents clinically in the neonatal age
-Vermian dysgenesis is the key feature

-Respiratory disturbances
-Abnormal eye movement
-Facial Asymmetry
-Ataxia
-Psychomotor retardation

-Small dysplastic or aplastic cerebellar vermis,
unlike Dandy Walker complex, hydrocephalus
& a large posterior fossa cyst are uncommon
-The posterior fossa typically shows a bat wing
4th
ventricle
-The mid brain has a characteristic molar tooth
configuration
-Cleft between the two adjoining cerebellar
hemispheres

Cleft between the two adjoining cerebellar hemispheres ( arrow )

Coronal T2 shows complete absence of the cerebellar vermis and the
presence of a narrow interhemispheric cleft (arrow heads) that connects
the 4th
ventricle with the cisterna magna

2-Walker-Warburg Syndrome (WWS) :
-Sometimes known as HARDE syndrome
-Is an extremely rare lethal form of congenital
muscular dystrophy
-It is primarily characterized by :
1-Hydrocephalus
2-Agyria (Cobble-stone lissencephaly)

3-Retinal Dysplasia
4-DW Continuum (enlargement of the 4th
ventricle , a retrocerebellar cyst and no
enlargement of the posterior fossa )
5-Encephalocele

(a) Sagittal T1 shows hypoplasia of the cerebellar vermis (arrow) and a
posterior fossa cyst communicating with the 4th
ventricle , also note the
associated parietal encephalocele , (b) Axial PD shows the abnormal
right globe (arrow) , the patient had persistent hyperplastic primary
vitreous , (c) Axial PD shows the smooth contour of the cerebral cortex
(lissencephaly) and the enlarged ventricular system

Coronal T1 shows marked ventriculomegaly and cobblestone cortex

3-Muscle-Eye-Brain Syndrome (MEB) :
-Finland remains the country with the largest
group of MEB patients
-Floppy infants with visual problems and severe
mental retardation

4-Rhombencephalosynapsis :
a) Definition
b) Radiographic Features

a) Definition :
-All patients with rhombencephalosynapsis had
absence of the cerebellar vermis with midline
fusion of the two cerebellar hemispheres

1-Vermian abnormalities :
-Absent anterior (rostral) vermis
-Deficient posterior (caudal) vermis
2-Fusion of the cerebellar hemispheres
3-This usually results in an abnormally small
posterior fossa and an abnormally shaped fourth
ventricle which takes on a (diamond shaped or
key hole)

Axial T2 MRI at the level of the posterior fossa showing AP elongation of the fourth
ventricle giving it a "diamond shaped" appearance

(a) Axial IR (b) Axial T1 (c) Sagittal T1 (d) Coronal T1 , the posterior fossa is small ,
cerebellar convolutions are orientated transversely and the white matter is
continuous across the mid-line (a,b) , the tonsils and the vallecula are not
visible (b,d) On a mid-sagittal section (c) , the vermis is actually a mid-line cut
through the monolobated cerebellum whose fissures are clearly visible (c)

5-Tectocerebellar dysraphism :
a) Definition

a) Definition :
-This rare abnormality is characterized by
vermian hypo-aplasia , occipital cephalocele
and marked deformation of the quadrigeminal
plate and brain stem , the colliculi are fused to
form a beak pointing towards the site of the
cephalocele

-Vermian hypo-aplasia is well depicted and the
tectal beak is visible both in the sagittal and
axial planes
-The cerebellar hemispheres usually tend to
engulf the brain stem
-Associated supratentorial anomalies and
hydrocephalus are common findings

(a,b) Sagittal T1 , (c) Axial T1 (d) Coronal T1 , the brain stem is markedly distorted and stretched
towards the cephalocele site (thick arrow, a) , the corpus callosum is thin and the
mammillary bodies are hypoplastic (arrow, b) , the mesial cortex is diffusely arranged into
multiple small gyri (stenogyria) (a) , there is extreme beaking of the quadrigeminal plate (thin
arrows, a,c) , the vermis is agenetic and the two cerebellar hemispheres face one another at
the mid-line (arrowheads, d) , the falx cerebri is fenestrated resulting in interdigitation of gyri
across the interhemispheric fissure (arrows, d)

e) Neurocutaneous syndromes
(Phakomatoses):
1-Tuberous Sclerosis
2-Neurofibromatosis
3-Sturge-Weber Syndrome
4-Von Hippel-Lindau (VHL) disease
5-Osler-Weber-Rendu

1-Tuberous Sclerosis : (Bourneville disease)
a) Clinical Picture

a) Clinical Picture :
-Tuberous sclerosis is a hamartomatous disorder
affecting several organ systems with multiple
skin manifestations
-Presenting in childhood with a triad of :
1-Seizures :
- Present in about 3/4 of patients
2-Mental retardation :
-Up to half have normal intelligence
3-Adenoma sebaceum :
-Nodular rash originating in the nasolabial folds
-Present in about 3/4 of patients

1-CNS Lesions
2-Kidney
3-Bone
4-Chest

1-CNS Lesions : Four major CNS lesions
a) Subependymal Hamartoma
b) Cortical / Subcortical Tubers
c) Subependymal Giant Cell Astrocytoma
d) White Matter Abnormalities

a) Subependymal Hamartoma :
-88% are associated with calcification, although
calcification absent in early childhood
-Visible within the first 6 months of age
-Variable signal, frequently high T1 and iso to
high T2
-Enhancement is variable

(a) NECT reveals subependymal calcifications , a hypointense right frontal
lesion represents a white matter lesion or tuber , it extends from the
lateral ventricle through the cerebral cortex , (b) CT+C shows no
enhancement in the white matter lesion in the right frontal lobe

b) Cortical / Subcortical Tubers :
-50 % are in the frontal lobe
-Low T1 and high T2 with only 10 % of tubers
showing enhancement

CT+C reveals a low-attenuating cortical tuber (arrow) in
a 10-year-old patient with tuberous sclerosis

T2 shows numerous bilateral T2 hyperintense cortical tubers (yellow arrows) ,
subcortical tubers (blue arrows) & subependymal tubers (blue arrows) &
subependymal nodules (red arrows)

Sagittal T1 shows multiple hyperintense cortical and
subependymal nodules

c) Subependymal Giant Cell Astrocytoma :
1-Incidence
2-Location
3-Radiographic Features
4-Differential Diagnosis

1-Incidence :
-Are benign tumors seen almost exclusively in
tuberous sclerosis (TS)
-Peak occurrence 8-18 years
-The tumor arises when a subependymal
nodule transforms into SGCA over a period of
time

2-Location :
-Located at foramen of Monro
3-Radiographic Features :
a) CT
b) MRI

a) CT :
-Typically appears as an intraventricular mass near the
foramen of Monro
-They are usually larger than 1 cm
-Lesions are iso or slightly hypo-attenuating to grey
matter
-Calcification is common and hemorrhage is possible
-Hydrocephalus may be present
-Marked contrast enhancement (differentiating feature
from a subependymal nodule)

b) MRI :
*T1: Heterogenous and hypo to isointense to
grey matter
*T2 : Heterogenous and hyperintense to grey
matter , calcific components can be
hypointense
*T1+C : Marked enhancement

An intraventricular , ovoid , voluminous mass is observed which produces
hydrocephalus as it occludes foramen of Monro , this mass is
hyperintense on T2 (a) , isointense on T1 (b) and is significantly enhanced
after the administration of contrast (c)

4-Differential Diagnosis :
-In known cases of TS, the appearance is virtually
pathognomonic and the main differential is between
a subependymal nodule and SGCA, serial imaging is
most helpful here as growth implies SCGA
-Other general considerations include :
1-Central Neurocytoma
2-Choroid plexus papilloma (CPP)
3-Choroid plexus carcinoma (CPC)

d) White matter abnormalities : Radial bands sign
-Refers to linear bands seen on MRI radiating from
the periventricular white matter to the
subcortical region , thought to be specific for
tuberous sclerosis
-MRI :
These radial bands appear a linear regions of signal
abnormality extending form the ventricle to the
cortex , slightly fanning out as it reaches the
periphery , best appreciated on a FLAIR & PD
sequences

Hyperintense radial bands extending linearly at the level of right cerebral
hemisphere and a cortical tuber located at left parietal lobe in FLAIR in a
case with tuberous sclerosis complex

Radial band sign , (a) PD in a patient with TS shows hyperintense bands in the white
matter radiating from the ventricular margin to the subcortical region (arrows) ,
(b) FLAIR shows irregular hyperintense areas in the subcortical white matter
suggestive of subcortical tubers. A large hyperintense nodule is seen in the region
of the foramen of Monroe , representing a subependymal giant cell astrocytoma
(thick arrow)

2-Kidney :
a) Angiomyolipoma :
50 %, usually multiple and bilateral
b) Multiple cysts
3-Bone :
-Bone islands in multiple bones
-Periosteal thickening of long bones
-Bone cysts

4-Chest :
a) Pulmonary Lymphangioleiomyomatosis
b) Spontaneous pneumothorax , 50%
c) Chylothorax
d) Cardiac rhabdomyomas, 5%
e) Aortic aneurysm

LAM with spontaneous pneumothorax

2-Neurofibromatosis :
a) Types
b) NF1
c) NF2

a) Types :
NF1 NF2
1-Name von Recklinghausen
disease
Bilateral acoustic
neuroma
2-Defect Chromosome 17 Chromosome 22
3-Incidence 90% 10%
4-Skin changes Prominent Minimal
5-Tumors Hamartomas, gliomas,
malignant nerve sheath
tumor
Meningiomas,
schwannoma,
ependymoma
6-Spine Neurofibroma Schwannoma

b) NF1 :
1-Definition
2-Diagnostic Criteria

1-Definition :
-NF1 also known as von Rechlinghausen disease , is a
multisystemic neurocutaneous disorder with
prominent skin manifestation (e.g. café au lait
spots) , peripheral nerve sheath tumors (e.g.
plexiform neurofibroma) , CNS malignancies (e.g.
optic nerve glioma) & bony abnormalities (e.g.
sphenoid wing dysplasia)
-AD in 50 % of cases & occurs sporadically in 50 % ,
caused by a defect in chromosome 17

2-Diagnostic Criteria : Need ≥2 criteria
1-≥6 cafe au lait spots
2-≥2 pigmented iris hamartomas (Lisch nodules)
3-Axillary , inguinal freckling
4-≥2 neurofibroma (or 1 plexiform neurofibroma)
5-Optic nerve glioma
6-First-degree relative with NF1
7-Dysplasia of greater wing of sphenoid

Café au lait spots , axillary freckling and neurofibromas

3-Radiographic Features : NF1 typically has lesions
of neurons and astrocytes
a) CNS
b) Spinal cord / Canal
c) Skull
d) Skeletal
e) Chest
f) Vascular
g) Other

a) CNS :
1-FASI (Focal Area of Signal Intensity)
2-Optic Nerve Glioma
3-Low Grade Pilocytic Astrocytoma
4-Diffuse Brain Stem Glioma
5-Moyamoya Cerebral Occlusive Disease
6-Aneurysms

1-FASI (Focal Areas of Signal Intensity) :
-Are bright areas on T2 commonly identified in the
basal ganglia (often the globus pallidus), thalamus,
brainstem (pons), cerebellum and subcortical white
matter
-FASI areas are the most common neuroimaging
feature in NF1 patients 1, with a significant
frequency (86%) of one or more FASI areas in
children with NF1
-FASI lesions are usually isointense on T , without
contrast enhancement and with a bright signal on T2
and FLAIR

T2 through the cerebellum shows hyperintense (unidentified
bright objects) of NF representing myelin vacuolation (arrows)

T2 shows hyperintense signals in the left globus pallidus and
bilateral posterior aspects of the thalami (white arrows)

FLAIR shows hyperintense signal changes on both sides in the
area of the basal ganglia , right more than left

2-Optic Nerve Glioma :
-Typically present in children, and often in the
setting of NF1
3-Low Grade Pilocytic Astrocytoma :
-Seen in up to 20% of all patients with NF1 and
typically manifest in early childhood
-Approximately 1/3 of pilocytic astrocytomas
involving the optic nerves have associated NF1

Optic nerve glioma in NF1 , (a) T1 reveals circumscribed enlargement of the optic
nerve with an isointense signal , (b) T2 shows hyperintense signaling of the mass
that is contained within the dura of the optic nerve , (c) T1+C shows enhancement
of the fusiform kinked shaped optic nerve tumor , (d) FLAIR shows the fusiform
image of the optic nerve tumor is again seen , also here evident are several high
signal lesions in the midbrain and cerebellum , consistent with the classic
hamartomatous CNS neurofibromas of NF1

Optic nerve glioma in NF1 , (a) T1 shows an Infiltrating lesion within the right
optic nerve with associated proptosis , (b) T1+C shows an enhancing
infiltrating mass extending from the right optic nerve to the chiasm and
into the suprasellar space

The lesion is hypointense on T1 and hyperintense on FLAIR , Optic chiasma
and left optic nerve are involved. It was enhancing uniformly on T1+C (not
shown) , the histopathologic diagnosis was pilocytic astrocytoma

4-Diffuse Brain Stem Glioma :
-Account for 60-75% of all brainstem gliomas
and most frequently arise in the pons
-Typically present in childhood (3 to 10 years of
age
-Hypo in T1 , Hyper in T2 , no enhancement or
enhances minimally , no diffusion restriction
5-Moyamoya Cerebral Occlusive Disease (rare)
6-Aneurysms

Diffuse brain stem glioma , (a) T1 , (b) T2 , (c) T1+C

Diffuse brain stem glioma , (a) T1 , (b) T2 , (c) T1+C , (d) Diffusion

b) Spinal cord / Canal :
1-Neurofibromas of exiting nerves :
-Enlarged neural foramen
-Intradural extramedullary tumors (classic dumbbell tumors)
-Neurofibromas are WHO grade I nerve sheath tumor
-The cutaneous & subcutaneous nerves are more commonly
involved than the more proximal peripheral nerves
-A plexiform subtype is more aggressive and consists of network
of fusiform-shaped masses with malignant degeneration (in 5
%)
-Like schwannomas, neurofibromas are likely of Schwann cell
origin
-The target sign can be seen with either neurofibromas or
schwannomas and reflects central T2 hypointensity thought
to be due to a fibrocollagenous core, the target sign is
suggestive of benignity
-In contrast to schwannomas, neurofibromas aren’t
encapsulated and involve the entire cross-sectional area of
the nerve , if a neurofibroma is resected, the parent nerve
must therefore be sacrificed

T2 shows L3 nerve root neuroma , note the target sign

Coronal T2 of the lumbar spine shows the characteristic Target
appearance of plexiform neurofibromas (red arrow) which are
hyperintense with central hypointensity

Right orbital plexiform neurofibroma , sphenoid wing hypoplasia
and likely optic nerve glioma

T2 shows subcutaneous mass over the left occipito-temporal region with
multiple serpiginous lesions and targetoid appearance manifested with
peripheral bright and central dark signal (arrow) suggestive of plexiform
neurofibroma

T2 shows plexiform neurofibroma

2-Dural Ectasia :
-Enlarged neural foramen
-Posterior vertebral scalloping
3-Low-grade cord astrocytoma

Dural ectasia , T2 showing posterior vertebral scalloping by dural ectasia
(asterisks)

c) Skull :
1-Hypoplastic sphenoid wing :
-Is a characteristic yet not a pathognomonic
feature of NF1, it can also occur in isolated
case
-Sphenoid wing dysplasia is seen in 5-10% of
cases of NF1 and is one of the diagnostic
criteria of NF1
It can be seen isolated or associated with
underlying plexiform neurofibroma
2-Macrocrania
3-Lambdoid suture defect

Absence of the right sphenoid wing and the intracranial and
orbital contents separated only by dura mater

Absence of the sphenoid wing with underlying plexiform
neurofibroma

d) Skeletal :
-50-80 %
-Erosion of bones and foramina by slow-growing
neuromas
-Bowing of tibia and fibula, pseudarthroses
-Unilateral overgrowth of limbs : focal gigantism
-Rib notching (Twisted ribbon ribs) : due to
erosion from neurofibromas of the intercostal
nerves
-Cervical kyphoscoliosis with a characteristic
acute angle

The PA chest film shows a rounded lesion with the (incomplete border sign) (medial
aspect outlined by air, lateral border not visible because in contact with chest wall)
, in addition , there is erosion of the lower border of the rib (arrow) , this
combination of signs is pathognomonic of a mass in the underside of the rib , CT
confirms the presence of a soft-tissue mass and the erosion of the rib (arrows)

e) Chest :
1-Progressive pulmonary fibrosis
2-Intrathoracic meningocele
3-Lung and mediastinal neurofibromas

NF1 , CT shows an associated large , lateral thoracic meningocele
(arrows)

Known patient with NF1 , (a) CT shows multiple large prevascular and
paratracheal neurofibromas , (b) CT shows paraesophageal and pleura-
based neurofibromas (arrows)

f) Vascular :
1-Renal artery stenosis
2-Renal artery aneurysm
3-Abdominal coarctation
g) Other :
-Pheochromocytoma

c) NF2 :
1-Definiton
2-Diagnostic Criteria

1-Definiton :
-Autosomal dominant neurocutaneous disorder
completely unrelated to NF1
-Despite the name , neurofibromas are not a
component of NF2
-Caused by a defect on chromosome 22 and is
approximately ten times less common than NF1
-The typical clinical presentation of NF2 is hearing loss
caused by bilateral vestibular schwannomas , the
presence of bilateral vestibular schwannomas is
diagnostic of NF2

2-Diagnostic Criteria : need ≥1 criterion
a) Bilateral acoustic neuromas
b) First-degree relative with NF2 and unilateral
acoustic neuroma or meningioma , glioma ,
schwannoma & neurofibroma (any two)

3-Radiographic Features : NF2 typically has lesions
of Schwann cells and meninges
-(MISME): Multiple Inherited Schwannomas ,
Meningiomas and Ependymomas
a) CNS :
1-Bilateral acoustic schwannoma (diagnostic)
2-Other cranial nerves schwannomas (Trigeminal
schwannoma)
3-Meningioma (often multiple)

Meningiomatosis & bilateral vestibular schwannomas in NF2 , multiple axial
T1+C show numerous enhancing extra-axial , dural based masses
bilaterally , representing meningiomas , there are bilateral enhancing
cranial nerve VIII schwannomas (arrows)

(a) Bilateral schwannomas , (b) Multiple Meningiomatosis

b) Spinal cord / Canal :
1-Intradural , extramedullary meningiomas
2-Schwannomas
3-Intramedullary ependymoma

Intradural extramedullary meningioma

3-Sturge-Weber Syndrome :
a) Definition
b) Clinical Picture
c) Radiographic Findings

a) Definition :
-A neurocutaneous disorder characterized by facial port-wine
stain (capillary malforamtion) , ocular abnormalities & failure
of normal cortical venous development
-It is a vascular disorder , thought to be caused by failure of
regression of the primitive embryologic cephalic venous
plexus , this developmental anomaly results in the formation
of leptomeningeal venous angiomatosis , which is a vascular
malformation characterized by dilated capillaries & venules
-The underlying vascular anomaly ultimately leads to chronic
ischemia , cortical atrophy & cortical calcification

1-Congenital facial cutaneous hemangioma (port
wine stain or facial naevus flammeus)
-Almost always present and usually involves the
ophthalmic division (V1) of the trigeminal nerve
2-Seizures , 90 %
3-Mentral Retardation
4-Ipsilateral Glaucoma
5-Hemiparesis , 50 %

c) Radiographic Findings :
1-CT :
-Tramtrack cortical calcifications (characteristic) that
follow cortical convolutions , most common in
parietal & occipital lobes
-Atrophic cortex with enlarged adjacent subarachnoid
space
-Ipsilateral thickening of skull and orbit
-Leptomeningeal venous angiomas : parietal > occipital
> frontal lobes , enhancement
-Enlargement and increased contrast enhancement of
ipsilateral choroid plexus

NECT shows subcortical calcification & cerebral atrophy

2-MRI :
*T1+C :
-Prominent leptomeningeal enhancement in
affected area
*GE / SWI / EPI :
-Sensitive to calcification

T1+C shows diffuse leptomeningeal enhancement , most
prominent in the RT occipital lobe and bilateral choroid plexus
engorgement

T1+C showing gyriform contrast enhancement in the right cerebral hemisphere , there
is brain atrophy on the right side , the cranial vault is asymmetric as secondary to
brain atrophy

-The differential is a combination of that for
multiple intracranial calcifications , cerebral
hemiatrophy and leptomeningeal
enhancement

4-Von Hippel-Lindau (VHL) disease :
a) Definition
b) Clinical Picture
c) Radiological Findings

a) Definition :
-Cerebelloretinal Hemangioblasotma
-Characterized by the presence of
hemangioblastomas and renal (renal cell
carcinoma and cysts) , adrenal , pancreatic
and scrotal abnormalities

1-Hemangioblastoma :
-50 %
-Cerebellum (most common location)
-Brainstem , spinal cord
-Retinal

2-Renal :
-RCC , 50 % ( bilateral in 65 % , multiple in 85 % )
-Benign Renal Cysts , 60 %
3-Adrenal Glands :
-Pheochromocytoma , 15 % , bilateral in 40 %

4-Pancreas :
-Multiple cysts , 70 %
-Cystadenocarcinoma
-Islet cell tumor
5-Scrotum :
-Epididymal cysts , 10 %
6-Other :
-Hepatic cysts , 20 %
-Splenic cysts , 10 %

c) Radiological Findings :
-Hemangioblastomas: See Brain tumors
-Multiple hemangioblastomas is diagnostic of VHL
disease
-MRI is the first study of choice
-CT is often used to evaluate kidneys , adrenals and
pancreas
-Most patients with solitary hemangioblastoma do
not have VHL disease

5-Osler-Weber-Rendu : ( Hereditary
Hemorrhagic Telangiectasia )
a) Embolic Infarcts :
-Emboli through pulmonary AV shunts
b) Cerebral Abscess :
-Septic emboli through pulmonary AV shunts
c) Vascular Malformations :
-Telangiectasia , cavernomas , AVM & AVF

Diagnostic Imaging of Congenital Central Nervous System Diseases

Diagnostic Imaging of Congenital Central Nervous System Diseases

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (19)

Similar to Diagnostic Imaging of Congenital Central Nervous System Diseases

Similar to Diagnostic Imaging of Congenital Central Nervous System Diseases (20)

More from Mohamed M.A. Zaitoun

More from Mohamed M.A. Zaitoun (20)

Recently uploaded

Recently uploaded (20)

Diagnostic Imaging of Congenital Central Nervous System Diseases