Diagnostic Imaging of Brain Tumors

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

Brain Tumors
1-Glial Tumors (Gliomas)
2-Meningeal and Mesenchymal Tumors
3-Neuronal & Mixed Glial / Neuronal Tumors
4-Germ Cell Tumors
5-PNETs
6-Pineal Region Tumors

7-Pituitary Tumors
8-Nerve Sheath Tumors
9-Hematopoietic Tumors
10-Tumor-Like Lesions
11-Metastases
12-Cystic Lesions
13-Brian Tumors In Children
14-Intraventricular Masses

1-Glial Tumors (Gliomas) :
a) Overview of Glial Cells
b) Incidence
c) Types

a) Overview of Glial Cells
-A glioma is a primary CNS tumor that arises from a glial cells ,
glial cells include astrocytes , oligodendrocytes , ependymal
cells and choroid plexus cells
-Astrocyte :
*The normal functions of an astrocyte are to provide
biochemical support to the endothelial cells that maintain the
blood brain barrier , to maintain extracellular ion balance and
to aid in repair after a neuronal injury
*Astrocytes are normally located throughout the entire brain
(primarily in the white matter) and spinal cord

-Oligodendrocyte :
*The normal function of an oligodendrocyte is to
maintain myelin around CNS axons , a single
oligodendrocyte can maintain the myelin of dozens
of axons
*The counterpart in the peripheral nervous system is
the Schwann cells , which maintains myelin around a
single peripheral nerve , unlike the
oligodendrocytes , each Schwann cell is in charge of
only single axon
*Oligodendrocytes are normally located throughout
the entire brain and spinal cord

-Ependymal Cells :
*The normal function of an ependymal cell is to circulate CSF
with its multiple cilia
*Ependymal cells line the ventricles and central canal of the
spinal cord
-Choroid Plexus Cells :
*The normal function of a choroid plexus cell is to produce CSF ,
a choroid plexus cell is a modified ependymal cell
*Choroid plexus cells are located intraventricularly , in the body
and temporal horn of each lateral ventricle , roof of the 3rd
ventricle and roof of the 4th
ventricle

b) Incidence :
-Most common primary brain tumors
c) Types :
1-Astrocytomas (most common glioma , 80%)
2-Oligodendroglioma , 5%-10%
3-Ependymal Tumors
4-Choroid Plexus Tumors

1-Astrocytomas :
a) Incidence
b) Associations
c) Classifications

a) Incidence :
-Astrocytomas represent 80% of gliomas
-Most tumors occur in cerebral hemispheres in
adults
-In children , posterior fossa and hypothalamus /
optic chiasm are more common locations
-The differentiation of types of astrocytoma is
made histologically not by imaging

b) Associations :
1-Tuberous sclerosis
2-Neurofibromatosis

c) Classifications :
(i) Fibrillary Astrocytomas :
1-Astrocytoma , WHO grade I (AI)
2-Astrocytoma , WHO grade II (AII)
3-Anaplastic Astrocytoma , WHO grade III
(AA III)
4-Glioblastoma Multiforme , WHO grade IV
(GBM IV)
5-Brain stem Glioma

(ii) Other Astrocytomas :
1-Multicentric (Multifocal) Glioma
2-Gliomatosis Cerebri (Grade IV)
3-Juvenile Pilocytic Astrocytoma (Grade I)
4-Giant cell astrocytoma (in tuberous sclerosis) ,
(Grade I)
5-Xanthoastrocytoma (Grade I)
6-Gliosarcoma (Grade IV)

-Fibrillary Astrocytomas :
1-Astrocytoma , WHO grade I (AI)
2-Astrocytoma , WHO grade II (AII)
3-Anaplastic Astrocytoma , WHO grade III
(AA III)
4-Glioblastoma Multiforme , WHO grade IV
(GBM IV)
5-Brain stem Glioma

1-Astrocytoma , WHO grade I (AI) :
-Focal
-Hemorrhage & edema are rare
-Hypo in T1 , Hyper in T2 with no enhancement
-Diffusion : no restricted diffusion

FLAIR shows subtle thickening and mild T2 prolongation in a single gyrus in
the left frontal lobe (arrows) , this lesion shows no enhancement (T1+C
isn't shown)

2-Astrocytoma , WHO grade II (AII) :
a) Incidence
b) Radiographic Features

a) Incidence :
-Low grade infiltrative astrocytoma (diffuse
astrocytoma)
-Represent 20% of all astrocytomas
-Peak age : 20 to 40 years
-Primary location is in the cerebral hemispheres

b) Radiographic Features :
1-CT :
-Typically low grade infiltrating astrocytomas
appear as isodense or hypodense regions of
positive mass effect , often without any
enhancement
-Calcification is not seldom (10-20% of cases)

Axial CT , precontrast and postcontrast shows a low-grade astrocytoma of the left
frontal lobe , the tumor is nonenhancing

2-MRI :
*T1 : isointense to hypointense compared to white
matter , usually confined to the white matters and
causes expansion of the adjacent cortex
*T2 : mass-like hyperintense signals
*T1+C : no enhancement is often the rule , if
enhancement is seen in certain areas within the
mass like lesion it is a warning sign for a progression
to a higher grade
*Diffusion : no restricted diffusion

3-Anaplastic Astrocytoma (AAIII) :
a) Incidence

a) Incidence :
-Represent 30% of all astrocytomas
-Peak age: 40 to 60 years
-Primary location is in the cerebral hemispheres

-Heterogeneous mass
-Calcification uncommon
-Edema common
-Enhancement (reflects blood brain barrier
disruption) , the key to distinguishing
anaplastic astrocytomas from low grade
tumors is the presence of enhancement
which should be absent in the latter

-Unlike Glioblastoma , anaplastic astrocytomas
lack frank necrosis and as such central non-
enhancing fluid intensity regions should be
absent
*T1 : hypointense compared to white matter
*T2 : generally hyperintense but can be
heterogeneous
*T1+C : very variable but usually at least some
enhancement present , presence of ring
enhancement suggests central necrosis and
thus Glioblastoma rather than anaplastic
astrocytoma

4-Glioblastoma Multiforme (GBM IV) :
a) Incidence
b) Tumor Spread
c) Radiographic Features

a) Incidence :
-Most common primary brain tumor (represents
55% of astrocytomas)
-Age: > 50 years
-Primary location is in the hemispheres :
Frontal lobe (genu)
Tempero-Occipital (splenium)

b) Tumor Spread :
-Tumor may spread along the following routes :
1-WM tracts
2-Across midline via commissures (e.g. corpus
callosum) , i.e. butterfly glioma
*N.B. : D.D. of transcallosal mass is : GBM , lymphoma
& demyelinating disease
3-Subependymal seeding of ventricles
4-CSF seeding of subarachnoid space

Transependymal spread of GBM , T1+C shows extensive abnormal
enhancement primarily in the left occipital lobe but extending into the
bilateral periventricular frontal lobes via the subependymal surface
(arrows)

c) Radiographic Features :
1-CT :
-Usually heterogeneous low-density mass
-Strong contrast enhancement
-Hemorrhage , necrosis (irregular hypodense center) common
-Calcification is uncommon
-Extensive vasogenic edema and mass effect
-Bihemispheric spread via corpus callosum or commissures
(butterfly lesion)
-CSF seeding : leptomeningeal drop metastases

CT showing hemorrhage inside the GBM

CT+C shows a peripherally enhancing GBM with central necrosis, to be
differentiated from cerebral abscess which shows diffusion restriction ,
while GBM shows no restriction, also GMB shows irregular margins while
abscess shows smooth margins

Diffusion GBM Diffusion Abscess

2-MRI :
*T1 :
-Hypo to isointense mass within white matter
-Central heterogenous signal (necrosis , intratumoral
hemorrhage)
*T2 :
-Hyperintense
-Surrounded by vasogenic edema
*T1+C :
-Enhancement is variable but is almost always present
-Heterogenous enhancement or peripheral and irregular with
nodular components , usually completely surrounds necrosis
*Diffusion :
-No diffusion restriction

5-Brain Stem Glioma :
a) Incidence
b) Clinical Picture
c) Types
d) Radiographic Features

a) Incidence : 3P (Pediatric, posterior fossa,
Pons)
-Common pediatric posterior fossa tumor
-Mean age : 10 years
-80% are anaplastic high grade , 20% are low
grade and grow slowly (WHO II to IV)
-Types :
*Diffuse brain stem glioma
*Focal brains tem glioma : tectal glioma
-Locations : pons > midbrain > medulla

b) Clinical Picture :
-Ataxia
-Cranial nerve VI and VII neuropathy
-Long tract signs
-Hydrocephalus

c) Types :
1-Medullary
2-Pontine
3-Mesencephalic (Midbrain)
4-Those associated with NF1

1-Medullary :
-Least common
-Young children
-Low attenuation (CT) , low signal T1 and high
signal T2
2-Pontine :
-Most common
-Diffuse tumors are low attenuation (CT) , low
signal T1 and high signal T2
-Flattening of the floor of the fourth ventricle
-Contrast enhancement is rare

3-Mesencephalic : (Midbrain)
-Focal tumors are more common than diffuse
4-Those associated with NF1 :
-Most commonly in the medulla

d) Radiographic Features :
1-Enlargement of brainstem
2-Posterior displacement of 4th ventricle
3-Enhancement occurs in 50% and is usually
patchy and variable
4-Exophytic extension into basilar cisterns
5-Hydrocephalus , 30%

*N.B. : Tectal Glioma
-Focal tumors localized to the tectal plate are termed tectal
gliomas and constitute a distinct subset of brainstem gliomas
-Because these tumors have good long-term prognosis and are
located deep , they are usually followed without biopsy and
with serial imaging to document stability
-Their expansion within the brainstem causes narrowing
the aqueduct of Sylvius and causing obstructive
hydrocephalus with presentation usually secondary to
headache
-If a lesion extends beyond the tectum but is still confined to the
midbrain , it is referred to as a peritectal tumor and carries a
worse prognosis than that for purely tectal lesions
-Peritectal tumors may be difficult to differentiate from pineal
region tumors

-Radiographic Findings :
*T1 : iso to slightly hypointense to grey matter
*T2 : hyperintense to grey matter
*T1+C : usually no enhancement

(ii) Other Astrocytomas :
1-Multicentric (Multifocal) Glioma
2-Gliomatosis Cerebri
3-Juvenile Pilocytic Astrocytoma
4-Giant cell astrocytoma (in tuberous sclerosis)
5-Pleomorphic Xanthoastrocytoma
6-Gliosarcoma

1-Multicentric (Multifocal) Glioma :
-The actual incidence of true multicentric
glioblastoma multiforme (GBM) varies
between 2.4 and 4.9% of all GBMs
-True multicentric tumors are described as
widespread lesions in different lobes or
hemispheres
-Differential Diagnosis : From Metastases (but
metastases is more common)

2-Gliomatosis Cerebri :
a) Definition
b) Incidence
d) Differential Diagnosis

a) Definition :
-Diffusely infiltrative glial tumor that involves at least
three lobes by definition plus extra-cortical
involvement of structures such as the basal ganglia ,
corpus callosum , brainstem or cerebellum
-Usually there are no gross mass lesions
-There often is an important discordance between
clinical and radiological findings as it may be clinically
silent while it appears as a very extensive
process radiologically

b) Incidence :
-Age : 30 to 40 years
-Rare
-WHO (Grade IV)

1-CT
2-MRI

1-CT :
-Can be normal because lesions often isodense to
normal brain parenchyma
-There is relative lack of mass effect and distortion
-There may be an ill defined asymmetry or subtle
hypoattenuation to the involved brain
parenchyma
-Usually nonenhancing lesions

2-MRI :
-Mass effect and enhancement are minimal
(typically doesn’t enhance)
-There is loss of GM / WM differentiation and
diffuse gyral thickening
-T1 : iso to hypointense to grey matter
-T2 : hyperintense to grey matter

FLAIR shows diffuse confluent T2 prolongation involving the right medial
temporal lobe , basal ganglia & frontal lobe white matter (arrows) , there
is mild mass effect and shift to the left

d) Differential Diagnosis : Diffuse T2
prolongation
1-PML : in immunocompromised patient , no
mass effect
2-Lymphomatosis Cerebri
3-Multicentric glioma
4-Viral Encephalitis
5-Vasculitis
6-ADEM

3-Juvenile Pilocytic Astrocytoma :
a) Incidence
b) Location
c) Association
e) Differential Diagnosis

a) Incidence :
-Most common in children (represents 30% of
pediatric gliomas)
-Second most common pediatric brain tumor
-WHO Grade I

b) Location :
-Most common location is the cerebellum
-Vermis (50%) or hemispheres (20%) or both sites
(30%)
-In general they typically arise from midline structures :
1-Optic nerve / optic chiasm ( 25-30% ) , very common
location in NF1
2-Hypothalamic / adjacent to third ventricle
3-Brainstem

c) Association :
-There is a strong association with
neurofibromatosis type 1 (NF1)
-NF1 associated tumors have a tendency to affect
the optic nerves and chiasm but not the posterior
fossa JPA
-Pilocytic astrocytomas are seen in up to 15-20% of
all patients with NF1 and typically manifest in
early childhood
-Approximately 1/3 of pilocytic astrocytomas
involving the optic nerves have associated NF1

-Cerebellar tumors are usually cystic and have intense
mural enhancement
-Calcification , 10%
-Optic chiasm / hypothalamic tumors are solid and
enhance
-Most in brainstem show little enhancement
-MRI :
*T1 : iso to hypointense solid component compared to
adjacent brain
*T2 : hyperintense solid component compared to
adjacent brain

T1+C shows a large posterior fossa cystic lesion with a superior heterogeneously
enhancing solid component (arrow) , the 4th
ventricle is completely effaced , the
brainstem is deformed and there is severe hydrocephalus

e) Differential Diagnosis :
1-Medulloblastoma :
-Typically arise from the midline (especially
vermis and roof of the fourth ventricle) rather
than cerebellar hemisphere
-Usually seen in younger patients (2-6 years of
age)

2-Ependymoma :
-Tends to fill the fourth ventricle and protrude
out of the foramen of Luschka and foramina
of Magendie
-Large cystic component less common
3-Hemangioblastoma :
-Usually seen in adults
-Associated with von Hippel Lindau disease

4-Pleomorphic Xanthoastrocytoma (PXA) :
-Almost ( 98% ) located supratentorially
5-Cerebellar Abscess :
-Has a different clinical presentation and has no
enhancing nodule

*N.B. :
-Tumors with a cyst and an enhancing nodule :
2-Hemangioblastoma
3-Pleomorphic Xanthoastrocytoma
4-Ganglioglioma

4-Subependymal Giant Cell Astrocytoma :
a) Incidence
b) Location

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

b) Location :
-Located at foramen of Monro
1-CT
2-MRI

1-CT :
-Typically appears as an enhancing intraventricular
mass in the lateral ventricle 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)

2-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

d) 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)

5-Pleomorphic Xanthoastrocytoma :
a) Incidence
b) Location

a) Incidence :
-Type of rare low grade astrocytoma (WHO
Grade I)
-Typically these tumors are found in young
patients (children or young adults) and as they
have a predilection for the temporal lobe,
they most frequently present with temporal
lobe seizures

b) Location :
-PXAs are almost invariably (98%) located
supratentorially , typically located superficially
(peripherally) involving the cortex and
overlying leptomeninges
-Approximately half are located in the temporal
lobe

1-CT :
-Often there is a cystic component ( 50-60% ) with
an enhancing mural nodule
-They are one of the tumors that may exhibit a
dural tail which is reactive rather than due to
direct dural invasion , which is rare
-Hypo or isodense and may be well or poorly
demarcated usually with little surrounding
edema

2-MRI :
*T1 :
-Iso to hypointense
-Leptomeningeal involvement seen in over 70% of
cases
*T2 :
-Iso to hyperintense
-Little surrounding vasogenic edema
*T1+C :
-Solid component usually enhances vividly

(a) T2 , (b) T1+C show a large right temporal predominantly cystic mass , the
mass has enhancing nodularity laterally (red arrow) , the overlying dura is
thickened and enhancing (yellow arrow) , there is relatively little
surrounding edema given the large size of the lesion

-The main differential diagnosis both by imaging
and clinical presentation is Ganglioglioma ,
however ganglioglioma doesn’t usually cause
dural thickening

6-Gliosarcoma :
a) Incidence

a) Incidence :
-Are rare highly malignant (WHO grade IV) primary
intra-axial neoplasms
-They are often considered a histological variant
of glioblastoma multiforme (GBM)
-Peak presentation is around the 6th decade
-The tumor is very similar to (GBM) but with an added
sarcomatous component (the tumor comprises of
both glial and mesenchymal elements)

-Can be very similar to glioblastoma multiforme
(GBM)
-There may be slight predilection towards the
temporal lobes
-May demonstrate dural invasion

2-Oligodendroglioma :
a) Incidence
b) Types
c) Location

a) Incidence :
-These are usually tumors of middle-aged adults
occurring most commonly in the 4th
and 5th
decades of life
-Due to their usual cortical involvement ,
presentation is most frequently as a result of
seizure

b) Types :
1-Oligodendroglioma (WHO grade II / low grade)
2-Anaplastic Oligodendroglioma (WHO grade
III / high grade) , much more aggressive than
oligodendroglioma
3-Oligoastrocytoma (mixed oligodendroglioma
and astrocyoma) , much more aggressive than
oligodendroglioma

c) Location :
-Tumors are typically located supratentorially
(85%) involving the white matter and
overlying cortex
-They are most commonly found in the frontal
lobes

1-CT :
-Tumors are of mixed density (hypodense to
isodense)
-Calcification (70-90% of are calcified) , calcification
can be located centrally , peripherally or they can
be ribbon-like
-50% enhance , degree of enhancement is
extremely variable (no enhancement to striking)

CT shows a hypoattenuating mass in the left frontal lobe containing coarse
calcifications , the lack of significant edema suggests a slow growing lesion

2-MRI :
*T1 :
-Typically hypointense
*T2 :
-Typically hyperintense (except calcific areas)
*T1+C :
-Contrast enhancement is common but it is not a
reliable indicator of tumor grade with only 50%
enhancing to a variable degree and usually
heterogeneously

3-Ependymal Tumors :
a) Types
b) Ependymoma
c) Subependymoma

a) Types :
-The ependyma refers to a layer of ciliated cells lining
the ventricular walls and the central canal
-There are several histologic variants of ependymal tumors:
1-Ependymoma (children)
2-Subependymoma (older patients)
3-Anaplastic Ependymoma
4-Myxopapillary Ependymoma of Filum Terminale
5-Ependymoblastoma (PNET)

b) Ependymoma :
1-Incidence
2-Location
3-Association
4-Radiographic Features
5-Differerntial Diagnosis

1-Incidence :
-Most common in children
-Age : 1 to 5 years

2-Location :
-Usually located in or adjacent to ventricles within
the parenchyma
-The majority of intracranial ependymomas (60%)
are located in the posterior fossa (infratentorial)
usually arising from the floor of the fourth
ventricle , this is especially true in children
-The remainder (40%) are located supratentorially
and up to half of these are intraparenchymal

a) Floor of the fourth ventricle , 70%
(commonest location in children)
b) Lateral ventricle or periventricular
parenchymal , 30% , more common in adults
c) Spinal cord ependymoma (in adults)
d) Supratentorial ependymoma

3-Association :
-Spinal ependymomas are associated with
neurofibromatosis type 2 (NF2)

4-Radiographic Features : Heterogenous
1-CT :
-Growth pattern depends on location :
a) Supratentorial : tumors grow outside
ventricle (i.e. resembles astrocytoma) ,
remember to include ependymoma in the
differential diagnosis of a supratentorial
parenchymal mass lesion particularly in a child

b) Infratentorial : tumors grow inside 4th
ventricle and extend through foramen of
Luschka into CPA and cisterna magna , this
appearance is characteristic (plastic
ependymoma) and often helps to differentiate
an ependymoma from a medulloblastoma
-Hydrocephalus is virtually always present when
in posterior fossa
-Fine calcifications , 50%
-Cystic areas , 50%
-Heterogenous enhancement
-A small proportion can have hemorrhage

2-MRI :
*T1 :
-Solid portions of ependymoma typically are
isointense to hypointense
*T2 :
-Hyperintense
*T1+C :
-Enhancement present but heterogeneous

(a) T1 , (b) T1+C show a lobulated isointense , avidly enhancing mass arising
from the 4th
ventricle (arrows) , there is kinking of the brainstem and
obstructive hydrocephalus of the 3rd
ventricle

5-Differerntial Diagnosis :
a) Medulloblastoma :
-Similar demographic especially if around the
4th
ventricle
-Arises from vermis
-Less plastic , does not tend to extend through
foramina
-Enhancement more homogenous &
calcification less common

b) Subependymoma :
-Tends to occur in older individuals
c) Choroid Plexus Papilloma :
-In children usually in the trigone of the lateral
ventricles
-In adults usually in the fourth ventricle (i.e.
opposite to ependymoma)
-More vividly and homogeneously enhancing

d) Choroid Plexus Metastases :
-Can appear similar
-Older individuals , usually with a history of malignancy
e) Glioblastoma :
-Difficult to distinguish from intraparenchymal
supratentorial ependymoma
-Usually older patients
-Epicenter usually in the white matter
f) Central Neurocytoma :
-Usually arises from / in contact with septum
pellucidum
-Less vivid enhancement

c) Subependymoma :
1-Incidence
2-Location
4-Differential Diagnosis

1-Incidence :
-Middle aged to older individuals ( typically 5th
to
6th
decades )
-Asymptomatic fourth ventricular tumor found
in elderly males

2-Location :
-2/3 arise in the fourth ventricle (inferior 4th
ventricle)
-1/3 in lateral ventricles (foramen of Monro)

4th
ventricle Lateral ventricle

3-Radiographic Features : No enhancement
a) CT :
-Isodense to hypodense intraventricular mass compared
to adjacent brain which doesn’t usually enhance
-If large , it may have cystic or even calcific (up to half of
cases) components
-Surrounding vasogenic edema is usually absent
-Unlike ependymomas , these tumors tend not to seed
the subarachnoid space
-Lesions often are multiple

b) MRI :
*T1 :
-Iso to hypointense
-Usually homogenous but may be heterogenous in
larger lesions
*T2 :
-Hyperintense to adjacent white and grey matter
*T1+C :
-Usually no enhancement , although at times may
demonstrate mild enhancement

T1 shows an isointense mass in the inferior 4th
ventricle (arrows) ,
the 4th
ventricle is normal in size

(a) FLAIR shows the inferior 4th
ventricular mass (arrow) is slightly FLAIR
hyperintense , (b) T1+C shows absolutely no enhancement within the
lesion , these lesions can be easily missed on axial T1 with or without
contrast

4-Differential Diagnosis :
a) Ependymoma
b) Intraventricular Meningioma
c) Central Neurocytoma
d) Cerebral Metastases

4-Choroid Plexus Papilloma / Carcinoma :
a) Incidence
b) Location
d) Complications

a) Incidence :
-Peak age : < 5 years (85%)
-Most common brain tumor in babies < 1 year
old , but it may also occur in adults
-90% represent choroid plexus papilloma (WHO
I) , 10% choroid plexus carcinoma (WHO III)

b) Location :
-Unlike most other brain tumors which are more
common in the posterior fossa in children and
supratentorial compartment in adults , the
relationship is reversed for choroid plexus
papilloma
-In adults these tumors most often (70%) occur in
the fourth ventricle , In the pediatric age group
the lateral ventricles are the commonest location
with a predilection for the trigone

1-CT :
-Intraventricular mass , the tumors are usually well
defined lobulated masses , either iso or
somewhat hyperdense compared to the adjacent
brain
-Ventricular dilatation due to CSF overproduction or
obstruction
-Intense contrast enhancement
-Calcifications , 25%

2-MRI :
*T1 :
-Typically isointense to hypointense
*T2 :
-Iso to hyperintense
*T1+C :
-Marked enhancement , tends to be
homogenous

d) Complications :
1-Hydrocephalus
2-Drop metastases to spinal dural space

2-Meningeal and Mesenchymal Tumors :
a) Meningioma
b) Meningeal Hemangiopericytoma
c) Hemangioblasotma

a) Meningioma :
1-Incidence
2-Classification
3-Location
4-Morphological Types
6-Malignant Meningioma

1-Incidence :
-Most common extra-axial tumor
-Age: 40 to 60 years
-Three times more common in females
-Represents 20% of all brain tumors
-Meningiomas are uncommon in children and if present
are commonly associated with NF2
-90% are supratentorial
-Multiple meningiomas are seen in NF2 or following
radiation therapy

2-Classification :
a) Typical (benign) meningioma , 93% (WHO I)
b) Atypical meningioma , 5% (WHO II)
c) Anaplastic (malignant) meningioma , 1%-2%
(WHO III)
d) Meningioma with sarcomatous
degeneration , extremely rare

3-Location :
1-Convexity meningioma 20%
2-Parasagittal / falcine meningioma 25%
3-Sphenoid wing 20%
4-Olfactory groove 10%
5-Suprasellar/Parasellar 10%
6-Posterior fossa/ CPA meningioma 10%
7-Intraventricular 2%
8-Intraorbital < 2%
9-Tentorial < 2%
10-Foramen magnum meningioma < 2%

Frequent locations of meningiomas : 1-Convexity , 2-Parasagittal/falcine , 3-
Sphenoid wing , 4-Olfactory groove , 5-Suprasellar/Parasellar , 6-Posterior
fossa/ CPA

Rare locations of meningiomas : 1-intraventricular , 2-
intraorbital , 3-tentorial , 4-foramen magnum

Convexity meningioma with a dural tail

Parafalcine (arising the meningeal layer between
the hemispheres of the brain)

Typical parasagittal lobulated hyperdense
meningioma

Olfactory groove meningioma isointense signal on T1 (a), isointense on T2 (b),
with homogeneous gadolinium enhancement on T1+C (c,d,e)

(a) CT shows Left parasellar region meningioma
nearly isodense to the normal brain , (b) CT+C
shows homogeneously enhancing meningioma

Meningioma in the right posterior fossa

Large meningioma on the right posterior fossa ,
extending to the middle fossa

Large enhancing meningioma occupying part of the
right posterior fossa

Cerebellopontine angle meningioma

Left CPA homogeneously enhancing meningioma

Homogeneous enhancing meningioma in the
posterior surface of the right temporal bone

Intraventricular meningioma in the right occipital horn with its mild dilatation
: isointense signal on T1 (b), hyperintense on T2 (axial - c) and FLAIR (Cor -
a) with circumscribed peritumoral edema , hyperintense on DWI (d) and
homogeneous Gadolinium enhancement (e)

Calcified meningioma in atrium of right lateral ventricle

Intraorbital / optic nerve sheath meningioma

Tentorium cerebelli meningioma with homogeneous
enhancement on CECT (a) Cor , (b) axial , (c) Sag

A densely calcified meningioma in the right
tentorium

Right tentorial calcified meningioma

Clivus meningioma , occupying the prepontine cistern and
compressing the pons

Homogeneously enhancing meningioma of the
clivus compressing the pons

Meningioma of the clivus extending across the
tentorial hiatus to the suprasellar region

Large pineal region meningioma

Giant pineal region meningioma with hydrocephalus

Crista galli meningioma, partially calcified small mass on axial NECT (a, b),
with hyperostosis of the crista galli on Cor NECT (c)

4-Morphological Types :
a) Globose
b) En plaque Meningioma
c) Intraosseous Meningioma
d) Intraventricular Meningioma
e) Lipomatous

a) Globose :
-Globular , well-demarcated neoplasm with wide dural
attachment
b) En plaque Meningioma :
-Represents a morphological subgroup within the meningiomas
defined by a carpet or sheet-like lesion that infiltrates the
dura and sometimes invades the bone
-The en plaque variants commonly involve fronto-parietal ,
juxtaorbital , sphenoid wing , diffuse calvarial or rarely spinal
region
-Due to difficulty in complete resection , the recurrence rate of
en plaque meningiomas is higher than the usual counterpart
-These tumors are also more prone to develop malignant change
(11%) when compared to intracranial meningiomas (2%)

Globose meningioma En plaque meningioma

c) Intraosseous Meningioma :
-Frontoparietal and orbital regions are the most
common locations for intraosseous meningiomas
-Calvarial meningiomas are more prone to develop
malignant changes (11%) compared with intracranial
meningiomas (2%) and the association of osteolysis
with a soft-tissue mass is a strong reason to suspect
a malignant meningioma
-May mimic fibrous dysplasia

d) Intraventricular Meningioma :
-In the trigone / atrium of the lateral ventricle mostly
the left
e) Lipomatous :
-Uncommon subtype of meningiomas with radiological
features of conventional meningioma
-Arachnoidal cap cells , from which meningiomas arise
may undergo gradual transformation into other cell
types such as fat , bone , cartilage and myxoid tissue
but studies of lipomatous meningioma have shown
that lipid-laden cells retained meningothelial
characteristics , so lipomatous meningioma should
no longer be considered as a metaplasia and that
lipid accumulation results from a metabolic
abnormality of the neoplastic cells

Lipoblastic meningioma , CT (a,b) show tumor left frontal cerebral falx hypodense &
heterogeneous , MRI T1-fatsat (c) shows loss of mass signal , SWI (d) there is
significant magnetic susceptibility , T1+C (e) mass extraxial in cerebral falx strongly
enhance after contrast injection , T2 with mild edema peritumoral , findings
consistent with lipoblastic meningioma , mimicking a dermoid tumor in CT

5-Radiographic Features :
a) CT
b) MRI
c) Angiography
d) Atypical Meningioma

a) CT :
1-Signal Intensity
2-Morphology
3-Bony Abnormalities

1-Signal Intensity :
-Hyperdense (75%) or isodense (25%) on
noncontrast CT
-Strong homogeneous enhancement (90%)
(hallmark)
-Calcifications , 20%
-Cystic areas , 15%

Typical parasagittal meningioma on plain (A) and contrast-
enhanced (B) brain CT

Different patients with calcified meningiomas on Axial brain CT

2-Morphology :
-Round unilobulated sharp margin (most
common)
-En plaque , pancake spread along dura (rare)
-Dural tail : extension of tumor or dural reaction
along a dural surface
-Edema is absent in 40% because of the slow
growth

Left sided sphenoid wing en plaque meningioma , a - CT
scan bone window showing the bone involvement; b -
T1+C showing typical sheet-like dural involvement

Meningioma (yellow arrows) with clear brain
edema (red arrows)

3-Bony Abnormalities : 20 %
-No changes (common)
-Hyperostosis (common)
-Bone erosion (rare , if present may indicate
malignant meningioma)

Sphenoid wing meningioma showing an enhancing intracranial
component (small arrows) with intraorbital extension , note
reactive hyperostosis of the sphenoid bone (large arrows)

A, CT without contrast shows hyperostosis and bony erosion (arrow) at the
right anterior clinoid process , B, Postcontrast CT shows a well-enhancing
mass arising from right sphenoid ridge , C-E, Axial T1 (C) , contrast-
enhanced axial (D) and coronal (E) T1 show a marked enhancing extra-
axial mass at the sphenoid ridge

b) MRI :
-Tumors are typically isointense with GM
-Strong gadolinium enhancement
-Dural tail (60%) is suggestive but not specific for
meningioma
-May show cystic areas (15 %)
-Low signals inside the lesion on T1+C :
1-Calcification (Low T1 & T2)
2-Vessels (Low T1 & T2)
3-Minute areas of breakdown (Low T1 & High T2)

Cystic meningioma , Sagittal T1 (a) , T2 (b), T1+C sagittal and axial (c,d) Mass
right frontal meningioma and a large intratumoral cyst with rim
enhancement after contrast injection

c) Angiography :
-Spokewheel appearance
-Dense venous filling
-Persistent tumor blush (comes early and stays
late) = Mother’s in law sign
-Well-demarcated margins
-Dural vascular supply

d) Atypical Meningioma :
-5 % of all meningiomas
-Necrosis causing nonhomogeneous
enhancement
-Hemorrhage

6-Malignant Meningioma :
-1 to 3 %
-Rapid growth
-Extensive brain or bone invasion
-Bright on T2W imaging relative to brain
(indicating meningothelial , angioblastic ,
hemangiopericytic elements as opposed to
T2W hypointense benign meningiomas
containing primarily calcified or fibrous
elements)

-Histologically , malignant meningiomas include
the following cell types :
1-Hemangiopericytoma
2-Malignant Fibrous Histiocytoma (MFH)
3-Papillary Meningioma
4-Benign Metastasizing Meningioma

**N.B. :
Dural Metastases :
-The most common tumors to metastasize to
the dura are breast (most common) ,
lymphoma , small cell lung cancer &
melanoma

Dural metastases , (a) FLAIR shows a right frontal mass (yellow arrows) with
vasogenic edema affecting the right frontal lobe , (b) T1+C shows that the
mass (yellow arrow) is dural based and is associated with adjacent dural
enhancement (red arrows) , this was a case of metastatic breast cancer

b) Meningeal Hemangiopericytoma :
1-Incidence

1-Incidence :
-Are rare tumors and account for less than 1% of
all intracranial tumors
-They were previously classified as angioblastic
sub-type meningiomas
-They are more aggressive than meningiomas,
have a higher frequency of recurrence, and
are considered a grade II tumor in the WHO
Classification (c.f. grade I for meningioma)

-Distinguishing a Hemangiopericytoma from a
meningioma can be difficult as they have
similar appearances on both CT and MRI
-Helpful features include :
1-Lobulated contour
2-Absence of calcification and hyperostosis
3-Extensive brain or bone invasion (skull ,
common)

4-Bright on T2W imaging relative to brain
(indicating meningothelial , angioblastic ,
hemangiopericytic elements as opposed to T2W
hypointense benign meningiomas containing
primarily calcified or fibrous elements)
5-Multiple flow voids on MRI (need to distinguish from
spoke-wheel appearance of meningioma)
6-Corkscrew arteries
7-May have a narrow base of dural attachment

c) Hemangioblasotma :
1-Incidence
2-Location
3-Associations

1-Incidence :
-Typically occur in the young adult and although
they are the most common posterior fossa mass
in a young adult , they accounts for only 1-2.5%
of all intracranial tumors and approximately 10%
of all posterior fossa tumor
-Represents the most common primary cerebellar
tumor in adult patients with VHL syndrome ,
hemangioblastoma occur in 35% to 60% of VHL
patients

2-Location :
-Cerebellum > spinal cord (usually associated
with syrinx) > medulla
3-Associations :
-Von Hippel Lindau (VHL) disease
-Pheochromocytoma
-Polycythaemia

a) CT :
-Three different appearances :
1-Cystic lesion with an enhancing mural nodule ,
75%
2-Solid enhancing neoplasm , 10%
3-Enhancing lesion with multiple cystic areas , 15%

b) MRI :
*T1 :
-Hypointense to isointense mural nodule
-Fluid filled cyst
*T2 :
-Hyperintense mural nodule
-Flow voids due to enlarged vessels may be evident
especially at the periphery of the cyst , seen in
60-70% of cases
-Fluid filled cyst , similar to CSF

*T1+C :
-The tumors typically comprise of a cyst with
non-enhancing walls except for a mural
nodule which vividly enhances and often has
prominent serpentine flow voids

Medullary Hemangioblastoma , (a) T1 , (b) T2 showing well defined cystic
lesion at the level of medulla oblongata with a dorsally located mural
nodule

Medullary Hemangioblastoma , (a) T1 , (b)T2 , (c) FLAIR showing
well defined cystic lesion at the level of medulla oblongata

a) Metastases :
-Although single posterior fossa metastases are
uncommon they are still the most common
diagnosis if the patient is middle aged or older
b) Astrocytoma :
-Pilocytic Astrocytoma in children
-GBM in adults

c) Ependymoma
d) Vascular Lesions :
-AVM with subacute bleed
-Cavernoma with subacute bleed
-Subacute infarction

3-Neuronal & Mixed Glial / Neuronal Tumors :
a) Ganglioglioma / Ganglioneuroma
b) DNET
c) Central Neurocytoma

a) Ganglioglioma / Ganglioneuroma :
1-Incidence
2-Location

1-Incidence :
-Benign neoplasm of children / young adults
with glial and neural elements
-Low grade and slow growing (WHO I)
-Often presents with seizures

2-Location :
-Temporal > frontal > parietal
-The most common presentation is with
temporal lobe epilepsy , presumably due to
the temporal lobes being a favored location

a) CT :
-Typically presents as cyst with enhancing mural nodule
but may be entirely solid (isodense or hypodense)
-Calcification in up to 50%
-The ganglioglioma is usually well circumscribed and
located peripherally
-May occasionally erode the inner table of the adjacent
calvaria (indicate the slow growing nature of the
tumor)

Ganglioglioma in the right occipital lobe presenting as a cystic mass with rim
enhancement , notice calcification on CT

b) MRI :
*T1 :
-Iso to hypointense
*T2 :
-Hyper intense solid component with variable signal
in the cystic component depending on amount of
proteinaceous material or presence of blood
products
*T1+C :
-Variable contrast enhancement

(a) T2 , (b) T1+C show ganglioglioma in a young child , note large cyst with
enhancement of mural solid tissue

Axial FLAIR shows a cystic lesion in the right temporal lobe with an associated
large solid nodule (arrows) , there is mild surrounding edema and mild
mass effect with midline shift to the left

Axial T1 (a) shows heterogeneous signal intensity lesion in the left high parietal
region , Axial T2 (b) shows expansion of the overlying cortex and mass effect on
the medial aspect of the body of the left lateral ventricle , no surrounding edema
is seen , the heterogeneous signal intensity results from calcification/hemorrhage
within the lesion , T1+C (c) shows heterogeneous enhancement

-If in the temporal lobe consider :
a) PXA
b) Pilocytic Astrocytoma
c) DNET
d) Cystic Metastases

b) Dysembryoplastic Neuroepithelial Tumor
(DNET) :
1-Incidence
2-Location

1-Incidence :
-Occurs in younger patients
-Low grade (WHO I)
-Strongly associated with epilepsy
2-Location :
-Temporal lobe is common (>60%) and the lesion
often involves or lies close to mesial temporal
structures
-Other locations include frontal lobe followed by
parietal and/or occipital lobes

3-Radiographic Features : Cortical Lesion
a) CT :
-A well circumscribed hypodense often mixed
cystic and solid cortically based lesion in a
patient with long standing seizure should
bring DNET to mind
-If cortical may scallop the inner table of the
skull vault (44-60%) but no erosion
-No enhancement

CT+C shows a non enhancing wedge shaped cortical hypodense mass lesion with
Scalloped inner table

CT shows cortical and subcortical left frontal lobe DNET , note the scalloping
of the frontal bone

b) MRI :
-Typically seen as a cortical lesion with hardly any
surrounding vasogenic edema
*T1 :
-Generally low signal
*T2 :
-Generally high signal with focally brighter areas
*T1+C :
-No enhancement
-May show enhancement in 20-30% of cases

T1 shows low signal intensity cortical mass , T1+C shows No enhancement

T2 shows hyperintense cortical mass with focally brighter areas without any
surrounding edema / mass effect

-If in the mesial temporal lobe consider :
a) PXA
b) Oligodendroglioma
c) Pilocytic Astrocytoma
d) Ganglioglioma
e) Cystic Metastases

-If cortical consider :
1-Low grade astrocytoma
2-Ganglioglioma
3-PXA
4-Oligoastrocytoma / Oligodendroglioma

c) Central Neurocytoma :
1-Incidence
2-Location

1-Incidence :
-Typically seen in young patients (20 - 40 years
of age)
-Accounts for less than 1% of intracranial tumors
- WHO (Grade II) neuroepithelial intraventricular
tumors with typical imaging features

2-Location :
-Lateral ventricles around foramen of Munro
(most common) : 50% , It is usually attached
to the septum pellucidum when arising from
the lateral ventricle
-Both lateral and 3rd
ventricles : 15%
-Bilateral : 15%
-3rd
ventricle in isolation : 5%

3-Radiographic Features : Heterogenous
a) CT :
-Typical imaging appearance is a lobulated mass attached
to the septum pellucidum with numerous intratumoral
cystic areas
-Usually hyperattenuating compared to white matter
-Calcification seen in over half of cases usually punctate in
nature
-Cystic regions are frequently present , especially in larger
tumors
-Contrast enhancement is usually mild to moderate
-Accompanying ventricular dilatation often present

b) MRI :
*T1 :
-Isointense to grey matter
-Heterogenous
*T2 :
-Typically iso to somewhat hyperintense compared to
brain
-Numerous cystic areas (bubbly appearance) , many of
which completely attenuate on FLAIR
-Prominent flow voids may be seen
*T1+C :
-Mild to moderate heterogeneous enhancement

(a) T1+C , (b) T2 show a lobulated mass in the body of the lateral ventricle
(arrow) attached to the septum pellucidum the mass enhances and
contains foci of cystic change (seen as hyperintense foci on the T2)

4-Differential Diagnosis : Intraventricular Tumors
2-Ependymoma
3-Intraventricular Meningioma
4-Subependymoma
5-Subependymal giant cell astrocytoma
6-Choroid Plexus Papilloma
7-Intraventricular Metastasis

1-Central Neurocytoma :
-Common in young adults from teenager to young middle
aged-patients
-Typical imaging appearance is a lobulated mass attached
to the septum pellucidum with numerous intratumoral
cystic areas , calcification is common
2-Ependymoma :
-More frequent in childhood
-More commonly in 4th ventricle
-Supratentorial tumors (especially in children) often have a
significant extraventricular (parenchymal) component

3-Intraventricular Meningioma :
-Appears as solid
-Homogeneous contrast enhancement
-Well circumscribed mass
4-Subependymoma :
-Typically found in the 4th
ventricle
-Usually older individuals
5-Subependymal giant cell astrocytoma :
-In patients with tuberous sclerosis
-Vivid contrast enhancement

6-Choroid Plexus Papilloma :
-Mainly in children
-Typically show intense contrast enhancement
7-Intraventricular Metastasis :
-Older patients
-Usually stronger contrast enhancement
-History of primary (e.g. RCC)

4-Germ cell tumors :See (Pineal Region Tumors)
a) Germinoma
b) Teratoma
c) Embryonal Cell Carcinoma
d) Choriocarcinoma

5-Primitive Neuroectodermal Tumor (PNET) :
1-Incidence
2-Types
3-Medulloblastoma
4- Primary cerebral neuroblastoma

1-Incidence :
-Common in children
-Undifferentiated aggressive tumors that arise
from multipotent embryonic neuroepithelial
cells

2-Types :
a) Medulloblastoma (infratentorial PNET)
b) Primary Cerebral Neuroblastoma
(supratentorial PNET)
c) Retinoblastoma
d) Pinealoblastoma
e) Ependymoblastoma

3-Medulloblastoma :
a) Incidence
b) Location
c) Association
e) Tumor Spread
f) Tumor Recurrence
g) Differential Diagnosis

a) Incidence :
-Most common in childhood
-The most common pediatric posterior fossa
tumor
-Peak age : 2 to 8 years
-30-40% of posterior fossa tumors

b) Location :
-The vast majority (94%) of medulloblastomas
arise in the cerebellum and the majority of
these , from the vermis (80%) , they tend to
protrude into the fourth ventricle from its roof
and may even grow directly into
the brainstem
-Cerebellar midline mass in 80% , lateral
cerebellum 20% (in young adults)

(midline = medulloblastoma , hemispheric = pilocytic astrocytoma , arising in
4th ventricle = ependymoma and anterior to the 4th ventricle = brainstem
glioma)

c) Association :
-Gorlin's syndrome (basal cell nevi , odontogenic
keratocysts & falx calcification)
-Turcot's syndrome (colonic polyps & CNS
malignancy)

1-CT :
-Dense cell packing (small cell tumor) ,
hyperdense on noncontrast CT
-Typically intense and homogeneous
enhancement (hallmark)
-Hydrocephalus , 90%
-Rapid growth into cerebellar hemisphere ,
brainstem and spine

-Calcification (in 10%) is usually small homogeneous
and eccentric , dystrophic calcification occurs
after radiotherapy
-CSF seeding to spinal cord and meninges , 30%
-Systemic metastases can occur and appear as
sclerotic lesions in bone , metastases to
abdominal cavity may occur via a
ventriculoperitoneal (VP) shunt
-Atypical appearance and lateral cerebellar location
are more common in older children

2-MRI :
*T1 :
-Hypointense
*T2 :
-Iso to hyperintense to grey matter
-Heterogeneous due to calcification , necrosis and cyst
formation
*T1+C :
-90% enhance , often heterogeneously
*ADC :
-Low ADC value due to densely packed cells , the low ADC values
can be useful finding to differentiate medulloblastoma from
ependymoma & pilocytic astrocytoma , the two most
common childhood posterior fossa tumors

e) Tumor Spread :
1-Seeding of the subarachnoid space ,
leptomeningeal metastatic disease is present
in 33 % of patients , sugar coating
(Zuckerguss) is icing-like enhancement over
the brain surface , imaging of the entire brain
& spine should be performed prior to surgery
2-Retrograde ventricular extension
3-Extracranial metastases to bone , lymph nodes
or soft tissues

f) Tumor Recurrence :
-Recurrence of tumor is demonstrated by :
1-Enhancement at the site of the lesion
2-Enhancement of the subarachnoid space
(basal cisterns , sylvian fissures , sulci and
ependymal surfaces of ventricles)
3-Progressive ventricular enlargement

g) Differential Diagnosis :
a) Ependymoma :
-Usually arises from the floor of the 4th
ventricle
-Typically squeezes out the foramen of Luschka
b) Choroid Plexus Papilloma (CPP) :
-More common in lateral ventricles in children
c) Pilocytic Astrocytoma :
-Cyst with enhancing mural nodule in the
cerebellar hemispheres

d) Atypical Teratoid / Rhabdoid Tumor (ATRT) :
-WHO IV aggressive tumor that may appear
similar to medulloblastoma but occurs in
slightly younger patients
-The majority occurs in the posterior fossa
-ATRT is associated with malignant rhabdoid
tumor of the kidney

4-Primary Cerebral Neuroblastoma :
a) Incidence

a) Incidence :
-Rare , malignant tumor
-80% in first decade
-Most in the parietal & temporal lobes

-Large supratentorial mass
-Necrosis , hemorrhage cyst formation common
-Variable enhancement (neovascularity)

T1+C reveals enhancement of the lateral aspect, with a cystic
component medially

6-Pineal Region Tumors :
-See Pineal Region Tumors
7-Pituitary Tumors :
-See Pituitary Tumors
8-Nerve Sheath Tumor :
-See Cerebellopontine Angle Masses

9-Hematopoietic Tumors :
Central Nervous System Lymphoma
a) Primary CNS Lymphoma
b) Secondary CNS Lymphoma

a) Primary CNS Lymphoma (PCNSL) :
1-Incidence
2-Location

1-Incidence :
-1% of brain tumors , typically patients diagnosed with
PCNSL are over the age of 50
-Usually B-cell non Hodgkin's lymphoma (NHL)
-High incidence in immunocompromised hosts :
a) HIV : approximately 2-6% of patients with HIV will
develop PCNSL
b) Prior EBV infection
c) Post transplantation
d) IgA deficiency
-PCNSL is known to (melt away) with chemoradiation but
tends to recur aggressively

2-Location :
-Supratentorial (75-85%)
a) Basal ganglia , 50%
b) Periventricular deep WM
c) Corpus callosum , mimics butterfly glioma

-The most helpful imaging pattern :
1-Periventricular CT hyperdense enhancing mass
(High cellularity)
2-With MRI :
-T1 hypointense
-T2 iso to hypointense
-Vivid homogeneous enhancement
-Restricted diffusion

a) CT :
-Most lesions are hyperdense with less mass effect
than the size of the lesion
-Shows enhancement
-There are often multiple lesions in patients with HIV
-Calcification , hemorrhage , necrosis : multiple & large
areas are typical in AIDS (immunocompromised) ,
absent in immunocompetent patients
-The tumor is very radiosensitive and lesion may
disappear after a short course of steroids , this may
render the biopsy nondiagnostic

CT before (A) and after contrast (B) , an irregular mass which is hyperdense to grey matter
expands the splenium of the corpus callosum and extends into the left hemisphere , it is
surrounded by extensive white matter edema and enhances avidly with contrast

(a) Hyperattenuated lesion in the frontal lobe on noncontrast CT , (b) marked
enhancement at CT+C , (c) marked contrast enhancement is seen in a
lesion in the corpus callosum

b) MRI :
*T1 :
-Hypointense to white matter
*T2 :
-Majority are iso to hypointense
-Hyperintense more common in tumors with necrosis
*T1+C :
-Dense homogeneous enhancement is most common (in
immunocompetent)
-Ringlike (central necrosis) : more common in AIDS (in
immunocompromised) , D.D. toxoplasmosis
*Diffusion :
-Restricted with low ADC

(a) T1 shows the mass is isointense , (b) T1+C shows intense relatively
homogeneous enhancement of the mass , there is no appreciable central
necrosis

Restricted diffusion with low ADC (due to Hypercellularity)

(a) FLAIR shows a heterogeneous mass (arrows) in the left basal ganglia with
associated vasogenic edema , (b) ADC map shows that the epicenter of
the mass is dark (arrows) suggestive of reduced diffusivity due to
hypercellularity

a) Secondary CNS Lymphoma :
-Indisguishable on imaging
-PCNSL rarely involves spine , whereas
secondary CNS involvement with systemic
lymphoma commonly involves both brain and
spine

b) Toxoplasmosis :
1-Multiplicity :
-HIV lymphoma also is far more frequently a
solitary lesion , whereas toxoplasmosis is usually
multifocal
2-Location :
-Primary CNS lymphoma typically demonstrates
sub-ependymal spread , whereas toxoplasmosis
tends to be scattered thought the basal ganglia
and at the corticomedullary junction

3-Enhancement :
-Both entities enhance , however typically
lymphoma is solid whereas toxoplasmosis
demonstrates ring or nodular enhancement
4-SPECT :
-Thallium 201 Chloride SPECT demonstrates
increased uptake in lymphoma whereas it is
decreased in toxoplasmosis

5-PET :
-CNS lymphoma tends to be high grade and metabolically
active , toxoplasmosis usually doesn’t have avid FDG
uptake
6-MRS :
-Lymphoma typically demonstrates marked increase in
choline , whereas it is reduced in toxoplasmosis
-Both entities have increased lactate and lipids , this tends
to be less marked in lymphoma
7-MR Perfusion :
-Increased cerebral blood volume (rCBV) in lymphoma
whereas decreased centrally within toxoplasmosis

Lymphoma Toxoplasmosis
1-Multiplicity Single lesion Multiple lesions
2-Location Subependymal spread Scattered though basal
ganglia and
corticomedullary junction
3-Enhancement Solid enhancement Ring or nodular
enhancement
4-Thalium SPECT Positive Negative
5-PET High grade and
metabolically active
Usually doesn’t have avid
FDG uptake
6-MRS Increased choline (Cho( Decreased choline (Cho(
7-MR Perfusion Increased rCBV Decreased rCBV

c) Butterfly glioma / GBM :
-More commonly centrally necrotic
d) Tumefactive MS / ADEM
e) Cerebral Abscess :
-Peripheral enhancement of PCNSL is thicker
-Central restricted diffusion
e) Neurosarcoidosis

b) Secondary CNS Lymphoma (SCNSL) :
1-Incidence

1-Incidence :
-15% in patients with systemic lymphoma
-Typically a non-Hodgkin lymphoma and by definition
has systemic disease at the time of presentation with
secondary involvement of the central nervous
system
-Unlike primary CNS lymphoma it more commonly
involves the leptomeninges and is uncommonly
detectable on CT/MR with malignant cells found of
CSF aspiration

-Leptomeningeal spread
-Leptomeningeal lymphoma accounts for two third
cases of secondary CNS lymphomas , rest of the one
third secondary CNS lymphomas present like PCNSL
(parenchymal disease)
-MRI , T1+C is the modality of choice , imaging features
of leptomeningeal secondary CNS lymphoma include
leptomeningeal , dural , subependymal and cranial
nerve enhancement , communicating
hydrocephalus may be present

Axial (a) and sagittal (b) T1+C in a patient with CNS metastases from NHL
show diffuse subependymal contrast enhancement (arrows) and 2
parenchymal lesions (open arrows) in the right basal ganglia (A) and left
cerebellum (B)

10-Tumor-like Lesions :
1-Epidermoid / Dermoid
2-Hypothalamic (Tuber Cinereum) Hamartoma
3-Lipoma

1-Epidermoid / Dermoid :
-Epidermoid (See Cerebellopontine angle
masses)
-Dermoid (See later)
2-Hypothalamic (Tuber Cinereum) Hamartoma:
-See Suprasellar masses

3-Lipoma :
a) Incidence
b) Location

a) Incidence :
-Asymptomatic nonneoplastic tissue
(malformation , not a true tumor)
-50% are associated with other brain
malformations

b) Location :
-Intracranial lipomas are widely distributed in
the intracranial compartment and although
they can be found essentially anywhere :
1-Pericallosal lipoma (45%) :
-Associated with agenesis of the corpus
callosum in 50% of cases
-Divided morphologically into tubulonodular and
curvilinear types

Pericallosal lipoma , curvilinear type

Pericallosal lipoma , tubulonodular variety

2-Quadrigeminal cistern lipoma (25%) :
-Associated with underdevelopment of the inferior
colliculus or agenesis of the corpus callosum
3-Suprasellar cistern lipoma
4-CPA Lipoma (10%) :
-The facial nerve and vestibulocochlear nerve often
courses through the lipoma
5-Sylvian Fissure (5%)

T1 shows quadrigeminal cistern lipoma

1-CT :
-Typically appears as a mass with uniform fat density
(negative HU values)
-It has a lobulated soft appearance conforming to
adjacent anatomy
-No enhancement
-Tubulonodular variety may demonstrate peripheral
curvilinear calcification sometimes referred to as
the bracket sign (best seen on coronal
reconstruction)

2-MRI :
*T1 :
-High signal intensity
*T2 :
-High signal intensity
*T1+C :
-No enhancement
*Fat Saturated Sequences :
-Low signal

Curvilinear pericallosal lipoma and dysgenesis of the corpus callosum in a 16-year-old
girl, (a, b) Axial (a) and sagittal (b) T1 show a linear hyperintense mass along the
dorsal aspect of the corpus callosum (arrow) , the splenium of the corpus callosum
is absent, (c) Coronal T2 shows the same high signal intensity lesion (arrow) with a
chemical shift artifact along its edge in the frequency-encoding direction, (d) Axial
CT reveals the homogeneous low attenuation of fat within the lesion (arrow)

-The differential is essentially that of masses which
contain fat and therefore includes :
1-Intracranial dermoid :
-if ruptured will often have multiple droplets
scattered through the subarachnoid space
-Usually midline
2-Intracranial Teratoma
3-Lipomatous transformation of neoplasm :
-PNET , ependymoma & glioma

11-Metastases :
a) Incidence
b) Etiology
c) Location
e) Carcinomatous Meningitis

a) Incidence :
-Account for 30% of intracerebral tumors

b) Etiology :
-The most common primary lesions are :
1-Bronchogenic Carcinoma (50%)
2-Breast (20%)
3-Colon , Rectum (15%)
4-Kidney (10%)
5-Melanoma (10%)

c) Location :
-Location in order of frequency :
1-Junction GM and WM (most common)
2-Deep parenchymal structures (common)
3-Brainstem (uncommon)
4-Metastases also occur in dura , leptomeninges
and calvaria

Metastases in the deep parenchymal structures, (a) T1, (b) T2 &
(c) T1+C

Brain metastasis in the deep parenchymal structures, (a) Axial T2 through the
lateral ventricles reveals two isodense masses, one in the subependymal
region and one near the cortex (arrows), (b) T1+C at the same level as
(a) reveals enhancement of the two masses seen on the T2 image as well
as a third mass in the left frontal lobe (arrows)

Metastases in the brain stem, axial T1 shows metastatic deposits with
hemorrhage involving the pons (a), CT image reveals aggravation of
hemorrhagic mass lesions in the right temporal lobe and pons with brain
stem compression (b)

Skull metastases with parenchymal extension

Calvarial and dural metastases

T1+C shows leptomeningeal metastases

1-CT :
-On precontrast imaging the mass may be iso to
hypodense surrounded by variable amounts
of vasogenic edema
-Following administration of contrast ,
enhancement is also variable and can be
intense , punctate , nodular or ring enhancing
if the tumor has out grown it's blood supply

2-MRI :
*T1 :
-Typically iso to hypointense
-If hemorrhagic may have intrinsic high signal
-Melanoma metastases also hyperintense due to the
paramagnetic properties of melanin
*T2 :
-Typically hyperintense
-Hemorrhage may alter this
*T1+C :
-Enhancement pattern can be uniform , punctate or ring-
enhancing but it is usually intense

T1 shows hemorrhagic metastases

**N.B. : Primary malignancies responsible
for hemorrhagic metastases (MR CT BB) :
M melanoma
R renal cell carcinoma
C choriocarcinoma
T thyroid carcinoma, teratoma
B bronchogenic carcinoma
B breast carcinoma

e) Carcinomatous Meningitis :
-Leptomeningeal metastases are more common
than dural metastases , although the two may
coexist
-Common primary neoplasms that cause
carcinomatous meningitis include breast , lung
and skin (melanoma)
- MRI is more sensitive than CT for detection

CT+C showing enhancement throughout the leptomeningeal spaces of the
posterior fossa, highlighting the Zuckerguss pattern around the
cerebellum and brain stem (white arrows)

T1+C showing enhancement throughout the leptomeningeal spaces of the
posterior fossa, highlighting the Zuckerguss pattern around the
cerebellum (white arrows)

12-Cystic lesions :
-Various types of nonneoplastic , noninflammatory cysts
are found intracranially :
1-Arachnoid Cyst
2-Epidermoid Cyst
3-Dermoid Cyst
4-Colloid Cyst
5-Rathke’s Cleft Cyst
6-Neuroepithelial Cyst
7-Enterogenous Cyst (Neurenteric)
8-Porenchyphalic Cyst
9-Neuroglial Cyst
10-Pineal Cyst
11-Enlarged Virchow-Robin Spaces

1-Arachnoid cyst (Leptomeningeal cyst) :
a) Incidence
b) Location
d) Differential diagnosis (From Epidermoid)

a) Incidence :
-Not a true neoplasm , probably arises from
duplication or splitting of the arachnoid
membrane (meningeal maldevelopment)
-75% occur in children

b) Location :
1-Middle cranial fossa , sylvian fissure part
against greater wing of sphenoid (most
common)
2-Posterior fossa
3-Suprasellar , quadrigeminal cisterns
4-CPA
5-Cisterna magna

Most common site (middle cranial fossa)

-Extra-axial mass with CSF density (CT) and
intensity (MRI in all sequences)
Diffusion imaging : Follows CSF
FLAIR imaging : Suppresses like CSF
-Slow enlargement with compression of
adjacent parenchyma (can cause local mass
effect and obstructive hydrocephalus)
-No communication with ventricles
-Pressure erosion of calvaria

-From Epidermoid (see table)

Arachnoid Epidermoid
1-Signal intensity Isointense to CSF on T1
Isointense to CSF on PD
Isointense to CSF on T2
Mildly hyperintense to CSF
Hyperintense to CSF on PD
Isointense to CSF on T2
2-Enhancement No No
3-Margin of lesion Smooth Irregular
4-Effect on adjacent
structures
Displaces Engulfs , insinuates
5-Pulsation artifact Present Absent
6-Diffusion imaging Follows CSF Hyperintense to CSF
7-FLAIR imaging Suppresses like CSF Hyperintense to CSF
8-Calcification No May occur

Arachnoid Cyst T1 Epidermoid Cyst T1

Arachnoid Cyst T2 Epidermoid Cyst T2

Arachnoid Cyst ( Flair ) Epidermoid Cyst ( Flair )

Arachnoid Cyst ( DW ) Epidermoid Cyst ( DW )

2-Epidermoid Cyst :
-See (CPA masses)

3-Dermoid :
a) Incidence
b) Location
c) Radiographic Findings
d) Complications

a) Incidence :
-Rare benign congenital ectodermal inclusion
cysts that account for approximately 0.3% of
all intracranial tumors
-Most common in young adult males in the
posterior fossa but may occasionally occur in
the parasellar region

b) Location :
-Intracranial dermoid cysts most commonly
occur at the midline in the sellar and
parasellar compartments , fourth ventricle
and vermis

c) Radiographic Findings :
1-CT :
-Usually well-defined nonenhancing masses with
fat attenuation
2-MRI :
*T1 : High signal intensity
*T2 : Variable signal intensity
*T1+C : Lack of enhancement

CT (non-contrast) Brain CT strongly hypodense lesion in the right
frontal lobes with negative Houndsfield values

Suppression of the lipid content of the mass

d) Complications :
-Dermoid cyst rupture is a rare complication
that can cause severe chemical meningitis or
ventriculitis and sensory or motor
hemisyndrome
-This complication manifests at T1 as scattered
high signal intensity foci within the ventricles
or subarachnoid spaces

-Ruptured dermoid
cyst in a 44 year old
woman
Sagittal T1 shows an
ovoid
heterogeneously
hyperintense midline
suprasellar mass
(arrow) and numerous
punctate high signal
intensity foci
scattered throughout
the subarachnoid
space

-From Epidermoid
-See (Epidermoid cyst, CPA masses)

4-Colloid Cyst :
a) Incidence
b) Location
c) Clinical Picture

a) Incidence :
-Account for 0.5-3% of primary brain tumors and
15-20% of intraventricular masses
-Early middle age (30-40 years of age)
b) Location :
-They are located anterior to the 3rd
ventricle at
the foramen of Monro in 99% of cases

c) Clinical Picture :
-In the vast majority of cases , colloid cysts are
found incidentally and are asymptomatic
-Their position in the roof of the third ventricle
immediately adjacent foramen of Monro can
on occasion result in sudden obstructive
hydrocephalus and can present with
a thunderclap headache & ataxia

1-CT :
-Typically seen as a well defined rounded lesion
at the roof of the 3rd
ventricle
-Unilocular
-Typically hyperdense
-Isodense and hypodense cysts are uncommon
-Calcification is uncommon

2-MRI :
*T1 :
-Typically high T1 signal
*T2 :
-Hypointense
*T1+C :
-Only rarely demonstrates thin rim enhancement
but usually this represents enhancement of the
adjacent and stretched septal veins

Colloid cyst in a 31-year-old woman , axial (a) and sagittal (b) T1 show an
ovoid homogeneously hyperintense lesion at the left foramen of Monro
(arrows)

-There are usually no differential diagnoses for a colloid
cyst , in atypical cases it is worth considering other
masses which arise in the region of the foramen of
Monro including :
1-Subependymoma :
-Less dense on non contrast CT
2-Astrocytoma :
-Isointense or hypointense on T1
3-Calcified Hyperdense Meningioma
4-Lymphpma
6-Tumefactive Intraventricular Hemorrhage
7-Intraventricular Neurocysticercosis

5-Rathke’s Cleft Cyst :
-See (Intrasellar masses)

6-Neuroepithelial Cyst :
Heterogeneous group of cysts comprising :
a) Intraventricular ependymal cysts
b) Choroid plexus cysts
c) Choroid fissure cysts

a) Intraventricular ependymal cysts :
1-Location

1-Location :
-Rare benign ependymal-lined cysts of the
lateral ventricle or juxtaventricular region of
the temporoparietal region and frontal lobe
-A nonenhancing thin walled CSF containing cyst
of the lateral ventricle

FLAIR shows ependymal cyst within enlarged atrium of the left lateral
ventricle (open arrow), signal intensity was isointense to CSF at all pulse
sequences, note lateral displacement of choroid plexus (solid arrow)

b) Choroid Plexus Cysts :
1-Incidence
2-Location

1-Incidence :
-The most common of all intracranial
neuroepithelial cysts
-Typically in neonates and older adults
2-Location :
-Most are bilateral and located in the lateral
ventricular atria

a) CT :
-Slightly hyperattenuating compared with CSF
-Peripheral calcification is common
-The cysts show enhancement that varies from
none to striking

Two images form an unenhanced axial CT of the brain show
ring-like calcifications in the region of the choroid plexus representing
choroid plexus cysts

b) MRI :
*T1 :
-Most are iso- or hyperintense
*T2 :
-Hyperintense
*T1+C :
-Rim or nodular contrast enhancement may be
seen

(a) Transverse graphic representation shows multiple cystic masses in the choroid
plexus glomi (arrows), most CPCs are actually degenerative xanthogranulomas,
(b) T1+C in a healthy 52-year-old man shows bilateral CPCs with peripheral and
nodular enhancement (arrows)

(a) axial Flair shows nodular masses in bilateral atria of lateral
ventricles, non enhancing on post contrast T1 (b)

c) Choroid Fissure Cysts :
1-Incidence

a) Incidence :
-They are uncommon representing fewer than
1% of intracranial cysts

a) CT :
-Well delineated homogeneous low density mass
with attenuation characteristics similar to CSF
-Calcification and contrast enhancement are absent
b) MRI :
-Similar to CSF on all sequences
-The cyst walls are thin
-Contrast enhancement , surrounding edema and
gliosis are absent

A well delineated homogeneous low density cyst-like mass located in the left
medial temporal lobe

7-Enterogenous Cyst (Neurenteric) :
a) Location

a) Location :
-Intracranial cysts are most often found in the
posterior fossa
-They are typically midline , anterior to the brain
stem or in the CPA
-They have also been described in the fourth
ventricle

(a) Sagittal T1 shows an ovoid mass (arrows) in the midline anterior to the
pontomedullary junction, the cyst is hyperintense to brain parenchyma
and CSF, (b) Axial FLAIR scan in the same patient shows that the mass
remains hyperintense and extends from the midline into the right lower
cerebellopontine angle

1-CT :
-The best diagnostic clue for a neurenteric cyst
is a round and/or lobulated, nonenhancing,
slightly hyperintense mass in front of the
medulla

Axial non-contrast CT shows lobulated extra-axial hyperdense
lesions anterolateral to the lower brainstem

2-MRI :
*T1 :
-Most are proteinaceous with a T1 signal that is
isointense to slightly hyperintense compared
with CSF
*T2 :
-Typically very hyperintense
*T1+C :
-Rim enhancement is a very rare finding

(a) Axial T1 shows an ovoid mass (arrow) slightly to the left of midline at the
level of the pontomedullary junction, it is hyperintense to CSF and
isointense to the surrounding brain parenchyma, (b) Axial T2 in the same
patient demonstrates that the cyst is isointense to slightly hyperintense
compared with CSF (arrow)

8-Porenchyphalic Cyst :
a) Etiology

a) Etiology :
1-Congenital
2-Acquired :
-2ry to injury later in life and are usually
secondary to trauma , surgery , ischemia or
infection

-Cystic space in the brain parenchyma that
communicates with an enlarged adjacent
ventricle
-The cysts have the same appearance as CSF at
all MR sequences
-Adjacent white matter typically shows
hyperintensity on T2 and FLAIR images

Coronal T1 shows enlarged left temporal horn (black arrow) that
communicates with peripherally located porencephalic cyst (white
arrows). Cyst extends to the brain surface

9-Neuroglial Cyst :
a) Incidence
b) Location

a) Incidence :
-Neuroglial (also called glioependymal) cysts are
benign epithelial-lined lesions that occur
anywhere in the neuraxis
-They are uncommon, representing fewer than
1% of intracranial cysts

b) Location :
-While they may occur in myriad locations, the
frontal lobe is the most typical location
-Intraparenchymal neuroglial cysts are more
common than extraparenchymal cysts

-The best diagnostic clue to a neuroglial cyst is a
nonenhancing CSF-like parenchymal cyst with
minimal to no surrounding signal intensity
abnormality
-The cysts are benign-appearing lesions with
smooth, rounded borders
-Size is variable

FLAIR shows typical neuroglial cyst (straight arrow) adjacent to left temporal
horn, the cyst appears well demarcated without surrounding gliosis and
has the same appearance as CSF at all sequences, this cyst does not
communicate with the ventricle (curved arrow)

10-Pineal Cyst :
-See (Pineal Masses)

11-Enlarged Virchow-Robin Spaces :
a) Incidence
b) Location

a) Incidence :
-Enlarged PVSs, also known as Virchow-Robin
spaces, are pial-lined interstitial fluid-filled
structures that accompany penetrating
arteries and vein
-They do not communicate directly with the
subarachnoid space
- They are common, incidental, “leave me
alone” lesions that should not be mistaken for
more ominous disease

b) Location :
- They frequently appear in the inferior basal ganglia,
clustering around the anterior commissure and
surrounding the lenticulostriate arteries as they
superiorly course through the anterior perforated
substance
-Other common locations include the midbrain, deep
white matter, and subinsular cortex. They can also
be found in the region of the thalami, dentate nuclei,
corpus callosum, and cingulate gyrus

-Prominent PVSs are considered a normal variant
-Most appear as smoothly demarcated fluid-filled cysts, typically
less than 5 mm in diameter, and often occur in clusters in the
basal ganglia or midbrain
-They are isointense to CSF at all sequences, including FLAIR
-Most show normal signal intensity in the adjacent brain; 25%
may have a small rim of slightly increased signal intensity
-They do not enhance, cause focal mass effect, or restrict on
diffusion-weighted images
-In older patients, basal ganglia PVSs sometimes become
prominent and sievelike, a condition known as état criblé, or
cribriform state

13-Brian Tumors In Children :
(i) Supratentorial
(ii) Infratentorial
-Primary CNS tumors are the second most
common malignancy in children (leukemia is
the commonest)
-Overall , supratentorial and infratentorial
tumors occur with equal incidence

(i) Supratentorial
1-Craniopharyngioma
2-Optic Nerve Glioma
3-Giant Cell Astrocytoma
4-Germ Cell Tumors
5-PNET
6-DNET
7-Ganglioglioma
9-Ependymoma
10-Hemispheric Astrocytoma
(ii) Infratentorial
1-Juvenile Pilocytic
Astrocytoma
2-Medulloblastoma
3-Ependymoma
4-Brain Stem Glioma

Supratentorial
1-Craniopharyngioma
2-Optic Nerve Glioma
3-Giant Cell Astrocytoma
4-Germ Cell Tumors
5-PNET
6-DNET
7-Ganglioglioma
9-Ependymoma
10-Hemispheric Astrocytoma

1-Craniopharyngioma :
-More than half of all craniopharyngiomas occur
in children (8-14 years)
-Cystic/solid partially calcified suprasellar mass
presenting with headache , visual disturbance
and endocrine abnormalities

2-Optic Nerve Glioma :
-Low grade
-Associated with NF1
-Solid enhancing tumours that extend along the
length of the anterior optic pathways and may
invade adjacent structures (e.g.
hypothalamus) and extend posteriorly into the
optic tracts and radiations

3-Giant Cell Astrocytoma :
-Associated with Tuberous Sclerosis
-Slow growing partially cystic partially calcified
tumor
-Located at the foramen of Monro and presents
with obstructive hydrocephalus

4-Germ Cell Tumors :
-Germinomas , Teratomas
5-PNET :
-Large heterogeneous hemispheric mass
presenting in neonates and small infants
-Necrosis , hemorrhage and enhancement are
common

6-DNET :
-Benign cortical tumour often presenting with seizures
-Cortical (temporal) mass usually small
-May demonstrate internal cyst formation and
calcification
7-Ganglioglioma :
-Well circumscribed peripheral tumour that often
presents with seizures
-Cystic tumour with mural nodule ± calcification

8-Choroid Plexus Papilloma :
-Presents in young children with hydrocephalus
-Most occur in the atrium of the lateral ventricle
(fourth ventricle in adults) and appear as a
well-circumscribed multilobulated avidly
enhancing intraventricular mass ± calcification
-Invasion of brain suggests choroid plexus
carcinoma

9-Ependymoma :
-Often in the frontal lobe adjacent to the frontal
horn but not usually within the ventricular
system

10-Hemispheric Astrocytoma :
-Associated with NF1
-Most are low grade
-Solid with a necrotic centre or cystic with a mural
nodule
-Usually large at presentation and can involve the
basal ganglia and thalami
-Enhancement does not correlate with histological
grade

Infratentorial
-These comprise 50% of pediatric cerebral tumors
-The majority arise from the cerebellar parenchyma
, cerebellar astrocytomas , medulloblastomas and
ependymomas present with symptoms of raised
intracranial pressure and ataxia
-Brainstem gliomas involve the cranial nerve nuclei
and long tracts at an early stage

2-Medulloblastoma
3-Ependymoma
4-Brain Stem Glioma

1-Juvenile Pilocytic Astrocytoma :
-20-25% of posterior fossa tumours
-Vermis (50%) or hemispheres (20%) or both
sites (30%) ± extension into the cavity of the
fourth ventricle
-Calcification in 20 %
-Large lesion displacing the fourth ventricle →
obstructive hydrocephalus

2-Medulloblastoma :
-80% located in the vermis , 30% extend into the
brainstem
-Short history

3-Ependymoma :
-8-15% of posterior fossa tumors
-Most commonly in the floor of the fourth
ventricle
-Usually a long clinical history
4-Brain Stem Glioma :

14-Intraventricular Masses :
2-Ependymoma
3-Intraventricular Meningioma
4-Subependymoma
5-Subependymal giant cell astrocytoma
7-Intraventricular Metastasis

Approach to a Case of Brain Tumor
a) Introduction
b) Tumor Spread
c) Tumor-related Complications
d) CT & MRI Characteristics
e) Enhancement
f) Differential Diagnosis For Specific Anatomic Area
g) Tumor Mimics
h) Cerebral Edema

a) Introduction :
1-Incidence of CNS Tumors
2-Age Distribution

1-Incidence of CNS Tumors :
-Roughly one-third of CNS tumors are metastatic lesions, one
third are gliomas and one-third is of non-glial origin
-Glioma is a non-specific term indicating that the tumor
originates from glial cells like astrocytes, oligodendrocytes,
ependymal and choroid plexus cells
-Astrocytoma is the most common glioma and can be subdivided
into :
a) Low-grade pilocytic type
b) Intermediate anaplastic
c) High grade malignant glioblastoma multiforme (GBM)
-GBM is the most common type (50% of all astrocytomas)
-The non-glial cell tumors are a large heterogenous group of
tumors of which meningioma is the most common

2-Age Distribution :
-The age of the patient is an important factor for the
differential diagnosis
-Specific tumors occur under the age of 2 , like choroid
plexus papillomas , anaplastic astrocytomas and
teratomas
-In the first decade : medulloblastomas , astrocytomas ,
ependymomas, craniopharyngeomas and gliomas are
most common, while metastases are very rare ,
when they do occur at this age , metastases of a
neuroblastoma are the most frequent
-Although cancer is rare in children , brain tumors are
the most common type of childhood cancer after
leukemia and lymphoma , most of the tumors in
children are located infratentorially

-In adults about 50% of all CNS lesions are metastases ,
other common tumors in adults are astrocytomas ,
glioblastoma multiforme , meningiomas ,
oligodendrogliomas , pituitary adenomas and
schwannomas
-Astrocytomas occur at any age , but glioblastoma
multiforme is mostly seen in older people
-Particularly in the posterior fossa , metastases should
be in the top 3 of the differential diagnostic list ,
hemangioblastoma is an uncommon tumor but it is
the most common primary intra-axial tumor in the
adult
-Supratentorially , metastases are also the most
common tumors followed by gliomas

b) Tumor Spread :
1-Intra-axial versus Extra-axial
2-Local Tumor Spread
3-Crossing Midline
4-Multifocal Disease
5-Cortical Based Tumors

1-Intra-axial versus Extra-axial :
-When we study an intracranial mass , the first thing we
want to know is whether the mass lies inside or
outside of the brain
-If it is outside the brain or extra-axial (external to the
pial membrane) , then the lesion is not actually a
brain tumor but derived from the lining of the brain
or surrounding structures , 80 % of these extra-axial
lesions will be either a meningioma or a
schwannoma
-On the other hand , in an adult an intra-axial tumor
(within the brain parenchyma itself , underneath the
pial membrane) will be a metastasis or astrocytoma
in 75% of cases

-Signs of Extra-Axial Location :
1-CSF cleft sign :
-The cleft represents a thin rim of CSF between tumor
and brain parenchyma , however , it often is of high
signal on FLAIR imaging
2-Pial vascular structures interposed between the
tumor and the brain surface :
-The subarachnoid vessels that run on the surface of
the brain are displaced by the lesion
3-Buckling of cortical grey matter and grey matter
between mass & white matter

The cleft sign : thin rim of CSF surrounding this large
meningioma

(a) Pial vascular structures (short arrows) and cerebrospinal fluid cleft sign
(large arrow) on Sagittal T1 , (b) Cerebrospinal fluid cleft sign (arrow) and
perilesional edema (asterisk) on Axial T2

The subarachnoid vessels that run on the surface of the brain are displaced
by the lesion (arrow)

(a) Axial T2 shows thin CSF cleft sign (yellow arrow) & grey matter buckling
(blow arrow) , (b) Coronal T1+C shows grey matter interposed between
the mass & the white matter (red arrows)

T2 shows a schwannoma located in the cerebellopontine angle (CPA) , there
is a CSF cleft (yellow arrow) , the subarachnoid vessels that run on the
surface of the brain are displaced by the lesion (blue arrow) , there is gray
matter between the lesion and the white matter (curved red arrow)

The tumor in the case on the left was thought to be a falcine meningioma , i.e. extra-axial and
was presented for surgery , this lesion surely has the appearance of a meningioma : these
tumors can be hypointense on T2 due to a fibrocollageneous matrix or calcifications and
frequently produce reactive edema in the adjacent white matter of the brain , however ,
there is gray matter on the anteromedial and posteromedial side of the lesion (red arrow). ,
this indicates that the lesion is intra-axial , if the lesion was extra-axial the gray matter should
have been pushed away , this proved to be a melanoma metastasis

4-Displace & expand the subarachnoid spaces
5-Broad dural base
6-Bony reaction

(a) Meniscus sign, displacement of the subarachnoid veins inward and buckling of the
gray-white matter interface (b) The extra-axial mass (M) expands the
subarachnoid space at its borders (straight arrow), has a dural base (arrow heads),
displaces blood vessels in the subarachnoid space medially (curved arrow)

Axial T1+C shows Meningioma with dural tail , hyperostosis and
enhancement of adjacent bone , typical signs of an extra-axial tumor

Axial CT-scan : bone hyperostosis

-Signs of Intra-axial Location :
1-It expands the cortex of the brain
2-There is no expansion of the subarachnoid
space
3-The lesion spreads across well-defined
boundaries
4-The hypointense dura and pial blood vessels
are peripheral to the mass

T1+C shows nonenhancing right frontal anaplastic
oligoastrocytoma (biopsy proven), it shows the typical signs of
intra-axial location

2-Local Tumor Spread :
-Astrocytomas spread along the white matter tracts
and do not respect the boundaries of the lobes ,
because of this infiltrative growth , in many cases the
tumor is actually larger than can be depicted with
MRI
-Ependymomas of the fourth ventricle in children tend
to extend through the foramen of Magendie to the
cisterna magna and through the lateral foramina of
Luschka to the cerebellopontine angle
-Oligodendrogliomas typically show extension to the
cortex

Ependymoma with extension to the prepontine area (blue
arrows) and into the foramen magnum (red arrow)

-Subarachnoid seeding :
*Some tumors show subarachnoid seeding and form
tumoral nodules along the brain and spinal cord
*This is seen in PNET , ependymomas , GBMs ,
lymphomas , oligodendrogliomas and choroid plexus
papillomas
*Primitive neuroectodermal tumors (PNET) form a rare
group of tumors which develop from primitive or
undifferentiated nerve cells , these include
medulloblastomas and pineoblastomas

-Extent of the Tumor :
*One of the most important roles of imaging is to
assess the extent of a tumor
*Another important consideration is the effect on the
surrounding structures
*Primary brain tumors are derived from brain cells and
often have less mass effect for their size than you
would expect due to their infiltrative growth , this is
not the case with metastases and extra-axial tumors
like meningiomas or schwannomas which have more
mass effect due to their expansive growth

Extra-axial tumor in the region of the left cavernous sinus , there is homogeneous
enhancement with a broad dural tail , this is typical for a meningioma , the tumor
is situated in the pterygopalatine fossa and extends into the orbit , it also spreads
anteriorly into the middle cranial fossa

Diffusely infiltrating intra-axial tumor occupying most of the right hemisphere
with only a minimal mass effect , this is typical for the infiltrative growth
seen in primary brain tumors , there is no enhancement so this would
probably be a low-grade astrocytoma

3-Crossing Midline :
-The ability of tumors to cross the midline limits the differential
diagnosis :
1-Glioblastoma multiforme (GBM) frequently crosses the midline
by infiltrating the white matter tracts of the corpus callosum
2-Radiation necrosis can look like recurrent GBM and can
sometimes cross the midline
3-Meningioma is an extra-axial tumor and can spread along the
meninges to the contralateral side
4-Lymphoma is usually located near the midline
5-Epidermoid cysts can cross the midline via the subarachnoid
space
6-MS can also present as a mass lesion in the corpus callosum

4-Multifocal Disease :
-Multiple tumors in the brain usually indicate
metastatic disease
-Primary brain tumors are typically seen in a single
region but some brain tumors like lymphomas ,
multicentric glioblastomas and gliomatosis cerebri
can be multifocal
-Some tumors can be multifocal as a result of seeding
metastases , this can occur in medulloblastomas
(PNET-MB) , ependymomas , GBMs and
oligodendrogliomas , meningiomas and
schwannomas can be multiple, especially in
neurofibromatosis type II

LEFT : Metastases , RIGHT : Multiple meningiomas and a
schwannoma in a patient with Neurofibromatosis II

-Multiple brain tumors can be seen in phacomatoses :
1-Neurofibromatosis I : optic gliomas and astrocytomas
2-Neurofibromatosis II : meningiomas , ependymomas
& schwannoma
3-Tuberous Sclerosis : subependymal tubers ,
intraventricular giant cell astrocytomas &
ependymomas
4-von Hippel Lindau : hemangioblastomas
-Many non-tumorous diseases like small vessel
disease , infections (septic emboli , abscesses) or
demyelinating diseases like MS can also present as
multifocal disease

5-Cortical Based Tumors :
-Most intra-axial tumors are located in the white
matter
-Some tumors , however , spread to or are located in
the gray matter
-The differential diagnosis for these cortical based
tumors includes oligodendroglioma , ganglioglioma
and Dysembryoplastic Neuroepithial Tumor (DNET)
-A DNET is a rare benign neoplasm, usually in a cortical
and temporal location
-Patients with a cortically based tumor usually present
with complex seizures

CT shows a mass with calcifications which extends all the way to the cortex ,
although this is a large tumor there is only limited mass effect on
surrounding structures which indicates that this is an infiltrating tumor ,
the most likely diagnosis is oligodendroglioma , the differential diagnosis
includes a malignant astrocytoma or a glioblastoma

45-year-old female with a stable seizure disorder (complex-partial) for 15
years , there is a non-enhancing cortically based tumor , this is a
ganglioglioma , the differential diagnosis includes DNET and pilocytic
astrocytoma

c) Tumor-related Complications :
-The three emergent complications of a brain tumor
are the three H (Hemorrhage , Hydrocephalus &
Herniation)
1-Hemorrhage :
-Primary or metastatic brain tumors are often
associated with neovascularity and tumoral vessels
are more prone to hemorrhage than normal
vasculature
-The most common primary brain tumor to
hemorrhage is a glioblastoma
-Hemorrhagic metastases include melanoma , renal cell
carcinoma , thyroid carcinoma and choriocarcinoma

2-Hydrocephalus :
-A tumor can cause hydrocephalus by blocking the flow
of CSF
-Posterior fossa tumors have increased risk of causing
hydrocephalus by effacing the 4th
ventricle
3-Herniation :
-The overall mass effect from tumor is a combination of
the tumoral mass and associated vasogenic edema
which may contribute to brain herniation

d) CT & MRI Characteristics :
1-Fat
2-Calcification
3-Cystic Versus Solid
4-High on T1
5-Low on T2
6-Diffusion Weighted Images
7-Perfusion Weighted Images

1-Fat :
-Fat has a low density on CT (- 100HU)
-On MRI , fat has a high signal intensity on both T1 & T2
, sequences with fat suppression fat can be
differentiated from high signal caused by subacute
hematoma , melanin , slow flow etc
-Fat within a tumor is seen in lipomas , dermoid cysts
and teratomas
-N.B. : Some tumors can have a high density on CT , this
is typically seen in lymphoma , colloid cyst and PNET-
MB (medulloblastoma)

Ruptured dermoid cyst , Coronal T1 (left) and NECT (right)

2-Calcification :
-Calcification is seen in many CNS tumors :
a) Intra-axial tumors :
1-Astrocytoma (20 %)
2-Oligodendroglioma (90 %)
3-Metastases
4-Ependymoma (50 %)
5-Choroid plexus papilloma (25 %)
6-Gangloglioma (40 %)

Oligodendroglioma with calcification (PDWI and CT)

b) Extra-axial tumors :
1-Meningioma (25 %)
2-Craniopharyngioma (90 %)
3-Chordoma
4-Chondrosarcoma

Pattern of calcification (long arrow) and parenchymal edema surrounding the
lesion (short arrows) in two patient with meningiomas

Calcified mass in the suprasellar region causing obstructive hydrocephalus ,
this location in the suprasellar region and the calcification are typical for a
craniopharyngioma

-When we think of a calcified intra-axial tumor , we
think oligodendroglioma since these tumors nearly
always have calcifications , however an intra-axial
calcified tumor in the brain is more likely to be an
astrocytoma than a oligodendrogliomas since
astrocytomas , although less frequently calcified , are
far more common
-A Pineocytoma itself does not calcify but instead it
(explodes) the calcifications of the pineal gland

3-Cystic Versus Solid :
-There are many cystic lesions that can simulate a CNS tumor
-These include : epidermoid , dermoid , arachnoid , neuroenteric
and neuroglial cysts
-Even enlarged perivascular spaces of Virchow Robin can
simulate a tumor
-In order to determine whether a lesion is a cyst or cystic mass
look for the following characteristics :
1-Morphology
2-Fluid/fluid level
3-Content usually isointense to CSF on T1 , T2 and FLAIR
4-DWI : restricted diffusion
-An arachnoid cyst is isointense to CSF on all sequences , tumor
necrosis may sometimes look like a cyst, but it is never
completely isointense to CSF and tends to be surrounded by
enhancing tumor

On the far left a craniopharyngioma with an enhancing rim surrounding the
cystic component , in the middle a neuroenteric cyst with the contents of
which have the same signal intensity as CSF , on the right a glioblastoma
multiforme (GBM) with a central cystic component , the enhancement in
GBM is usually more irregular

4-High on T1 : (See MRI Sequences in Neuroradiology)
-Most tumors have a low or intermediate signal intensity on T1
-Calcifications are mostly dark on T1 but depending on the
matrix of the calcifications they can sometimes be bright on
T1
-Exceptions to this rule can indicate a specific type of tumor :
a) Methemoglobin :
-Pituitary apoplexy
-Hemorrhagic tumor or metastases
-Thrombosed aneurysm
b) High Protein :
-Cyst with proteinaceous fluid
-Neuroenteric cyst
-Dermoid cyst

T1 show (a) hemorrhagic metastases , (b) Hemorrhagic tumor

Ruptured Dermoid cyst , (A) Sagittal and (B) axial T1 show the mass to be
heterogeneously hyperintense. Multiple focal areas of T1 shortening are
present within the subarachnoid space , note the presence of a fluid-fluid
level into the ventricles (arrow) , (C) Axial T2 shows a prominent chemical
shift artifact (arrowhead) that confirms lipid content

c) Fat :
-Lipoma
-Dermoid cyst
d) Cholesterol :
-Colloid cyst
e) Melanin :
-Melanoma metastases
f) Flow Effects :
-Slow flow
g) Paramagnetic Cations :
-(Cu , Mn , etc)

5-Low on T2 : (See MRI Sequences in
Neuroradiology)
-Most tumors will be bright on T2 due to a high
water content
-When tumors have a low water content they
are very dense and hypercellular and the cells
have a high nuclear-cytoplasmasmic ratio ,
these tumors will be dark on T2
-The classic examples are CNS lymphoma and
PNET (also hyperdense on CT)
-Calcifications are mostly dark on T2

a) Hypercellularity :
-Lymphoma , meningioma , PNET , Germinoma , GBM ,
Oligodendroglioma , Mucinous-adeno metastases (GIT , Lung ,
Breast & GUT)
b) Calcification :
-See before
c) Blood :
-Old hemorrhage in tumor or vascular malformation
d) Protein :
-Colloid cyst
e) Melanin :
-Melanoma metastases
f) Flow void :
-Hemangioblastoma & vascular malformations

6-Diffusion Weighted Images :
-Normally water protons have the ability to diffuse
extracellularly and loose signal
-High intensity on DWI indicates restriction of the
ability of water protons to diffuse extracellularly
-Restricted diffusion is seen in :
*Abscesses (due to the viscosity of pus)
*Epidermoid cysts and acute infarction (due to
cytotoxic edema)
-In most tumors there is no restricted diffusion , even in
necrotic or cystic components , this results in a
normal low signal on DWI

Left frontal abscess in a 57-year-old man, (a) T1+C demonstrates a rim-
enhancing mass with surrounding edema, (b) Axial diffusion-weighted
image shows restricted diffusion

7-Perfusion Weighted Images :
-Perfusion imaging can play an important role in
determining the malignancy grade of a CNS tumor
-Perfusion depends on the vascularity of a tumor and is
not dependent on the breakdown of the blood-brain
barrier
-The amount of perfusion shows a better correlation
with the grade of malignancy of a tumor than the
amount of contrast enhancement
-Differentiate recurrence of the tumor from radiation
necrosis
-Used to determine optimal biopsy site

(a) T1+c shows a ring-enhancing glioblastoma in the left parietal
lobe with avid increase of rCBV (b) extending beyond the
extent of the contrast enhancement

Grade III astrocytoma, (a) T1+C shows inhomogeneous mass in right frontal lobe,
anterior portion of the mass (arrowhead) shows contrast enhancement; posterior
half of the mass does not, (b) rCBV map shows that anterior portion of the mass
(corresponding to contrast-enhanced portion in (a) has high rCBV (red and yellow),
and posterior portion has low rCBV (blue)

The tumor region is easily detectable in the CBV image as an area of
increased blood volume, reflecting angiogenesis. Higher-grade tumors
tend to have higher values, as in this glioblastoma

(A) T1+c of a patient with renal cell carcinoma who was treated with stereotactic
radiosurgery for a brain metastasis , the heterogeneous enhancing right insular
metastasis was slightly larger following radiotherapy (B) The relative cerebral
blood volume map shows marked decreased blood volume in the region of
enhancement, which is consistent with radiation necrosis as the dominant
underlying cause of enhancement

Use of rCBV map to determine optimal biopsy site in a 44-year-old woman
with seizures who was suspected of having a brain tumor, subsequent
biopsy showed World Health Organization grade III astrocytoma, (a) T2
shows hyperintense region (arrow) in left frontal lobe, (b) T1+C shows no
areas of abnormal contrast enhancement, making determination of region
of optimal biopsy site difficult, (c) rCBV map (red and yellow = high rCBV,
green and blue = low rCBV). A high rCBV area (arrow) corresponds to
region of hyperintense abnormality in a

e) Enhancement :
-Blood Brain Barrier :
*The brain has a unique triple layered blood brain barrier (BBB)
with tight endothelial junctions in order to maintain a
consistent internal milieu , contrast will not leak into the brain
unless this barrier is damaged , enhancement is seen when a
CNS tumor destroys the BBB
*Extra-axial tumors such as meningiomas and schwannomas are
not derived from brain cells and do not have a blood-brain
barrier , therefore they will enhance , there is also no blood-
brain barrier in the pituitary , pineal, tuber cinereum, choroid
plexus regions and area postrema
*Some non-tumoral lesions enhance because they can also
break down the BBB and may simulate a brain tumor , these
lesions include like infections , demyelinating diseases (MS)
and infarctions

RT CPA Schwannoma, T1+C shows a rounded tumor in the
right CPA with extension into the internal auditory
meatus, the IAM is expanded, this is the ice-cream cone
sign

Tuber cinereum (a) T1, (b) T1+C

T2 shows the approximate location of the circumventricular area postrema
(yellow circle) in the dorsal medulla adjacent

Multiple ring enhancing tuberculomas

MS, T1+C shows incomplete ring enhancement

-Enhanced CT images of a
patient with an infarction
in the territory of the MCA
-There is extensive gyral
enhancement (luxury
perfusion)
-Sometimes this luxury
perfusion may lead to
confusion with tumoral
enhancement
-Luxury perfusion used to
describe the dilation of
numerous vascular
channels observed within
the relatively avascular
infarcted area of the brain
24-48 h after an ischemic
stroke , these are
predominantly venous
channels but arterial
channels open up as well

-Contrast enhancement cannot visualize the full
extent of a tumor in cases of infiltrating
tumors , like gliomas , the reason for this is
that tumor cells blend with the normal brain
parenchyma where the blood brain barrier is
still intact , tumor cells can be found beyond
the enhancing margins of the tumor and
beyond any MR signal alteration , even
beyond the area of edema

On the T2 there is a lesion in the left temporal lobe , found incidentally ,
there was no enhancement and the DWI was normal , during follow-up
there was a slight increase in size , this was diagnosed as a low-grade
astrocytoma , it is not possible to resect such a lesionsince the infiltrating
tumors cells are within the normal-appearing brain tissue

-In gliomas like astrocytomas , oligodendrogliomas and
glioblastoma multiforme , enhancement usually
indicates a higher degree of malignancy , therefore
when during the follow up of a low-grade glioma the
tumor starts to enhance , it is a sign of malignant
transformation
-Gangliogliomas and pilocytic astrocytomas are the
exceptions to this rule : they are low-grade tumors
but they enhance vividly

Low grade tumors with enhancement: ganglioglioma (left) and a
pilocytic astrocytoma (right)

-Conspicuity of tumors with contrast :
*Some tumors appear only after contrast
enhancement
*Leptomeningeal metastases are usually not
seen without the administration of
intravenous contrast

This is a patient with Neurofibromatosis II , after the administration of
contrast the two meningiomas and the schwannoma are easily seen

Abnormal enhancement along the brainstem , along the folia of the
cerebellum (yellow arrow) and along the fifth intracranial nerve (blue
arrow) in a patient with leptomeningeal metastases

-Patterns of Enhancement :
1-No Enhancement
2-Homogenous Enhancement
3-Patchy Enhancement
4-Ring Enhancement

1-No Enhancement :
-Low grade astrocytomas
-Cystic non-tumoral lesions :
Dermoid cyst
Epidermoid cyst
Arachnoid cyst

Intra-axial tumor in an adult , it is centered in the temporal lobe and involves
the cortex , although there is massive infiltrative growth involving a large
part of the right cerebral hemisphere , there is only minimal mass effect ,
there is no enhancement , these features are typical for a low-grade
astrocytoma

2-Homogenous Enhancement :
-Metastases
-Lymphoma
-Germinoma and other pineal gland tumors
-Pituitary macroadenoma
-Pilocytic astrocytoma and hemangioblastoma (only the
solid component)
-Ganglioglioma
-Meningioma and Schwannoma

3-Patchy Enhancement :
-Metastases
-Oligodendroglioma
-Glioblastoma multiforme
-Radiation necrosis

Glioblastoma multiforme (GBM) , the enhancement indicates that this is a high-grade
tumor but only parts of it enhance , notice that there is also a cystic component
with ring enhancement , the tumor cells probably extend beyond the area of
edema as seen on the FLAIR image, this is because gliomas grow infiltratively into
normal brain , initially without any MR changes

A tumor located in the right hemisphere , although is a large tumor , the
mass-effect is limited , this indicates that there is marked infiltrative
growth , a characteristic typical for gliomas , notice the heterogeneity on
both T2 and FLAIR , there is patchy enhancement , all these findings are
typical for a GBM

4-Ring Enhancement :
-Metastases and high-grade gliomas
-It is also seen in non-tumorous lesions like
abscesses , some MS-plaques and sometimes
in an old hematomas

f) Differential Diagnosis For Specific Anatomic
Area :
1-Skull Base
2-Sella / Suprasellar
3-CPA
4-Pineal Region
5-Intraventricular

1-Skull Base :
-Chordoma (midline)
-Chondrosarcoma (off midline)
-Metastases
-Paraganglioma
-Sinonasal carcinoma

Midline tumor arising from the clivus , this is the typical presentation of a
chordoma , the differential diagnosis would include a metastasis and a
chondrosarcoma

Skull base tumor located off midline , this is a typical presentation for a
chondrosarcoma , the differential diagnosis would include a metastasis
and a paraganglioma

2-Sella / Suprasellar :
-Pituitary adenoma
-Craniopharyngioma
-Meningioma
-Rathke’s cleft cyst
-Chiasmatic glioma
-Dermoid
-Epidermoid
-Germinoma
-Schwannoma
-Metastases

3-CPA Masses :
-Schwannoma
-Meningioma
-Epidermoid cyst
-Arachnoid cyst
-Paraganglioma
-Metastases

4-Pineal Region :
-Pineocytoma
-Germ cell tumors
-PNET
-Tectal glioma
-Meningioma
-Dermoid
-Arachnoid

5-Intraventricular Masses :
-Ependymoma
-Subependymoma
-CPP
-Central Neurocytoma
-Colloid cyst
-Meningioma
-Giant cell astrocytoma

-N.B. : Tumors of the 4th
ventricle
*In children tumors in the 4th ventricle are very
common :
Astrocytomas are the most common followed by
medulloblastomas (or PNET-MB) , ependymomas
and brainstem gliomas with a dorsal exophytic
component
*In adults tumors in the 4th ventricle are uncommon :
Metastases are most frequently seen , followed by
hemangioblastomas , choroid plexus papillomas and
dermoid and epidermoid cysts

g) Tumor Mimics :
Many non-tumorous lesions can mimic a brain tumor :
1-Abscesses can mimic metastases
2-Multiple sclerosis can present with a mass-like lesion
with enhancement , also known as Tumefactive
multiple sclerosis
3-In the parasellar region one should always consider
the possibility of a aneurysm
4-Infections and vascular lesions can also mimic a CNS
tumor

h) Cerebral Edema :
-Edema within the brain can be caused by cell death ,
altered capillary permeability or hemodynamic
forces
1-Cytoxic Edema :
-Is cell swelling caused by damaged molecular sodium-
potassium ATPase ion pumps , it can affect both gray
& white matter
-Caused by cell death , most commonly due to infarct ,
water ions trapped inside swollen cells feature
reduced diffusivity

2-Vasogenic Edema :
-Is interstitial edema caused by increased capillary
permeability
-It is seen primarily in the white matter, as there is
more interstitial space
-Caused most commonly by neoplasm , infection or
infarct
3-Interstitial Edema :
-Caused by imbalance in CSF flow , most commonly due
to obstructive hydrocephalus
-Presents on imaging as periventricular fluid , often
called (transependymal flow of CSF)

Vasogenic edema surrounds cerebral metastases

Diagnostic Imaging of Brain Tumors

Diagnostic Imaging of Brain Tumors

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