Brain Tumor Amogh

8/3/2019 Brain Tumor Amogh

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APPROACH TO BRAIN

TUMORS

DR AMOGH R

FINAL YR DMRD


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RADIOLOGICAL

INVESTIGATIONS IN

INTRACRANIAL TUMOURS


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PLAIN RADIOGRAPHY

Plain radiographic findings in brain tumours are

of historical interest, but radiologists should still

be familiar with signs of raised intracranial

pressure (ICP) such as erosion of the laminadura of the dorsum sellae, or a J-shaped sella.

Skull radiography may also demonstrate tumour

calcification and enlargement of middle

meningeal artery grooves in meningiomas.


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Diagnostic catheter angiography

The use of diagnostic catheter angiography forbrain tumours has dramatically decreased withthe advances in cross-sectional imaging.

It is occasionally performed to assess thevascular supply of meningiomas pre-operatively.

Otherwise it is now mostly performed inconjunction with pre-operative or palliative

tumour embolizations or intra-arterialchemotherapy for treatment of high-gradegliomas


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Magnetic resonance imaging

MRI is the preferred investigation of patients with

suspected intracranial tumours.

It provides a better soft-tissue differentiation and

tumour delineation than CT and advanced MRimaging techniques, such as diffusion-weighted

(DWI) and perfusion-weighted (PWI) imaging

and MR spectroscopy (MRS), allow the

assessment of physiological and metabolicprocesses


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SPECTROSCOPY


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DWI


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FMRI


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COMPUTED TOMOGRAPHY

Most clinically symptomatic brain tumours

are detectable on CT, by virtue of mass

effect and/or altered attenuation.

Intra-axial tumours are usually of low

attenuation on non-enhanced CT images.

High attenuation areas within a tumour

indicate tumour calcification or recent

intratumoural haemorrhage.

ABBREVIATED WHO


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ABBREVIATED WHO

CLASSIFICATION OF BRAIN

TUMOURS


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Approach

Age of the patient. Intra- or extra-axial and in what anatomical compartment does it lie? Is it a solitary mass or is there multi-focal disease? On CT and MR we look for tissue characteristics like calcifications,

fat, cystic components, contrast enhancement and signal intensity

on T1WI, T2WI and DWI. Most brain tumors are of low signal intensity on T1WI and high onT2WI.

Therefore high signal intensity on T1WI or low signal on T2WI canbe an important clue to the diagnosis.

Lesion that simulates a tumor - like an abscess, MS-plaque,

vascular malformation, aneurysm or an infarct with luxury perfusion.


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Incidence of CNS tumors


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Age distribution

Specific tumors occur under the ageof 2, like choroid plexus papillomas,anaplastic astrocytomas andteratomas.

In the first decademedulloblastomas, astrocytomas,ependymomas,

craniopharyngeomas and gliomasare most common, whilemetastases are very rare.When they do occur at this age,metastases of a neuroblastoma arethe most frequent.

In adults about 50% of all CNSlesions are metastases. Other

common tumors in adults areastrocytomas, glioblastomamultiforme, meningiomas,oligodendrogliomas, pituitaryadenomas and schwannomas.

Astrocytomas occur at any age, butglioblastoma multiforme is mostlyseen in older people.


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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.

The most common supra-and infratentorial tumors

are listed in the table on

the left.


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The most common tumors in adults

Note that metastases are byfar the most common.It is important to realise that50% of metastases aresolitary.

Particularly in the posteriorfossa, metastases should be inthe top 3 of the differentialdiagnostic list.Hemangioblastoma is anuncommon tumor, but it is the

most common primary intra-axial tumor in the adult.Supratentorially, metastasesare also the most commontumors, followed by gliomas.


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TUMOR SPREAD


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Intra- versus Extraaxial

When we study an intracranialmass, the first thing we want toknow is whether the mass liesin- or outside of the brain.If it is outside the brain orextra-axial, then the lesion is

not actually a brain tumor, butderived from the lining of thebrain or surroundingstructures.Eighty percent of these extra-axial lesions will be either ameningioma or aschwannoma.On the other hand, in an adultan intra-axial tumor will be ametastasis or astrocytoma in75% of cases.


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Schwannoma in CPA-region with

typical features of an extraaxial

tumor (T2WI)


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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 subarachnoid space is widened because growth of an extra-axial lesion tends topush away the brain.

All these signs indicate that this is a typical extra-axial tumor.In the region of the CPA 90% of the extra-axial tumors are schwannomas.


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Coronal enhanced T1WI. Meningioma with dural tail, hyperostosis of

adjacent bone and homogeneous enhancement

Another sign of an extra-axialorigin is a broad dural base ora dural tail of enhancement asis typically seen inmeningiomas.

This may also occur in other

extra-axial tumors, but it is lesscommon.

Another sign of an extra-axialorigin are bony changes. Bonychanges are seen in bonetumors like chordomas,

chondrosarcomas andmetastases.They can also be secondary,as is seen in meningiomas andother tumors


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Melanoma metastasis

This lesion surely has the appearance of a meningioma: these tumors canbe hypointense on T2 due to a fibrocollageneous matrix or calcificationsand frequently produce reactive edema in the adjacent white matter of thebrain.

However, there is gray matter on the anteromedial and posteromedial sideof the lesion (red arrow).

This indicates that the lesion is intra-axial.


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Local tumor spread

Astrocytomas spread along the white matter tracts and do not respect the bounderiesof the lobes.

Because of this infiltrative growth, in many cases the tumor is actually larger than canbe depicted with MR.

Ependymomas of the fourth ventricle in children tend to extend through the foramenof Magendie to the cisterna magna and through the lateral foramina of Luschka to thecerebellopontine angle

Oligodendrogliomas typically show extension to the cortex.


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Subarachnoid seeding

Some tumors show subarachnoid seeding andform tumoral nodules along the brain and spinalcord.

This is seen in PNET, ependymomas, GBMs,lymphomas, oligodendrogliomas and choroidplexus papillomas.

Primitive neuroectodermal tumours (PNET) form

a rare group of tumors, which develop fromprimitive or undifferentiated nerve cells.These include medulloblastomas andpineoblastomas


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One of the most important roles of imaging is to assess the extent ofa tumor.

This is shown in the case on the left in a patient who presented withmultiple cranial nerve abnormalities.On the images we see an extra-axial tumor in the region of the leftcavernous sinus. There is homogeneous enhancement with a broaddural tail.This is typical for a meningioma.


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MASS EFFECT

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 sizethan 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.


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Diffusely infiltrating intra-axial tumor occupying most ofthe right hemisphere with only a minimal mass effect.

This is typical for the infiltrative growth seen in primarybrain tumors. There is no enhancement so this would probably be a

low-grade astrocytoma.


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MIDLINECROSSING


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Multifocal disease

Multiple tumors in the brain usually indicatemetastatic disease

Primary brain tumors are typically seen in asingle region, but some brain tumors like

lymphomas, multicentric glioblastomas andgliomatosis cerebri can be multifocal.

Some tumors can be multifocal as a result ofseeding metastases: this can occur in

medulloblastomas (PNET-MB), ependymomas,GBMs and oligodendrogliomas. Meningiomas and schwannomas can be

multiple, especially in neurofibromatosis type II.


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Multiple brain tumors can be seen

in phacomatoses:

1. Neurofibromatosis II: meningiomas,

ependymomas, optic nerve gliomas,

choroid plexus papillomas

2. Tuberous Sclerosis: subependymal

tubers, intraventricular giant cell

astrocytomas, ependymomas

3. von Hippel Lindau: hemangioblastomas


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Many non-tumorous diseases like small

vessel disease, infections (septic emboli,

abscesses) or demyelinating diseases like

MS can also present as multifocal disease.


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LEFT: Metastases.

RIGHT: Multiple meningiomas and a schwannoma

in a patient with Neurofibromatosis II


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Cortical based tumors

Most intra-axial tumors are located in thewhite matter.Some tumors, however,spread to or are located in the gray matter.

The differential diagnosis for these corticalbased tumors includes oligodendroglioma,ganglioglioma and DysembryoplasticNeuroepithial Tumor (DNET).

Patients with a cortically based tumorusually present with complex seizures.

A DNET is a rare benign neoplasm, usually in a cortical and temporal location.


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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.


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These cortically based tumors have to be

differentiated from non-tumorous lesions

like cerebritis, herpes simplex

encephalitis, infarction and post-ictalchanges.


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Oligodendroglioma

52-year-old female who, overthe period of one year,complained of headache andneck pain. There is a recentonset of tonic-clonic seizures.The CT shows a mass with

calcifications, which extendsall the way to the cortex.Although this is a large tumorthere is only limited masseffect on surroundingstructures, which indicates thatthis is an infiltrating tumor.

The most likely diagnosis is.The differential diagnosisincludes a malignantastrocytoma or a glioblastoma.


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CT and MR Characteristics


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Fat - Calcification - Cyst

Fat has a low density on CT (- 100HU).On MR, fat has a high signal intensity on both T1- andT2WI.

On sequences with fat suppression fat can be

differentiated from high signal caused by subacutehematoma, melanin, slow flow etc.

When you see high signal on T1WI always look forchemical shift artefact, as this indicates the presence offat.The chemical shift artefact occurs as alternating bands

of high and low signal on the boundaries of a lesion and isseen only in the frequency encoding direction.


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Ruptured dermoid cyst.

Fat within a tumor is seen in lipomas, dermoidcysts and teratomas.

Some tumors can have a high density on CT.This is typically seen in lymphoma, colloid cyst

and PNET-MB (medulloblastoma


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Calcification


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Calcified mass in the

suprasellar region,

causing obstructive

hydrocephalus. This location in the

suprasellar region and

the calcification are

typical for acraniopharyngioma.


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Craniopharyngiomas are slow growing,

extra-axial, squamous epithelial, calcified,

cystic tumors arising from remnants of

Rathke's cleft.

They are located the (supra)sellar region

and primarily seen in children with a small

second peak incidence in older adults.


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The calcification is not appreciated on the MR images, but

is easily seen on CT.

The calcification and the extension of the tumor to the

cortex are very typical for an oligodendroglioma.

An astrocytoma should be in the differential.


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Calcified meningioma

A patient with progressive visual loss.On the coronal and sagittal TW1I there is a large mass centeredaround the sella with a broad dural base.

There is extension into the sella.This patient was booked for decompression.

Only after the CT was performed, was it appreciated how denselycalcified this tumor is.


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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.


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In order to determine whether a lesion

is a cyst or cystic mass look for the

following characteristics:

Morphology

Fluid/fluid level

Content usually isointense to CSF on T1,

T2 and FLAIR

DWI: restricted diffusion


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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.


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Craniopharyngioma with an enhancing rim surrounding the cysticcomponent.

Neuroenteric cyst with the contents of which have the same signalintensity as CSF.

Glioblastoma multiforme (GBM) with a central cystic component.The enhancement in GBM is usually more irregular.


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MOST LESIONS ARE LOW ON

T1 AND HIGH ON T2

BUT.......


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A patient who presented with apoplexy. The high signal is due tohemorrhage in a pituitary macroadenoma.

The patient in the middle has a glioblastoma multiforme, whichcaused a hemorrhage in the splenium of the corpus callosum.

On the right is a patient with a metastasis of a melanoma.The high signal intensity is due to the melanin content.


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Low on T2

Most tumors will be bright on T2WI due toa high water content.

When tumors have a low water content

they are very dense and hypercellular andthe cells have a high nuclear-cytoplasmasmic ratio.

These tumors will be dark on T2WI.The classic examples are CNS lymphomaand PNET (also hyperdense on CT).


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Calcifications are mostly dark on T2WI. Paramagnetic effects cause a signal drop and

are seen in tumors that contain hemosiderin. Proteinaceous material can be dark on T2

depending on the content of the protein itself.A classic example of this is the colloid cyst.

Flow voids are also dark on T2 and indicate thepresence of vessels or flow within a lesion.

This is seen in tumors that contain a lot ofvessels like hemangioblastomas, but also innon-tumorous lesions like vascularmalformations


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Melanoma metastases have a low SI on T2WI as a result of themelanin.

GBM can have a low SI on T2WI because sometimes they have a

high nuclear-cytoplasmic ratio. Most GBM's, however, arehyperintense on T2WI. PNET typically has a high nuclear-cytoplasmic ratio. PNET is

mostly located in the region of the 4th ventricle, but another, lesscommon, location is in the region of the pineal gland.


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Mucinous metastases can have a low SI on T2WI because theyoften contain calcifications..

Meningiomas are mostly of intermediate signal.

They can have a high SI on T2WI if they contain a lot of water.They can have a low SI on T2WI if they are very dense andhypercellular or when they contain calcifications.


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Diffusion weighted imaging

Normally water protons have the ability to diffuseextracellularly and loose signal.High intensity on DWI indicates restriction of the ability ofwater protons to diffuse extracellularly.Restricted diffusion is seen in abscesses, epidermoidcysts and acute infarction (due to cytotoxic edema).

In cerebral abscesses the diffusion is probably restricteddue to the viscosity of pus, resulting in a high signal onDWI.

In most tumors there is no restricted diffusion - even innecrotic or cystic components.This results in a normal, low signal on DWI.


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Perfusion Imaging

Perfusion imaging can play an important role in

determining the malignancy grade of a CNS

tumor.

Perfusion depends on the vascularity of a tumorand 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 atumor than the amount of contrast enhancement.


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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 tumordestroys the BBB.


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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 and choroid plexus

regions.


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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.


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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 withthe 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 signalalteration - even beyond the area of edema.


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42 y/o male with mild head trauma. On the T2WI 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.


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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 malignanttransformation..


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Gangliogliomas and pilocytic astrocytomas are

the exceptions to this rule: they are low-grade

tumors, but they enhance vividly.


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The amount of enhancement depends onthe amount of contrast that is delivered tothe interstitium.

In general, the longer we wait, the betterthe interstitial enhancement will be.The optimal timing is about 30 minutesand it is better to give contrast at the start

of the examination and to do theenhanced T1WI at the end.


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LEFT: Schwannoma extending into the middle

cranial fossa with homogeneous enhancement

RIGHT: Primary Lymphoma known for its vividenhancement


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No enhancement is seen in

Low grade astrocytomas

Cystic non-tumoral lesions:

Dermoid cyst

Epidermoid cyst

Arachnoid cyst


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An 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 ofthe right cerebral hemisphere, there is only minimal mass effect.

There is no enhancement.

These features are typical for a low-grade astrocytoma.

H h


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Homogeneous enhancement

Metastases

Lymphoma

Germinoma and other pineal gland tumors Pituitary macroadenoma

Pilocytic astrocytoma and hemangioblastoma(only the solid component)

Ganglioglioma Meningioma and Schwannoma


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P t h h t


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Patchy enhancement

Metastases

Oligodendroglioma

Glioblastoma multiforme

Radiation necrosis


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Gioblastoma multiforme (GBM). The enhancement indicates that this is a high-grade tumor, but only

parts of it enhance. There is also a cystic component with ringenhancement.

The tumor cells probably extend beyond the area of edema as seenon the FLAIR image.This is because gliomas grow infiltratively into normal brain - initiallywithout any MR changes.


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Although is a large tumor, the mass-effect is limited.This indicates that there is marked infiltrative growth, acharacteristic typical for gliomas.

Notice the heterogeneity on both T2WI and FLAIR.

There is patchy enhancement.All these findings are typical for a GBM.Virtually no other tumor behaves in this way.


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Ri h t


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Ring enhancement

Ring enhancement is seen in metastasesand high-grade gliomas.

It is also seen in non-tumorous lesions like

abscesses, some MS-plaques andsometimes in an old hematomas.


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Conspicuity of tumors with contrast

This is a patient with Neurofibromatosis II.

After the administration of contrast the twomeningiomas and the schwannoma are easilyseen.


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Leptomeningeal metastases are usually not seen without theadministration of intravenous contrast.

The case on the left demonstrates the abnormal enhancement

along the brainstem, along the folia of the cerebellum (yellow arrow)and along the fifth intracranial nerve (blue arrow) in a patient withleptomeningeal metastases.


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Differential diagnosis

for specific anatomic area


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Sk ll base


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Skull base

These tumors either arise fromextracranial structures like the sinuses

(sinonasal carcinoma), or from the skull

base itself (chordoma, chondrosarcoma,fibrous dysplasia).

Chordoma is usually located in the

midline, while chondrasarcoma usuallyarises off the midline.


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Midline tumorarising from theclivus.

This is the typical

presentation of achordoma.The differentialdiagnosis would

include ametastasis and achondrosarcoma.


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Skull base tumor locatedoff midline.

This is a typicalpresentation for achondrosarcoma.

The differential diagnosiswould include ametastasis and aparaganglioma.Chondrosarcomas canbe located in the midline

and chordomas aresometimes located offmidline but those casesare exceptional.

Skull Base Paraganglioma


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Skull Base Paraganglioma.


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58-year-old male with a gradual onset of right facial pain andnumbness and a recent onset of double vision.

There is an enhancing mass anterior to the skull base and also inthe region of the right cavernous sinus.In the bone window setting there is sclerosis of the skull base,particularly in the region of the clivus.

PTO

CONTD


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A normal clivus is bright on T1WI as a result of the fatty bonemarrow.

There is an enhancing mass anterior to the clivus.

On the coronal images we see the enhancement extending throughthe foramen ovale to the right of the cavernous sinus.


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The diagnosis is a nasopharyngealsquamous cell carcinoma with intracranial

extension.

The differential diagnosis would include:skull base metastasis, lymphoma, chronic

infection and even a meningioma -

although this would be an unusual way fora meningioma to spread.


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Mass in the suprasellar cistern. On the NECT we can see that it contains calcium. On the T1WI there is a hyperintense area that shows no

enhancement (i.e. cystic). There are other components that show enhancement. The tumor is complicated by a hydrocephalus.

These findings are very specific for a craniopharyngeoma.


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PTO


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Notice the normal inferiorly displacedpituitary gland.

This means it is not a macroadenoma.

The diagnosis is a craniopharyngioma. The differential diagnosis would include an

astrocytoma and a meningioma.


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52-year-old male with hearing loss on the right.The images show an unusual cystic mass with enhancingseptations.

There is also some enhancement within the internal acoustic canal.Based on the images the most likely diagnosis would be a cysticschwannoma, but this happened to be an uncommon, cysticpresentation of a meningioma.


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Based on these images the differentialdiagnosis would include:

Meningioma

Pineocytoma

Germ Cell Tumor

This happened to be a meningioma.

Ruptured pineal region dermoid


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Ruptured pineal region dermoid.


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12 y/o male with upward gaze paralysis.

There is a tumor located in the pineal region. The tumor contains calcifications. There is homogeneous enhancement, which is common for a tumor

in the pineal regionBased on the age of the patient, the location and the tumorcharacteristics, this is most likely a germinoma.


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Giant cell astrocytoma


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Giant cell astrocytoma.

4th ventricle


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4th ventricle


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In children tumors in the 4th ventricle are verycommon.

Astrocytomas are the most common followed bymedulloblastomas (or PNET-MB),

ependymomas and brainstem gliomas with adorsal exophytic component.

In adults tumors in the 4th ventricle areuncommon.

Metastases are most frequently seen, followedby hemangioblastomas, choroid plexuspapillomas and dermoid and epidermoid cysts.

Tumor Mimics


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Many non-tumorous lesions can mimic abrain tumor.

Abscesses can mimic metastases.

Multiple sclerosis can present with amass-like lesion with enhancement, also

known as tumefactive multiple sclerosis..

In the parasellar region one should alwaysconsider the possibility of a aneurysm


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References
http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552


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References

Brain Lesion Locator: Differential Diagnosis by Locat

by James Smirniotopoulos

Diagnostic Neuroradiology by Anne G. Osborn

Textbook ofRadiology and Imaging David

Sutton 7ed

Grainger & Allison's Diagnostic Radiology

www.radiologyassistant.nl
http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://rad.usuhs.mil/rad/location/location_frame.htmlhttp://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://www.elsevier.com/wps/product/authors/712552http://thepiratebay.org/torrent/4265111/Textbook_of_Radiology_and_Imaging_David_Sutton_7edhttp://thepiratebay.org/torrent/4265111/Textbook_of_Radiology_and_Imaging_David_Sutton_7edhttp://thepiratebay.org/torrent/4265111/Textbook_of_Radiology_and_Imaging_David_Sutton_7edhttp://thepiratebay.org/torrent/4265111/Textbook_of_Radiology_and_Imaging_David_Sutton_7edhttp://thepiratebay.org/torrent/4265111/Textbook_of_Radiology_and_Imaging_David_Sutton_7edhttp://rad.usuhs.mil/rad/location/location_frame.html


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