The Radiology Assistant Brain Tumor - Systematic Approach.pdf

5/27/2018 The Radiology Assistant Brain Tumor - Systematic Approach.pdf


10/31/13,The Radiology Assistant : Brain Tumor - Systematic Approach

Pahttp://www.radiologyassistant.nl/en/p47f86aa182b3a

Incidence of CNS tumors

Roughly one-third of CNS tumors are metalesions, one third are gliomas and one-thirdnon-glial origin.Glioma is a non-specific term indicating thtumor originates from glial cells like astro

oligodendrocytes, ependymal and choroid pcells.Astrocytoma is the most common glioma anbe subdivided into the low-grade pilocytic the intermediate anaplastic type and thegrade malignant glioblastoma multiforme (GGBM is the most common type (50% of all cytomas).The non-glial cel tumors are a large hetenous group of tumors of which meningioma most common.

Age distribution

The age of the patient is an important factthe differential diagnosis.Specific tumors occur under the age of 2choroid plexus papillomas, anaplastic astomas and teratomas.In the first decade medulloblastomas, astomas, ependymomas, craniopharyngeoma

gliomas are most common, while metastasevery rare.When they do occur at this age, metastaseneuroblastoma are the most frequent.In adults about 50% of all CNS lesionmetastases.Other common tumors in adults are astomas, glioblastoma multiforme, meningioligodendrogliomas, pituitary adenomas schwannomas.Astrocytomas occur at any age, but glioblamultiforme is mostly seen in older people.




Although cancer is rare in children, brain tare the most common type of childhood cafter leukemia and lymphoma.Most of the tumors in children are locatefratentorially.The most common supra- and infratentormors are listed in the table on the left.

Intra- versus Extraaxial

When we study an intracranial mass, thething we want to know is whether the mas

in- or outside of the brain.If it is outside the brain or extra-axial, thelesion is not actually a brain tumor, but defrom the lining of the brain or surrounding tures.Eighty percent of these extra-axial lesions weither a meningioma or a schwannoma.On the other hand, in an adult an intra-axmor will be a metastasis or astrocytoma in

The most common tumors in adults are lis

the table on the left.Note that metastases are by far the mostmon.It is important to realize that 50% of metasare solitary.Particularly in the posterior fossa, metashould be in the top 3 of the differential diatic list.Hemangioblastoma is an uncommon tumor,is the most common primary intra-axial tumthe adult.

Supratentorially, metastases are also the common tumors, followed by gliomas.

Tumor spr
http://www.radiologyassistant.nl/data/bin/a50979783f3b6b_TABTumors-in-Adult.pnghttp://www.radiologyassistant.nl/data/bin/a50979783f3642_TABTumors-in-Pediatr.png




of cases.

The T2W-images show a schwannoma locathe cerebellopontine angle (CPA).This case nicely demonstrates the typical sian extra-axial tumor.There is a CSF cleft (yellow arrow).

The subarachnoid vessels that run on the sof the brain are displaced by the lesion (blurow).There is gray matter between the lesion anwhite matter (curved red arrow).The subarachnoid space is widened begrowth of an extra-axial lesion tends to away the brain.All these signs indicate that this is a typictra-axial tumor.In the region of the CPA 90% of the extra

tumors are schwannomas.

Another sign of an extra-axial origin is a dural base or a dural tail of enhancementtypically seen in meningiomas.This may also occur in other extra-axial tubut it is less common.Another sign of an extra-axial origin are changes.Bony changes are seen in bone tumors likedomas, chondrosarcomas and metastases.They can also be secondary, as is seen in mgiomas and other tumors.

On the left an example of a meningioma wbroad dural base and a dural tail of enhment.There is hyperostosis in the adjacent bonthe lesion enhances homogeneously.Extra-axial tumors are not derived from brasue and do not have a blood-brain-barrimost of them enhance homogeneously.

Schwannoma in CPA-region with typical features ofan extraaxial tumor (T2WI)

Coronal enhanced T1WI. Meningioma with dural tail,hyperostosis of adjacent bone and homogeneousenhancement




Intra- vs Extra-axial (2)The differentiation between intra-axial versutra-axial is usually straight forward, but times it can be very difficult and imaging intiple planes may be necessary.

The tumor in the case on the left was thoube a falcine meningioma, i.e. extra-axial anpresented for surgery.This lesion surely has the appearance of a mgioma: these tumors can be hypointense due to a fibrocollageneous matrix or calcificand frequently produce reactive edema in thjacent white matter of the brain.However, there is gray matter on the anteroal and posteromedial side of the lesion (rerow).This indicates that the lesion is intra-axial.If the lesion was extra-axial the gray mshould have been pushed away.This proved to be a melanoma metastasis.

Local tumor spread (1)

Astrocytomas spread along the white mtracts and do not respect the bounderies lobes.Because of this infiltrative growth, in many the tumor is actually larger than can be dewith MR.Ependymomas of the fourth ventricle in ch

tend to extend through the foramen of Magto the cisterna magna and through the foramina of Luschka to the cerebellopontingle (figure).Oligodendrogliomas typically show extensithe cortex.

Subarachnoid seeding

Some tumors show subarachnoid seeding

Melanoma metastasis: T2WI and T1WI

Ependymoma with extension to the prepontine area(blue arrows) and into the foramen magnum (redarrow).




Only by studying all the images we do apprthat the actual extent of the tumor is gthan expected.The tumor is situated in the pterygopalatinsa and extends into the orbit.It also spreads anteriorly into the middle cfossa

form tumoral nodules along the brain and cord.This is seen in PNET, ependymomas, GBMsphomas, oligodendrogliomas and choroid ppapillomas.Primitive neuroectodermal tumours (PNET)a rare group of tumors, which develop from itive or undifferentiated nerve cells.These include medulloblastomas and pinetomas.

One of the most important roles of imagingassess the extent of a tumor.This is shown in the case on the left in a pwho presented with multiple cranial nerve amalities.On the images we see an extra-axial tumor region of the left cavernous sinus.

There is homogeneous enhancement wbroad dural tail.This is typical for a meningioma.

Local tumor spread (2)Another important consideration is the effethe surrounding structures.Primary brain tumors are derived from brainand often have less mass effect for theithan you would expect, due to their infiltgrowth.This is not the case with metastases and axial tumors like meningiomas or schwannwhich have more mass effect due to their esive growth.

On the left is an image of a diffusely infilt

Low grade astrocytoma




Midline crossing

The ability of tumors to cross the midline the differential diagnosis.

Glioblastoma multiforme (GBM) frequecrosses the midline by infiltrating the wmatter tracts of the corpus callosum.Radiation necrosis can look like recurrGBM and can sometimes cross the midMeningioma is an extra-axial tumor anspread along the meninges to the

contralateral side.Lymphoma is usually located near themidline.Epidermoid cysts can cross the midlinethe subarachnoid space.MS can also present as a mass lesion corpus callosum.

intra-axial tumor occupying most of the hemisphere with only a minimal mass effectThis is typical for the infiltrative growth seprimary brain tumors.There is no enhancement so this would probe a low-grade astrocytoma.

Multifocal disease

Multiple tumors in the brain usually inmetastatic disease (figure).

Primary brain tumors are typically seen in gle region, but some brain tumors likephomas, multicentric glioblastomas gliomatosis cerebri can be multifocal.Some tumors can be multifocal as a resseeding metastases: this can occur in mloblastomas (PNET-MB), ependymomas, and oligodendrogliomas.Meningiomas and schwannomas can be mu

Tumors and tumor-like masses that cross the midline

LEFT: Metastases. RIGHT: Multiple meningiomas anda schwannoma in a patient with Neurofibromatosis II
http://www.radiologyassistant.nl/data/bin/a5097978404b28_multifocal1.jpg




especially in neurofibromatosis type II.

Multiple brain tumors can be seen in pmatoses:

Neurofibromatosis I: optic gliomas andastrocytomasNeurofibromatosis II: meningiomas,

ependymomas, choroid plexus papillom(figure)Tuberous Sclerosis: subependymal tubintraventricular giant cell astrocytomaependymomasvon Hippel Lindau: hemangioblastoma

Many non-tumorous diseases like small disease, infections (septic emboli, abscess

demyelinating diseases like MS can also pras multifocal disease.

Cortical based tumors

Most intra-axial tumors are located in the matter.Some tumors, however, spread to or are loin the gray matter.The differential diagnosis for these cortical tumors includes oligodendroglioma, goglioma and Dysembryoplastic Neuroepithimor (DNET).A DNET is a rare benign neoplasm, usuallycortical and temporal location.Patients with a cortically based tumor upresent with complex seizures.

On the left a 45-year-old female with a seizure disorder (complex-partial) for 15 yeThere is a non-enhancing, cortically based tuThis is a ganglioglioma.The differential diagnosis includes DNET and

cytic astrocytoma.

These cortically based tumors have to be entiated from non-tumorous lesions like cetis, herpes simplex encephalitis, infarctiopost-ictal changes.




On the left are images of a 52-year-old fwho, over the period of one year, complainheadache and neck pain.There is a recent onset of tonic-clonic seizur

The CT shows a mass with calcifications, extends all the way to the cortex.Although this is a large tumor there is onlyed mass effect on surrounding structures, indicates that this is an infiltrating tumor.The most likely diagnosis is oligodendrogliomThe differential diagnosis includes a malastrocytoma or a glioblastoma.

Fat - Calcification - Cyst - High dens

Fat has a low density on CT (- 100HU).On MR, fat has a high signal intensity on botand T2WI.On sequences with fat suppression fat can bferentiated from high signal caused by subhematoma, melanin, slow flow etc.

When you see high signal on T1WI alwaysfor chemical shift artefact, as this indicatepresence of fat.The chemical shift artefact occurs as alternbands of high and low signal on the boundaa lesion and is seen only in the frequency eing direction.

Fat within a tumor is seen in lipomas, de

CT and MR Characteris

Ruptured dermoid cyst. Coronal T1WI (left) andNECT (right).



Paghttp://www.radiologyassistant.nl/en/p47f86aa182b3a

On the left are images of a tumor with a calcification. .The calcification is not appreciated on the Mages, but is easily seen on CT.The calcification and the extension of the to the cortex are very typical for an oligdroglioma.

An astrocytoma should be in the differential

cysts and teratomas.On the left a patient with the classical findia ruptured dermoid cyst.

Some tumors can have a high density on CTThis is typically seen in lymphoma, colloidand PNET-MB (medulloblastoma).

Calcification

Calcification is seen in many CNS tumors (TaWhen we think of a calcified intra-axial tumothink oligodendroglioma since these tumorsly always have calcifications.However an intraaxial calcified tumor in theis more likely to be an astrocytoma than a dendrogliomas, since astrocytomas, althougfrequently calcified, are far more common.

A pineocytoma itself does not calcify, but init 'explodes' the calcifications of the pineal g

On the left is an image of a calcified mass suprasellar region, causing obstructive hcephalus.This location in the suprasellar region ancalcification are typical for a craniopharyngioCraniopharyngiomas are slow growing, extral, squamous epithelial, calcified, cystic tuarising from remnants of Rathke's cleft.They are located the (supra)sellar region anmarily seen in children with a small secondincidence in older adults.

Oligodendroglioma with calcification (PDWI and CT)




On the left are images of a patient with prosive visual loss.On the coronal and sagittal TW1I there is a

mass centered around the sella with a broadal base.There is extension into the sella.This patient was booked for decompression.Only after the CT was performed, was it apated how densely calcified this tumor is.It would be impossible to operate this tumopreserve the patient's vision.

Cystic versus SolidThere are many cystic lesions that can simuCNS tumor.These include epidermoid, dermoid, aracneuroenteric and neuroglial cysts.Even enlarged perivascular spaces of ViRobin can simulate a tumor.In order to determine whether a lesion is or cystic mass look for the following charactics:

MorphologyFluid/fluid level

Content usually isointense to CSF on Tand FLAIRDWI: restricted diffusion

An arachnoid cyst is isointense to CSF on aquences.Tumor necrosis may sometimes look like abut it is never completely isointense to CSF.

On the far left a craniopharyngioma with a

hancing rim surrounding the cystic componeIn the middle a neuroenteric cyst with thetents of which have the same signal intensCSF.On the right a glioblastoma multiforme with a central cystic component.The enhancement in GBM is usually more ilar.

Calcified meningioma




High on T1

Most tumors have a low or intermediate sigtensity on T1WI.Exceptions to this rule can indicate a specifiof tumor.On the left is a list of causes for T1-shorten

Calcifications are mostly dark on T1WI, bupending on the matrix of the calcificationscan sometimes be bright on T1.Especially on gradient echo images slow flobe seen as bright signal on T1WI and shoube confused with enhancement.This is particularly pronounced on gradientimages.

If you only do an enhanced scan, remembehigh signal is not always enhancement.

On the left are some images of tumors withsignal intensities on T1WI.On the far left images of a patient who preswith apoplexy.The high signal is due to hemorrhage in aitary macroadenoma.The patient in the middle has a glioblastomatiforme, which caused a hemorrhage in thenium of the corpus callosum.On the right is a patient with a metastasi

melanoma.The high signal intensity is due to the mcontent.

Low on T2

Most tumors will be bright on T2WI due to awater content.When tumors have a low water content thevery dense and hypercellular and the cells hhigh nuclear-cytoplasmasmic ratio.

These tumors will be dark on T2WI.The classic examples are CNS lymphomaPNET (also hyperdense on CT).Calcifications are mostly dark on T2WI.The differential diagnosis of calcified tumordiscussed above.Paramagnetic effects cause a signal drop anseen in tumors that contain hemosiderin.Proteinaceous material can be dark on T




On the left some examples of tumors with signal intensity on T2WI.

1. Melanoma metastases have a low SI oT2WI as a result of the melanin.

2. GBM can have a low SI on T2WI becausometimes they have a high nuclear-cytoplasmic ratio. Most GBM's, howevehyperintense on T2WI.

3. PNET typically has a high nuclear-

cytoplasmic ratio. PNET is mostly locatthe region of the 4th ventricle, but anoless common, location is in the region the pineal gland.

4. Mucinous metastases can have a low ST2WI because they often containcalcifications..

5. Meningiomas are mostly of intermediasignal.They can have a high SI on T2WI if thcontain a lot of water.They can have a low SI on T2WI if thevery dense and hypercellular or when contain calcifications.

pending on the content of the protein itself.A classic example of this is the colloid cyst.Flow voids are also dark on T2 and indicatpresence of vessels or flow within a lesion.This is seen in tumors that contain a lot osels like hemangioblastomas, but also in nmorous lesions like vascular malformations.




Diffusion weighted imaging

Normally water protons have the ability to d

extracellularly and loose signal.High intensity on DWI indicates restriction ability of water protons to diffuse extracelluRestricted diffusion is seen in abscesses, emoid cysts and acute infarction (due to cytedema).

In cerebral abscesses the diffusion is probabstricted due to the viscosity of pus, resultinhigh signal on DWI.In most tumors there is no restricted diffueven in necrotic or cystic components.

This results in a normal, low signal on DWI.

Perfusion Imaging

Perfusion imaging can play an important rdetermining the malignancy grade of a CNmor.Perfusion depends on the vascularity of a and is not dependent on the breakdown o

blood-brain barrier.The amount of perfusion shows a better cotion with the grade of malignancy of a than the amount of contrast enhancement.

Enhancem




Blood brain barrierThe brain has a unique triple layered bloodbarrier (BBB) with tight endothelial junctioorder to maintain a consistent internal milieContrast will not leak into the brain unlesbarrier is damaged.Enhancement is seen when a CNS tumostroys the BBB.

Extra-axial tumors such as meningiomasschwannomas are not derived from brainand do not have a blood-brain barrier.Therefore they will enhance.There is also no blood-brain barrier in theitary, pineal and choroid plexus regions.

Some non-tumoral lesions enhance becausecan also break down the BBB and may simu

brain tumor.These lesions include like infections, demyeing diseases (MS) and infarctions.

Contrast enhancement cannot visualize thextent of a tumor in cases of infiltrating tulike gliomas.The reason for this is that tumor cells blendthe normal brain parenchyma where the brain barrier is still intact.Tumor cells can be found beyond the enhamargins of the tumor and beyond any MR alteration - even beyond the area of edema

On the left is an image of a 42 y/o malemild head trauma.On the T2WI there is a lesion in the left temlobe, found incidentally.There was no enhancement and the DWnormal.During follow-up there was a slight increasize.

This was diagnosed as a low-grade astrocytoIt is not possible to resect such a lesion, the infiltrating tumors cells are within themal-appearing brain tissue.




The amount of enhancement depends oamount of contrast that is delivered to the stitium.In general, the longer we wait, the better tterstitial enhancement will be.The optimal timing is about 30 minutes anbetter to give contrast at the start of the e

nation and to do the enhanced T1WI at the

In gliomas - like astrocytomas, oligdrogliomas and glioblastoma multiforme

hancement usually indicates a higher degmalignancy.Therefore when during the follow up of agrade glioma the tumor starts to enhance, sign of malignant transformation..Gangliogliomas and pilocytic astrocytomathe exceptions to this rule: they are low-tumors, but they enhance vividly.

As discussed above, it recently has been sthat tumor angiogenesis as shown by perMR correlates better with tumor grade thahancement after the administration of venous contrast.

No enhancementis seen in:

Low grade astrocytomasCystic non-tumoral lesions:

Dermoid cystEpidermoid cystArachnoid cyst

On the left is an image of an intra-axial tuman adult.It is centered in the temporal lobe and invthe cortex.Although there is massive infiltrative growvolving a large part of the right cerebral

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

LEFT: Schwannoma extending into the middle cranialfossa with homogeneous enhancement RIGHT:Primary Lymphoma known for its vivid enhancement

Low grade astrocytoma. No enhancement.




Homogeneous enhancementcan be seen

MetastasesLymphomaGerminoma and other pineal gland tumPituitary macroadenomaPilocytic astrocytoma andhemangioblastoma (only the solidcomponent)GangliogliomaMeningioma and Schwannoma

sphere, there is only minimal mass effect.There is no enhancement.These features are typical for a low-grade cytoma.

Patchy enhancementcan be seen in:

MetastasesOligodendrogliomaGlioblastoma multiformeRadiation necrosis

On the left is an example of a glioblastoma

forme (GBM).The enhancement indicates that this is a grade tumor, but only parts of it enhance.Notice that there is also a cystic componenring enhancement.The tumor cells probably extend beyond theof edema as seen on the FLAIR image.This is because gliomas grow infiltrativelynormal brain - initially without any MR chan

GBM with patchy enhancement and cystic componentwith ring enhancement




Patchy enhancement (2)On the left are images of a tumor located right hemisphere.Although is a large tumor, the mass-effect ited.This indicates that there is marked infilt

growth, a characteristic typical for gliomas.Notice the heterogeneity on both T2WIFLAIR.There is patchy enhancement.All these findings are typical for a GBM.Virtually no other tumor behaves in this way

Ring enhancementRing enhancement is seen in metastasehigh-grade gliomas.

It is also seen in non-tumorous lesions likscesses, some MS-plaques and sometimes old hematomas.

On the left three different ring enhancing le

Conspicuity of tumors with contrast

The case on the left demonstrates the vaGadolinium in the conspicuity of tumors.This is a patient with Neurofibromatosis II.After the administration of contrast themeningiomas and the schwannoma are seen.
http://www.radiologyassistant.nl/data/bin/a5097978421661_Enhancement-ring.png




Leptomeningeal metastases are usually not

without the administration of intravenoustrast.The case on the left demonstrates the abnenhancement along the brainstem, along thof the cerebellum (yellow arrow) and alonfifth intracranial nerve (blue arrow) in a pwith leptomeningeal metastases.

Skull base

Common skull base tumors are listed in theon the left.These tumors either arise from extracstructures like the sinuses (sinonasal carcinor from the skull base itself (chordoma, drosarcoma, fibrous dysplasia).

Chordoma is usually located in the midline,chondrasarcoma usually arises off the midlin

Differential diagnosis for specific anatomic a

Leptomeningeal metastases




On the left a midline tumor arising fromclivus.This is the typical presentation of a chordomThe differential diagnosis would include a mtasis and a chondrosarcoma.




On the left another skull base tumor locatmidline.This is a typical presentation for a chondrosma.The differential diagnosis would include a mtasis and a paraganglioma.Chondrosarcomas can be located in the mand chordomas are sometimes located off mbut those cases are exceptional.




On the left an example of a Skull Base Parglioma.

On the left CT images of a 58-year-old malea gradual onset of right facial pain and numand a recent onset of double vision.First study the images, than continue.

There is an enhancing mass anterior to thebase and also in the region of the right cavesinus.In the bone window setting there is sclerothe skull base, particularly in the region oclivus.Continue with the MR images.




Sella/suprasellar

On the left is a list of common sellarsuprasellar tumors.In this region it is important to keep the posty of an aneurysm in the differential diagnos

On the left enhanced sagittal and coronal T1The most striking finding is the black clivuto the sclerosis.A normal clivus is bright on T1WI as a resthe fatty bone marrow.

There is an enhancing mass anterior tclivus.On the coronal images we see the enhanceextending through the foramen ovale to theof the cavernous sinus.The diagnosis is a nasopharyngeal squamoucarcinoma with intracranial extension.The differential diagnosis would include:base metastasis, lymphoma, chronic infand even a meningioma - although this woan unusual way for a meningioma to spread

On the left are images of a mass in the suplar cistern.On the NECT we can see that it contains calOn the T1WI there is a hyperintense areashows no enhancement (i.e. cystic).There are other components that show enhment.

The tumor is complicated by a hydrocephaluThese findings are very specific for a craniryngeoma.




On the left NECT and enhanced CT-image

33-year-old female with severe headache (in the a.m.), reduction in visual acuity and fields and papilledema.Continue with the MR images.

Notice the normal inferiorly displaced pitgland.This means it is not a macroadenoma.The diagnosis is again a craniopharyngiomaThe differential diagnosis would include an cytoma and a meningioma.




Cerebello-pontine angle

Common CP Angle Tumors are listed in theon the left.

Pineal region

Common pineal region tumors are listed table on the left.

On the left a 52-year-old male with hearinon the right.The images show an unusual cystic massenhancing septations.There is also some enhancement within the nal acoustic canal.Based on the images the most likely diagwould be a cystic schwannoma, but thispened to be an uncommon, cystic presentata meningioma.
http://www.radiologyassistant.nl/data/bin/a5097978432ce6_TAB-Pineal.png




On the left a tumor located in the pineal reg

Based on these images the differential diawould include:

MeningiomaPineocytomaGerm Cell Tumor

This happened to be a meningioma.

On the left are typical images of a ruppineal region dermoid.




On the left images of a 12 y/o male with ugaze paralysis.There is a tumor located in the pineal regionThe tumor contains calcifications.There is homogeneous enhancement, whcommon for a tumor in the pineal regioncussed above).

Based on the age of the patient, the locatiothe tumor characteristics, this is most likgerminoma.

Intraventricular

Common intraventricular Tumors are listed table on the left.




On the left a tumor located in the 3rd ventri

The tumor contains calcifications.The diagnosis is a giant cell astrocytoma.

4th ventricle

In children tumors in the 4th ventricle arecommon.Astrocytomas are the most common followmedulloblastomas (or PNET-MB), ependym

and brainstem gliomas with a dorsal exocomponent.

In adults tumors in the 4th ventricle are umon.Metastases are most frequently seen, followhemangioblastomas, choroid plexus papiland dermoid and epidermoid cysts.




Many non-tumorous lesions can mimic a bramor.Abscesses can mimic metastases.Multiple sclerosis can present with a mass-lsion with enhancement, also known as tumtive multiple sclerosis..In the parasellar region one should alwayssider the possibility of a aneurysm.

Infections and vascular lesions can also mCNS tumor.

Tumor Mim

1. Brain Lesion Locator: Differential Diagnosis by Location

by James Smirniotopoulos

2. Primary Lymphoma of the Central Nervous System: Typical and Atypical CT and MR Imaging

Appearances

by Namik Erdag et al.

AJR 2001; 176:1319-1326

3. Diagnostic Neuroradiology by Anne G. Osborn

Mosby 1994
http://www.ajronline.org/cgi/content/full/176/5/1319http://rad.usuhs.mil/rad/location/location_frame.html

The Radiology Assistant Brain Tumor - Systematic Approach.pdf

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