radiological imaging of intracranial cystic lesions

Dr. Vishal Sankpal

Imaging of intracranial cystic lesions

Non-neoplasticNon-infectious

Neoplastic

Intracranial cystic lesions

Infectious

Associated with congenital malformations

•Dermoid cyst•Epidermoid cyst•Arachnoid cyst•Colloid cyst•Neuroectodermal cyst•Neuroglial cyst•Ependymal cyst•Porencephalic cyst•Choroid plexus cyst•Pineal cyst

•Hydatid•NCC•Abscesses

•Dandy-Walker malformation

•Pilocytic astrocytoma•Craniopharyngioma•Ganglioglioma•Hemangioblastoma

Non-neoplastic Non-infectious Cysts

Cysts occurring as normal anatomic variants

Enlarged perivascular (Virchow-Robin) spaces

Congenital inclusion cystsDermoid cystEpidermoid cystArachnoid cyst

Non-neoplastic Non-infectious Cysts

Cysts derived from embryonic endo- or ectoderm•Colloid cyst•Neuroectodermal (neurenteric) cyst

Miscellaneous cysts•Neuroglial cyst•Ependymal cyst•Porencephalic cyst•Choroid plexus cyst (xanthogranuloma)•Pineal cysts

ARACHNOID CYST

Intra-arachnoid CSF-filled sac that does not communicate with ventricular system

Location50-60% middle cranial fossa 10% cerebellopontine angle 10% suprasellar arachnoid cyst

ARACHNOID CYST

CT Findings

NECT Usually CSF densityHyperdense, if intracyst hemorrhage present

(rare) May expand, thin/remodel bone

CECT: Doesn't enhance

CTA: Posterior displacement of MCA in MCF ACs

CT: Cisternography may demonstrate communication with subarachnoid space

MR Findings

TlWI: Sharply-marginated extra-axial fluid collection isointense with CSF

T2WI: Isointense with CSFFLAIR: Suppresses completely

T2* GRE: No blooming unless hemorrhage present(rare)

DWI: No restriction

T1 C+: Doesn't enhance

MRA: Cortical vessels displaced away from calvarium

Phase-contrast cine MR - flow quantification can help distinguish AC from enlarged subarachnoid space

Ultrasonographic Findings• Real Time: Useful for demonstrating

sonolucent Acs in infants < 1 Y

Angiographic FindingsMCA displaced posteriorly in MCF Acs

Nuclear Medicine FindingsSPECT - May show hypoperfusion in brain

adjacent to cyst

Imaging RecommendationsBest imaging tool: MR without, with contrastProtocol advice: Add FLAIR, DWI

TYPICAL ARACHNOI

D CYST

DIFFERENTIAl. DIAGNOSIS

Epidermoid cyst Scalloped margins Insinuating growth pattern -

Creeps along, into CSF cisterns

Surrounds, engulfs vessels and nerves

Doesn't suppress on FLAIR Shows restricted diffusion

(bright) on DWI

Chronic subdural hematoma Signal not identical to CSF Often bilateral, lentiform-

shaped May show enhancing

membrane

Porencephalic cyst•Surrounded by gliotic brain, not compressed cortex•History of trauma, stroke common

Neurenteric cyst•Rare; spine, posterior fossa = most common locations•Often proteinaceous fluid

Neuroglial (glioependyma) cyst•Rare•Usually intra-axial

Staging, Grading or Classification Criteria Galassi classification:

Type I: Small, spindle shaped, limited to anterior MCF

Type II: Superior extent along sylvian fissure; temp lobe displaced

Type III: Huge, fills entire MCF; frontal/temp/parietal displacement

Treatment• Often none• Resection (may be endoscopic)• Fenestration• Shunt (cystoperitoneal is common option)

COLLOID CYST

EtiologyFrom embryonic endoderm, not neuroectoderm!Similar to other foregut-derived cysts

(neurenteric, Rathke)Contents accumulate from mucinous secretions

desquamated epithelial cells

Epidemiology 0.5-1.0% primary brain tumors 15-20% intraventricular massesAssociated abnormalities: Variable hydrocephalus

COLLOID CYST

Presentation

Headache (50-60%)Less common = nausea, vomiting, memory

loss,altered personality, gait disturbance, visual changes

Acute foramen of Monro obstruction may lead torapid onset hydrocephalus, herniation, death

40-50% asymptomatic, discovered incidentally

Best diagnostic clue: Hyperdense foramen of Monro mass on NECT

Location> 99% wedged into foramen of Monro Attached to anterosuperior 3rd ventricular roofPillars of fornix straddle, drape around cyst Posterior part of frontal horns splayed laterally around cyst < 1% other sites - Lateral, 4th ventricles, Parenchyma

(cerebellum), Extra-axial (prepontine, meninges)

SizeVariable (few mm up to 3 cm)Mean size == 15 mm

Imaging findings -

CT Findings

NECTDensity correlates inversely with hydration state2/3 hyperdense1/3 iso/hypodense+/- HydrocephalusRare

Hypodense Change in density/size Hemorrhage (cyst "apoplexy") Calcification

CECTUsually doesn't enhanceRare == rim enhancement

MR Findings

TlWI Signal correlates with cholesterol concentration2/3 hyperintense on Tl WI1/3 isointense (small CCs may be difficult to see!)May have associated ventriculomegaly

T2WISignal more variableGenerally reflects water contentMajority isointense to brain on T2WI (small cysts

may be difficult to see!)

FLAIR: Does not suppress

DWI: Does not restrict

Tl C+Usually no enhancementRare: May show peripheral (rim)

enhancement

Differential diagnosis -

NeurocysticercosisMultiple lesions within parenchyma and cisternsAssociated ependymitis or basilar meningitis commonCa++ commonLook for scolex

CSF flow artifact (MR "pseudocyst")Multiplanar technique confirms artifact

SubependymomaFrontal horn of lateral ventricleAttached to septum pellucidumPatchy/solid enhancement

Natural History & Prognosis

90% stable or stop enlargingOlder ageSmall cystNo hydrocephalusHyperdense on NECT, hypointense on T2

weightedMR

10% enlargeYounger patients Larger cyst, hydrocephalusIso/hypodense on NECT, often hyperintense on

T2WIMay enlarge rapidly, cause coma/death!

Dermoid Cyst

Etiology

Embryology (two theories)Sequestration of surface ectoderm at lines of epithelial

fusion/along the course of normal embryonic invaginations Inclusion of cutaneous ectoderm at time of neural tube

closure; 3rd-5th week of embryogenesis

Three classifications of dermoid inclusions, based on pathogenesis -

1. Congenital cystic teratoma (true neoplasm derived from all three embryonic germ layers)

2. Congenital dermoid inclusion cyst (nonneoplastic epithelial-lined inclusion cyst)

3. Acquired implantation cyst (trauma, surgery, LP)

General Features

Best diagnostic clue: Fat appearance + droplets in cisterns, sulci, ventricles if ruptured

Location Most often in sellar/parasellar/frontonasal region Posterior fossa - midline vermis & 4th ventricle Intraventricular within tela choroidea in lateral, 3rd, or 4th

ventricles Extracranial sites = spine, orbit Ruptured: Subarachnoid/intraventricular spread of contents

Size: Variable

Morphology: Well-circumscribed lipid containing mass

Imaging findings -

CT Findings

NECTRound/lobulated, well-delineated, cystic massFat hypodensity20% capsular Ca++With rupture, droplets of fat disseminate in

cisterns, may cause fat-fluid level within ventriclesSkull/scalp dermoid expands diploeFrontonasal: Bifid crista galli, large foramen

cecum + sinus tractRare "dense" dermoid: Hyperattenuating on CT

CECT: Generally no enhancement

MR Findings

TlWI Unruptured: Hyperintense on Tl WI Ruptured: Droplets very hyperintense on Tl WI

o Fat suppression sequence confirms o Fat-fluid level in cyst, ventricles common

Rare "dense" dermoid: Very hyperintense on Tl WI

T2WI Unruptured: Heterogeneous, from hypo- to hyperintense on T2WI Chemical shift artifact in frequency encoding direction with long TR Ruptured: Typically hyperintense droplets on T2WI Rare "dense" dermoid: Very hypointense on T2 With hair: Fine curvilinear hypointense elements

Tl C+: With rupture: Extensive MR enhancement possible from chemical meningitis

MRS: Very strong and broad resonances from mobile lipids at 0.9 and 1.3 ppm

Angiographic FindingsNormal or avascular mass effectIf ruptured, can see vasospasm Dermoid-encased vessels may have increased

rupture risk

Imaging RecommendationsBest imaging tool: MRI, especially in setting of

ruptureProtocol advice

Use fat-suppression sequence to confirm diagnosis

Chemical shift-selective sequence useful to detect tiny droplets


Epidermoid cyst Most epidermoid cysts resemble CSF, not fat No dermal appendages 4-9x more common than dermoid Off-midline> midline: 40-50% in CPA, 10-15% para sellar/middle fossa,

10% diploic MRI: Isointense to CSF except restricts on diffusion

Teratoma Location similar, but usually pineal region Mixture of two or more embryologic layers; ectoderm, mesoderm,

endoderm Often multicystic/multiloculated Heterogeneous appearance containing calcification, CSF, lipid, and soft tissue components

Lipoma • Homogeneous fat> heterogeneous lipid

Treatment

Complete microsurgical excision Residual capsule may lead to recurrence Rare SCCa degeneration within surgical remnants

Subarachnoid dissemination of contents may occur during operative/postoperative course Cause aseptic meningitis or other complications

(hydrocephalus, seizures, CN deficits) Alternatively, disseminated fat particles can remain silent without radiological/neurological change

Justifies wait-and-see approach

Regular MRI and clinical exams are necessary to avoid complication

Epidermoid Cyst

EtiologyCongenital: Arise from ectodermal inclusions

during neural tube closureAcquired: Develop as a result of trauma

Uncommon etiology for intracranial tumors More common as spine etiology following LP

Epidemiology4-9x more common than dermoidThird most common CPA/lAC mass, after vestibular

schwannoma & meningiomaAssociated abnormalities: May have

occipital/nasofrontal dermal sinus tract

Epidermoid Cyst

General Features •Best diagnostic clue: CSF-like mass insinuates cisterns, encases

nerves/vessels

Location 90% intradural, primarily in basal cisterns

Cerebellopontine angle (CPA) = 40-50% Fourth ventricle = 17% Para sellar/middle cranial fossa = 10-15% Rarely in cerebral hemispheres = 1.5% Brain stem location exceedingly rare Intraventricular within tela choroidea of temporal horn, 3rd, or 4th

ventricles 10% extradural: Skull (intradiploic within frontal, parietal, occipital,

sphenoid skull) as well as spine

Size: Variable

Morphology: Lobulated, irregular, "cauliflower-like“ mass with "fronds"

Imaging findings

CT Findings

NECTRound/lobulated mass> 95% hypodense, resembling CSF10-25% Ca++ Intradiplioc epidermoid: Bony erosion with

sharply corticated marginsRare variant = "dense" epidermoid

Secondary to hemorrhage, high protein, saponification of cyst debris to calcium soaps or iron-containing pigment

CECT: Usually none, although margin of cyst may show minimal enhancement

MR Findings

TlWI Uncommonly hyperintense to brain ("white epidermoid") due to high

triglycerides & unsaturated fatty acids Uncommonly hypointense to CSF ("black epidermoid")

Presence of solid crystal cholesterol & keratin Lack of triglycerides & unsaturated fatty acid

T2WI Often isointense (65%) to slightly hyperintense (35%) to CSF on T2WI

FLAIR: Usually doesn't completely null

DWI: Restricted diffusion

Tl C+ margin of cyst may show minimal enhancement (35%) With malignant degeneration changes into enhancing tumour

MRS: Resonances from lactate

Imaging RecommendationsBest imaging tool: MRIProtocol advice

FLAIR will often distinguish where as conventional sequences may not

Diffusion definitively distinguishes from arachnoid cyst

Differential Diagnosis – Arachnoid cyst Completely nulls on FLAIRNo restricted diffusionRather than insinuate and engulf local structures, ACs

displace them Smooth surface, unlike lobulations of epidermoids

Cystic neoplasmAttenuation/signal intensity not that of CSFOften enhances

Dermoid cystUsually at or near midlineResembles fat, not CSFcontains dermal appendages

Neuroglial Cyst

Etiology

IntraparenchymalLining of embryonic neural tube becomes

sequestered within developing WMEvagination of neuroectoderm along choroidal

fissureMay contain ependymal or choroid cells as cyst

lining

Subarachnoid spaceLeptomeningeal neuroglial heterotopia postulated

Epidemiology: Uncommon « 1% of intracranial cysts

General Features

Best diagnostic clue: Nonenhancing CSF-like parenchymal cyst with minimal/no surrounding signal abnormality

LocationMay occur anywhere throughout neuraxisFrontal lobe most common site Intraparenchymal > extraparenchymal

Size: Varies from a few mm up to several cm

Morphology: Smooth, rounded, unilocular benign-appearing cyst

Imaging findings -

CT Findings

NECTWell-delineated low density

cyst UnilocularNo Ca++

CECT: Wall does not enhance

MR Findings

Tl WI: Usually hypo intense, resembles CSFT2WI: HyperintenseFLAIR: Usually suppressesDWI: Typically no diffusion restrictionTl C+: No enhancement

Imaging Recommendations• Best imaging tool: MR without, with contrast• Protocol advice: Include FLAIR, DWI

Differential diagnosis –

Porencephalic cyst Communicates with ventricles Usually adjacent brain shows gliosis, spongiosis

Enlarged perivascular spaces (PVSs) Clusters of variable-sized cysts> single, unilocular cyst Usually midbrain, around anterior commissure

Arachnoid cyst • Extra-axial • Does not have epithelial lining

Infectious cyst Cysts usually in subarachnoid space, ventricles Ca++, enhancement common Cysts usually < 1 cm

Enlarged Perivascular Spaces

Definition:Pial-lined interstitial fluid (ISF)-filled structures that

accompany penetrating arteries but do not communicate directly with subarachnoid space

PresentationUsually normal, discovered incidentally at imaging/autopsy

DemographicsPVSs occur in all locations, at all ages and are easily seen

in most patients on 3T imagingPresent in 25-30% of children (benign normal variant)Enlarged PVSs - Mean age = mid 40sGender: Giant PVSs: M:F = 1.8: 1

Enlarged Perivascular Spaces

General Features

Best diagnostic clue: Fluid-filled spaces that look like CSF, surround/accompany penetrating arteries

Location Most common site for normal PVSs = basal ganglia(cluster

around anterior commissure) Other common locations

Midbrain Deep white matter Subinsular cortex, extreme capsule

Most common location for expanded ("giant" or "tumefactive") PVSs = midbrain Can be found almost anywhere BUT almost never involve cortex (PVSs expand within subcortical

white matter)

Imaging findings -

CT Findings

NECTClusters of

round/ovoid/linear/punctate cyst-like lesions

Low density (attenuation = CSF)No Ca++

CECT: Don't enhance

MR Findings

TlWI Multiple well-delineated cysts isointense with CSF Midbrain enlarged PVSs may compress aqueduct/3rd ventricle, cause

hydrocephalus

T2WI Appear isointense with CSF No edema in adjacent brain

FLAIR Suppress completely 25% have minimal increased signal in brain surrounding enlarged

PVSs

T2* GRE: No bloomingDWI: No restricted diffusionTl C+ No enhancement +/- Visualization of penetrating arteries with contrast


Lacunar infarcts• Older patients• Common in basal ganglia,

white matter• Adjacent parenchymal

hyperintensity

Infectious/inflammatory cystsNeurocysticercosisscolexmost are < 1 cmdon't typically occur in clustercyst walls often enhancessurrounding edema often

present

Other parasitesHydatid cysts often unilocular, almost all in childrenMultilocular parasitic cysts typically enhance, mimic neoplasm more than PVS

Natural History & Prognosis Usually remain stable in sizeOccasionally continue to expand

Treatment"Leave me alone" lesion that should not

be mistaken for serious diseaseShunt ventricles if midbrain lesions

cause obstructive hydrocephalus

Pineal Cyst

Etiology-pathogenesis: 3 major theoriesEnlargement of embryonic pineal cavityIschemic glial degeneration +/-

hemorrhagic expansionSmall pre-existing cysts enlarge with

hormonal influences

Epidemiology1-4% prevalence at imaging20-40% microscopic cysts within pineal

gland found at autopsy

Pineal Cyst

General FeaturesBest diagnostic clue: Homogeneous fluid-filled mass above,

clearly distinct from tectum

Location: Above tectum, below internal cerebral veins(ICVs)

Size: Most are small « 1 cm, but may be up to 2 cm or more

MorphologyRound/ovoid, relatively thin-walled cystMay flatten tectum, occasionally compressaqueductvariable hydrocephalus (enlarged 3rd, lateral ventricles;

normal 4th V) with large cysts

Imaging findings

CT Findings

NECTSharply-demarcated, smooth cyst behind 3rdVentricleFluid iso-/slightly hyperdense to CSF25% Ca++ in cyst wallRare: Very hyperdense cyst with acute

hemorrhage("pineal apoplexy")

CECT: Rim or nodular enhancement

MR Findings

TlWI 55-60% slightly hyperintense to CSF on Tl WI 1-2%: Hemorrhage (heterogenous signal intensity)

T2WI: Iso / hyperintense to CSF

FLAIR: Doesn't suppress (moderately hyperintense)

T2* GRE Uncommon: Blooming caused by old or recent hemorrhage

Tl C+ 60% enhance Partial/complete rim, nodular Cystic areas may fill in on delayed scans, resemble solid tumor

MRV: Internal cerebral veins (ICVs) may be elevated by large lesions

Imaging RecommendationsBest imaging tool: MR without, with contrastProtocol advice: Use thin sections (3 mm or

less) for detecting, defining lesions in this anatomically complex region

DIFFERENTIAL DIAGNOSIS

Normal pineal gland (can be cystic)Three anatomic appearances on contrast-enhanced

imaging Nodule (52%) Crescent (26%) Ring-like (22%)

PineocytomaUsually solid components present; purely cystic tumors

occur but are less commonCystic pineocytomas occur, may be indistinguishable on

imaging studies, require histology for definitive diagnosisBoth pineal cyst, indolent pineocytoma may not change

on serial imaging

Natural History & PrognosisSize generally remains unchanged in males Cystic expansion of pineal in some females

begins in adolescence, decreases with agingRare: Sudden expansion, hemorrhage

("pineal apoplexy")

TreatmentUsually none Atypical/symptomatic lesions may require

stereotactic aspiration or biopsy/resectionPreferred approach == infra tentorial supra

cerebellar

Choroid Plexus Cyst

CPC commonly found at autopsy or imaging in middle-aged, older adults

EtiologyLipid from desquamating, degenerating choroid epithelium

accumulates in choroid plexusLipid provokes xanthomatous response

Epidemiology Most common type of neuroepithelial cyst 1% of all pregnancies on routine US50% of fetuses with Trisomy 18Small asymptomatic CPCs found incidentally in >1/3 of all

autopsied adults

Choroid Plexus Cyst

AgeAdult CPC: Prevalence increases with age Fetal CPC: Prevalence decreases with age

Associated abnormalitiesFetal CPC

Trisomy 18 (mildly increased risk < 2x baseline risk)

Trisomy 21 (only if other markers present)Adult CPC: May cause obstructive

hydrocephalus (rare)

General Features

Best diagnostic clue Older patient with "bright" choroid plexi on MRI Fetus or newborn with large (> 2 mm) choroid plexus cyst(s) on US

Location Atria of lateral ventricles most common site

Attached to or within choroid plexus Usually bilateral

Size Usually small (2-8 mm) Often multiple Rare: Large cysts (> 2 cm)

Morphology: Cystic or nodular/partially cystic mass(es) in choroid plexus glomi

Imaging findings -

CT Findings

NECT Iso- or slightly hyperdense compared to CSF Irregular, peripheral Ca++ in majority of adult cases

CECT: Varies from none to rim or solid enhancement

MR FindingsT1 WI: Iso/slightly hyperintense compared to CSFT2WI: Hyperintense compared to CSFFLAIR: 2/3rd iso-, 1/3rd hypointense on FLAIRT2* GRE: Blooms with intracystic hemorrhage (rare)DWI: 65% show restricted diffusion (high signal)Tl C+

Enhancement varies from none to strong variable pattern (solid, ring, nodular) Delayed scans may show filling in of contrast within cysts

Ultrasonographic Findings

Prenatal USCyst> 2 mm surrounded by echogenic

choroidIn absence of other abnormalities, low

risk for chromosomal abnormalities

Imaging Recommendations

Best imaging toolAdults: MR without, with contrastFetus, newborn

Antenatal: Maternal US or MR Postnatal: US of infant with anterior, posterior,

mastoid fontanelles as acoustic windows

Protocol adviceMR without/with contrast, FLAIRU/S transverse view of lateral ventricle at

atrial level


Ultrasound "pseudolesion" Tiny anechoic areas in fetal choroid are normal, not CPC Normal fluid-filled atria can be confused with CPC on

transverse view "Split" or "truncated" choroid can mimic CPC

Ependymal cyst Doesn't enhance Usually unilateral Attenuation, signal more like CSF

Neoplasm Choroid plexus papilloma (children < 10 y; strong relatively

uniform enhancement; cystic variant reported but rare) Metastasis (rarely cystic) Cystic astrocytoma (rare in older patients)

Sturge-Weber syndromeEnlarged "angiomatous" choroid plexus

ipsilateral tomalformation

Infectious/inflammatory cystsNeurocysticercosis

Multiple cysts common (parenchyma, subarachnoid space, ventricles)

Not associated with choroid plexus May be migratory Look for scolex, other signs of NCC (e.g.,

parenchymal Ca++)

Villous hyperplasia of choroid plexusVery rareOften overproduces CSFCauses hydrocephalus

Choroid plexus infarctUsually seen in choroid artery infarctMay cause increased intraventricular signal

on DW


Fetal CPCs Transient finding; typically resolve in 3rd trimester regardless

of whether isolated or with associated anomalies CPC + minor markers = 20% risk for chromosome abnormality CPC + major markers = 50% risk for chromosome abnormality

Adult CPCs Usually remain asymptomatic, nonprogressive

TreatmentAdult CPC: Usually none Rare: Shunt for obstructive hydrocephalus

Fetal CPC In absence of other markers, none With other markers, amniocentesis warranted

Ependymal Cyst

Etiology: Thought to arise from sequestration of developing neuroectoderm

Demographics - Age: Typically young adults, less than 40

yearsGender: Male predominance

Ependymal Cyst

General FeaturesBest diagnostic clue: Non-enhancing thin-walled

cyst with CSF density/intensity

Location Intraventricular common, typically lateral ventricle Intraparenchymal, central white matter of

temporo-parietal and frontal lobesSubarachnoid space, less common

Size: Variable, typically small, 2-3 mm up to 8-9 cm

Morphology: Smooth, thin-walled cyst

Imaging findings -

CT FindingsNECT: Cyst is isodense to CSF; Ca++

extremely rareCECT: No enhancement

MR FindingsTl WI: Isointense to CSF, cyst wall may be

seenT2WI: Isointense to hyperintense to CSF

(protein content)FLAIR: Isointense to CSFDWI: No diffusion restrictionTl C+: No enhancement


Choroid plexus cyst• May be indistinguishable• Typically bilateral and arise in choroid plexus

glomus• Commonly DWI positive, enhance

Arachnoid cyst• May be indistinguishable; CSF intensity

Porencephalic cyst• Focal encephalomalacia, +/- surrounding gliosis• Typically communicates with the ventricle

Natural History & PrognosisUncommon so natural history is unknownInterval follow-up typically shows no clinical

or imaging changes in asymptomatic lesionsRecurrence after surgical intervention

uncommon

TreatmentIf symptomatic, surgical excision or

decompressionRapid resolution of symptoms after surgeryConservative management if asymptomatic

Porencephalic Cyst

Definition - CSF-filled cavity with smooth walls, lined by whitematter of cerebral hemisphere

Etiology Congenital: In utero destructive process caused by cerebral

vascular events or infectious injury (CMV)Acquired: Injury later in life, following head trauma, vascular

occlusion, or infection

Associated abnormalities Amygdala-hippocampal atrophy often coexists with

congenital porencephaly (95% in some reports) This atrophy may be bilateral despite unilateral porencephalic

cystsFamilial porencephaly may be associated with inherited

thrombophilia

Porencephalic Cyst

General FeaturesBest diagnostic clue: Cystic space in brain

parenchyma, enlarged adjacent ventricle on CT, MRI

LocationUsually corresponds to territories supplied by

cerebral arteries (ischemic injury in mid-gestation)Cortical/subcortical cavity, unilateral/bilateralUsually connected with one of the lateral ventricles

Size: Variable

Morphology: Rounded or oval

Imaging findings -

CT Findings

NECTIntraparenchymal smooth-walled cavity,

CSF-isointenseCommunication with ventricle or

separating membrane

CECT: No contrast enhancement of fluid-filled cavity

CTA: Absence of vessels at site of porencephaly

MR Findings

Tl WI: Smooth-walled cavity within brain parenchyma, isointense to CSF

T2WI: Common adjacent brain atrophy, gliosis

FLAIRAccurately depicts CSF content of cystMore accurate in differentiating neoplastic/inflammatory

from porencephalic cysts

Tl C+: Nonenhancing cyst

MRA: Absence of vessels at site of porencephaly

MRS: Absence of normal brain metabolites

USGPrenatal ultrasound for congenital porencephaly

Imaging RecommendationsBest imaging tool: MRProtocol advice: FLAIR Assess hippocampal structures in patients withporencephaly-related seizures

Treatment

Usually no treatment is required

Indications for surgery: Mass effect (hemimacrocephaly, midline displacement), ocalized/generalized symptoms

ProceduresCystoperitoneal shunt (preferred) If no communication with ventricular system:

Fenestration or partial resection of cyst wallChildren with intractable seizures and

porencephalybenefit from uncapping and cyst fenestration to lateral ventricle

Neurenteric Cyst

AKA – enterogenous cys

Etiology: Persistent neurenteric canal (connectionbetween embryonic foregut, developing neural tube)

EpidemiologyOnly 35 intracranial cases reported< 1% of all spinal masses

Associated abnormalitiesVertebral anomalies in 50% of spinal NECsAnterior segmentation defects

Neurenteric Cyst

General FeaturesBest diagnostic clue: Round/lobulated nonenhancing, slightly

hyperintense (to CSF) mass in front of medulla

Location Spine> > brainMost of intracranial NECs found in posterior fossa

Midline, anterior to brain stemOther: CPA, clivusRare: Suprasellar, quadrigeminal cisterns; anterior fossa

Size: Variable; usually < 2 cm

Morphology: Smooth, lobulated, well-demarcated

Imaging findings -

CT Findings

NECT: Hypo-/isodense mass anterior to brainstem

CECT: No enhancement

MR Findings

T1WI: Iso-/slightly hyperintense to CSFT2WI: Hyperintense to CSFFLAIR: Hyperintense to CSFT2* GRE: No bloomingTl C+: No enhancement


Epidermoid or dermoid cystCPA most common site for epidermoid"White" epidermoid (rare) is hyperintense

on Tl WI, can be difficult to distinguish if midline

Arachnoid cystLike CSF on all sequencesConsider• A midline mass in front of the brain stem that isslightly hyperdense/intense to CSF may be an NEC


Neoplastic


Infectious





•Pilocytic astrocytoma•Ganglioglioma•Hemangioblastoma•Cystic metastases

• Pilocytic astrocytoma• Pleomorphic

xanthoastrocytoma• Craniopharyngioma• Ganglioglioma• Hemangioblastoma

Tumours with cystic component

Pilocytic Astrocytoma

Etiology: Astrocytic precursor cell

Epidemiology5-10% of all gliomasMost common primary brain tumor in children

Associated abnormalities Major source of morbidity in NF l

15% of NF l patients develop PAs, most commonly in optic pathway

Up to 1/3 of patients with optic pathway PAs have NF l

Frequently causes obstructive hydrocephalus May be a greater clinical management problem than

tumor itself

Demographics

Age> 80% under 20 yPeak incidence: 5-15 years of ageOlder than children with

medulloblastoma

Gender: M = F

WHO grade I

General Features

Best diagnostic clueCystic cerebellar mass with enhancing mural

noduleEnlarged optic nerve/chiasm/tract with variable

enhancement

Location: Cerebellum (60%) > optic nerve/chiasm (25-30%) > adjacent to 3rd ventricle> brainstem

SizeLarge lesions in cerebellumOptic nerve lesions typically smaller

Imaging findings -

CT Findings

NECTDiscrete cystic/solid massMay have little or no surrounding edemaSolid component hypo- to isodenseCa++ 20%, hemorrhage rareOften cause obstructive hydrocephalus

CECT50% non enhancing cyst, strongly enhancing

mural noduleCyst may accumulate contrast on delayed images

MR Findings

TlWI Solid portions iso/hypointense to GM Cyst contents iso- to slightly hyperintense to CSF

T2WI Solid portions hyperintense to GM Cyst contents hyperintense to CSF

FLAIR Solid portions hyperintense to GM Cyst contents do not suppress: Hyperintense to CSF

T1 C+Intense but heterogeneous enhancement of solid portionCyst wall occasionally enhances

MRSAggressive-appearing metabolite pattern - High choline, low NAA, high

lactateParadoxical finding: MRS does not accurately reflect historical behavior of

tumor


Best imaging tool: Contrast-enhanced MR

Protocol adviceMultiplanar or 3D volume post contrast

imaging key to showing point of origin and degree of extension

MRS pattern is contradictory to clinical behavior

Small residual tumor on post-operative studies may not negatively impact prognosis


GangliogliomaDiscrete, solid/cystic, cortically-based

enhancing massCa++ common

HemangioblastomaLarge cyst with small enhancing mural noduleAdult tumor!Associated with von Hippel Lindau disease


Tumor may spread through subarachnoid space in rare cases (but is still WHO grade I)

Median survival rates at 20 y > 70%

Treatment

Cerebellar or hemispheric: Resection Adjuvant chemotherapy or radiation only if residual

progressive unresectable tumor

Opticochiasmatic/hypothalamic: Often none Stable or slowly progressive tumors watched Debulking or palliative surgery considered after vision loss Radiation or chemotherapy for rapidly progressive disease

Pleomorphic Xanthoastrocytoma

Epidemiology< 1% of all astrocytomas Rare but important cause of temporal lobe epilepsy

WHO grade II

AgeTumor of children/young adultsTypically first three decades 2/3 < 18 years

Gender: No gender predominance

Pleomorphic Xanthoastrocytoma

General Features

Best diagnostic clue Supratentorial cortical mass with adjacent enhancing dural "tail" Cyst and enhancing mural nodule typical

Location Peripherally located hemispheric mass, often involves cortex and

meninges 98% supratentorial Temporal lobe most common Parietal> occipital> frontal lobes Rarely found in cerebellum, sella, spinal cord, retina

Morphology 50-60% cyst + mural nodule that abuts meninges (may be solid)

Imaging findings -

CT Findings

NECTCystic/solid mass: Hypodense with mixed

density noduleMinimal or no edema is typicalCa++, hemorrhage, frank skull erosion rare

CECT: Strong, sometimes heterogeneous enhancement of tumor nodule

MR Findings

TlWI Cystic portion isointense to CSF Associated cortical dysplasia may be seen (rare)

T2WI Hyperintense or mixed signal intensity mass Cystic portion isointense to CSF Surrounding edema rareFLAIR Hyperintense or mixed signal intensity mass Cystic portion isointense to CSF

T1 C+ Enhancement usually moderate/strong, well-delineated Enhancement of adjacent meninges, dural"tail“ common

(approximately 70%) Enhancing nodule often abuts pial surface

Rare: Deep tumor extension, distant metastases


Best imaging toolMultiplanar MR is most sensitiveCT may be helpful for calvarial changes

Protocol advice: Contrast-enhanced MR including

coronal images to better evaluate temporal lobes


Ganglioglioma Cortically based hemispheric mass, solid/cystic or solid Mural nodule typical, often not adjacent to meninges no enhancing dural "tail" Ca++ is common

Pilocytic astrocytoma Supratentorial location other than hypothalamus/chiasm

rare Enhancement but no dural "tail"

Dysembryoplastic neuroepithelial tumor (DNET) Superficial cortical tumor, well demarcated Multicystic "bubbly" ,appearance T2 hyperintense mass with rare, mild enhancement May remodel calvarium

TreatmentSurgical resection is treatment of choiceRepeat resection for recurrent tumorsRadiation therapy and chemotherapy show no

significant improvement in outcome

REMEMBER !!!Cortical mass & meningeal thickening in a youngadult with long seizure history? Think PXA!Meningioma-like lesion in young patient should

raise suspicion of PXAGanglioglioma may mimic PXA clinically and by

imaging

Ganglioglioma

Well differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells

WHO grade I or II

Most common neoplasm causing chronic temporal lobe epilepsy

AgeTumor of children, young adults80% of patients < 30 yearsGender: Slight male predominance

Ganglioglioma

General Features

Best diagnostic clue: Partially cystic, enhancing, cortically-based mass in child/young adult with TLE

Location Can occur anywhere but most commonly superficial hemispheres, temporal

lobe Parietal and frontal lobes next most common

Size Variable, typically 2-3 cm in adults Larger in children, typically> 4 cm

Morphology - Three patterns Most common: Circumscribed cyst + mural nodule Solid tumor (often thickens, expands gyri) Calcification is common In younger patients « 10 years), gangliogliomas are larger and more cystic

Imaging findings -

CT Findings

NECTVariable density40% hypodense30% mixed hypodense (cyst), isodense (nodule)Ca++ common, 35-50% Superficial lesions may expand cortex, remodel

bone

CECTApproximately 50% enhanceVaries from moderate, uniform to heterogeneousCan be solid, rim or nodular

MR Findings

TIWI Mass is hypointense to isointense to gray matter Ca++ may be variable intensity May see associated cortical dysplasia

T2WI Hyperintense mass typical May be heterogeneous

T2* GRE: May show Ca++ as areas of "blooming"

Tl C+ Variable enhancement, usually moderate but heterogeneous May be minimal, ring-like, homogeneous Meningeal enhancement rarely seen

MRS: Elevated Cho has been described

PETTypically decreased activity with FDG-

PET indicating tumour hypometabolism

Imaging RecommendationsBest imaging tool: Multiplanar MRProtocol advice: Contrast-enhanced MR

to include coronal T2 images to better evaluate temporal lobes


Pleomorphic xanthoastrocytoma (PXA)• Supratentorial cortical mass, dural "tail" common• Often cyst and mural nodule, may be solid• Enhancing nodule abuts pial surface• Temporal lobe most common location

Dysembryoplastic neuroepithelial tumor(DNET)• Superficial cortical tumor, well demarcated• Multicystic "bubbly" appearance• T2 hyperintense mass with rare, mild enhancement• May remodel calvarium

Natural History & PrognosisExcellent prognosis if surgical resection completeWell-differentiated tumor with slow growth patternMalignant degeneration is rare, approximately 5-10%

(glial component)

TreatmentSurgical resection is treatment of choiceRadiation therapy and/or chemotherapy for aggressiveor

unresectable tumors

REMEMBER !!! In children under 10 years old, gangliogliomas are larger

and more cystic In young patient with history of temporal lobe epilepsy,

think ganglioglioma

Hemangioblastoma

Vascular tumor of unknown origin WHO grade I

Age Sporadic HGBL

Peak 40-60 y Rare in children

Familial VHL-associated HGBLs occur at younger age but are

rare < 15Y Retinal HGBL: Mean onset 25 y

Gender: Slight male predominance

Hemangioblastoma

General features –

Best diagnostic clue – adult with intra-axial posterior fossa cystic mass with enhancing mural nodule abuttin pia

Location – 90-95% posterior fossa (80% cerebellar hemispheres)

Morphology – 60% with cyst + mural nodule

Imaging findings –

CT

NECT – mural nodule is isodense to brain fluid density surrounding cyst.

CECT – Bright enhancement of the noduleThe cyst walls do not usually enhance. Calcification is not a feature.

Imaging findings -

MRI

T1hypo intense to iso intense mural nodule,

vividly enhancingfluid filled cyst

T2hyper intense mural noduleflow-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

Angiographic FindingsHighly vascular noduleProlonged blush+/- AV shunting (early draining vein)

Imaging RecommendationsBest imaging tool: Contrast-enhanced MR

(sensitivity > > CT for small HGBLs)

Protocol adviceBegin MRI screening of patients from VHL

families after age 10 Y Screen complete spine


Metastasismost common parenchymal posterior

fossa mass in middle-aged, older adults is metastasis!

Solid> cysticMultiple> single

Pilocytic astrocytomausually in children

Natural History & PrognosisUsually benign tumor with slow growth

patternSymptoms usually associated with cyst

expansion (may occur rapidly)

TreatmentEn bloc surgical resection (piecemeal

may result in catastrophic hemorrhage)Pre-operative embolization

Sometimes used if large tumor nodule present (3.5 cm)

Squamous cell ca lungAdenocarcinoma lungCarcinoma thyroid

MultipleTypically at gray-white matter

junctionDisproportionate edemaMay show peripheral enhancement

Cystic Metastases


Neoplastic


Infectious






• Hydatid• NCC• Abscesses

Infectious Cysts -

Neurocysticercosis

Vesicular stage: Larva is a small, marginal nodule projecting into small cyst

with clear fluid little or no inflammation May remain in this stage for years or degenerate

Colloidal vesicular stage: Larva begins to degenerate Scolex shows hyaline degeneration, slowly shrinks Cyst fluid becomes turbid and capsule thickens Surrounding edema and inflammation

Granular nodular stage: Cyst wall thickens and scolex is mineralized granule Surrounding edema regresses

Nodular calcified stage: Lesion is completely mineralized and small; no edema

Neurocysticercosis

Best diagnostic clue: Cyst with "dot" inside

LocationMay involve cisterns> parenchyma> ventriclesParenchymal cysts often hemispheric, at gray-

white junctionIntraventricular cysts are often isolated

Fourth ventricle is most commonRare CNS locations: Sella, orbit, spinal cord

SizeCysts variable, typically 1 cm, range from 5-20 mm scolex 1-4 mm

Imaging findings -

Morphology

Rounded or ovoid cyst, solitary in 20-50%Disseminated form ("miliary" NCC) rareImaging varies with development stage,

host response Lesions may be at different stages in same

patient Inflammatory response around cyst may seal

sulcus, make lesions appear intra-axial

CT Findings

NECT Vesicular stage (viable larva): Smooth, thin-walled cyst, isodense to

CSF, no edema Hyperdense "dot" within cyst = proto scolex

Colloidal vesicular stage (degenerating larva): Hyperdense cyst fluid with surrounding edema

Granular nodular (healing) stage: Mild edema Nodular calcified (healed) stage: Small, Ca++ nodule

CECT Vesicular stage: No (or mild) wall enhancement Colloidal vesicular stage: Thick ring-enhancing fibrous capsule Granular nodular stage: Involuting enhancing nodule Nodular calcified stage: Shrunken, calcified nodule Subarachnoid lesions: Multiple isodense cysts without scolex, may

cause meningitis Intraventricular cysts not well seen on CT, may see hydrocephalus

MR Findings

TlWI Vesicular stage: Cystic lesion isointense to CSF

May see discrete, eccentric scolex (hyperintense) Colloidal vesicular stage: Cyst is mildly hyperintense to CSF Granular nodular stage: Thickened, retracted cyst wall Nodular calcified stage: Shrunken, Ca++ lesion Useful to detect intraventricular cysts

T2WI Vesicular stage: Cystic lesion isointense to CSF

May see discrete, eccentric scolex No surrounding edema

Colloidal vesicular stage: Cyst is hyperintense to CSF Surrounding edema, mild to marked

Granular nodular stage: Thickened, retracted cyst wall; edema decreases

Nodular calcified stage: Shrunken, Ca++ lesion

FLAIRVesicular stage: Cystic lesion isointense to CSF

• May see discrete, eccentric scolex (hyperintense to CSF); no edema

Colloidal vesicular stage: Cyst is hyperintense to CSFSurrounding edema, mild to marked

Useful to detect intraventricular cysts (hyperintense)

T2* GRE: Useful to demonstrate calcified scolex

DWI: Cystic lesion typically isointense to CSF ADC values usually higher than tuberculomas

TI C+ Vesicular stage: No enhancement typical

May see discrete, eccentric scolex enhancement Colloidal vesicular stage: Thick cyst wall enhances

Enhancing marginal nodule (scolex) Granular nodular stage: Thickened, retracted cyst wall; may have

nodular or ring-enhancement Nodular calcified stage: rare minimal enhancement

In children, may see "encephalitic cysticercosis" with multiple small enhancing lesions and diffuse edema

Intraventricular cysts may cause ventriculitis and/or hydrocephalus

Cisternal NCC may appear racemose (multilobulated, grape-like), typically lacks scolex)

Complications: Meningitis, hydrocephalus, vasculitis


Arachnoid cystSolitary lesion with CSF density/intensityNo enhancement

Enlarged perivascular spacesFollow CSF on all MR sequencesNo enhancement

TuberculosisTuberculomas often occur with meningitisTypically not cysticUsually lower ADC values

Natural History & PrognosisMost common cause of epilepsy in endemic areasIntraventricular NCC has increased morbidity and

mortality Increased morbidity related to acute obstructive

hydrocephalus

TreatmentOral albendazole (reduces parasitic burden, seizures)Steroids often required to decrease edema during

medical therapyCSF diversion often required - hydrocephalusEndoscopic resection of intraventricular lesions in

selected casesAntiparasitic agents contraindicated in patients with

encephalitic cysticercosis

Parietal lobe common; MCA territoryLarge uni- or multilocular cyst +/-detached germinal

membrane, daughter cysts, no edema

CT Findings

NECTUnilocular or multilocular cyst isodense to CSFno edemaCa++ rare (< 1%)

CECT – No enhancement typical

Hydatid Cysts

MR Findings

TlWICyst isointense to CSF

T2WICyst isointense to CSF with hypointense rimNo perilesional edema

Tl C+No enhancement typicalMay see fine peripheral enhancement


Neoplastic


Infectious






Dandy Walker Malformation

Best diagnostic clue Large PF + big cerebrospinal fluid (CSF) cyst + normal 4th ventricle (V) absent

Location: Posterior fossa

Classic" DWM: Small hypoplastic vermis - superiorly rotated by cyst torcular arrested in fetal position (cyst mechanically hinders caudal

migration)

Dandy Walker Variant (DWV) - mild form of DW complex Variable vermian hypoplasia no or small cyst normal sized PF/brainstem

Dandy Walker Malformation

Radiography – Enlarged calvarium, particularly posterior fossaLambdoid-torcular inversion (transverse sinus grooves

elevated above lambda) Sinuses are originally above lambda in fetus, cyst

mechanically hinders descent

CT Findings

NECTLarge posterior fossaVariable-sized cyst communicates with 4th VTorcular-lambdoid inversion (torcular above lambdoid

sutureOccipital bone may appear scalloped

Imaging findings -

MR Findings

TIWI Floor 4th V present 4th v opens dorsally to variable-sized CSF cyst Cyst wall difficult to discern Vermian remnant - rotated up +/- Remnant fused to tentorium Elevated torcular with high/steeply sloping tentorium (classic)

T2WI Associated anomalies

Cortical dysplasia, heterotopias, myelination delays (syndromic DWS)

FLAIR: Very slight differentiation between cyst, compressed basal cisterns may be present

DWI: Very slight diffusion restriction in cyst may be seenMRV: Elevated torcular Herophili (DWM)

Cystic intracranial lesions – varied etiology

MRI – preferred modality

FLAIR and DWI – important sequences

Prenatal diagnosis – congenital lesions

Diagnosis important – treatment varies

Conclusions

Diagnostic Imaging, Brain – first edition, Osborn.

www.radiopedia.org

References -

radiological imaging of intracranial cystic lesions

Health & Medicine

internal cerebral

diffusion

enhancement

restricted

superficial

temporal lobe

retracted

contrast protocol