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
Differential diagnosis -
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
Differential diagnosis –
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
Differential diagnosis -
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
Natural History & Prognosis
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
Differential diagnosis –
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
Differential diagnosis -
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
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•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
Imaging Recommendations
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
Differential diagnosis -
GangliogliomaDiscrete, solid/cystic, cortically-based
enhancing massCa++ common
HemangioblastomaLarge cyst with small enhancing mural noduleAdult tumor!Associated with von Hippel Lindau disease
Natural History & Prognosis
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
Imaging Recommendations
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
`
Differential diagnosis –
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
Differential diagnosis –
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
Differential diagnosis –
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
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
• 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
Differential diagnosis –
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
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
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 -