6. Intra-arachnoid CSF-filled sac that does not
communicate with ventricular system
Location
50-60% middle cranial fossa
10% cerebellopontine angle
10% suprasellar arachnoid cyst
7. CT Findings
NECT
Usually CSF density
Hyperdense, 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
8. MR Findings
TlWI: Sharply-marginated extra-axial fluid collection
isointense with CSF
T2WI: Isointense with CSF
FLAIR: 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
9. Ultrasonographic Findings
• Real Time: Useful for demonstrating sonolucent Acs
in infants < 1 Y
Angiographic Findings
MCA displaced posteriorly in MCF Acs
Nuclear Medicine Findings
SPECT - May show hypoperfusion in brain adjacent to
cyst
Imaging Recommendations
Best imaging tool: MR without, with contrast
Protocol advice: Add FLAIR, DWI
13. 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
14. 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)
16. Etiology
From 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 masses
Associated abnormalities: Variable hydrocephalus
17. 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
18. Best diagnostic clue: Hyperdense foramen of Monro mass
on NECT
Location
> 99% wedged into foramen of Monro
Attached to anterosuperior 3rd ventricular roof
Pillars 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)
Size
Variable (few mm up to 3 cm)
Mean size == 15 mm
19. CT Findings
NECT
Density correlates inversely with hydration state
2/3 hyperdense
1/3 iso/hypodense
+/- Hydrocephalus
Rare
Hypodense
Change in density/size
Hemorrhage (cyst "apoplexy")
Calcification
CECT
Usually doesn't enhance
Rare == rim enhancement
20. MR Findings
TlWI
Signal correlates with cholesterol concentration
2/3 hyperintense on Tl WI
1/3 isointense (small CCs may be difficult to see!)
May have associated ventriculomegaly
T2WI
Signal more variable
Generally reflects water content
Majority isointense to brain on T2WI (small cysts
may be difficult to see!)
21. FLAIR: Does not suppress
DWI: Does not restrict
Tl C+
Usually no enhancement
Rare: May show peripheral (rim)
enhancement
25. Differential diagnosis -
Neurocysticercosis
Multiple lesions within parenchyma and cisterns
Associated ependymitis or basilar meningitis common
Ca++ common
Look for scolex
CSF flow artifact (MR "pseudocyst")
Multiplanar technique confirms artifact
Subependymoma
Frontal horn of lateral ventricle
Attached to septum pellucidum
Patchy/solid enhancement
26. Natural History & Prognosis
90% stable or stop enlarging
Older age
Small cyst
No hydrocephalus
Hyperdense on NECT, hypointense on T2 weightedMR
10% enlarge
Younger patients
Larger cyst, hydrocephalus
Iso/hypodense on NECT, often hyperintense on T2WI
May enlarge rapidly, cause coma/death!
28. 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)
29. 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
30. CT Findings
NECT
Round/lobulated, well-delineated, cystic mass
Fat hypodensity
20% capsular Ca++
With rupture, droplets of fat disseminate in cisterns, may
cause fat-fluid level within ventricles
Skull/scalp dermoid expands diploe
Frontonasal: Bifid crista galli, large foramen cecum +
sinus tract
Rare "dense" dermoid: Hyperattenuating on CT
CECT: Generally no enhancement
31. 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
32. Angiographic Findings
Normal or avascular mass effect
If ruptured, can see vasospasm
Dermoid-encased vessels may have increased
rupture risk
Imaging Recommendations
Best imaging tool: MRI, especially in setting of
rupture
Protocol advice
Use fat-suppression sequence to confirm diagnosis
Chemical shift-selective sequence useful to detect
tiny droplets
35. 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
36. 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
38. Etiology
Congenital: Arise from ectodermal inclusions during
neural tube closure
Acquired: Develop as a result of trauma
Uncommon etiology for intracranial tumors
More common as spine etiology following LP
Epidemiology
4-9x more common than dermoid
Third most common CPA/lAC mass, after vestibular
schwannoma & meningioma
Associated abnormalities: May have
occipital/nasofrontal dermal sinus tract
39. 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"
40. CT Findings
NECT
Round/lobulated mass
> 95% hypodense, resembling CSF
10-25% Ca++
Intradiplioc epidermoid: Bony erosion with sharply
corticated margins
Rare 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
41. 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
42. Imaging Recommendations
Best imaging tool: MRI
Protocol advice
FLAIR will often distinguish where as conventional
sequences may not
Diffusion definitively distinguishes from
arachnoid cyst
45. Differential Diagnosis –
Arachnoid cyst
Completely nulls on FLAIR
No restricted diffusion
Rather than insinuate and engulf local structures, ACs
displace them
Smooth surface, unlike lobulations of epidermoids
Cystic neoplasm
Attenuation/signal intensity not that of CSF
Often enhances
Dermoid cyst
Usually at or near midline
Resembles fat, not CSF
contains dermal appendages
47. Etiology
Intraparenchymal
Lining of embryonic neural tube becomes sequestered
within developing WM
Evagination of neuroectoderm along choroidal fissure
May contain ependymal or choroid cells as cyst lining
Subarachnoid space
Leptomeningeal neuroglial heterotopia postulated
Epidemiology: Uncommon « 1% of intracranial cysts
48. General Features
Best diagnostic clue: Nonenhancing CSF-like parenchymal
cyst with minimal/no surrounding signal abnormality
Location
May occur anywhere throughout neuraxis
Frontal lobe most common site
Intraparenchymal > extraparenchymal
Size: Varies from a few mm up to several cm
Morphology: Smooth, rounded, unilocular benign-appearing
cyst
50. MR Findings
Tl WI: Usually hypo intense, resembles CSF
T2WI: Hyperintense
FLAIR: Usually suppresses
DWI: Typically no diffusion restriction
Tl C+: No enhancement
Imaging Recommendations
• Best imaging tool: MR without, with contrast
• Protocol advice: Include FLAIR, DWI
52. 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
54. Definition:
Pial-lined interstitial fluid (ISF)-filled structures that accompany
penetrating arteries but do not communicate directly with
subarachnoid space
Presentation
Usually normal, discovered incidentally at imaging/autopsy
Demographics
PVSs occur in all locations, at all ages and are easily seen in most
patients on 3T imaging
Present in 25-30% of children (benign normal variant)
Enlarged PVSs - Mean age = mid 40s
Gender: Giant PVSs: M:F = 1.8: 1
55. 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)
56. CT Findings
NECT
Clusters of round/ovoid/linear/punctate cyst-
like lesions
Low density (attenuation = CSF)
No Ca++
CECT: Don't enhance
57. 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 blooming
DWI: No restricted diffusion
Tl C+
No enhancement
+/- Visualization of penetrating arteries with contrast
61. Differential diagnosis –
Lacunar infarcts
• Older patients
• Common in basal ganglia,
white matter
• Adjacent parenchymal
hyperintensity
Infectious/inflammatory cysts
Neurocysticercosis
scolex
most are < 1 cm
don't typically occur in cluster
cyst walls often enhances
surrounding edema often
present
Other parasites
Hydatid cysts often
unilocular, almost all in
children
Multilocular parasitic cysts
typically enhance, mimic
neoplasm more than PVS
62. Natural History & Prognosis
Usually remain stable in size
Occasionally continue to expand
Treatment
"Leave me alone" lesion that should not be
mistaken for serious disease
Shunt ventricles if midbrain lesions cause
obstructive hydrocephalus
64. Etiology-pathogenesis: 3 major theories
Enlargement of embryonic pineal cavity
Ischemic glial degeneration +/- hemorrhagic
expansion
Small pre-existing cysts enlarge with hormonal
influences
Epidemiology
1-4% prevalence at imaging
20-40% microscopic cysts within pineal gland
found at autopsy
65. General Features
Best 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
Morphology
Round/ovoid, relatively thin-walled cyst
May flatten tectum, occasionally compressaqueduct
variable hydrocephalus (enlarged 3rd, lateral ventricles;
normal 4th V) with large cysts
66. CT Findings
NECT
Sharply-demarcated, smooth cyst behind 3rd
Ventricle
Fluid iso-/slightly hyperdense to CSF
25% Ca++ in cyst wall
Rare: Very hyperdense cyst with acute hemorrhage
("pineal apoplexy")
CECT: Rim or nodular enhancement
67. 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
68. Imaging Recommendations
Best imaging tool: MR without, with contrast
Protocol advice: Use thin sections (3 mm or less) for
detecting, defining lesions in this anatomically
complex region
72. DIFFERENTIAL DIAGNOSIS
Normal pineal gland (can be cystic)
Three anatomic appearances on contrast-enhanced imaging
Nodule (52%)
Crescent (26%)
Ring-like (22%)
Pineocytoma
Usually solid components present; purely cystic tumors occur
but are less common
Cystic pineocytomas occur, may be indistinguishable on
imaging studies, require histology for definitive diagnosis
Both pineal cyst, indolent pineocytoma may not change on
serial imaging
73. Natural History & Prognosis
Size generally remains unchanged in males
Cystic expansion of pineal in some females
begins in adolescence, decreases with aging
Rare: Sudden expansion, hemorrhage ("pineal
apoplexy")
Treatment
Usually none
Atypical/symptomatic lesions may require
stereotactic aspiration or biopsy/resection
Preferred approach == infra tentorial supra
cerebellar
75. CPC commonly found at autopsy or imaging in middle-aged, older
adults
Etiology
Lipid from desquamating, degenerating choroid epithelium
accumulates in choroid plexus
Lipid provokes xanthomatous response
Epidemiology
Most common type of neuroepithelial cyst
1% of all pregnancies on routine US
50% of fetuses with Trisomy 18
Small asymptomatic CPCs found incidentally in >1/3 of all
autopsied adults
76. Age
Adult CPC: Prevalence increases with age
Fetal CPC: Prevalence decreases with age
Associated abnormalities
Fetal CPC
Trisomy 18 (mildly increased risk < 2x baseline
risk)
Trisomy 21 (only if other markers present)
Adult CPC: May cause obstructive
hydrocephalus (rare)
77. 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
78. 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 Findings
T1 WI: Iso/slightly hyperintense compared to CSF
T2WI: Hyperintense compared to CSF
FLAIR: 2/3rd iso-, 1/3rd hypointense on FLAIR
T2* 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
79. Ultrasonographic Findings
Prenatal US
Cyst> 2 mm surrounded by echogenic choroid
In absence of other abnormalities, low risk for
chromosomal abnormalities
80. Imaging Recommendations
Best imaging tool
Adults: MR without, with contrast
Fetus, newborn
Antenatal: Maternal US or MR
Postnatal: US of infant with anterior, posterior,
mastoid fontanelles as acoustic windows
Protocol advice
MR without/with contrast, FLAIR
U/S transverse view of lateral ventricle at atrial level
84. 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)
85. Sturge-Weber syndrome
Enlarged "angiomatous" choroid plexus ipsilateral
tomalformation
Infectious/inflammatory cysts
Neurocysticercosis
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++)
86. Villous hyperplasia of choroid plexus
Very rare
Often overproduces CSF
Causes hydrocephalus
Choroid plexus infarct
Usually seen in choroid artery infarct
May cause increased intraventricular signal on DW
87. 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
Treatment
Adult CPC: Usually none
Rare: Shunt for obstructive hydrocephalus
Fetal CPC
In absence of other markers, none
With other markers, amniocentesis warranted
89. Etiology: Thought to arise from sequestration of
developing neuroectoderm
Demographics -
Age: Typically young adults, less than 40 years
Gender: Male predominance
90. General Features
Best 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 lobes
Subarachnoid space, less common
Size: Variable, typically small, 2-3 mm up to 8-9 cm
Morphology: Smooth, thin-walled cyst
91. CT Findings
NECT: Cyst is isodense to CSF; Ca++ extremely
rare
CECT: No enhancement
MR Findings
Tl WI: Isointense to CSF, cyst wall may be seen
T2WI: Isointense to hyperintense to CSF (protein
content)
FLAIR: Isointense to CSF
DWI: No diffusion restriction
Tl C+: No enhancement
93. 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
94. Natural History & Prognosis
Uncommon so natural history is unknown
Interval follow-up typically shows no clinical or
imaging changes in asymptomatic lesions
Recurrence after surgical intervention uncommon
Treatment
If symptomatic, surgical excision or decompression
Rapid resolution of symptoms after surgery
Conservative management if asymptomatic
96. Definition - CSF-filled cavity with smooth walls, lined by white
matter 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
cysts
Familial porencephaly may be associated with inherited
thrombophilia
97. General Features
Best diagnostic clue: Cystic space in brain parenchyma,
enlarged adjacent ventricle on CT, MRI
Location
Usually corresponds to territories supplied by cerebral
arteries (ischemic injury in mid-gestation)
Cortical/subcortical cavity, unilateral/bilateral
Usually connected with one of the lateral ventricles
Size: Variable
Morphology: Rounded or oval
98. CT Findings
NECT
Intraparenchymal smooth-walled cavity, CSF-
isointense
Communication with ventricle or separating
membrane
CECT: No contrast enhancement of fluid-filled
cavity
CTA: Absence of vessels at site of porencephaly
99. MR Findings
Tl WI: Smooth-walled cavity within brain parenchyma,
isointense to CSF
T2WI: Common adjacent brain atrophy, gliosis
FLAIR
Accurately depicts CSF content of cyst
More 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
100. USG
Prenatal ultrasound for congenital porencephaly
Imaging Recommendations
Best imaging tool: MR
Protocol advice: FLAIR
Assess hippocampal structures in patients with
porencephaly-related seizures
103. Treatment
Usually no treatment is required
Indications for surgery: Mass effect
(hemimacrocephaly, midline displacement),
ocalized/generalized symptoms
Procedures
Cystoperitoneal shunt (preferred)
If no communication with ventricular system:
Fenestration or partial resection of cyst wall
Children with intractable seizures and
porencephalybenefit from uncapping and cyst
fenestration to lateral ventricle
105. AKA – enterogenous cys
Etiology: Persistent neurenteric canal (connection
between embryonic foregut, developing neural tube)
Epidemiology
Only 35 intracranial cases reported
< 1% of all spinal masses
Associated abnormalities
Vertebral anomalies in 50% of spinal NECs
Anterior segmentation defects
106. General Features
Best diagnostic clue: Round/lobulated nonenhancing,
slightly hyperintense (to CSF) mass in front of medulla
Location
Spine> > brain
Most of intracranial NECs found in posterior fossa
Midline, anterior to brain stem
Other: CPA, clivus
Rare: Suprasellar, quadrigeminal cisterns; anterior fossa
Size: Variable; usually < 2 cm
Morphology: Smooth, lobulated, well-demarcated
107. CT Findings
NECT: Hypo-/isodense mass anterior to brainstem
CECT: No enhancement
MR Findings
T1WI: Iso-/slightly hyperintense to CSF
T2WI: Hyperintense to CSF
FLAIR: Hyperintense to CSF
T2* GRE: No blooming
Tl C+: No enhancement
110. Differential diagnosis -
Epidermoid or dermoid cyst
CPA most common site for epidermoid
"White" epidermoid (rare) is hyperintense on Tl
WI, can be difficult to distinguish if midline
Arachnoid cyst
Like CSF on all sequences
Consider
• A midline mass in front of the brain stem that is
slightly hyperdense/intense to CSF may be an NEC
114. Etiology: Astrocytic precursor cell
Epidemiology
5-10% of all gliomas
Most 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
115. Demographics
Age
> 80% under 20 y
Peak incidence: 5-15 years of age
Older than children with medulloblastoma
Gender: M = F
WHO grade I
116. General Features
Best diagnostic clue
Cystic cerebellar mass with enhancing mural
nodule
Enlarged optic nerve/chiasm/tract with variable
enhancement
Location: Cerebellum (60%) > optic nerve/chiasm
(25-30%) > adjacent to 3rd ventricle> brainstem
Size
Large lesions in cerebellum
Optic nerve lesions typically smaller
117. CT Findings
NECT
Discrete cystic/solid mass
May have little or no surrounding edema
Solid component hypo- to isodense
Ca++ 20%, hemorrhage rare
Often cause obstructive hydrocephalus
CECT
50% non enhancing cyst, strongly enhancing mural
nodule
Cyst may accumulate contrast on delayed images
118. 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 portion
Cyst wall occasionally enhances
MRS
Aggressive-appearing metabolite pattern - High choline, low NAA, high lactate
Paradoxical finding: MRS does not accurately reflect historical behavior of tumor
119. Imaging Recommendations
Best imaging tool: Contrast-enhanced MR
Protocol advice
Multiplanar 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
122. Differential diagnosis -
Ganglioglioma
Discrete, solid/cystic, cortically-based enhancing
mass
Ca++ common
Hemangioblastoma
Large cyst with small enhancing mural nodule
Adult tumor!
Associated with von Hippel Lindau disease
123. 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
125. Epidemiology
< 1% of all astrocytomas
Rare but important cause of temporal lobe epilepsy
WHO grade II
Age
Tumor of children/young adults
Typically first three decades
2/3 < 18 years
Gender: No gender predominance
126. 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)
127. CT Findings
NECT
Cystic/solid mass: Hypodense with mixed
density nodule
Minimal or no edema is typical
Ca++, hemorrhage, frank skull erosion rare
CECT: Strong, sometimes heterogeneous
enhancement of tumor nodule
128. 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 rare
FLAIR
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
129. Imaging Recommendations
Best imaging tool
Multiplanar MR is most sensitive
CT may be helpful for calvarial changes
Protocol advice: Contrast-enhanced MR
including
coronal images to better evaluate temporal
lobes
132. 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
133. Treatment
Surgical resection is treatment of choice
Repeat resection for recurrent tumors
Radiation therapy and chemotherapy show no
significant improvement in outcome
REMEMBER !!!
Cortical mass & meningeal thickening in a young
adult with long seizure history? Think PXA!
Meningioma-like lesion in young patient should raise
suspicion of PXA
Ganglioglioma may mimic PXA clinically and by
imaging
135. 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
Age
Tumor of children, young adults
80% of patients < 30 years
Gender: Slight male predominance
136. 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
137. CT Findings
NECT
Variable density
40% hypodense
30% mixed hypodense (cyst), isodense (nodule)
Ca++ common, 35-50%
Superficial lesions may expand cortex, remodel bone
CECT
Approximately 50% enhance
Varies from moderate, uniform to heterogeneous
Can be solid, rim or nodular
138. 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
139. PET
Typically decreased activity with FDG-PET
indicating tumour hypometabolism
Imaging Recommendations
Best imaging tool: Multiplanar MR
Protocol advice: Contrast-enhanced MR to
include coronal T2 images to better evaluate
temporal lobes
142. 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
143. Natural History & Prognosis
Excellent prognosis if surgical resection complete
Well-differentiated tumor with slow growth pattern
Malignant degeneration is rare, approximately 5-10% (glial
component)
Treatment
Surgical resection is treatment of choice
Radiation 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
145. 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
146. 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
147. CT
NECT –
mural nodule is isodense to brain
fluid density surrounding cyst.
CECT –
Bright enhancement of the nodule
The cyst walls do not usually enhance.
Calcification is not a feature.
148. MRI
T1
hypo intense to iso intense mural nodule, vividly
enhancing
fluid filled cyst
T2
hyper intense mural nodule
flow-voids due to enlarged vessels may be evident
especially at the periphery of the cyst, seen in 60-
70% of cases
fluid filled cyst, similar to CSF
149. Angiographic Findings
Highly vascular nodule
Prolonged blush
+/- AV shunting (early draining vein)
Imaging Recommendations
Best imaging tool: Contrast-enhanced MR (sensitivity
> > CT for small HGBLs)
Protocol advice
Begin MRI screening of patients from VHL families
after age 10 Y
Screen complete spine
152. Differential diagnosis –
Metastasis
most common parenchymal posterior fossa mass
in middle-aged, older adults is metastasis!
Solid> cystic
Multiple> single
Pilocytic astrocytoma
usually in children
153. Natural History & Prognosis
Usually benign tumor with slow growth pattern
Symptoms usually associated with cyst expansion
(may occur rapidly)
Treatment
En bloc surgical resection (piecemeal may result
in catastrophic hemorrhage)
Pre-operative embolization
Sometimes used if large tumor nodule present (3.5
cm)
154. Squamous cell ca lung
Adenocarcinoma lung
Carcinoma thyroid
Multiple
Typically at gray-white matter junction
Disproportionate edema
May show peripheral enhancement
158. 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
159. Best diagnostic clue: Cyst with "dot" inside
Location
May involve cisterns> parenchyma> ventricles
Parenchymal cysts often hemispheric, at gray-white
junction
Intraventricular cysts are often isolated
Fourth ventricle is most common
Rare CNS locations: Sella, orbit, spinal cord
Size
Cysts variable, typically 1 cm, range from 5-20 mm
scolex 1-4 mm
160. Morphology
Rounded or ovoid cyst, solitary in 20-50%
Disseminated form ("miliary" NCC) rare
Imaging 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
161. 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
162. 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
163. FLAIR
Vesicular stage: Cystic lesion isointense to CSF
• May see discrete, eccentric scolex (hyperintense to
CSF); no edema
Colloidal vesicular stage: Cyst is hyperintense to CSF
Surrounding 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
164. 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
165. Differential diagnosis –
Arachnoid cyst
Solitary lesion with CSF density/intensity
No enhancement
Enlarged perivascular spaces
Follow CSF on all MR sequences
No enhancement
Tuberculosis
Tuberculomas often occur with meningitis
Typically not cystic
Usually lower ADC values
167. Natural History & Prognosis
Most common cause of epilepsy in endemic areas
Intraventricular NCC has increased morbidity and
mortality
Increased morbidity related to acute obstructive
hydrocephalus
Treatment
Oral albendazole (reduces parasitic burden, seizures)
Steroids often required to decrease edema during medical
therapy
CSF diversion often required - hydrocephalus
Endoscopic resection of intraventricular lesions in selected
cases
Antiparasitic agents contraindicated in patients with
encephalitic cysticercosis
168. Parietal lobe common; MCA territory
Large uni- or multilocular cyst +/-detached germinal
membrane, daughter cysts, no edema
CT Findings
NECT
Unilocular or multilocular cyst
isodense to CSF
no edema
Ca++ rare (< 1%)
CECT – No enhancement typical
169. MR Findings
TlWI
Cyst isointense to CSF
T2WI
Cyst isointense to CSF with hypointense rim
No perilesional edema
Tl C+
No enhancement typical
May see fine peripheral enhancement
173. 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
174. Radiography –
Enlarged calvarium, particularly posterior fossa
Lambdoid-torcular inversion (transverse sinus grooves
elevated above lambda)
Sinuses are originally above lambda in fetus, cyst mechanically
hinders descent
CT Findings
NECT
Large posterior fossa
Variable-sized cyst communicates with 4th V
Torcular-lambdoid inversion (torcular above lambdoid suture
Occipital bone may appear scalloped
175. 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 seen
MRV: Elevated torcular Herophili (DWM)