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Radiological imaging of intracranial cystic lesions
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Radiological imaging of intracranial cystic lesions


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basic imaging features of common intracranial cystic lesions

basic imaging features of common intracranial cystic lesions

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  • 1. Dr. Vishal Sankpal
  • 2. Non-neoplastic Non-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
  • 3. Cysts occurring as normal anatomic variants  Enlarged perivascular (Virchow-Robin) spaces Congenital inclusion cysts  Dermoid cyst  Epidermoid cyst  Arachnoid cyst 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
  • 4.  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
  • 5. 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
  • 6. 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
  • 7. 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
  • 9. 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
  • 10. 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)
  • 11. 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
  • 12. 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
  • 13.  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
  • 14. 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
  • 15. 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!)
  • 16. FLAIR: Does not suppress DWI: Does not restrict Tl C+  Usually no enhancement  Rare: May show peripheral (rim) enhancement
  • 17. 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
  • 18. 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!
  • 19. 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)
  • 20. 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
  • 21. 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
  • 22. 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
  • 23. 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
  • 24. 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
  • 25. 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
  • 26. 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
  • 27. 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"
  • 28. 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
  • 29. 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
  • 30. Imaging Recommendations  Best imaging tool: MRI  Protocol advice  FLAIR will often distinguish where as conventional sequences may not  Diffusion definitively distinguishes from arachnoid cyst
  • 31. 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
  • 32. 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
  • 33. 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
  • 34. CT Findings NECT  Well-delineated low density cyst  Unilocular  No Ca++ CECT: Wall does not enhance
  • 35. 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
  • 36. 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
  • 37. 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
  • 38. 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)
  • 39. CT Findings NECT  Clusters of round/ovoid/linear/punctate cyst- like lesions  Low density (attenuation = CSF)  No Ca++ CECT: Don't enhance
  • 40. 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
  • 41. 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
  • 42. 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
  • 43. 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
  • 44. 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
  • 45. 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
  • 46. 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
  • 47. 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
  • 48. 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
  • 49. 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
  • 50. 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
  • 51. 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)
  • 52. 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
  • 53. 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
  • 54. Ultrasonographic Findings Prenatal US  Cyst> 2 mm surrounded by echogenic choroid  In absence of other abnormalities, low risk for chromosomal abnormalities
  • 55. 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
  • 56. 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)
  • 57. 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++)
  • 58. 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
  • 59. 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
  • 60.  Etiology: Thought to arise from sequestration of developing neuroectoderm Demographics -  Age: Typically young adults, less than 40 years  Gender: Male predominance
  • 61. 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
  • 62. 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
  • 63. 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
  • 64. 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
  • 65. 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
  • 66. 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
  • 67. 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
  • 68. 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
  • 69. USG  Prenatal ultrasound for congenital porencephaly Imaging Recommendations  Best imaging tool: MR  Protocol advice: FLAIR  Assess hippocampal structures in patients with  porencephaly-related seizures
  • 70. 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
  • 71. 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
  • 72. 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
  • 73. 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
  • 74. 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
  • 75. Non-neoplastic Non-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
  • 76. • Pilocytic astrocytoma • Pleomorphic xanthoastrocytoma • Craniopharyngioma • Ganglioglioma • Hemangioblastoma
  • 77. 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
  • 78. Demographics Age  > 80% under 20 y  Peak incidence: 5-15 years of age  Older than children with medulloblastoma Gender: M = F WHO grade I
  • 79. 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
  • 80. 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
  • 81. 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
  • 82. 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
  • 83. 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
  • 84. 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
  • 85. 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
  • 86. 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)
  • 87. 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
  • 88. 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
  • 89. 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
  • 90. 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
  • 91. 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
  • 92.  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
  • 93. 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
  • 94. 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
  • 95. 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
  • 96. 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
  • 97. 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
  • 98. 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
  • 99.  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
  • 100. 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
  • 101. 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.
  • 102. 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
  • 103. 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
  • 104. 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
  • 105. 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)
  • 106.  Squamous cell ca lung  Adenocarcinoma lung  Carcinoma thyroid  Multiple  Typically at gray-white matter junction  Disproportionate edema  May show peripheral enhancement
  • 107. Non-neoplastic Non-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
  • 108. • Hydatid • NCC • Abscesses
  • 109. 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
  • 110. 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
  • 111. 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
  • 112. 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
  • 113. 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
  • 114. 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
  • 115. 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
  • 116. 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
  • 117. 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
  • 118.  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
  • 119. 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
  • 120. Non-neoplastic Non-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
  • 121. 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
  • 122. 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
  • 123. 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)
  • 124.  Cystic intracranial lesions – varied etiology  MRI – preferred modality  FLAIR and DWI – important sequences  Prenatal diagnosis – congenital lesions  Diagnosis important – treatment varies
  • 125.  Diagnostic Imaging, Brain – first edition, Osborn. 