Neurosurgical Atlas Flashcards
Basic description of pilocytic astrocytomas.
- Slow growing, well circumscribed tumor arising from astrocytic precursors.
- Most common pediatric primary intracranial neoplasm.
Pathology of pilocytic astrocytomas.
- Biphasic pattern of astrocytes (Rosenthal fibers and multipolar cells).
- Syndromic or sporadic (optic nerve/chiasm PAs associated with NF1).
CT findings of pilocytic astrocytomas.
- Mixed solid-cystic mass with minimal surrounding edema.
- May have calcification.
- Strong mural nodular enhancement, non-enhancing cystic component.
T1WC+C findings of pilocytic astrocytomas.
- Enhancing solid component with/without cyst wall enhancement.
Basic description of pleomorphic xanthoastrocytoma.
- Supratentorial cortical/peripheral astrocytic tumor.
Pathology of pleomorphic xanthoastrocytoma.
- Astrocyte pleomorphism and lipid-containing cells.
2. May show anaplastic features (10-15%).
General imaging features of pleomorphic xanthoastroctyoma.
- Temporal lobe > frontoparietal > occipital.
- Classically cystic with solid mural nodule, often abuts pial surface.
- May have enhancing dural tail of leptomeningeal attachment.
CT findings of pleomorphic xanthoastrocytoma.
- Hypodense cystic component.
2. Minimal to moderate adjacent edema.
T1WC + C findings of pleomorphic xanthoastrocytoma.
- Generally strong enhancement, sometimes enhancing dural tail/leptomeninges.
Basic description of anaplastic astrocytoma.
Infiltrating malignant astrocytoma with ill-defined tumor margins and extensive edema.
Pathology of anaplastic astrocytoma.
- Usually develops from malignant degeneration of low-grade astrocytoma.
- Commonly dedifferentiates into GMB (-50%) within 2 years.
- Focal or diffuse anaplasia, highly proliferative.
- Increased cellularity and nuclear atypia, usually no necrosis or microvascular proliferation.
General imaging characteristics of anaplastic astrocytoma.
- Ill-defined, infiltrating white matter mass.
- Location in frontal and temporal lobes most common, brainstem and spinal cord uncommon.
- Spreads along white matter tracts, but may spread via CSF, leptomeninges, and ependymal.
CT findings of anaplastic astrocytoma.
- Hypodense, ill-defined white matter mass.
2. Usually does not enhance on contrast-enhanced CT.
Basic description of GBM.
- Malignant, rapidly enlarging astrocytic tumor with microvascular proliferation and necrosis.
- Most common primary intracranial neoplasm.
Pathology of GBM.
- Necrosis and microvascular proliferation are characteristic features.
- Develops do novo (primary) or from malignant dedifferentiation of AA (secondary).
- Associated with NF-1, Turcot, Li-Fraumeni, and Maffuci syndromes.
Clinical features of GBM.
- Median survival < 1 year (better prognosis with younger age, greater resection, and MGMT-positive genetics).
CT features of GBM.
- Irregular hypo-to isodense mass with central hypodensity (necrosis).
- Surrounding vasogenic edema.
- Irregular, heterogenous ring of enhancement on contrast-enhanced CT.
T1WI of GBM.
- Irregular, hypointense white matter mass, areas of hyperintensity may represent subacute hemorrhage.
T2WI of GBM.
- Heterogeneously hyperintense, surrounding vasogenic edema, presence of flow voids suggests neovasculatiry.
T1WI+C of GBM.
- Thick, irregular ring of peripheral enhancement.
2. Enhancement may be ring, nodular, homogenous or patchy.
MRS of GBM.
- Decreased NAA and myoinositol.
- Increased choline, lipid/lactate peak indicating anaerobic metabolism of necrosis.
- Increased relative CBV compared with lower grade astrocytomas.
Pathology of posterior fossa ependymoma.
- 3 histological subtypes (PF-ependymoma, PF-ependymoma type A, PF ependymoma type B).
- Subtype A highly malignant.
General imaging features of posterior fossa ependymoma.
- Well-marginated, lobulated mass.
- Majority arise within 4th ventricle and extend through/widen ventricular foramina into adjacent parenchymal and basal cisterns.
- Displaces rather than invades adjacent parenchyma.
CT of posterior fossa ependymoma.
- Lobulated, often calcified mass arising within inferior portion of 4th ventricle.
T1WI of posterior fossa ependymoma.
- Heterogeneous, often hypointense, areas of calcification and hemorrhage appear hyperintense.
T1WI+C of posterior fossa ependymoma.
- Variable enhancement.
MRS of posterior fossa ependymoma.
- Elevated choline and lactate.
- Decreased NAA.
- MRS not generally helpful in distinguishing between posterior fossa medulloblastomas and astrocytomas.
Basic description of supratentorial ependymomas.
- Hemispheric glial-cell tumor arising from ependymal cells.
- Extraventricular subependymomas may arise from fetal ependymal rests.
Pathology of supratentorial ependymomas.
- WHO I: myxopapillary ependymoma (more often occurring at the conus medulluaris).
- WHO II: cellular, papillary, clear cell, and tanycytic variants.
- WHO III: most common in adults, trisomy 19 and anaplastic variants.
Histology of supratentorial ependymomas.
- Perivascular and ependymal rosettes.
Imaging features of supratentorial ependymomas.
- Heterogeneous, mixed solid-cystic supratentorial mass.
- Often large at presentation (>4cm).
- Majority are extraventricular.
- 3rd ventricle most common intraventricular location.
CT imaging of supratentorial ependymomas.
- Heterogeneously iso-to hypodense.
2. Calcification common.
T2*/GRE/SWI of supratentorial ependymomas.
- Black signal blooming secondary to calcification and/or hemosiderin deposition from blood products.
Pathology of oligodendrogliomas.
- Arises from malignant transformation of mature oligodendrocytes or glial precursor cells.
- Calcification and cystic degeneration common.
- “Fried egg” appearance due to rounded nuclei and clear cytoplasm.
- Associated with IDH1 or MGMT positive genetics.
General imaging features of oligodendrogliomas.
- Usually supratentorial location (frontal lobe»_space; temporal, parietal, and occipital lobes).
- Calcification present in 40-80%.
- Usually minimal to no peritumoral edema.
MRS of oligodendrogliomas.
- elevated choline, decreased NAA, absent lipid/lactate peak (unlike anaplastic oligodendroglioma).
- Unique characteristic of elevated relative CBV in spite of lower grade due to pathologic feature of “chicken-wire vascularity”.
Pathology of atypical/malignant meningiomas.
- WHO grade II (atypical) and WHO grade III (malignant).
- Most likely arise from dedifferentiation of traditional meningiomas.
- Increased mitoses, nucleus-to-cytoplasm ratio, necrosis, and nuclear atypia compared to traditional meningioma’s.
General imaging features of atypical/malignant meningiomas.
- Dural based, extra-axial mass with necrosis, invasion of adjacent brain, and extensive peritumoral brain edema.
- May arise within any location in the neuraxis. (AMs: CPA cistern, tentorium most common; MM: parasagittal or cerebral convexity).
CT findings of atypical/malignant meningiomas.
- Ill-defined, hyperdense mass extending intra-and extra cranially.
- Minimal calcification compared to traditional meningiomas.
- Extensive hypodense peritumoral edema.
- Avid enhancement on contrast-enhanced CT.
FLAIR imaging of atypical/malignant meningiomas.
- often marked hyperintense peritumoral edema.
T1WI+C of atypical/malignant meningiomas.
- Avid enhancement with enhancing margins invading adjacent structures.
DWI of atypical/malignant meningiomas.
- Reduced diffusivity (bright DWI, dark ADC).
Basic description of craniopharyngiomas.
- Benign tumor arising from Rathke pouch epithelium.
2. Most common pediatric nonglial-origin tumor.
Pathology of craniopharyngiomas.
- Two histological types (adamantinomatous - partially cystic mass in children, papillary - solid mass in adults).
- Cysts with viscous “crankcase oil” or “motor oil” contents.
Age distribution of craniopharyngiomas.
- Adamantinomatous - ages 5-15 years.
2. Papillary - > 50 years.
General imaging features of craniopharyngiomas.
- Multilobulated or multicystic mass.
- Location may be suprasellar, supra and intrasella, or completely intrasellar.
- Adamantinomatous - mixed solid-cystic or predominantly cystic.
- Papillary - predominantly solid.
CT of adamantinomatous craniopharyngiomas.
- Cystic components are hypodense, solid components are isodense.
- 90% with calcifications.
- 90% enhance (nodule or rim enhancement).
CT of papillary craniopharyngiomas.
- Isodense solid tumor.
2. Calcification much more rate.
T1WI of craniopharyngiomas.
- Often hyperintense due to proteinaceous material.
2. Isointense or heterogenous solid tumor component.
T1WI+C of craniopharyngiomas.
- Enhancement of cyst wall and solid tumor components.
Basic description of vestibular schwannomas.
- Benign peripheral nerve sheath tumor arising from Schwann cells of CN 8 (vestibular portion) within the CPA-IAC.
Pathology of vestibular schwannomas.
- CN 8 superior vestibular branch > inferior branch.
2. Variable hpercellular (Antoni A) and more hypocellular (Antoni B) areas are characteristic.
General imaging features of vestibular schwannomas.
- Well-marginated, enhancing mass within the CPA or CPA-IAC with “ice cream on cone” morphology.
- Expansion of the IAC (in contrast to meningiomas).
- Calcification, cystic degeneration may be seen.
T2WI of vestibular schwannomas.
- High resolution sequences (SPACE, CISS, or FIESTA) optimize visualization.
- Appears as a hypo-to isointense CPA-IAC filling defect.
Basic description of pineocytomas.
- Slow-growing pineal parenchymal tumor.
Pathology of pineocytomas.
- Arises from pineocytes or pineocyte precursors.
- Well-differentiated tumor without mitoses or necrosis.
- Small, uniform cells arranged in sheets with intervening septae are typical microscopic features.
General features of pineocytomas.
- Peripherall-calcified, well circumscribed pineal region mass.
- Calcifications and cysts are often present.
- Rare intraventricular extension, CSF dissemination or parenchymal invasion.
CT findings of pineocytomas.
- Well-circumscribed, iso to hypodense pineal mass.
2. +/- peripheral calcification.
Basic description of pineoblastomas.
- Malignant, invasive pineal parenchymal tumor arising from embyronic pineocyte precursors (PNET).
Pathology of pineoblastomas.
- Invades adjacent structures often including the cerebral aqueduct.
- CSF dissemination common.
- Hypercellularity and increased mitoses are characteristic features.
- Associated with germline DICER1 mutations (DICER! syndrome) and RB1 (bilateral retinoblastomas and pineoblastoma).
General imaging features of pineoblastoma.
- Lobulated, poorly marginated pineal mass.
- Often larger and more invasive than pineocytomas.
- Peripheral (“exploded”) calcifications common.
- Commonly invades adjacent structures including cerebral aqueduct, corpus callosum, thalamus, brainstem and vermis.
- May see superior displacement of cerebral veins and mass effect on the tectum.
CT findings of pineoblastoma.
- Heterogenous density, irregular pineal mass.
2. Peripheral calcification.
T1WI+C of pineoblastoma.
- Heterogenous enhancement.
MRS of pineoblastoma.
- Elevated choline.
2. Decreased NAA.
Basic description of germinoma.
- Intracranial germ cell tumor often occurring in the pineal region.
Pathology of germinoma.
- WHO grade II(pure germinoma) or grade III (syncytiophoblastic giant cells).
- Associated with Down’s, Klinefelter, and NF-1 syndromes.
- Polygonal primitive germ cells and lymphocytic infiltrates are common microscopic features.
Gender predilection for germinomas.
- Marked male gender predilection in pineal region germinomas.
- Females more commonly afflicted with suprasellar germinomas.
Lab findings for germinomas.
- Increased serum/CSF B-hcg.
CT findings for germinomas.
- Lobulated, hyperdense mass.
- +/- cysts, hemorrhage.
- Avid, homogeneous enhancement on contrast enhanced CT +/- CSF dissemination.