KEY FACTS Terminology Brain metastases in locations other than skull/meninges or parenchyma Imaging General features > 95% of brain metastases parenchymal Only 1-2% in ventricles, pituitary gland, etc. Sites generally very vascular Extraventricular metastases more diffuse, infiltrative than parenchymal metastases (usually round) Location Choroid plexus ± ventricular ependyma Pituitary gland infundibulum Eye (choroid) Cranial nerves Pineal gland Preexisting neoplasm (“collision tumor”) Best imaging tool: MR with…

KEY FACTS Terminology Secondary brain tumors (metastases) arise from Tumors outside CNS spreading to CNS (usually via hematogenous dissemination) Primary CNS neoplasms spreading from 1 site to another (usually geographic extension, e.g., along WM tracts) Imaging General features Round enhancing lesion(s) at gray-white interface (arterial border zones) Most metastases are circumscribed/discrete > > infiltrating, spherical > > linear 50% are solitary; 20% have 2 metastases 30%…

KEY FACTS Terminology Acute or chronic myeloid or lymphoid white blood cell neoplasia with spinal involvement as component of systemic disease Imaging Radiographs/CT Diffuse osteopenia with multiple vertebral fractures ± lytic spine lesions Variable enhancing isodense soft tissue mass with adjacent bone destruction MR T1WI: Hypointense marrow and focal tumor masses T2WI: Hyperintense marrow ± focal vertebral mass, cord signal abnormality T1WI C+: Abnormal enhancement of…

KEY FACTS Terminology Rare malignancy characterized by intravascular proliferation of lymphoid cells with predilection for CNS and skin Imaging T2/FLAIR multifocal hyperintensities in deep white matter, cortex, and basal ganglia May mimic infarct Diffusion restriction common GRE/SWI: Multifocal hemorrhage often seen Linear and punctate enhancement typical May see meningeal &/or dural enhancement Often mimics vasculitis Top Differential Diagnoses Vasculitis Multi-infarct dementia Primary CNS lymphoma Neurosarcoid Pathology…

KEY FACTS Terminology Malignant primary CNS neoplasm primarily composed of B lymphocytes (PCNSL) Imaging Best diagnostic clue: Enhancing lesion(s) within basal ganglia &/or periventricular white matter 60-80% supratentorial Often involve, cross corpus callosum Frequently contact, extend along ependymal surfaces Classically hyperdense on CT (helpful for diagnosis) Diffusely enhancing periventricular mass in immunocompetent patients May see hemorrhage or necrosis in immunocompromised patients DWI: Low ADC values PWI:…

KEY FACTS Terminology Hemangioblastoma (HGBL): Highly vascular tumor of adults most commonly found in posterior fossa (PF), spinal cord 25-40% of HGBLs in von Hippel-Lindau disease (VHL) Imaging Best diagnostic clue: Adult with cerebellar mass with cyst and enhancing mural nodule General features 50-60% cyst + “mural” nodule; 40% solid enhancing mass 90-95% in posterior fossa 5-10% supratentorial (around optic pathways, hemispheres; usually in VHL) Top…

KEY FACTS Terminology Medulloblastoma (MB) Malignant, invasive, highly cellular embryonal tumor 4 distinct MB molecular subgroups Wingless (WNT) Sonic hedgehog (SHH) Group 3 Group 4 Imaging MB subgroups arise in different locations Midline (4th ventricle) – Predominately (but not exclusively) groups 3 and 4 Cerebellar peduncle/CPA cistern: WNT Cerebellar hemispheres (lateral): SHH NECT: 90% hyperdense (Ca++, hemorrhage uncommon) MR: > 90% enhance (group 4 minimal/no enhancement)…

KEY FACTS Terminology Intracranial germ cell tumor (iGCT) iGCTs are intracranial homologue of gonadal germinomas (ovarian dysgerminoma, testicular seminoma) Imaging Most common: In/near midline (80-90%) Pineal region ~ 50-65% Suprasellar ~ 25-35% Less common: Basal ganglia/thalami ~ 5-10% 20% multiple Most common = pineal with suprasellar Pineal germinoma Hyperdense pineal region mass engulfs pineal Ca++ Strong, often heterogeneous enhancement T2/FLAIR hyperintensity in surrounding brain = inflammation/granulomatous…

KEY FACTS Terminology Primary parenchymal neoplasm of pineal gland Intermediate in malignancy between pineoblastoma and pineocytoma Imaging General features Aggressive-looking pineal mass in adult Extension into adjacent structures (ventricles, thalami) is common Lobulated, moderately vascular Size varies from small (< 1 cm) to large (~ 6 cm) CT Hyperdense mass centered in pineal region Engulfs pineal gland Ca++ Hydrocephalus MR T1: Mixed iso-/hypointense mass T2: Isointense…

KEY FACTS Terminology Pineocytoma (PC), pineal parenchymal tumor (PPT) PCs are composed of small, uniform, mature cells Cells resemble pineocytes Imaging General features: Circumscribed, enhancing pineal mass May mimic benign pineal cyst or PPT of intermediate differentiation (PPTID) Typically < 3 cm May compress adjacent structures Rarely extends into 3rd ventricle, rarely invasive Can compress aqueduct → hydrocephalus Occasionally hemorrhages CT Circumscribed iso-/hypodense pineal region mass…

KEY FACTS Terminology Central neurocytoma (CN) = intraventricular neuroepithelial tumor with neuronal differentiation Imaging Best diagnostic clue: “Bubbly” mass in frontal horn or body of lateral ventricle May involve 3rd ventricle CT: Usually mixed solid and cystic mass with calcification Hydrocephalus common Rarely complicated by hemorrhage MR: Heterogeneous, T2 hyperintense, “bubbly” appearance May be predominantly solid mass Moderate to strong heterogeneous enhancement MRS: ↑ Cho, ↓…

KEY FACTS Terminology Dysembryoplastic neuroepithelial tumor (DNET) Benign mixed glial-neuronal neoplasm Frequently associated with cortical dysplasia Imaging May occur in any region of supratentorial cortex Temporal lobe most common, followed by frontal lobe Mass frequently “points” toward ventricle Sharply demarcated, wedge-shaped Cystic (“bubbly”) intracortical mass Minimal/no mass effect No surrounding edema Slow growth over years Usually does not enhance Faint focal punctate or ring enhancement in…

KEY FACTS Terminology Well-differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells Most common neoplastic cause of temporal lobe epilepsy (TLE) Imaging Best diagnostic clue: Partially cystic, enhancing, cortically based mass in child/young adult with TLE Can occur anywhere, but most commonly superficial hemispheres, temporal lobe (> 75%) Circumscribed cyst with mural nodule most common May be solid and appear well…

KEY FACTS Terminology Choroid plexus tumor (CPT) 3 types of CPTs – Choroid plexus papilloma (CPP) (WHO grade I) – Atypical CPP (aCPP) (grade II) – Choroid plexus carcinoma (CPCa) (grade III) Imaging Classic: Child with enhancing lobulated (cauliflower-like) mass in atrium of lateral ventricle CPPs occur in proportion to amount of choroid plexus 50% in lateral ventricle (usually atrium) 40% in 4th ventricle &/or foramina…

KEY FACTS Terminology Rare, benign, well-differentiated, intraventricular ependymal tumor, typically attached to ventricular wall Imaging Intraventricular, inferior 4th ventricle typical (60%) Other locations: Lateral > 3rd ventricle > spinal cord T2/FLAIR hyperintense intraventricular mass Heterogeneity related to cystic changes; blood products or Ca++ may be seen in larger lesions Variable enhancement, typically none to mild T2WI and FLAIR are often most sensitive sequences Top Differential Diagnoses…

KEY FACTS Terminology Posterior fossa ependymoma (PF-EPN) Imaging Ependymoma can occur anywhere in neuraxis Most common site: Posterior fossa (2/3 of cases) Lobulated mass in body/inferior 4th ventricle – Soft or “plastic” tumor □ Accommodates to shape of ventricle □ Squeezes through foramen of Magendie into cisterna magna □ ± extension through foramina of Luschka into cerebellopontine angle cisterns NECT Ca++ common (50%) ± cysts, hemorrhage…

KEY FACTS Terminology Oligodendroglioma with focal or diffuse histologic features of malignancy Imaging Best diagnostic clue: Calcified frontal lobe mass involving cortex and subcortical white matter Frontal lobe is most common location, followed by temporal lobe Majority have nodular or clumped calcification May see hemorrhage or necrosis Variable enhancement Anaplastic oligodendroglioma more likely to enhance than low-grade oligo Neoplastic cells almost always found beyond areas of…

KEY FACTS Terminology Well-differentiated, slowly growing but diffusely infiltrating cortical/subcortical tumor Imaging Most common site is frontal lobe (50-65%) Best diagnostic clue: Partially calcified subcortical/cortical frontal mass in middle-aged adult Typically T2 heterogeneous, hyperintense mass ~ 50% enhance Heterogeneous enhancement is typical New enhancement in previously nonenhancing oligodendroglioma suggests malignant progression Top Differential Diagnoses Anaplastic oligodendroglioma Low-grade diffuse astrocytoma Ganglioglioma Dysembryoplastic neuroepithelial tumor Pleomorphic xanthoastrocytoma Cerebritis…

KEY FACTS Terminology Diffusely infiltrating, frequently bilateral glial tumor involving at least 3 lobes Infiltrative extent of tumor is out of proportion to histologic and clinical features Imaging T2 hyperintense infiltrating mass with enlargement of involved structures Typical cerebral hemispheres (75%) Brain architecture enlarged, distorted, but preserved Typically no or minimal enhancement Enhancement may indicate malignant progression or focus of malignant glioma MRS: Increased choline, decreased…

KEY FACTS Terminology Rapidly enlarging malignant astrocytic tumor characterized by necrosis and neovascularity Most common of all primary intracranial neoplasms Imaging Best imaging clue: Thick, irregularly enhancing rind of neoplastic tissue surrounding necrotic core Heterogeneous, hyperintense mass with adjacent tumor infiltration/vasogenic edema Necrosis, cysts, hemorrhage, fluid/debris levels, flow voids (neovascularity) may be seen Supratentorial white matter most common location Cerebral hemispheres > brainstem > cerebellum Viable…