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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues
- General rule: Decreased diffusion = higher grade
Helpful Clues for Common Diagnoses
- Posterior Fossa (most common location) - Pilocytic astrocytoma - Low-density NECT - Solid, enhancing nodule and cyst: Classic appearance - Solid nodule has increased diffusion = good prognosis - Off midline compared to classic 4th ventricular tumors but may pedunculate into ventricle - Characterized by KIAA1549::BRAF fusion - Medulloblastoma - Hyperdense posterior fossa mass on NECT - Decreased diffusion - Molecular subgroups predicts outcome - WNT-activated: Up to 90% overall survival, 4th ventricle and cerebellopontine angle (CPA) location, rarest subgroup - SHH-activated: Poor to good prognosis, cerebellar hemispheric location, + TP53 mutation = poor prognosis - Group 3: Worst prognosis with frequent metastases, midline 4th ventricle - Group 4: Intermediate prognosis with occasional metastases, midline 4th ventricle, minimal to no enhancement, most common subgroup - Ependymoma - Less common than pilocytic astrocytoma and medulloblastoma - 60% posterior fossa - "Plastic" tumor in 4th ventricle, extrudes through foramina - Can have mixed calcification and cysts - Molecular subgroups predict outcome - Posterior fossa type A: Younger children, lateral location, characterized by H3 K27 alteration, poor outcome - Posterior fossa type B: Adolescents, midline location, good outcome, uncommon - Diffuse midline glioma, H3 K27-altered - Diffuse intrinsic pontine glioma - T2-hyperintense expansion of pons, little to no enhancement - Can also involve cerebellum and spinal cord - Poor prognosis
- Supratentorial(more common in infants and adolescents) - Craniopharyngioma - Nearly 1/2 of pediatric suprasellar masses, typically adamantinomatous - 90% calcification/cystic/enhance - Squamous cell from Rathke cleft - Pilocytic astrocytoma - Commonly involves optic pathway or around 3rd ventricle, tectal plate - Optic "gliomas" are commonly associated with NF1 - Heterogeneous appearance and enhancement - Pilomyxoid astrocytoma variant is more locally aggressive and more likely to present with leptomeningeal metastases - Similar genetic and molecular characteristics; was removed as separate grading designation in WHO 2016 - Supratentorial likely to have BRAFV600E mutation - Diffuse low-grade glioma, pediatric - Hemispheres, thalami (can be bithalamic), tectum - 50% of brainstem "gliomas" are low-grade diffusely infiltrating astrocytomas - Can be poorly marginated or focal - Hypointense on T1WI, hyperintense on T2WI, little to no enhancement - WHO 2021 has 4 tumor types in this family - Diffuse astrocytoma, MYB- or MYBL1-altered - Diffuse low-grade glioma, MAPK pathway-altered - Polymorphous low-grade neuroepithelial tumor of the young (PLNTY): Commonly cortical with heterogeneous T2 signal from calcification - Angiocentric glioma - Subependymal giant cell astrocytoma - Seen in tuberous sclerosis - Location at foramina of Monro is typical - Look for cortical/subcortical tubers and subependymal nodules - Heterogenous calcification, marked enhancement
Helpful Clues for Less Common Diagnoses
- Intraaxial: Peripheral and Cortical - Dysembryoplastic neuroepithelial tumor - Bubbly-appearing, cortically based mass - Bright ring sign on FLAIR MR - Almost all in patients < 20 years old, chronic epilepsy - Pleomorphic xanthoastrocytoma - Cortically based tumor (temporal lobe most common) - Enhancing mass + cyst, dural reaction (tail) common - Majority demonstrate BRAFV600E mutation - Ganglioglioma - Temporal lobe predilection with seizure presentation - Solid or solid with cyst, ± enhancement - Oligodendroglioma - Cortically based, frontal lobe predominance - Calcification common - Predominantly T2 hyperintense ± enhancement - Characterized by 1p/19q codeletion; if 1p/19q intact, represents astrocytoma with poorer outcome
- Intraaxial: Deep and Hemispheric - Diffuse high-grade glioma, pediatric - Diffusely infiltrating, heterogeneous, ± enhancement - WHO 2021 has 4 tumor types in this family (all have poor outcome) - Diffuse midline glioma, H3 K27-altered: Central location, involves thalami and brainstem - Diffuse hemispheric glioma, H3 G34-mutant - Diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype - Infant-type hemispheric glioma - CNS embryonal tumor - Primitive neuroepithelial tumor terminology removed from 2016 WHO CNS tumors - Infant with large, bulky, complex hemispheric mass - Calcification, hemorrhage, necrosis common - Peritumoral edema sparse/absent, less than expected for size - Supratentorial ependymoma - Diffuse infiltrating, heterogeneously enhancing tumor - Origin is periventricular from ependymal rests - Molecular subgroups predict outcome - ZFTA fusion-positive, younger children, poor outcome - YAP1 fusion-positive, older children, good outcome, rare
- Extraaxial - Choroid plexus tumor - Intraventricular: Lateral > 4th > 3rd ventricles - Densely enhancing, frond-like - Although choroid plexus carcinoma may show parenchymal invasion, it is not reliably distinguished from papilloma on imaging - Neurofibromatosis type 2 - Vestibular schwannomas - If multiple schwannomas, think neurofibromatosis type 2 - Look for "hidden" dural-basedmeningiomas
- Midline Pineal and Suprasellar Location - Germ cell tumor - Organized by cell lineage and maturity - Germinomatous germ cell tumor - Germinoma: Common in older children and adolescents, excellent prognosis - Homogeneous with enhancement and decreased diffusion in pure germinomas - Nongerminomatous germ cell tumors - Teratoma: Fetal life to adolescence; mature teratomas may have fat and calcification; smaller teratomas that are easily resected have good prognosis; immature teratomas have poor prognosis - Embryonal carcinoma**,** yolk sac tumor**, and** choriocarcinoma: Rare; older children and adolescents, poor prognosis - Heterogeneous with enhancement - Mixed germ cell tumor: Includes germinomatous and nongerminomatous components - Worse prognosis than pure germinomas due to nongerminomatous components - Suprasellar + pineal lobular, enhancing masses together best clue - Engulfs pineal calcification on CT - Pineoblastoma - Decreased diffusion - Look for CSF spread (ventricles, ependyma) - Difficult to distinguish from germinoma - "Exploding" pineal calcification on CT - Pineoblastoma more common than lower grade varieties, such as pineocytoma and pineal parenchymal tumor of intermediate differentiation
Helpful Clues for Rare Diagnoses
- Atypical Teratoid-Rhabdoid Tumor - Heterogeneous intracranial mass in infants and children - 50% infratentorial; early CSF spread - Typically decreased diffusion, greater amount of cysts than medulloblastoma
- Astroblastoma,MN1-Altered - Typically peripheral, well circumscribed - Solid and cystic heterogeneous enhancement
- Central Neurocytoma - "Bubbly," lobulated mass in body of lateral ventricle - Often along septum pellucidum
- Dysplastic Cerebellar Gangliocytoma - Not associated with PTEN hamartoma syndrome in children - T2-hyperintense, striated cerebellum with enlarged folia

References

Selected References

Images

Selected Images

Pilocytic Astrocytoma Axial T2 FS MR shows a solid tumor with a cyst in the right cerebellar hemisphere effacing the 4th ventricle . The solid component has relative increased T2 signal, suggesting a low-grade tumor.

Pilocytic Astrocytoma Axial T1 C+ MR shows homogeneous enhancement of the solid component. A low-grade glial tumor, such as a pilocytic astrocytoma, has fluffy-appearing enhancement as much of the enhancement is from vessel leakage.

Pilocytic Astrocytoma Axial b=1000 DWI MR shows the solid component has similar signal to the brain , not suggesting decreased diffusion, which is compatible with a low-grade neoplasm.

Medulloblastoma Axial T1 C+ MR shows a heterogeneously enhancing mass in the 4th ventricle . Adjacent nodules of enhancement are seen in the cerebellar hemisphere from leptomeningeal metastases . WNT medulloblastomas have a > 90% survival rate despite metastatic disease.

Medulloblastoma Axial T1 C+ MR shows a heterogeneous mass with central necrosis in the left cerebellar hemisphere . This was an SHH medulloblastoma, which typically presents in the cerebellar hemispheres.

Medulloblastoma Axial b=1000 DWI MR shows the cerebellar hemisphere mass has decreased diffusion consistent with a high-grade neoplasm . This SHH medulloblastoma is TP53-wildtype, which has a better prognosis than SHH medulloblastoma with TP53 mutation.

Medulloblastoma Axial T1 C+ MR demonstrates a small, 4th ventricle, enhancing mass with diffuse leptomeningeal enhancement from metastatic disease in this group 3 medulloblastoma. With the exception of WNT, metastasis increases the risk for any subtype.

Ependymoma Axial T1 C+ MR shows a heterogeneously enhancing mass extending through right foramen of Luschka in this posterior fossa type A (PFA) ependymoma, which are more laterally located and have a worse prognosis compared to posterior fossa type B.

Diffuse Midline Glioma, H3 K27-Altered Axial T1 C+ MR shows a heterogeneous enhancing mass in the left thalamus . This was an H3 K27-mutant diffuse midline glioma. These have poor prognosis and are located in the thalami, brainstem, and spinal cord.

Diffuse Midline Glioma, H3 K27-Altered Axial b=1000 DWI MR shows the right thalamic tumor has some areas of decreased diffusion , suggesting a high-grade neoplasm.

Craniopharyngioma Sagittal NECT shows a mass in the suprasellar cistern with a hyperdense cyst and calcification , consistent with craniopharyngioma. This is the most common suprasellar tumor in children.

Pilocytic Astrocytoma Coronal T1 C+ MR shows a solid and cystic mass in the right thalamus with "fluffy" enhancement . This child has neurofibromatosis type 1 (NF1), and the tumor was a pilocytic astrocytoma.

Pilocytic Astrocytoma Axial b=1000 DWI MR of the tumor in the right thalamus in the same patient demonstrates low signal or increased diffusion, consistent with a low-grade pilocytic astrocytoma.

Diffuse Low-Grade Glioma, Pediatric Sagittal T2 MR shows a T2-hyperintense mass in the tectal plate obstructing the cerebral aqueduct. Despite the lack of biopsy, this is most commonly a low-grade diffuse glioma or tectal glioma. The course is generally indolent and commonly requires ventricular shunting.

Subependymal Giant Cell Astrocytoma Axial T1 C+ MR shows a lobular, enhancing mass near the foramen of Monro . Subependymal giant cell astrocytomas are invariably located at this location. Other subependymal nodules and cortical tubers should be sought to confirm tuberous sclerosis.

Dysembryoplastic Neuroepithelial Tumor Coronal FLAIR MR shows a cortically based, triangular mass that is well circumscribed . There is no contrast enhancement (not shown). Dysembryoplastic neuroepithelial tumors are typically cortically based, low-grade tumors that can have a cystic appearance.

Pleomorphic Xanthoastrocytoma Coronal T1 C+ MR shows a cyst and a solid enhancing, cortically based mass with a broad dural base . The broad dural base of this cortically based intraaxial tumor is a typical appearance for pleomorphic xanthoastrocytoma.

Ganglioglioma Coronal T1 C+ MR shows a heterogeneous, large, enhancing mass in the temporal lobe . This was a ganglioglioma at resection. The temporal lobe is a common location for this tumor when there is seizure presentation.

Diffuse High-Grade Glioma, Pediatric Axial T1 C+ MR shows an enhancing mass in the posterior temporal lobe with a satellite nodule . This was a diffuse, high-grade glioma with H3 K27 mutation at resection.

Supratentorial Ependymoma Axial T1 C+ MR shows a large right frontal mass with central cystic change . Supratentorial ependymomas are usually periventricular and are thought to arise from ependymal rests in the periventricular white matter.

Choroid Plexus Tumor Axial T1 C+ MR shows a frond-like mass within the left temporal horn, consistent with a choroid plexus papilloma . Choroid plexus tumor locations follow larger volumes of choroid: Lateral ventricle > 4th > 3rd.

Neurofibromatosis Type 2 Axial T1 C+ MR shows bilateral enhancing tumors in the internal auditory canals compressing the brainstem , consistent with bilateral vestibular schwannomas, pathognomonic for neurofibromatosis type 2. Search for additional cranial nerve schwannomas and dural margin meningiomas.

Germ Cell Tumor Sagittal NECT shows a heterogeneous mass with fat and calcification in the pineal region extending to the 3rd ventricle, consistent with mature teratoma. There is a small amount of intraventricular air from recent biopsy.

Pineoblastoma Sagittal T1 C+ MR shows a large, enhancing mass in the pineal region . This was a pineoblastoma at resection. High-grade pineoblastomas are the most common pineal parenchymal tumor.

Atypical Teratoid-Rhabdoid Tumor Axial T1 C+ MR shows a heterogeneous mass in the inferior left frontal lobe . This was an atypical teratoid-rhabdoid tumor at resection. DWI images demonstrate decreased diffusion (not shown), consistent with a high-grade neoplasm.

Astroblastoma, MN1-Altered Axial T1 C+ MR shows a large, heterogeneous mass with a solid periphery involving the cortex and central cyst. There is resulting subfalcine herniation. Although rare, "bubbly," solid peripheral tumors with a cyst are the typical appearance for astroblastomas.

Additional Images

Pilocytic Astrocytoma Axial NECT shows a typical midline cystic tumor with a large, low-density mural nodule . There is hydrocephalus with interstitial edema. Low density on CT is typical of low-grade tumors.

Pilocytic Astrocytoma Axial T2 MR shows the nodule to be high signal intensity, a clue to the low nuclear:cytoplasmic ratio in cerebellar juvenile pilocytic astrocytoma tumors.

Pilocytic Astrocytoma Axial T2 MR shows a large, hyperintense, well-circumscribed mass. It arises from the hypothalamic region and demonstrates no edema of adjacent structures. Pilomyxoid astrocytomas often arise from similar locations as pilocytic astrocytomas but are more locally aggressive with higher likelihood of leptomeningeal enhancement.

Medulloblastoma Axial T1 C+ MR in a child with metastatic medulloblastoma shows enhancement of the interfoliate sulci and circummesencephalic cistern .

Medulloblastoma Axial T2 MR shows a low-signal midline tumor. There is an associated cyst . Low T2 signal of the solid component of tumors typically correlates with higher grade malignancy.

Medulloblastoma Axial DWI MR shows diffusion restriction within the tumor nodule, an excellent clue to the high-grade nature of the lesion.

Medulloblastoma Axial CECT in metastatic medulloblastoma shows comb-like enhancement of the interfoliate sulci . Note moderately enlarged lateral ventricles caused by extraventricular obstructive hydrocephalus from diffuse cisternal metastases.

Ependymoma Sagittal T2 MR shows a large, heterogeneous, low-signal mass that widens the tegmenta-cerebellar angle and extends through the inferior recesses of the 4th ventricle. There is extension into the upper cervical spinal canal .

Diffuse Midline Glioma, H3 K27-Altered Sagittal T2 MR shows diffuse expansion of the pons and medulla due to an infiltrating glioma.

Diffuse Midline Glioma, H3 K27-Altered Axial FLAIR MR shows brainstem expansion and signal increase. The tumor expands to engulf the basilar artery .

Diffuse Low-Grade Glioma, Pediatric Coronal T2 MR shows an ill-defined, T2-hyperintense infiltrating mass involving the basal ganglia, temporal lobe, and frontal lobes . This is typical of diffuse astrocytomas and was WHO grade 2 at biopsy. The term gliomatosis cerebri, which described a diffusely infiltrating astrocytoma involving at least 3 lobes of the brain, has been removed for the 2016 WHO classification of CNS tumors.

Craniopharyngioma Sagittal T1 MR shows a suprasellar collection of cysts of many signal intensities. One is very high signal intensity, likely due to protein; another extends behind the clivus ; and the remainder herniate into the 3rd ventricle. Calcification is noted in the solid component above the dorsum sella.

Craniopharyngioma Coronal T2 MR shows a mixed solid , cystic , and calcified suprasellar tumor, which herniates into the 3rd ventricle and causes obstructive hydrocephalus.

Subependymal Giant Cell Astrocytoma Coronal T1 C+ MR shows bilateral, asymmetric enhancing lesions at the foramina of Monro. The location is characteristic for subependymal giant cell astrocytoma. The child also had skin and other brain lesions typical of tuberous sclerosis.

Germ Cell Tumor Sagittal T1 C+ MR shows a medium-sized pineal mass with central necrosis . There is a very small, enhancing mass in the infundibular recess .

Pineoblastoma Axial NECT shows a dense lesion, correlating with the increased cellularity known to be present in pineoblastoma.

Pineoblastoma Sagittal T2 MR shows a low-signal pineal mass that obstructs the aqueduct. This lesion was dense on NECT and restricted on DWI.

Dysembryoplastic Neuroepithelial Tumor Coronal FLAIR MR in a child with seizures shows an insular-based lesion with a partial bright ring , the dysembryoplastic neuroepithelial tumor FLAIR ring sign.

Dysembryoplastic Neuroepithelial Tumor Axial T1 C+ MR shows a very low-density, nonenhancing dysembryoplastic neuroepithelial tumor .

Pleomorphic Xanthoastrocytoma Coronal T1 C+ MR shows a cortically based temporal lobe tumor. It is ill defined, invades adjacent brain tissue, enhances, and contains a rim-enhancing cyst .

Ganglioglioma Axial T1 C+ MR shows a cystic and solid thalamic mass. This lesion was heavily calcified on NECT (not shown).

Ganglioglioma Axial DWI MR in the same case shows a lack of diffusion restriction, indicating a low-grade tumor.

Ganglioglioma Axial T2 MR shows a cystic and solid thalamic ganglioglioma. The lesion was heavily calcified on NECT, but only a few calcifications are identified on T2 MR imaging.

CNS Embryonal Tumor Coronal T1WI MR shows marked expansion of the left temporal lobe by a hemorrhagic mass .

Supratentorial Ependymoma Axial T2 MR shows bithalamic involvement by homogeneous tumor, which did not enhance on T1 C+ MR (not shown).

Choroid Plexus Tumor Coronal T1 C+ MR shows a large, enhancing mass within the right lateral ventricle. The surface is frond-like, and there is no brain invasion. The appearance is typical for a choroid plexus papilloma.

Choroid Plexus Tumor Coronal T2 MR shows a large intraventricular mass with central necrosis and speckled calcification .

Choroid Plexus Tumor Axial T1 C+ MR shows a large, heterogeneously enhancing trigonal mass with brain invasion and ependymal spread .

Choroid Plexus Tumor Axial ADC map shows diffusion restriction in the same lesion.

Neurofibromatosis Type 2 Coronal TI MR shows multiple dural-based meningiomas at the vertex. There are also bilateral, asymmetric, vestibular schwannomas in this teen with neurofibromatosis type 2.

Atypical Teratoid-Rhabdoid Tumor Axial T2 MR shows a mixed-signal mass obstructing both the right and left foramina of Monro.

Atypical Teratoid-Rhabdoid Tumor Axial DWI MR in the same patient shows extensive diffusion restriction in the left frontal atypical teratoid-rhabdoid tumor.

Atypical Teratoid-Rhabdoid Tumor Axial T1 C+ MR shows a large, heterogeneously enhancing caudate mass.

Dysplastic Cerebellar Gangliocytoma Axial T1 MR shows a striated appearance of extremely low-signal dysplastic gangliocytoma, a.k.a. Lhermitte-Duclos disease. The gyri are in disarray.

Ganglioglioma Coronal FLAIR MR shows a T2-hyperintense mass located in the right fusiform gyrus in this child presenting with intractable temporal lobe seizures. Gangliogliomas are a common cause of tumor-related temporal lobe seizures.

Dysplastic Cerebellar Gangliocytoma Axial FLAIR MR shows a well-circumscribed mass of the left cerebellar hemisphere. There is persistent faint visualization of cerebellar folia within the tumor , consistent with dysplastic cerebellar gangliocytoma.

Central Neurocytoma Axial T2 MR shows a heterogeneous, partially cystic mass along the left septum pellucidum . This is a classic location of a central neurocytoma with a bubbly, cystic appearance.

Atypical Teratoid-Rhabdoid Tumor Coronal T1 C+ MR shows a heterogeneously enhancing, centrally necrotic mass in the right thalamus . This was an atypical teratoid-rhabdoid tumor at resection. These rare tumors will typically have decreased diffusion, consistent with high-grade malignancy.

Choroid Plexus Tumor Axial CT shows a calcified mass in the anterior 3rd ventricle with associated hydrocephalus . Although 3rd ventricular choroid plexus tumors are uncommon, dense calcification of an intraventricular tumor is suggestive of this entity.

Neurofibromatosis Type 2 Coronal T1 C+ MR shows a dural-based, homogeneous enhancing, extraaxial mass, consistent with a meningioma . Given the bilateral enhancing schwannomas in the internal auditory canals , this is diagnostic of neurofibromatosis type 2.

CNS Embryonal Tumor Axial T1 C+ MR shows a heterogeneously enhancing mass in the right parietal and occipital lobes, which invades the right lateral ventricle. By the 2016 WHO CNS tumor classification, PNETs are now CNS embryonal tumors. In young children, they tend to present as a large, lobar tumor.

Supratentorial Ependymoma Axial T1 C+ MR shows a heterogeneously enhancing mass in the left insula, basal ganglia, and temporal lobe. There is central necrosis . WHO 2016 CNS tumor classification has removed "multiforme" from glioblastoma.

Supratentorial Ependymoma An rCBV map from DSC perfusion shows increased perfusion of the mass, indicating a high-grade tumor consistent with glioblastoma. Note the area of increased perfusion that did not enhance on a conventional T1 C+ sequence, indicating nonenhancing tumor.

Oligodendroglioma Axial T2 MR shows a well-circumscribed, peripheral, homogeneously T2-hyperintense mass in the right frontal lobe involving both the cortex and subcortical white matter. The frontal lobe is the most common location for oligodendrogliomas.

Pleomorphic Xanthoastrocytoma Coronal T1 C+ MR shows a heterogeneous enhancing mass at the periphery of the left parietal lobe. Note enhancement of the overlying dura , which is a characteristic finding of pleomorphic xanthoastrocytoma.

Dysembryoplastic Neuroepithelial Tumor Axial T2 MR shows a "bubbly" mass centered in the left temporal lobe, particularly involving the hippocampus and medial cortex. There is minimal to no adjacent T2 hyperintensity. This bubbly appearance is a typical appearance for dysembryoplastic neuroepithelial tumors.

Pineoblastoma Coronal CT shows an iso- to hyperdense mass in the pineal region . Note the peripheral "exploded" calcification , consistent with a pineal parenchymal tumor, such as pineoblastoma in this case.

Germ Cell Tumor Sagittal T1 C+ MR shows lobular enhancing masses in both the pineal region and suprasellar cistern . Note the central dark structure , consistent with engulfed pineal calcification within a germ cell tumor, specifically germinoma.

Craniopharyngioma Sagittal CT shows an isodense mass in the suprasellar cistern with coarse calcification . Given the calcification and suggestion of cystic mass in the suprasellar cistern, craniopharyngioma is suspected.

Craniopharyngioma Sagittal T1 C+ MR shows thin enhancement of the cyst wall. Thicker, solid enhancement is seen above the flattened pituitary gland , consistent with a unilocular craniopharyngioma.

Subependymal Giant Cell Astrocytoma Axial T1 C+ MR shows a heterogeneous enhancing mass at the right foramen of Monro . Given the involvement of the septum pellucidum, a central neurocytoma can be considered. In a child with tuberous sclerosis, this is a subependymal giant cell astrocytoma.

Diffuse Low-Grade Glioma, Pediatric Coronal FLAIR MR shows a focal lesion with ill-defined borders in the left deep periventricular white matter . This is a biopsy-proven low-grade astrocytoma.

Diffuse Midline Glioma, H3 K27-Altered Axial FLAIR MR shows an expansile mass of the pons with diffuse involvement and expansion. Note the encasement of the basilar artery . This appearance is typical of diffuse intrinsic pontine glioma, which typically has poor outcome with a median survival < 1 year.

Diffuse Midline Glioma, H3 K27-Altered Axial T2 MR shows a heterogeneous, hyperintense mass expanding the right dorsal medulla and inferior cerebellar peduncle. Pedunculated focal brainstem gliomas are typically low grade with favorable outcome.

Ependymoma Axial T2 MR shows a heterogeneous mass asymmetrically located in the inferior 4th ventricle and extending out of the right foramen of Luschka with mass effect on the dorsal medulla. Extension of ependymoma through the 4th ventricle foramina is a typical finding.

Medulloblastoma Axial T2 MR shows a heterogeneous mass within and expanding the 4th ventricle. The solid component is T2 iso- to hypointense to the brain parenchyma, which is typical of high-grade neoplasms like medulloblastoma.

Medulloblastoma Axial DWI MR shows hyperintensity compared to surrounding cerebellum consistent with decreased diffusion (ADC map not shown). Medulloblastomas, like other high-grade tumors, have decreased diffusion.

Pilocytic Astrocytoma Sagittal 3D T1 C+ SPGR MR shows an enhancing mass with a large cyst , consistent with a classic cyst and mural nodule appearance. Note the effacement of the 4th ventricle , indicating a cerebellar origin.

64 KiB Raw Blame History

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Helpful Clues for Common Diagnoses

Helpful Clues for Less Common Diagnoses

Helpful Clues for Rare Diagnoses