Neuro -- Supratentorial Neoplasms

Front 1

1. What are the imaging characteristics of low grade astricytoma?
2. Wha can low grade astrocytomas be confused with?
3. What is the major cause of mortality in patients with low grade astrocytomas?

Back 1

1.
- On CT, low density mass on NECT. little or no contrast enhancement.
- On MRI: well circumscribed mass lesion with low SI on T1WI and high SI on T2WI. Little or no surrounding vasogenic edema.
2. Low grade gliomas may be mistaken for an infarct. However, strokes evolve over a short period of time, while low grade tumors reman stable.
3. Major cause of mortality from a low grade astrocytoma is dedifferentiation into a high grade astrocytoma.

Front 2

1. What are the imaging findings of non aids related Cns lymphoma?
2. What are the imaging findings of aids related Cns lymphoma?
3. What are the imaging findings of secondary Cns lymphoma?
4. How is lymphoma treated?

Back 2

1.
- Non aids related lymphoma typically enhances intensely and homogeneously. It does no show areas of necrosis.
- Intrinsic hyper density due to high cytoplasmic to nuclear ratio.
- location in the deep gray nuclei or periventicular region with extension to ependymal surfaces.
- often involves the corpus callosum and mimics a butterfly glioma.
- may be solitary mass, multiple lesions, or diffusely infiltrative (indistinguishable from gliomatosis cerebri).
2. AIDS related lymphoma is centrally necrotic demonstrating rim enhancement.
3. Secondary Cns lymphoma manifests as either leptomeningeal or dural based disease. It is very rare for secondary lymphoma to present as an isolated parenchymal mass.
4. Lymphoma is very sensitive to radiation and steroids bit frequently recurs rapidly.

Front 3

1. What are the imaging findings of high grade gliomas?
2. What does the t2 hyperintensity along the tumor represent?
3. What is a gliosarcoma?

Back 3

1. Large, irregular lesions with indistinct margins that show severe surrounding edema and mass effect. Foci of hemorrhage may be seen. Calcifications are unusual. Post contrast images demonstrate heterogeneous, ring like enhancement with thick, irregular, nodular walls. The heterogeneity is due to hemorrhage, necrosis, cyst formation, and varying degrees of cellularity.
2. T2 hyperintensity may reflect a combination of edema and tumor infiltration. It typically does not enhance.
3. Rare primary bran tumor tha is composed of neoplastic glial cells mixed wit spindle cell sarcomatous elements derived from vascular elements within the GBM. On imaging, they are indistinguishable from GBM.

Front 4

What does a dual tail sign indicate?

Back 4

- most commonly associated with meningima.
- can also be seen with other extra-axial tumors such as acoustic neuroma, mets, chloroma, sarcoidosis.
- NOTE: peripherally located intraaxial lesions such as gliomas may invade the dura or incite an inflammatory response.

Front 5

1. What are the imaging findings in oligodendroglioma?

Back 5

1.
- located in the peripheral aspect of the brain. They typically begin in the hemispheric white matter and grow toward the cortex.
- calcifications is the hallmark finding.
- may contain areas of cystic degeneration.
- large peripherally located tumors may erode and remodel the calvarium.

Front 6

1. What is the ddx of cortically based mass?

Back 6

1. Ganglioglioma:
- slow growing tumor containing both neuronal and glial elements.
- Usually T1 hypo- and T2 hyperintense. MC appearance is cyst with nodule.
- Most commonly located in the temporal lobes.
- Uncommonly found in the posterior fossa (where it may mimic Lhermitte-Duclos disease).
- May erode the inner table of the skull.
2. Gangliocytoma:
- contains only neural elements
- differentiated from ganglioglioma pathologically
3. Low grade astrocytoma, especially pleomorphic xanthoastrocytoma.
4. DNET:
- favors the frontal and anterior temporal lobes.
- found in adolescents and young adults with history of long standing seizures.
- well-circumscribed often cystic and solid cortically based lesion.
- Low density on CT; may contain cysts; Ca+2 in <25% of cases.
- Low SI on T1 and high SI on T2; may have some enhancement.
- Little mass effect and no surrounding edema.
- associated with underlying cortical dysplasia.
5. Oligodendroglioma:
- larger and heterogeneous.

Front 7

1. What is glomatosis cerebri?
2. What are the imaging findings in glomatosis cerebri?
3. What s the ddx?

Back 7

1. Diffusely infiltrating tumor that does not alter the underlying architecture of the brain. Pts typically present with a slow decline in cognitive function.
2. Tumor infiltrates the brain involving multiple lobes. It crosses the midline via the corpus callosum or the interthalamic adhesion. It is very subtle on CT. Look for effacement of sulci and ventricles. Most obvious on T2WI -- infilrative T2 hyperintensity throughout the involved white matter. May have patchy subtle enhancement.
3.
- Viral encephalitis: more acute presentation, abnormal CSF.
- Demyelinating disease: ADEM or MS (may show enhancement).
- Vasculitis: usually causes multifocal areas of infarction with patchy enhancement.
- Multicentic glioma: usually not contiguous involvement of white matter. More mass effect and enhancement.
- Lymphamatosis cerebri: multifocal enhancement.

Front 8

What is a pitfall for intracortical mets?

Back 8

Intracortical mets do not elicit surrounding edema and will be missed if gad is not given. Also, there may be no edema with miliary mets.

Front 9

1. What is the ddx of periventicular mass?
2. What are important characteristics of ependymoma?
3. What are the imaging findings of ependymoma?

Back 9

1.
- Ependymoma
- Primitive neuroectodermal tumor (PNET): often more peripheral and more vasogenic edema.
- Malignant rhabdoid tumor: seen in infants and young children.
- GBM: significant vasogenic edema
- Anaplastic astrocytoma: less likely to be in proximity to a ventricular surface.
- Mets
2.
- 4-6x more common in children than adults.
- 60% are infratentorial and 40% are supratentorial.
- When supratentorial, majority of ependymomas are extraventricular in location, however, they arise close to the ventricular surface and may extend into the ventricle.
3.
- Heterogeneous mass lying close to a ventricular surface
- moderate heterogeneous enhancement.
- tumor heterogeneity may be due to necrosis, hemorrhage, and calcifications.
- may have large hemorrhagic cysts and significant surrounding edema similar to supratentorial PNET.
4. If a lesion extends into the ventricle, you should screen the spine preoperatively with contrast enhanced MRI to detect CSF spread of disease.

Front 10

1. How do you differentiate Cns lymphoma from toxoplasmosis?

Back 10

- Consider lymphoma if an enhancing lesion is intrinsically dense on ct scan or iso-/hypo intense on T2wi.
- consider toxoplasmosis if an eccentric enhancing nodule is seen within the ring enhancing lesion (eccentric target sign).
- toxo lacks subarachnoid and ependymal spread as seen with lymphoma.
- MR spect: PCNSL shows elevated choline, while toxoplasmosis shows elevated lipid and lactate.

Front 11

1. What is a PNET?
2. What are the imaging findings?

Back 11

1. AKA cerebral neuroblastoma. Large, heterogeneous Parenchymal supra tectorial mass occurring in children (may be congenital).
2. Heterogeneous mass with solid and cystic components. Cysts, calcification, and hemorrhage are common. Little edema relative to size of lesion. Hemorrhage is frequent and often occurs into tumor cysts.

Front 12

How do you differentiate arachnoid cyst from epidermoid?

Back 12

ARACHNOID CYST:
- smooth margins
- displaces adjacent structures
- Pulsation artifact is often present
- Follows CSF SI on DWI and FLAIR.

EPIDERMOID:
- Irregular margins
- Engulfs and insinuates adjacent structures
- Pulsation artifact is absent
- Hyperintense to CSF on DWI and FLAIR.

Front 13

Corpus Callosum lesions

Back 13

- GBM
- Lymphoma
- Demelinating disease
- DAI
- Machiafava-Bignami: chronic alcoholism and poor nutrition result in lesions involving predominantly the splenium of the CC. NOTE: findings of wernicke's encephalopathy are typically absent.

Front 14

Pleomorphic xanthoastrocytoma

Back 14

- supratentorial peripheral lesion
- most commonly occurs in the temporal region
- Cyst with enhancing nodule that abuts the meniinges with a dural tail.
- circumscribed with no significant edema