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42 Cards in this Set

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What does it mean when white matter is not brighter than gray matter on MRI?
Assuming no pathology, means that you are not looking at a T1W image.
If white matter is not brighter than gray matter, what sequences are possible?
T2

Proton density


FLAIR
Now what?
Just look at CSF.

Bright = T2


Dark = FLAIR


Intermediate = PD
T1W image. Enhanced?
Look at:



Nasal mucosa


Choroid plexus


Pituitary gland


Venous structures (superior sag sinus, etc).
Brain mass with calcification
First neoplastic thought:

OLIGODENDROGLIOMA
Brain mass without high signal on T2
1) Lymphoma


2) Meningioma


3) TB


4) Sarcoid


5) Prions?
Mass lesion next to ventricle
Lymphoma
Sagittal T1W image
Immediately look at:

1) Craniovertebral junction -- look at cerebellar tonsils and for basilar invagination


2) Sellar/Parasellar region


3) Corpus callosum -- It is a white matter tract, thus should be HIGH SIGNAL. If low signal or enlarged, that is abnormal.


4) Superior sagittal sinus -- should be flow void. If you see signal intensity there, it is thrombosed.
Sagittal T1W image
Must be sure it is unenhanced in order to call SSS thrombosis. Otherwise, signal there could be related to gado.

Look at nasal mucosa and pituitary gland (anterior).
Sagittal T1W image
Know where hypothalamus (tuber cinereum) is

Know where pituitary stalk is

Know your anatomy
Corpus callosum involved
1) GBM


2) Lymphoma


3) Demyelinating dz (MS)


4) Shear injury


5) Mets (mets can go anywhere, so thats why mets are included. Its not like they have any predilection for the CC).
White matter lesion with patchy enhancement pattern
Gliomatosis cerebri


The non-enhancing areas represent low grade tumor, and the enhancing areas represent high grade tumor all mixed together
White matter region tumor
Astrocytoma


Oligodendroglioma


Demyelinating dz
Differentiating point?
Orientation of the mass. If elongated/ovoid with long axis perpendicular to lat vent (horizontally oriented), suggestive of MS.
Why is that?
Myelination occurs starting from the germinal matrix outward as the cells migrated away from it. Thus the myelin sheaths still run horizontally, and since MS lesion will have most number and degree of involvement centrally, thus tapering at its ends and creating spindle shape.
What are possible patterns of enhancement of MS?
1) Normal

2) Ring enhancing

3) Horseshoe shaped
Leptomeningeal enhancement
Infectious meningitis


Carcinomatous meningitis (ask if pt has hx of primary tumor)
Carcinomatous meningitis: Most common causes?
Leukemia/lymphoma


AdenoCa of lung and breast


Melanoma
Dural based mass with dural tail
Meningioma


DURAL METASTASIS (don't forget me)
Hyperdense mass on CT next to lateral, third or 4th ventricle which enhances and demonstrates low signal on T2W images
LYMPHOMA
What would confirm the diagnosis?
Involvement of corpus callosum and/or deep gray matter structures
DDx for this appearance?
Periventricular meningioma
Hyperdense mass on CT
Meningioma


Lymphoma
ADEM
Postvaccination demyelination


Postviral demyelination


idiopathic


Prognosis: SELF LIMITED
High T1W signal lesion
1) FAT


2) HEMORRHAGE

(EARLY SUBACUTE OR LATE SUBACUTE)


3) MELANIN


4) PROTEINACEOUS FLUID


5) CONTRAST ENHANCEMENT


6) VASCULAR THROMBOSIS


7) CALCIFICATION (RARELY)
High T1W signal lesion in frontal midline
FALX LIPOMA


LIPOMA RELATED TO AGENESIS OF CORPUS CALLOSUM


If off midline, could be hemorrhage, but should see surrounding edema, as hemorrhage would be early or late SUBACUTE blood.
High T1W signal lesion in ventricle
WHERE IN VENTRICLE?
On top
RUPTURED DERMOID
WHERE DOES DERMOID LIVE BEFORE IT RUPTURES?
IN THE MIDLINE SOMEWHERE.
Imaging difference between dermoid and lipoma?
On T1WI, lipoma will be homogeneous high signal, whereas dermoid, with all of its other soft tissue components, will be heterogeneous high and intermediate to low signal.
Multiple bilateral lesions with high signal on T1W image
RUPTURED DERMOID


HEMORRHAGE


MELANOMA METS
Mass in atria of lateral ventricle which does not obstruct, yet there is unilateral hydrocephalus. Mass is low signal on T1 and on T2 and demostrates heavy contrast enhancement.
Choroid plexus papilloma.


-- Hydro is overproduction of CSF, not obstruction.
Cystic and solid intraventricular mass with extension outside of the ventricular wall. There is associated calcification. Solid portion enhances with contrast.
EPENDYMOMA


CHOROID PLEXUS CARCINOMA, as there is extension outside the ventricular wall (CPP will not).


Intraventricular meningioma is not likely as it tends NOT to invade outside of the ventricular wall.


Not oligodendroglioma, as most occur in cortex (although this is a possibility as I have seen in Osborns book)
What would help with differentiating those two?
Age. Young patient -- CPCa.
Intraventricular tumor confined to ventricular wall (no breakthrough) with relatively low signal on T2WI. Enhances homogeneously (except possibly for some puncate areas which are very low in signal).
MENINGIOMA.



Meningiomas do not break through, remaining confined to the ventricle.

The punctate nonenhancing areas are calcifications (present 20% meningiomas)
Isodense homogeneously enhancing intraventricular mass with multiple calcifications?
GIANT CELL ASTROCYTOMA -- ALWAYS at foramen of Monro. Never include for lesion in atria, etc.
Heterogeneous intraventricular mass with associated edema and some breakthrough to adjacent parenchyma.
ASTROCYTOMA

Very heterogeneous.


NO CALCIFICATION in astrocytoma
Hyperdense mass on CT located at Formen of Monro.

DDx, next step
COLLOID CYST

LOOK FOR HYDROCEPHALUS!!!


Actual location is anterosuperior aspect of 3rd ventricle, where the neuroepithelium that generates these cysts lives.

Treatment can be performed by percutaneous aspiration, but success rate is lower for more hyperdense masses and masses with low signal on T2WI. Thus, the imaging appearance is important for management.
What is DDx for mass at Foramen of Monro?
COLLOID CYST


SUBEPENDYMAL GIANT CELL ASTROCYTOMA


CENTRAL NEUROCYTOMA


SUBEPENDYMOMA


Distinguish them by their imaging characteristics (morphology, attenuation, signal, enhancement)
Any treatment of colloid cyst needed?
Yes, as they can cause acute obstructive hydrocephalus at the level of the 3rd ventricle inlets which can result in DEATH.
Cystic intraventricular mass, but contents do not look like CSF. High signal on FLAIR and T2WI. Post gado shows a septation.
INTRAVENTRICULAR NEUROCYSTICERCOSIS
How do you know its rotary subluxation and not just normal
The patients head is facing forward, but the spine is still twisted. When in the CT scanner, the patient has to keep head straight, so if there is sublux, it cant be physiologic. OR, the patient's head is stuck turned to the side, and is unable to rotate back to midline. But after the injury has occurred, the patient will compensate at other cervical levels, usually at the cervicocranial junction, to bring the head back to the midline.