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Glossary of Neuroradiology Fellowship 1

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Differentiate demyelinating disease from small vessel ischemic changes
1) Look for Dawson's fingers. The more linear the better.

2) Look for involvement of the optic nerves, optic pathways, corpus callosum, and U-fibers.
Best sequence on conventional MR to see gray matter lesions in MS?
FLAIR
Earliest sign of MS on conventional MR?
Enhancement
Then what?
Then the high signal on FLAIR develops. Much harder to see on T2WI.
Appearance of MS lesions on T1WI
Most commonly they are isodense to white matter. But, if they are seen, it means one of 2 things. . . severe active lesion with a lot of edema or chronic burned out lesion with irreparable brain injury.
How long does enhancement last?
Days to weeks
Appearance of enhancement in MS
Start out as homogeneously enhancing lesions, and progress to ring enhancing lesions. Shape of lesion is variable though.
Best method of assessing for active disease?
LOOK FOR ENHANCING LESIONS. Lesion enhancement is much more sensitive indicator of active disease than clinical exam because most MS lesions are clinically silent.
Affects ability to detect MS lesions
Field strength


Gado dose -- Triple dose detects more lesions and increases size of enhancing areas.
Differential for bilateral thalamic pathology
Infarct


Encephalitis


Lymphoma or GBM
Infarcts specifically
Arterial versus venous
Arterial infarcts
Determine based on which part of thalamus involved
Anterior thalamus only
Think basilar tip
More of thalamus involved
Think artery of Percheron
What is artery of Percheron
Arterial variant where single artery comes out of the basilar to supply much of the thalamus. If you have that variant, and it goes, you get screwed.
Venous
Deep venous system infarcts, like internal cerebral veins or vein of Galen.
Type of encephalitis
West Nile especially known for this
Why lymphoma and GBM affect thalamus bilaterally
They go across the massa intermedia (interthalamic adhesion) or habenula (posterior to interthalamic adhesion)

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