@TheAJNR 2/Everyone knows about the spot sign for intracranial hemorrhage
It’s when arterial contrast is seen within a hematoma on CTA, indicating active
extravasation of contrast into the hematoma.
But what if you want to know before the CTA?
@TheAJNR 3/Turns out there are non-contrast head CT signs that a hematoma may expand that perform similarly to the spot sign—and together can be very accurate.
How can you remember what they are?
@TheAJNR 4/If you are wondering if a hematoma will expand, look for the same features as the
most expansive thing in the universe: a black hole.
There are many signs, but 3 best are also seen w/black holes
@TheAJNR 5/First is the blend sign
Here, part of the hematoma has a different attenuation, meaning different age blood & thus active bleeding
It looks like a halo & black holes have halos in the event horizon!
@TheAJNR 6/Next is the black hole sign
Here, regions have very low density, indicating unclotted blood similar to water density.
If blood is still flowing like water, then hematoma may expand
Black holes obviously have black holes too!
@TheAJNR 7/Finally is the island sign
Here, there are satellite hematomas, indicating multiple regions of bleeding, increasing risk of expansion
Black holes usually have satellites orbiting around them from their gravitational pull!
@TheAJNR 8/In this month’s @theAJNR Tran et al. worked to optimize a deep learning model that could predict hematoma expansion with an AUC of 0.8!
In the future, AI may make all these signs obsolete!!
@TheAJNR 9/Now you know the imaging signs for hematoma expansion—until deep learning can assess it for you!
@TheAJNR 2/Perfusion imaging is based on one principle: When you inject CT or MR intravenous contrast, the contrast flows w/blood & so contrast can be a surrogate marker for blood.
This is key, b/c we can track contrast—it changes CT density or MR signal so we can see where it goes.
@TheAJNR 3/So if we can track how contrast gets to the tissue (by changes in CT density or MR signal), then we can approximate how BLOOD is getting to the tissue.
And how much blood is getting to the tissue is what perfusion imaging is all about.
1/Do you get a Broca’s aphasia trying remember the location of Broca's area?
Does trying to remember inferior frontal gyrus anatomy leave you speechless?
Don't be at a loss for words when it comes to Broca's area
Here’s a 🧵to help you remember the anatomy of this key region!
2/Anatomy of the inferior frontal gyrus (IFG) is best seen on the sagittal images, where it looks like the McDonald’s arches.
So, to find this area on MR, I open the sagittal images & scroll until I see the arches. When it comes to this method of finding the IFG, i’m lovin it.
3/Inferior frontal gyrus also looks like a sideways 3, if you prefer. This 3 is helpful bc the inferior frontal gyrus has 3 parts—called pars
Brain MRI anatomy is best understood in terms of both form & function.
Here’s a short thread to help you to remember important functional brain anatomy--so you truly can clinically correlate!
2/Let’s start at the top. At the vertex is the superior frontal gyrus. This is easy to remember, bc it’s at the top—and being at the top is superior. It’s like the superior king at the top of the vertex.
3/It is also easy to recognize on imaging. It looks like a big thumb pointing straight up out of the brain. I always look for that thumbs up when I am looking for the superior frontal gyrus (SFG)
If the patient is symptomatic & the greatest stenosis from the plaque is >70% of the diameter of normal distal lumen, patient will likely benefit from carotid endarterectomy
But that doesn’t mean the remaining patients are just fine!
3/Yes, carotid plaques resulting in high-grade stenosis are high risk
But assuming that stenosis is the only mechanism by which a carotid plaque is high risk is like assuming that the only way to kill someone is by strangulation.