2/In up to 25% of acute stroke patients, the time of last known well is well, not known. Then it’s important to use the stroke’s MR imaging features to help date its timing. Is it hyperacute? Acute? Subacute? Or are the “stroke” symptoms from a seizure from their chronic infarct?
3/Strokes evolve, or grow old, the same way people evolve or grow old. The appearance of stroke on imaging mirrors the life stages of a person—you just have to change days for a stroke into years for a person. So 15 day old stroke has features of a 15 year old person, etc.
4/Initially (less than 4-6 hrs), the only finding is restriction (brightness) on diffusion imaging (DWI). You can remember this bc in the first few months, a baby does nothing but be swaddled or restricted. So early/newly born stroke is like a baby, only restricted
5/ Remember, all diffusion does is detect how difficult it is for water to move. Anything that makes the space around water crowded and difficult to move will be bright on diffusion imaging
6/When cells run out of ATP, Na/K pump stops working & immediately water rushes in from osmotic pressure & the cells swell. The swollen cells fill the interstitium & restrict movement of water. This is why strokes are bright on DWI! This can happen early as 5 min or late as 3 hrs
7/The other sign you see in this hyperacute phase is bright signal on vessels on FLAIR from slow flow. The twisting bright vessels look like ivy vines (like the moya moya ivy sign). You can remember this bc restricted babies this young are just like potted plants or potted ivy
8/Next, at 4-6 hours, you see bright signal on FLAIR imaging. You can remember this bc after a few months, a baby starts to develop some personality or "flair". So after a few hours, the stroke gets some flair as well. So if you see FLAIR, stroke is old enough to have personality
9/Why does a stroke become FLAIR bright? It’s the first sign of blood brain breakdown. Brain realizes the stroke is a problem & opens the doors to let in leukocytes to clean up. It’s like an out-of-control party—it’s a few hours before police are called for help—same w/the brain
10/Even when the stroke has personality/FLAIR, it is still restricted/bright on DWI. You can remember this bc even after you form a personality & get some flair, you are still very restricted by your parents in your early months.
11/So early hyperacute strokes only have DWI (<4.5 hr), but late hyperacute (>4.5 hr) have both FLAIR & DWI
This DWI/FLAIR mismatch is used to date very early strokes
If FLAIR is seen, the region is old enough to have personality, but if it doesn’t, it’s still swaddling young
12/But it’s not exact. Seeing FLAIR signal is used to date a stroke as >4.5 hours, but the actual time depends on the collateral status. With poor collaterals, it can be seen as early as 3 hrs, but w/good collaterals, it could be seen as late as 6. This is important to remember
13/You can remember this by thinking of collaterals like siblings. The more siblings you have, the less attention you’re getting & so you’re probably going to develop a little on the later side & show off your personality/flair later. So lots of collaterals/siblings = late FLAIR
14/Next stage in life is when you go off to school to “enhance” your education beyond just your parents/family at home. This can be early, i.e. preschool (at like 3yrs) but usually its kindergarten (5 yrs). So most strokes start to enhance at 5 days, but can be a bit earlier
15/Now even when you are going off to school, you are still a little kid, so you are still very restricted by your parents. So at this age, a stroke is still restricted. Remember, if the enhancing infarct is DWI bright, you know it's at a young age in its schooling/enhancement
16/It’s not until you’re about 10 that your parents give you a little independence (loosen restrictions), liking letting you go away by yourself to camp. Same w/strokes, at about 10 days restricted diffusion ends—so if there’s no restriction, kid’s gotta be older than about 10
17/At about 15 is when you go through your rebellious phase. You start doing this like dyeing the tips of your hair. Same w/strokes—you start to see T1 bright signal along the tips of the cortex at about 15 days—called cortical laminar necrosis
18/What causes cortical laminar necrosis? Middle cortical layer 3 is the most metabolically active & most vulnerable to infarct first. It then spills T1 bright protein & blood products. It’s like an Oreo—there’s many layers, but it’s the middle layer that’s eaten first!
19/Enhancement ends from 15 to 40 days, very variable. It’s when you get tired of education/enhancement in life. For some it’s in their teens but others (doctors!) it’s not until later. But if you’re still in education/enhancement at age 50—it’s unusual & consider more imaging
20/In the later stages of life, you may not have the tips of your hair dyed, but you do have them colored—w/gray hair! So cortical laminar necrosis can continue—many times up to 60 days or even longer—just like you can have salt & pepper tips right up until old age.
21/Finally, the last stage is encephalomalacia—where you lose volume. And everyone knows that things start to go downhill after 40. Just like people lose volume & shrivel up as they age, so do strokes. Any stroke showing volume loss/encephalomalacia is always chronic
22/So now you know how to date a stroke on imaging, by using it’s imaging features to see what stage of life it is at.
Now when a stroke w/unknown onset comes in, you’ll be ready—right in the nick of time!
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If you don’t know the time of stroke onset, are you able to deduce it from imaging?
Here’s a thread to help you date a stroke on MRI!
2/Strokes evolve, or grow old, the same way people evolve or grow old.
The appearance of stroke on imaging mirrors the life stages of a person—you just have to change days for a stroke into years for a person
So 15 day old stroke has features of a 15 year old person, etc.
3/Initially (less than 4-6 hrs), the only finding is restriction (brightness) on diffusion imaging (DWI).
You can remember this bc in the first few months, a baby does nothing but be swaddled or restricted. So early/newly born stroke is like a baby, only restricted
1/”I LOVE spinal cord syndromes!” is a phrase that has NEVER, EVER been said by anyone.
Do you become paralyzed when you see cord signal abnormality?
Never fear—here is a thread on all the incomplete spinal cord syndromes to get you moving again!
2/Spinal cord anatomy can be complex. On imaging, we can see the ant & post nerve roots. We can also see the gray & white matter. Hidden w/in the white matter, however, are numerous efferent & afferent tracts—enough to make your head spin.
3/Lucky for you, for the incomplete cord syndromes, all you need to know is gray matter & 3 main tracts. Anterolaterally, spinothalamic tract (pain & temp). Posteriorly, dorsal columns (vibration, proprioception, & light touch), & next to it, corticospinal tracts—providing motor
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
1/Need help reading spine imaging? I’ve got your back!
It’s as easy as ABC!
A thread about an easy mnemonic you can use on every single spine study you see to increase your speed & make sure you never miss a thing!
2/A is for alignment
Look for: (1) Unstable injuries
(2) Malalignment that causes early degenerative change. Abnormal motion causes spinal elements to abnormally move against each other, like grinding teeth wears down teeth—this wears down the spine
3/B is for bones.
On CT, the most important thing to look for w/bones is fractures. You may see focal bony lesions, but you may not
On MR, it is the opposite—you can see marrow lesions easily but you may or may not see edema associated w/fractures if the fracture is subtle