Lea Alhilali, MD Profile picture
Feb 22, 2023 16 tweets 8 min read Read on X
1/Having trouble remembering how to differentiate dementias on imaging?

Here’s a #tweetorial to show you how to remember the imaging findings in dementia & never forget!

#medtwitter #meded #neurorad #radres #dementia #alzheimers #neurotwitter #neurology #FOAMed #FOAMrad #PET
2/The most common functional imaging used in dementia is FDG PET. And the most common dementia is Alzheimer’s disease (AD).

On PET, AD demonstrates a typical Nike swoosh pattern—with decreased metabolism in the parietal & temporal regions
3/The swoosh rapidly tapers anteriorly—& so does hypometabolism in AD in the temporal lobe. It usually spares the anterior temporal poles.

So in AD look for a rapidly tapering Nike swoosh, w/hypometabolism in the parietal/temporal regions—sparing the anterior temporal pole
4/Medially, in AD, there’s involvement of the precuneus & posterior cingulate. In fact, the earliest AD findings may be in the precuneus

So medially, instead of a Nike swoosh, you see an Adidas logo—w/a wedge in the region of the precuneus widening anteriorly to the cingulate
5/So in AD, look for the sneaker signs:

—Adidas logo medially in the region of the precuneus

—Nike swoosh along the parietal & temporal regions, sparing the anterior temporal pole.

So if you see sneaker logos—it’s AD. Just call it!
6/Dementia w/Lewy Bodies (DLB) also has temporoparietal hypometabolism—but it also involves the occipital cortex—a very specific finding for DLB. DLB also extends to the ant. temporal cortex.

Together, these regions of hypometabolism look more like an L. And Lewy starts w/an L
7/Next is frontotemporal dementia. As one might expect, it has hypometabolism in…wait for it…the frontal & temporal regions. This is one for Captain Obvious. However, it is a little more complicated than that.
8/Medially, frontotemporal dementia involves the anterior cingulate gyrus. I remember this bc the involvement of the anterior cingulate gyrus makes a hook—so it looks like a lowercase letter f—and frontotemporal starts with f
9/There are also variants of frontotemporal dementia that will not show the classic frontal & temporal involvement.

First, is the frontal variant. This only involves the frontal lobe. It presents w/disinhibition as one would expect to see with frontal lobe involvement
10/Temporal variant involves temporal lobe only. Language processing is here (Wernicke’s anyone?). So this presents w/language difficulties (semantic dementia)

So you DON’T have to have BOTH frontal & temporal involvement to have frontotemporal dementia bc there are variants
11/Corticobasilar degeneration involves the sensorimotor cortex & basal ganglia.

I remember this bc CORTICObasilar goes along the CORTICOspinal tract—so it has hypometabolism at the home of the corticospinal tract, the sensorimotor cortex
12/You also see basal ganglia & thalamus hypometabolism in corticobasilar degeneration. This makes sense bc corticobasilar contains “BASilar” referring to the BASal ganglia

So the 2 regions of hypometabolism in corticobasilar degeneration are in the name—cortex & basal ganglia
13/A rare dementia is posterior cerebral atrophy (PCA). As its name implies, hypometabolism is POSTERIOR—occipital cortex & post temporal lobe

I like to call it posterior CAPE atrophy bc the distribution looks a cape—w/arms (ant temporal lobes) sticking out from under the cape
14/You might say PCA looks like Lewy Body dementia—but PCA doesn’t usuallly involve the ant temporal lobes

So the ant temp lobe involvement that gave Lewy body its L shape is cut short—making the PCA distribution look more like a c than an L

Remember C is PCA & L is Lewy body
15/Finally, vascular dementia has a variable distribution, depending on the regions infarcted (V is both for Vascular & Variable)

These patients may have wedged shaped regions of hypometabolism corresponding to cortical infarcts—remember this bc a wedge is just an inverted V.
16/So now you know the patterns of hypometabolism on PET for the major dementias

This list isn’t all inclusive & there can be variations or even mixed dementias

But hopefully this gives you a starting point you won’t soon forget!

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More from @teachplaygrub

Apr 25
1/Radiologist not answering the phone?

Just want a quick read on that stat head CT?

Here's a little help on how to do it yourself w/a thread on how to read a head CT! Image
2/In bread & butter neuroimaging—CT is the bread—maybe a little bland, not super exciting—but necessary & you can get a lot of nutrition out of it

MRI is like the butter—everyone loves it, it makes everything better, & it packs a lot of calories. Today, we start w/the bread! Image
3/The most important thing to look for on a head CT is blood.

Blood is Bright on a head CT—both start w/B.

Blood is bright bc for all it’s Nobel prizes, all CT is is a density measurement—and blood is denser (thicker) than water & denser things are brighter on CT Image
Read 20 tweets
Apr 23
1/Time to FESS up! Do you understand functional endoscopic sinus surgery (FESS)?

If you read sinus CTs, you better know what the surgeon is doing or you won’t know what you’re doing!

Here’s a thread to make sure you always make the important findings! Image
2/The first step is to insert the endoscope into the nasal cavity.

The first two structures encountered are the nasal septum and the inferior turbinate. Image
3/So on every sinus CT you read, the first question is whether there is enough room to insert the scope.

Will it go in smoothly or will it be a tight fit? Image
Read 19 tweets
Apr 21
1/Ready for a throw down?

MMA fights get a lot of attention, but MMA (middle meningeal art) & dural blood supply doesn’t get the attention it deserves.

A thread on dural vascular anatomy! Image
2/Everyone knows about the blood supply to the brain.

Circle of Willis anatomy is king and loved by everyone, while the vascular anatomy of the blood supply to the dura is the poor, wicked step child of vascular anatomy that is often forgotten Image
3/But dural vascular anatomy & supply are important, especially now that MMA embolizations are commonly for chronic recurrent subdurals.

It also important for understanding dural arteriovenous fistulas as well. Image
Read 17 tweets
Apr 16
1/ Need a global perspective on dementia?

Do you know the global cortical atrophy (GCA) score for evaluating dementia patients—or are you still gestalting volume loss???

Don’t estimate when you can calculate!

Here’s a thread of what you need to know about the GCA score! Image
2/The global cortical atrophy score calculates cortical volume loss on a scale of 0-3 in 13 different regions & ventricular dilatation

Gyri shrink down w/atrophy, the same way your cheeks shrink down with aging! Image
3/Gyri look like lips with around a mouth of sulcal space.

Without volume loss, the gyri look like big fat pursed model lips

But w/volume loss they open up like the scream w/thinning of the lips Image
Read 9 tweets
Apr 14
1/Wish that your knowledge of autoimmune encephalitis was automatic?

Do you feel in limbo about limbic encephalitis?

Do you know the patterns?

Read on for what you need to know in this month's @RadioGraphics review!



@cookyscan1 @RadG_Editor doi.org/10.1148/rg.240…Image
@RadioGraphics @cookyscan1 @RadG_Editor 2/Two pearls:
(1) Most common pattern is limbic encephalitis
(2) Small cell can cause any autoimmune pattern.

You can remember the causes by the demographic:
Young man: testicular
Older: Small cell
Woman with psychiatric symptoms (limbic): breast Image
@RadioGraphics @cookyscan1 @RadG_Editor 3/Limbic encephalitis is the most common pattern

But it has many, many different causes

Remember--limbic involvement is shaped like a question mark!

So for limbic encephalitis, the cause remains a question bc differential is so broad

Must question & clinically correlate! Image
Read 8 tweets
Apr 2
1/One important aspect to stroke care is well, ASPECTS.

It’s a simple score system—but it’s important to understand all aspects!

Read on for the latest research on ASPECTS in this month’s @theAJNR SCANtastic!

ajnr.org/content/46/3/5…Image
2/ASPECTS stands for “Alberta Stroke Program Early CT Score.”

It’s meant to replace gestalt-ing what percent of the MCA territory is infarcted.

Instead, it uses a 10-pt score to semi-quantitate the infarcted tissue in the MCA territory on non-contrast head CT Image
3/You can think of it as a score card for the MCA.

For each region of MCA territory NOT infarcted, the pt gets one point—for a highest score of 10, and lowest score of 0 Image
Read 18 tweets

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