Lea Alhilali, MD Profile picture
Apr 14, 2025 8 tweets 4 min read Read on X
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
@RadioGraphics @cookyscan1 @RadG_Editor 4/Some other patterns to remember:

Multifocal = small cell and neuroendocrine

Remember:
Small cell gives you mets everywhere = small encephalitis everywhere

Neuroendocrine can arise from different places all over your body = encephalitis different places all over your brain Image
@RadioGraphics @cookyscan1 @RadG_Editor 5/Central/Deep gray = malignant thymoma

Remember: thymus is located central and deep in your chest, so its pattern is central and deep! Image
@RadioGraphics @cookyscan1 @RadG_Editor 6/Frontal = ovarian teratoma

Remember: ovaries are situated on the uterus right where the frontal lobes are situated on the brain! Image
@RadioGraphics @cookyscan1 @RadG_Editor 7/Brainstem = testicular

Remember: brainstem hangs down from the cerebrum like the testicles Image
@RadioGraphics @cookyscan1 @RadG_Editor This is NOT comprehensive, but a starting point, to point the direction to further workup!

Remember these patterns to get a bigger work up started

Check it out yourself:



Hopefully, the next time you see autoimmune encephalitis, you'll be on autopilot! doi.org/10.1148/rg.240…Image

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More from @teachplaygrub

Jan 27
1/The hardest thread yet! Are you up for the challenge?

How stroke perfusion imaging works!

Ever wonder why it’s Tmax & not Tmin?

Here’s what to know from @theAJNR SCANtastic!

ajnr.org/content/47/1/28Image
@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. Image
@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. Image
Read 19 tweets
Jan 19
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! Image
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. Image
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 Image
Read 13 tweets
Dec 5, 2025
1/They say form follows function!

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! Image
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. Image
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) Image
Read 12 tweets
Dec 1, 2025
1/To call it or not to call it? That is the question!

Do you feel a bit wacky & wobbly when it comes to calling normal pressure hydrocephalus on imaging?

You don’t want to overcall it, but you don’t want to miss it either!

Let me help you out w/a thread about imaging in NPH! Image
2/First, you must understand the pathophysiology of “idiopathic” or iNPH.

It was first described in 1965—but, of the original six in the 1965 cohort, 4 were found to have underlying causes for hydrocephalus.

This begs the question—when do you stop looking & call it idiopathic? Image
3/Thus, some don’t believe true idiopathic NPH exists.

After all, it’s a syndrome defined essentially only by response to a treatment w/o ever a placebo-controlled trial.

However, most believe iNPH does exist--but its underlying etiology is controversial. Several theories exist Image
Read 19 tweets
Nov 21, 2025
1/Time to go with the flow!

Hoping no one notices you don’t know the anatomy of internal carotid (ICA)?

Do you say “carotid siphon” & hope no one asks for more detail?

Here’s a thread to help you siphon off some information about ICA anatomy! Image
2/ICA is like a staircase—winding up through important anatomic regions like a staircase winding up to each floor Lobby is the neck.

First floor is skullbase/carotid canal. Next it stops at the cavernous sinus, before finally reaching the rooftop balcony of the intradural space.Image
3/ICA is divided into numbered segments based on landmarks that denote transitions on its way up the floors.

C1 is in the lobby or neck.

You can remember this b/c the number 1 looks elongated & straight like a neck. Image
Read 10 tweets
Nov 4, 2025
1/The 90s called & wants its carotid imaging back!

It’s been 30 years--are you still on NASCET?

Feeling vulnerable about plaque vulnerability?

This month’s @theAJNR SCANtastic has what you need to know about carotid plaque

ajnr.org/content/46/10/…Image
2/Everyone knows the NASCET criteria:

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! Image
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. Image
Read 13 tweets

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