Lea Alhilali, MD Profile picture
Sep 10, 2022 13 tweets 6 min read Read on X
1/Don't fall for the siren song of calling all bright round objects at foramen of Monro colloid cysts. Like a true siren song, this may be a trap!
A🧵about lesions in this region that can trap you
#medtwitter #FOAMed #FOAMrad #medstudent #neurorad #radres #meded #Neurosurgery
2/Here are 3 lesions, all round and bright and in the region of the foramen of Monro. Can you tell from the images which is a colloid cyst and which may be something else? Choose which one or ones you think are a colloid cyst
Choose which one you think is a colloid cyst
4/In this case it was A. B was a tortuous basilar and C was a cavernoma of the chiasm/hypothalamus that had bled and projected into the third ventricle.
5/Many lesions may mimic a colloid cyst at the foramen of Monro. Below is a list, but it is by no means exhaustive. So with so many mimickers, how can you know when to call a colloid cyst?
6/They say location is everything--especially in colloid cysts. 99% of them are located at the foramen of Monro, so if it isn't at the foramen, be suspicious that it isn't a colloid cyst
7/Another feature that makes it special is actually how few special features it has! It should be very featureless. Many imaging findings we use to characterize lesions (enhancement, calcification, diffusion restriction), should all be absent in a colloid cyst
8/I remember this bc colloid cysts are kind of cousins to other midline congenital cysts (Rathke's cyst & Thornwaldt cyst) & they behave similarly. So if there's a feature that would be weird in a Rathke's or Thornwald cyst (calcs, enhancement), it's weird for a colloid cyst
9/But recognizing a colloid cyst isn't enough. There are important things to mention in your report. You should mention anatomic variants of the septum & fornix that could affect the surgical approach. Also mention low T2 signal, as these cysts can be more difficult to resect
10/Another important issue is where along the 3rd ventricle the cyst extends. Zone 1 is anterior to the mass intermedia, Zone 2 is behind Zone 1 but anterior to the aqueduct, and Zone 3 is behind Zone 2. Zones 1 & 3 are higher risk
11/I hate it when classifications don't go in order. I want Zone 1 to be lowest risk and Zone 3 highest. I hate it when there is a sine wave of risk in the classification
12/But you can remember this by remembering that there are openings at the anterior & posterior 3rd ventricle. So anteriorly you are at risk of obstructing the foramen & posteriorly the aqueduct. Zone 2 is just the zone sandwiched between to the two openings, so it is low risk.
13/So remember, there are mimics of colloid cysts all around. So look at the imaging findings, instead of listening to the siren song!

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More from @teachplaygrub

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
Mar 21
1/Don't fall for the siren song of calling all bright round objects at foramen of Monro colloid cysts.

Like a true siren song, this may be a TRAP!

If you hear the call of colloid—read this first!

Here's a thread about lesions here that can trap you--& how you can avoid them! Image
2/Here are 3 lesions, all round and bright and in the region of the foramen of Monro.

Can you tell from the images which is a colloid cyst and which may be something else?

Choose which one or ones you think are a colloid cyst! Image
3/In this case it was A!

B was a tortuous basilar

C was a cavernoma of the chiasm/hypothalamus that had bled and projected into the third ventricle. Image
Read 12 tweets
Mar 16
1/Remembering spinal fracture classifications is back breaking work!

A thread to review the scoring system for thoracic & lumbar fractures—“TLICS” to the cool kids! Image
2/TLICS scores a fx on (1) morphology & (2) posterior ligamentous complex injury

Let's start w/morphology

TLICS scores severity like the steps to make & eat a pizza:

Mild compression (kneading), strong compression (rolling), rotation (tossing), & distraction (tearing in) Image
3/At the most mild, w/only mild axial loading, you get the simplest fx, a compression fx—like a simple long bone fx--worth 1 pt.

This is like when you just start to kneading the dough. There's pressure, but not as much as with a rolling pin! Image
Read 13 tweets
Mar 14
1/The 90s called & wants its carotid imaging back!

It’s been 30 years--why are you still just quoting NASCET?

Do you feel vulnerable when it comes to identifying plaque vulnerability?

Here’s a thread to help you identify high risk plaques with carotid plaque imaging 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 25 tweets
Mar 12
1/Do you know all the aspects of, well, ASPECTS?

Many know the anterior circulation stroke scoring system—but posterior circulation (pc) ASPECTS is often left behind

25% of infarcts are posterior circulation

Do you know pc-ASPECTS?!

Here’s how to remember pc-ASPECTS! Image
2/Many know anterior circulation ASPECTS.

It uses a 10-point scoring system to semi-quantitation the amount of the MCA territory infarcted on non-contrast head CT

If you need a review: here’s my thread on ASPECTS: Image
3/But it’s only useful for the anterior circulation.

Posterior circulation accounts for ~25% of infarcts.

Even w/recanalization, many of these pts do poorly bc of the extent of already infarcted tissue.

So there’s a need to quantitate the amount of infarcted tissue in these ptsImage
Read 12 tweets
Mar 10
1/I always say you can tell a bad read on a spine MR if it doesn’t talk about lateral recesses.

What will I think when I see your read? Do you rate lateral recess stenosis?

Here’s a thread on lateral recess anatomy & a grading system for lateral recess stenosis Image
2/First anatomy.

Thecal sac is like a highway, carrying the nerve roots down the lumbar spine.

Lateral recess is part of the lateral lumbar canal, which is essentially the exit for spinal nerve roots to get off the thecal sac highway & head out into the rest of the body Image
3/Exits have 3 main parts.

First is the deceleration lane, where the car slows down as it starts the process of exiting.

Then there is the off ramp itself, and this leads into the service road which takes the car to the roads that it needs to get to its destination Image
Read 21 tweets

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