Lea Alhilali, MD Profile picture
Feb 16, 2023 17 tweets 6 min read Read on X
1/Your baby’s all grown up! Cerebellum may mean “little cerebrum” but its jobs are anything but little

Do you know cerebellar anatomy beyond vermis & hemispheres?

Here’s a #tweetorial about the functional #anatomy of the cerebellum!
#medtwitter #neurotwitter #neurorad #meded Image
2/Cerebellum means “little cerebrum” or “little brain” bc it looks like a mini brain--a mini me to the cerebrum one might say.

However, it does not play a mini role. In fact, despite being significantly smaller than the cerebrum, it contains as many neurons as the cerebrum
3/When most people think of cerebellar function, they think of balance. And the first thing that comes to mind with cerebellar dysfunction is imbalance & dizziness.

However, the cerebellum is involved in much more, including cognitive functions
4/The cerebellum is divided into anterior & posterior lobes by the primary fissure. Then, along its undersurface is the flocculonodular lobe.

I think this anatomy looks like a dog with his tongue sticking out—the tongue being the flocculonodular lobe
5/Cerebellum has a homunculus. In fact, it has 2!

It has a primary homunculus in along the top of the anterior lobe & a secondary homunculus along the bottom of the posterior lobe—like a reflection of the primary homunculus along the bottom of the cerebellum
6/Cerebellar homunculus looks like 2 gymnasts spread over the top and bottom of the cerebellum.

You have to picture their arms going out laterally, because the homunculus of the cerebellum also spreads out from midline.
7/How to remember which way the gymnasts are facing?

Well, just like the homunculus in the cerebrum, the feet/legs hang over the edge.

So the feet of the cerebellar homunculus are dangling over the edge towards the fourth ventricle
8/Cerebellum is involved in a variety of functions. The functional regions are organized in a gradient.

Most medial regions are for sensory, slightly more lateral for motor, & finally most lateral is for cognitive functions. Bet you didn’t know your little brain was thinking!
9/This distribution actually reflects the evolution of the cerebellum.

As species evolved & the frontal cortex/cognitive functions became more pronounced, the lateral hemispheres of the cerebellum enlarged too—helping to serve these new cognitive functions
10/You can remember this distribution by thinking of the midline as home.

For sensory, you can only sense things close by (touch close by things, see things only in your line of sight).

Thus, sensory doesn’t take you far from home—you have to stay close (medial)
11/With motor functions (ie, walking, running), you can get a little bit away from home. You can run away—but you don’t get too far. There is only so far you can run!

So motor functions are slightly removed from midline
12/Finally is cognitive. With your mind, you can transport yourself anywhere—you can dream of places very far away from home.

So cognitive functions are the farthest removed from home—they are the most lateral
13/This gradient of sensorimotor function being more medial & cognitive functions being more lateral persists for the deep cerebellar nuclei.

There are three main deep nuclei: dentate, interposed (a combination of 2 small nuclei), & fastigial
14/Fastigial is the most medial. You can remember it’s mainly sensory bc fastigial sounds like fastidious, which means sensitive or picky.

Sensitive/sensory means most medial. Big role of fastigial is the sensory input from the vestibular system
15/Interposed is in between.

When you interpose yourself, you kind of insert yourself or intervene in an argument. You are interposed between the two sides.

That is exactly what the interposed nuclei are for—coordinating opposing muscles on the two sides of a motion
16/Last is the dentate nucleus. Dentate sounds like teeth & the dentate looks like teeth as well, with an irregular, almost jagged edge.

Your teeth are in your head, so the dentate is very involved in cognitive function (head = cognitive)
17/So now you know the functional anatomy of the cerebellum—the homunculus, the functional topology, and organization of the nuclei.

So when it comes to the “little brain,” your knowledge will be anything but little!

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More from @teachplaygrub

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
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

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