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

Jul 2
1/The medulla is anything but DULL!

Does seeing an infarct in the medulla cause your heart to skip a beat?

Does medullary anatomy send you into respiratory arrest?

Never fear, here is a thread on the major medullary syndromes! Image
2/The medulla is like a toll road.

Everything going down into the cord must pass through the medulla & everything from the cord going back up to the brain must too.

That’s a lot of tracts for a very small territory. Luckily you don’t need to know every tract Image
3/Medulla has 4 main vascular territories, spread out like a fan: anteromedial, anterolateral, lateral, and posterior.

You don’t need to remember their names, just the territory they cover—and I’ll show you how Image
Read 18 tweets
Jun 30
1/Time is brain! But what time is it?

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! Image
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. Image
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 Image
Read 10 tweets
Jun 27
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! Image
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. Image
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 Image
Read 20 tweets
Jun 23
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
Jun 19
1/Feeling intoxicated trying to remember all the findings in alcohol use disorder?!

Here’s something to put you in high spirits!

This month’s @Radiographics has the important neuroimaging findings alcohol use disorder!



@cookyscan1 @RadG_editor #RGphx pubs.rsna.org/doi/10.1148/rg…Image
2/There’s an easy rhyme to help you remember the important neuroimaging findings of alcohol use disorder

“Basal ganglia is white...”

Get intrinsic T1 shortening in the BG that makes it look white as a ghost! Image
3/Next “...Cortex is bright”

Acute hyperammonemic encephalopathy cause cortical restricted diffusion, especially the insula, so that it looks as bright as a light bulb! Image
Read 8 tweets
Jun 9
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! Image
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 Image
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 Image
Read 11 tweets

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