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

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
Jun 6
1/Raise your hand if you’re confused by the BRACHIAL PLEXUS!

I could never seem to remember or understand it—but now I do & I’ll show you how!

A thread so you will never fear brachial plexus anatomy again! Image
2/Everyone has a mnemonic to remember brachial plexus anatomy.

I’m a radiologist, so I remember one about Rad Techs.

But just remembering the names & their order isn’t enough.

That is just the starting point--let’s really understand it Image
3/From the mnemonic, we start with the roots—the cervical nerve roots.

I remember which roots make up the brachial plexus by remembering that it supplies the hand.

You have 5 fingers on your hand so we start with C5 & we take 5 nerve roots (C5-T1). Image
Read 20 tweets
Jun 4
1/Having trouble remembering what to look for in vascular dementia on imaging?

Almost everyone w/memory loss has infarcts. Which are important?

The latest @theajnr SCANtastic has what you need to know:

ajnr.org/content/46/5/1…Image
@TheAJNR 2/Vascular cognitive impairment, or its most serious form, vascular dementia, used to be called multi-infarct dementia.

It was thought dementia directly resulted from brain volume loss from infarcts, w/the thought that 50-100cc of infarcted related volume loss caused dementia Image
@TheAJNR 3/But that’s now outdated. We now know vascular dementia results from diverse pathologies that all share a common vascular origin.

It’s possible to lose little volume from infarct & still result in dementia.

So if infarcts are common—which contribute to vascular dementia? Image
Read 20 tweets
Jun 2
1/Having trouble remembering how to differentiate dementias on imaging?

Is looking at dementia PET scans one of your PET peeves?

Here’s a thread to show you how to remember the imaging findings in dementia & never forget! Image
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 Image
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 Image
Read 16 tweets

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