Thread by @MedinaRiojaMD

Anatomy of the cerebellum: the arbor vitae and more. 🧠🌳

🤔🧑‍🏫

#Neurology #Neurotwitter #Anatomy #Teaching #EndNeurophobia

Image from Bolk's "Das Cerebellum der Säugetiere" (1906)

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Introduction

Part of the brain in charge of integration of massive sensory and other inputs from many regions of the brain and spinal cord.

Also called "little brain" due to it's etimological origin. 🧠

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Introduction

👷‍♂️ Functions?

- Motor coordination 💪👀🤹‍♀️
- Motor planning 🤔
- Cognitive functions (visuospatial, executive, etc)
- Speech 🗣️

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Where is it⁉️

Easy, behind the brainstem.

Connected to it throught three little feet (or peduncles) 👣

Superior 🦶
Middle 🦶
Inferior 🦶

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How is it divided?

Three major ways to divide it:

Anatomical/macroscopic 🧠
Functional 🖥️
Evolutive 🦧

The last two overlap each other, therefore, let's begin with the anatomical/macroscopic.

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How is it divided?

Rotro-caudal: Anterior lobe, posterior lobe and flocculonodular lobe.
Medial-lateral: vermis-hemispheres.

🚨Lobes are divided by fissures 👇

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How is it divided?

Functional💻: vestibulocerebellum, spinocerebellum, cerebrocerebellum.

Evolutive🦧
Archi-cerebellum: antique 🪨
Paleo-cerebellum: not so antique🪵
Neo-cerebellum: new🛞

It will make more sense in a few tweets (promise)😕

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The vermis can be divided in 10 parts (👇)

Unless we are anatomists I don't it is useful or clinically relevant to learn them, but some senior residents love to ask them during rounds

(Hi all of you! I hope you are reading this). 🤪

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Before we go into details about circuits, cortex and deep nuclei...I think we should review what type of information comes IN and OUT from the cerebellum as well as HOW it goes to and from the cerebellum...

⬅️➡️↘️↙️

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Easy peasy.

Three feet (peduncles) 🦶🏻🦶🏻🦶🏻

Inferior: main pathway INTO cerebellum

Middle: bidirectional communication between pons and cerebellum

Superior: main pathway OUT the cerebellum

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🚨🚨Name of the tracts gives an idea about it's origin. Details about all the tracts that go in and out the "little brain" are outside the scope of this tweetorial.

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If we cut the cerebellum, we can appreciate more details about it's macroscopic anatomy:

- Cortex: inputs arrive straightforward to the cortex ➡️
- White matter: puts everything together ⚖️
- Deep nuclei: outputs to the rest of the CNS leave from deep nuclei ⬅️

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Deep nuclei: from lateral to medial.

-Dentate
-Emboliform + Globose = interposed
-Fastigial

"Don't Eat Greasy Foods" mnemonic some use to remember them.

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Ready for the microscopic anatomy🔬⁉️

Here are some drawings by the great #RamónYCajal to relax before we continue.

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Microscopic anatomy:

Cortex ➡️ Three layers (from exterior to interior)
- Molecular
- Purkinje
- Granular

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Microscopic anatomy:

5⃣ Types of cells distributed in the three layers:

- Molecular: stellate and basket
- Purkinje cells: dendrites of these cells are in the molecular layer
- Granular: granule and Golgi cells

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Microscopic anatomy:

2⃣ type of fibers arrive INTO the cerebellum and interact with the 5⃣ cells in the different layers.

Fibers come from tracts described in 10/

Final goal: reach molecular layer and synapse with Purkinje's cells dendrites.

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Microscopic anatomy:

2⃣ Types of fibers

- Climbing fiber: signals from inf. Olivary Nucleus ➡️reach molecular layer and synapse with Purkinje's dendrites

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Microscopic anatomy:

2⃣ Types of fibers

- Mossy fibers: come from other tracts ➡️ Synapse in Granular layer (with granular cells) ➡️ Axons from the granular layer form the parallel fibers which synapse with dendrites of Purkinje's cells at molecular layer

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Purkinje cells:

Are they importante? Yes

Really? Yes

Why? The carry signlas from the cerebellar CORTEX to the deep NUCLEI

And from there? To the rest of the CNS

Deep nuclei➡️ send signals outside the cerebellum to the rest of the CNS

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For details on clinical manifestations associated with cerebellar dysfunction I highly recomend this tweetorial (as well as part II) by the great @theneurolander
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https://twitter.com/theneurolander/status/1589350801029607424?s=20&t=_jWZDEnMhhGX4o8igc6gGg

This next paper is amazing as well.

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There is also Cognitive Dysfunction associated with Cerebellar lesions.

I think this is a great example of Brain Diaschisis or remote effects of a focal lesion on the function of
the brain.

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A few more final words:

Brain anatomy is complex, details come with time, repetition and practice. If we have the basis clear, the next steps will be much easier.

Hope you have enjoyed this brief introduction to cerebellar anatomy.

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Sources:
1.- Handb Clin Neurol. 2018;154:3-26.
doi: 10.1016/B978-0-444-63956-1.00001-1
2.- Neurol Clin. 2014 Nov;32(4):859-69.
doi: 10.1016/j.ncl.2014.07.01
3.- Handb Clin Neurol. 2018;154:85-108.
doi: 10.1016/B978-0-444-63956-1.00006-0

Sources:
4.- Blumenfeld H. Neuroanatomy Through Clinical Cases, 2010
5.- Front Syst Neurosci. 2021 Apr 9;15:646052.
doi: 10.3389/fnsys.2021.646052
6.- Board Review Series. Neuroanatomy. Fifth Ed. 2014
7.- Campbell W. DeJong’s The Neurologic Examination. Eight Edition,2019.

Sources:
8.- Mayo Clinic Neurology Board Review. 2015, Oxford Scientific press
9.- Cerebellum. 2016 Jun;15(3):369-91.
doi: 10.1007/s12311-015-0687-3
10.- Cerebellum. 2019 Oct;18(5):941-950.
doi: 10.1007/s12311-019-01060-2

Sources:
11.- Brain. 2018 Jan 1;141(1):248-270.
doi: 10.1093/brain/awx317

🤪