3 - Cerebellum Flashcards by John Castillo

How is the cerebellum connected to the thalamus?

Does the cerebellum connect directly to the psinal cord?

Deep Cerebellar Nuclei

No, cerebellum does not project directly to the spinal cord

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Major cerebellar contributions to the motor system?

Clinical overview?

Balance, equilibrium, posture, muscle tone, coordination, adjustment (voluntary motor activity)

NO direct projections to the cortical spinal system

Clinical: Voluntary movement dirorders

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Cerebellum attachment to pons and rostral medulla?

3x white matter peduncles

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Most common malignant brain tumor of childhood?

Medulloblastomas

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Lobes and Key Function of Cerebellum?

Anterior - Spinocerebellar

Posterior - Corticopontocerebellar

Flocculonodular - Flocculus and Nodulus (Vestibular system)

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Clinical: Tonsillar Herniation

High ICP (bleeds, etc) can push tonsil into foramen magnum and compress the medulla

Impinge the medullary respiratory centers and reticular activating system

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What is unique about the flocculonodular lobe?

Only cerebellar lobe which does not relay through a deep cerebellar nucleus

Key part of vestibular system

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What do cerebellum have in place of gyri?

Folia (‘leaves’)

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What are the three white matter peduncles of the cerebellum?

Superior (decussates)

Middle (Association Cortex, “where do I want to be”)

Inferior (priprioceptive, “where am I”)

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What separates the posterior and flocculonodular lobe?

Posterolateral fissure

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What is the major output from the cerebellum?

Target?

Unique feature?

Superior Cerebellar Peduncle or “Brachium Conjuntivum”

Target: Red Nucleus

Feature: Decussates

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Clinical: What side will symptoms usually present with cerebellar lesions?

Ipsilateral

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Middle Cerebellar Peduncle (Brachium Pontis)

Relative Size

Target

Function

Size: Largest Cerebellar Peduncle

Target: Pons

Function: Carries afferent pontocerebellar fibers to the cerebellum

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Inforerior Cerebellar Peduncle (restiform body)

Targets

Divisions

Function

Target: Medulla/Rostral Pons

Divisions:

Restiform Body - Afferent fiber system w/3 major tracts
Juxtarestiform Body - Afferent/Efference fiber tracts

Function: Conveys some efferent information to the vestibular nuclei

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Layers of the Foilia (“tree of life”):

Granule Cell Layer

Purkinje Cell Layer

Molecular Cell Layer

Granule Cell Layer - Small/tight packed layer of excitatory interneurons
Purkinje Cell Layer - Purkinje cell bodies
Molecular Cell Layer - Majority of synapses; has:
a. Unmyelinated granule axons
b. Purkinje cell dendrites
c. Interneurons

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Neuronal Organization within Folia:

Inputs

Output

Input (2)

Mossy Fibers - Excitatory
Climbing Fibers (inferior olive only) - Excitatory

- - -

Output (1)

Purkinje Cells - Inhibitory; All output (except flocculonodular lobe) to Deep Cerebellar Nuclei

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Neuronal Organization within the Folia:

Excitatory / Inhibitory Interneurons

Excitatory: Granule Cells - Granule Cell Layer

Inhibitory:

Golgi Cells - Granule Cell layer; Feedback inhibition on granule cells
Basket and Stellate Cells - Molecular layer; Provide Lateral inhibition of adjacent purkinje cells

What is the target of inhibitory purkinje cells?

Exceptions?

Synapse with neurons in the Deep Cerebellar Nuclei

Exception: Those coming from the flocculonodular lobe

Four Deep Cerebellar Nuclei?

Majority pass through?

D E G F

Destate Nuclei

Emoboliform Nuclei

Globose Nuclei

Fastigial Nuclei

E/G = Interposed Nuclei

Majority pass through superior cerebellar peduncle and relay in thalamus before projecting to cortex

Where does the flocculonodular lobe send projections?

What is the nature of information flow?

Goes to Vestibular Nuclei; coordination of reflexive equilibrium and balance

**BYPASS DEEP CEREBELLAR NUCLEI**

Direct and reciprocal

Cerebellar Afferents: Corticopontine Fibers

Connections

Inputs

Output

Entrance*

Connection: Frontal, Temporal, Parietal, Occipital Lobes

Input: Majority from sensory and motor cortex

Output: Project to ipsilateral pontine nuclei via Internal Capsule

Entrance: Middle Cerebellar Penducle (*exclusively afferent)

Cerebellar Afferents: Spinocerebellar Fibers

Dorsal Spinocerebellar tract (LLP)
Cuneocerebellar Tract (ULP)
Ventral Spinocerebellar Tract (LS)
Rostral Spinocerebellar Tract (US)

Dorsal Spinocerebellar tract (LLP) - Lower Limb motor, limb/proprioception
Cuneocerebellar Tract (ULP) - Upper Limb motor, limb/proprioception
Ventral Spinocerebellar Tract (LS) - Lower Limb sensory, spinal/interneurons
Rostral Spinocerebellar Tract (US) - Upper Limb sensory, spinal/interneurons

Cerebellar Pathways: Inferior Olivary Nuclear Complex

Arise from contralateral inferior olivary nucleus in medulla

Decussate then enter inferior cerebellar peducle

Large excitatory input onto purkinje neurons

Deep Cerebellar Nuclei and Efferents:

Dentate Nuclei

Input

Input from lateral cerebellar hemisphere

Largest deep cerebellar nuclei

Deep Cerebellar Nuclei and Efferents: Interposed Nuclei Input

Input: Intermediate part of cerebellum

Deep Cerebellar Nuclei and Efferents: Fastigial Nuclei Input

1. From Vermis/Medial part of cerebellum 2. Small input from flocculobodular lobe

Deep Cerebellar Nuclei and Efferents: Vestibular Nuclei (medulla) Input

Input: Inferior Vermis and flocculonodular love

Lateral vs Intermediate Hemispheres of Cerebellum Function Nuclei Output

Lateral Hemisphere: Function: Skilled motor activity Nuclei: Dentate Nuclei Output: Red Nucleus, VL Thalamus, Inferior Olive - - - Intermediate Hemisphere: Function: Muscle tone, posture, coordination; **moment to moment corrections** Nuclei: Interposed Nuclei Output: Red Nucleus, VL Thalamus

Deep Cerebellar Nuclei and Functional Divisions: **Vermis vs Vestibulocerebellum** Function Nuclei Peduncle Output

Vermis: Function: Mx and adjustment of trunk posture Nuclei: Fastigial Nucleus Peduncle: Superior Output: Vestibular nuclues, Reticular Formation, VL Thalamus - - - Vestibulocerebellum: Function: Posture, balance, and **coordination of eye movements** Nuclei: Vestibular Peduncle: Inferior (input and output)

Most common infarcts of cerebellum?

PICA / SCA Vertigo, nausea, vomiting, horizontal nystagmus, lumb ataxia, unsteady gait, headache

Clinical: General ipsilateral signs of cerebellar dysfunction?

Hypotonia - reduced muscle tone Ataxia Dysmetria - over/under shooting intended movement Vertigo Falling toward **ipsilateral side**

Clinical: Cerebellar Dysfunction - Midline (Vermis) Lesion

Bilateral deficits (midline.. duh) Symptoms: Truncal Ataxia - Fall/sway toward lesion Cerebellar Dysarthria (scanning speech) Nystagmus (**especialli if flocculonodular lobe is involved)**

Clinical: Nystagmus sympton in cerebellar lesion--what is likely involved?

Flocculonodular Lobe

Clinical: Cerebellar Dysfunction - Hemisphere Lesion

Hypotonia (reduced muslce tone) Intention Tremor (under voluntary movement) Dysmetria (finger to nose) Adiadochokinesis (rapid alternating movements)

Clinical: Cerebellar Dysfunction - Cerebellar Hemorrhage

Cause: Chronic Hypertension, trauma Symptoms: Headache, nausea, comiting, ataxia, nystagmus **Large Hemorrhage:** Sixth-Nerve palsies; impaired consciousness **Severe swelling can compomise respiration**

Clinical: Cerebellar Dysfunction - Friedreiche's Ataxia

Autosomal Recessive Neurodegenerative disorder Targets **dorsal** and **lateral column** Cerebellar: Peduncle, Dorsal / Ventral Spinocerebellar tracts, Purkinje Nuerons, Clark's Nucleus Symptoms: (around 5-15) Ataxia Areflexia Impaired fine touch Vibration Progressive weakness, **Babinksi**

Clinical: Cerebellar Dysfunction - Wernick'e Encephalopathy

Cause: Cerebellum sensitive to alcohol and malnourishment, **particularly Vitamin B1** Can affect cerebellum Symptom Triad: 1. Confusion 2. Gait Ataxia 3. Nystagmus **Wernicke-Korsakoff Syndrome -- Severe Amnesia and Confabulation** **"...ALCOHOLIC" stem, think this**

Clinical: Cerebellar Dysfunction - Medulloblastoma

20% of all intracranial tumors in young children Malignant invasive cancer that begins in posterior fossa, involves **vermis** Symptoms: Truncal Ataxia, Poor coordination, Headache, Nausea, Vomiting, Tiredness, Dizziness, Diplopia, Nystagmus, Tinnitis

Cerebellar Afferents: Dorsal Spinocerebellar vs Cuneocerebellar

Dorsal: Lower Body Enters dorsal root (C8 - L2) Gracile Fasciculus Inferior Cerebellar Peduncle Ipsilateral - - - Cuneo: Upper body Enters dorsal root Cuneate Fasciculus Inferiore Cerebellar Peduncle Ipsilateral

Cerebellar Afferents: Ventral Spinocerebellar vs Rostral Spinocerebellar

Ventral: Ventral Commissure - crossing Superior Cerebellar Peduncle - crossing Double Cross = Ipsilateral - - - Rostral: Inferior Cerebellar Peduncle Ipsilateral