3 - Cerebellum Flashcards
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
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
Cerebellum attachment to pons and rostral medulla?
3x white matter peduncles
Most common malignant brain tumor of childhood?
Medulloblastomas
Lobes and Key Function of Cerebellum?
Anterior - Spinocerebellar
Posterior - Corticopontocerebellar
Flocculonodular - Flocculus and Nodulus (Vestibular system)
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
What is unique about the flocculonodular lobe?
Only cerebellar lobe which does not relay through a deep cerebellar nucleus
Key part of vestibular system
What do cerebellum have in place of gyri?
Folia (‘leaves’)
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”)
What separates the posterior and flocculonodular lobe?
Posterolateral fissure
What is the major output from the cerebellum?
Target?
Unique feature?
Superior Cerebellar Peduncle or “Brachium Conjuntivum”
Target: Red Nucleus
Feature: Decussates
Clinical: What side will symptoms usually present with cerebellar lesions?
Ipsilateral
Middle Cerebellar Peduncle (Brachium Pontis)
Relative Size
Target
Function
Size: Largest Cerebellar Peduncle
Target: Pons
Function: Carries afferent pontocerebellar fibers to the cerebellum
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
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
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
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
- From Vermis/Medial part of cerebellum
- 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:
- Confusion
- Gait Ataxia
- 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
