Cerebellum Flashcards
Cerebellum
Posterior cranial fossa
Crosses midline
Vermis
Part that lies along midline
Gyri
Many narrow gyri
Mostly run medio-lateral
Primary fissure
Divides cerebellum into anterior and posterior lobe
Small third lobe
Flocculus, part of the flocculo-nodular lobe
On ventral surface of cerebellum, forming part of roof of 4th ventricle
Blood supply to cerebellum
Mainly through 3 pairs of arteries
SCA
Anterior inferior cerebellar artery
Posterior inferior cerebellar artery (PICA)
Most common site of infarct in posterior circulation
PICA
3 Layers in cerebellar cortex
Seen through Nissl or Thionin stain
Outer molecular layer
Middle layer
Inner layer
Outer molecular layer
Pale
Mostly axon + few cells
Middle layer
Single layer of Purkinje fibres
Inner layer
Granule layer
Thick
Contains vast number of granule cells
Superior cerebellar peduncle
Output fibres only
Middle cerebellar peduncle (largest)
Input fibres from (contralateral) cerebral cortex + cranial nerves
Inferior cerebellar peduncle
Input fibres from spinal cord
Dorsal (posterior) spinocerebellar tract
Ipsilateral
Passes up into brainstem + enters cerebellum in inferior cerebellar peduncle on same side
Carries info from proprioceptors
Relay cell in lamina VII
Ventral (anterior) spinocerebellar tract
Contralateral in spinal cord
Carries info about state of reflexes in spinal cord
Relay cell in lamina VII
Re-crosses in brain stem to end up on same side as it enters cord
Cerebellar signs
Always on same side as lesion
Inputs and outputs to cerebral cortex routed through the
Deep Cerebellar nuclei
Deep Cerebellar Nuclei
From M –> L
Fastigial –> Globose –> Emboliform –> Dentate
Hemispheres connect to
Dentate nuclei
Anterior lobe connects to
Globose and Emboliform
Vermis connects to
Fastigial
Flocculo-nodular lobe connect to
Lateral vestibular nuclei of pons (serves same function for F/N lobe as the deep nuclei do for other cerebellar zones)
Cerebellum + movement
Doesn’t initiate movement
Helps motor cortex produce accurate + smooth movements
–> modulates + refines motor cortex commands by using feedback from proprioceptors + other sensory organs
Cerebellar damage
Clumsiness, abnormal fatigue + instability of movement
–> extraocular eye movements particularly affected
Exhibits neuronal plasticity so partial recovery of function possible
Damage to deep nuclei
Persisting disability
Vestibulocerebellum
Flocculonodular lobe connected to lateral vestibular nucleus (in pons)
Spinocerebellum
Anterior lobe + vermis connected to fastigial, globose + emboliform nuclei
Cerebrocerebellum
Posterior lobe (cerebellar hemisphere) connected to dentate nucleus
Vestibulocerebellum function
Co-ordinates head and eye movements–> stability of gaze
Controls balance of head on body, via medial vestibulospinal tract
Helps balance body on ground, via lateral vestibulospinal tract
Vestibulocerebellum MOA
Info from vestibular apparatus about movement of head sent to vestibular nuclei in pons + medulla
Info combined with info coming from extra-ocular eye muscles + muscles in neck about head movements
Medial vestibulospinal tract
Motor commands to neck + eye muscles
Lateral vestibulospinal tract
Motor commands to legs
Spinocerebellum function
Controls locomotion + limb co-ordination
Sends motor commands down reticulospinal tracts to coordinate postural + locomotor movements
Cerebrocerebellum function
Coordinates movement initiated by motor cortex
–> includes speech, voluntary movements of hands + arms, and hand-eye coordination
Neocerebellum
Output - to motor (VL) thalamus via superior cerebral peduncle
Flocculonodular syndrome
Poor balance Disordered eye movements Nystagmus Ocular dysmetria Poor visual pursuit (tracking) Little control of axial muscles Wide based ataxic gait Tendency to fall to side of lesion Can't sit or stand without falling- severe
Floculonodular syndrome common in
Young children with medulloblastoma in 4th ventricle
Medulloblastoma
Originates 4th ventricle wall
Primitive neuroectodermal tumour
Most common malignant CNS tumour in children
Anterior lobe syndrome
Damage to spinocerebellum
Incoordination of limbs
Often seen in alcoholics due to malnutrition + lack of B vitamins
Anterior lobe damage signs
Ataxic gait
Hypotonia
Depressed or pendular reflexes (UMN lesions)
Neocerebellar syndrome
Loss of hand eye coordination
Dysmetria
Dysdiadochokinesis
Intention tremors- finger to nose)
Loss of good speech articulation (slurred speech)
–> stroke, tumour, trauma, degenerative diseases
Cerebellar stroke signs
Usually whole cerebellar cortex on one side
Headache, Vertigo, Nausea, Vomiting
Eye changes- typically one eye + contribute to vertigo
Dysarthria + Dysphagia
Ataxia
Arm weakness + incoordination- usually one arm
