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BB2 > Cerebellum > Flashcards

Cerebellum Flashcards

1
Q

What does cerebellum mean?

A

Little brain

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2
Q

Where is the cerebellum found?

A

In the posterior cranial fossa

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3
Q

What is the vermis?

A

seen from above
gyri lying along the midline
many narrow gyri

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4
Q

What divides the anterior and posterior lobe of the cerebellum in a sagittal section?

A

Primary fissure (sulcus)

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5
Q

What is the 3rd lobe of the cerebellum?

A

Seen on the ventral view of the brainstem

  • between the anterior and posterior lobes
  • flocculus: part of the flocculo-nodular lobe
  • forms part of the roof of the 4th ventricle
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6
Q

How would the cerebellum look like unrolled?

A
  • anterior lobe at the top (head)
  • posterior lobe (body)
  • flocculo-nodular lobe (tail)
  • primary fissure between anterior and posterior
  • horizontal fissure in the middle of posterior lobe
  • posterior fissure between posterior lobe and flocculonodular lobe
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7
Q

Which arteries supply blood to the cerebellum?

A

Superior cerebellar
Anterior inferior cerebellar
Posterior inferior cerebellar

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8
Q

What is the most common site of an infarct in the posterior circulation?

A

PICA

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9
Q

What are the 3 main layers seen in the cerebellar cortex?

A
  • pale outer molecular layer with axons
  • middle layer with Purkinje cells
  • thick inner layer with granule cells
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10
Q

What is input and output to the cerebellum mediated by?

A

Cerebellar peduncles

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11
Q

What are the roles of the superior, middle and inferior cerebellar peduncles?

A
  • superior: output fibres
  • middle: input from contralateral cerebral cortex and cranial nerves
  • inferior: input from spinal cord
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12
Q

What is the pathway of the dorsal (posterior) spinocerebellar tract?

A

Ipsilateral
- carries afferents muscle spindles and golgi tendon organs -> passes up into brainstem -> enters cerebellum in inferior peduncle on same side

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13
Q

What is the function of the dorsal (posterior) spinocerebellar tract?

A

Carries info. from proprioceptors (joints - Golgi tendon organs and muscle spindles)

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14
Q

What is the pathway of the ventral (anterior) spinocerbellar tract?

A

Contralateral in the spinal cord

  • but then recrosses in the brainstem so ends up on the same side it enters the cord in
  • essentially information is passed to the same side in the cerebellum meaning cerebellar signs are on the same side as the lesion
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15
Q

What is the function of the ventral anterior spinocerebellar tract?

A

Carries info. about state of reflexes in the cord

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16
Q

What are the inputs and outputs to the cerebellar cortex routed by?

A

Through deep cerebellar nuclei

- lie in white matter below the cortex

17
Q

What do the cerebellar nuceli connect to?

A
  • hemispheres connect to dentate nuclei (lateral)
  • anterior lobe connects to the globose and emboliform (interposed nuclei)
  • vermis connects to the fastigial nucleus (most medial)
  • flocculo-nodular lobe connects to the lateral vestibular nuclei of the pons
18
Q

What is the role of the cerebellum in movement?

A
  • helps motor cortex produce accurate and smooth movements

- modulates and refines motor cortex commands using feedback from proprioceptors and sensory organs

19
Q

How does cerebellar damage affect movement?

A

Produces clumsiness, abnormal fatigue and instability

  • extraocular eye muscles affected
  • deep nuclei damage = persisting disability
20
Q

What are the 3 functional zones of the cerebellum?

A
  • vestibulocerebellum (flocculonodular lobe connected to lateral vestibular nucleus in the pons)
  • spinocerebellum (anterior lobe and vermis connected to fastigual, globose and emboliform nucleus)
  • cerebrocerebellum (posterior lobe/cerebellar hemisphere connected to dentate nucleus)
21
Q

What is the function of the vestibulocerebellum?

A

Co-ordinates head and eye movments ensuring stability of gaze

  • controls balance of head on body
  • helps balance of body on ground
22
Q

How does the vestibulocerebellum function?

A

vestibular apparatus sends info. about movements of head -> vestibular nuclei (in pons and medulla) -> combined with info from extra-ocular eye muscles and neck muscles -> vestibular nuclei computes muscle actions -> eyes kept balanced in head and head balanced on body and body on ground

23
Q

How are motor commands sent from the vestibulocerebellum?

A
  • to neck and eye muscles via medial longitudinal fasciculus and medial vestibulospinal tract
  • to legs via lateral vestibulospinal tract
  • motor programs stored in cortex of flocculo-nodular lobe
24
Q

What is the function of the spinocerebellum?

A

Controls locomotion and limb co-ordination

- sends motor commands down reticulospinal tracts to co-ordinate postural and locomotor movements

25
Q

What is the function of the cerebrocerebellum?

A
  • coordinates movements initiated by the motor cortex (speech, voluntary hand and arm movements, hand-eye coordination)
26
Q

What are the parts of the neocerebellum?

A
  • cortex: cerebellar hemispheres
  • deep nuclei: dentate
  • input: from cerebral cortex via the middle cerebral peduncle
  • output: to motor thalamus via superior cerebral peduncle
27
Q

What are the 3 major distinguishable cerebellar syndromes?

A
  • flocculonodular syndrome
  • anterior lobe syndrome
  • neocerebellar syndrome
28
Q

What are flocculonodular syndromes characterised by?

A
  • little control of axial muscles
  • wide based ataxic gait/swaying
  • tendency to fall to side of lesion
  • nystagmus
  • severe = cannot sit/stand without falling
29
Q

Who is flocculonodular syndrome most common in?

A

Young children with medulloblastoma in 4th ventricle

30
Q

What is medulloblastoma?

A

One of cranial primitive neuroectodermal tumours

31
Q

What are the features of anterior lobe syndrome?

A
  • correlated with damage to spinocerebellum
  • inco-ordination of the limbs
  • ataxia
  • hypotonia (generalised muscle weakness and fatigue)
  • reflexes (depressed or pendular)
  • often seen in alcoholics due to malnutrition and lack of B vitamins
32
Q

What are the features of neocerebellar syndrome?

A
  • loss of hand eye co-ordination
  • dysmetria: inaccurate reaching with intention tremor (not resting)
  • dysdiadochokinesis (irregular rapid alternating movements of hands)
  • intention tremors (when attempt to touch an object, finger to nose and heel to knee tests)
  • loss of good speech articulation (slurred) as loss of co-ordination of muscles involved
  • loss of cognitive eye movement
  • selective attention & perception
33
Q

What are the most common causes of neocerebellar syndromes?

A

stroke, tumour, trauma, degenerative diseases

34
Q

What are the 2 main signs of cerebellar stroke?

A

1) headache/vertigo/nausea/vomiting (sudden, severe, intense, persistent, debilitating)
2) eye changes (typically only affect 1 eye, contribute to vertigo, nystagmus, ptosis)
3) dysarthria & dysphagia (drooling, difficulty chewing, inco-ordination/weakening of throat and oesophageal muscles)
4) ataxia (feet wide apart, wobble, lean)
5) arm weakness and inco-ordination (clumsiness, weakness, usually in 1 arm, trembling)

35
Q

Why may alcohol intoxication mimic features of cerebellar damage?

A

Cerebellum has many GABA-ergic interneurons which are sensitive to the effects of alcohol

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