Cerebellum Flashcards

1
Q

Where is the cerebellum found?

A

Posterior cranial fossa

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2
Q

What is the name given to the part of the cerebellum that lies along the midline?

A

Vermis

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3
Q

What divides the vermis and more lateral parts of the cerebellum into the anterior and posterior lobe?

A

Primary fissure

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4
Q

What is the flocculus? What does it help form?

A

Small lobe of the cerebellum at the posterior border of the middle cerebellar peduncle
Forms part of the roof of the 4th ventricle (flocculonodular lobe)

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5
Q

Describe the main blood supply to the cerebellum.

A

Supplied by 3 main arteries:

  1. Superior cerebellar artery
  2. Anterior inferior cerebellar artery
  3. Posterior inferior cerebellar artery (most common site of an infarct in the posterior circulation)
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6
Q

Describe the microanatomy of the cerebellum. (3 distinct layers; what is found in each)

A
  1. Outer molecular layer: pale with mostly axons and only a few cells
  2. Middle layer: single row of Purkinje cells
  3. Inner layer: granule layer - thick and contains vast numbers of granule cells
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7
Q

Where are the cerebellar input fibres located?

A

Middle cerebellar peduncle - input fibres from the contralateral cerebral cortex and cranial nerves
Inferior cerebellar peduncle - input fibres from the spinal cord

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8
Q

Where are the cerebellar output fibres located?

A

Superior cerebellar peduncle

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9
Q

Describe the course of the dorsal/posterior spinocerebellar tract in the body.

A

This is a column of relay neuron cell bodies within the medial gray matter within the spinal cord in layer VII, specifically between T1-L3

  • These neurons then send axons up the spinal cord
  • Project ipsilaterally to medial zones of the cerebellum through the inferior cerebellar peduncle

Carries information from proprioceptors (joints, muscle spindles, golgi apparatus)

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10
Q

Describe the course of the ventral/anterior spinocerebellar tract in the body.

A
  • Some neurons of the ventral spinocerebellar tract form synapses with neurons in layer VII of L4-S3
  • Most of these fibres cross over to the contralateral lateral funiculus via the anterior white commissure and through the superior cerebellar peduncle
  • The fibres then often cross over again within the cerebellum to end on the ipsilateral side. (globose and emboliform nuclei)
  • -> tract is sometimes termed the “double-crosser.”

Carries information about the state of reflexes in the spinal cord

(cerebellar signs are always on the same side as the lesion)

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11
Q

What are the deep cerebellar nuclei?

A

nuclei that lie in the white matter below the cortex through which all input/output to the cerebellar cortex pass
medial -> lateral: Fastigial nucleus; Globose nucleus; Emboliform nucleus; Dentate nucleus

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12
Q

Which parts of the cerebellar cortex are connected to each deep cerebellar nucleus?

A

Vermis -> Fastigial nucleus
Anterior lobe -> Globose and Emboliform nuclei
Hemispheres -> Dentate nucleus

(Flocculonodular connects to the lateral vestibular nuclei of the pons)

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13
Q

What is the role of the cerebellum in relation to movement?

A

Helps the motor cortex produce accurate and smooth movements
- modulates + refines motor cortex commands

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14
Q

What are signs of cerebellar damage?

A

Clumsiness
Abnormal fatigue
Instability
*extraocular eye msucles are particularly affected

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15
Q

What would happen if the deep nuclei were damaged?

A

Usually the cerebellum exhibits neuronal plasticity meaning that recovery after damage is possible
However, if the deep nuclei are damaged then there will be persistent disability

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16
Q

What are the functional zones of the cerebellum called and what parts of the cerebellum are they comprised of?

A
  1. Vestibulocerebellum - comprised of flocculonodular lobe, connected to the lateral vestibular nucleus
  2. Spinocerebellum - comprised of the vermis, anterior lobes, fastigial nucleus, globose and emboliform nucleus
  3. Cerebrocerebellum - comprised of the posterior lobe (cerebellar hemisphere) connected to dentate nucleus
17
Q

What is the role of the vestibulocerebellum?

A

Coordinates head + eye movements (stability of gaze)
Balance of head on the body - via the medial vestibulospinal tract
Balance of body on the ground - via the lateral vestibulospinal tract

18
Q

What is responsible for sending motor commands to the head and neck?

A

Medial longitudinal fasciculus

Medial vestibulospinal tract

19
Q

What is the role of the spinocerebellum?

A

Controls locomotion and limb coordination

Sends motor commands down the reticulospinal tract –> coordinate postural and locomotor movements

20
Q

What is the role of the cerebrocerebellum?

A

coordinates movement initiated by the motor cortex

speech, voluntary movement of head + arms, hand-eye coordination

21
Q

What part of the cerebellar cortex and which deep nuclei forms the neocerebellum?

A

Cerebellar cortex: cerebellar hemispheres

deep nucleus: dentate

22
Q

Describe the input and output of the neocerebellum.

A

Input: from the cerebral cortex via the middle cerebellar peduncle
Output: to the motor (VL) thalamus via the superior cerebellar peduncle

23
Q

What is flocculonodular syndrome and how does it often occur?

A

Little control of axial muscles - wide based ataxic gait, reeling and swaying, and there is a tendency to fall to the side of the lesion, can also have nystagmus
In severe cases –> cannot sit or stand without falling

Commonly occurs in young children with medulloblastoma in the 4th ventricle (wall)

24
Q

What is anterior lobe syndrome and how does it often occur?

A

Characterised by incoordination of the limbs
Ataxia/ataxic gait
Hypotonia
Reflexes may be depressed or pendular (UMN lesion)
It is often seen in alcoholics (malnutrition + lack fo vitamin b) and also associated with damage to the spinocerebellum

25
Q

What is neocerebellar syndrome and how does it often occur?

A

Loss of hand-eye coordination
Dysmetria (inaccuracy of reaching with intention tremor)
Dysdiadochokinesis (DDK = irregular performance of rapid, alternating movements of hands)
Kinetic tremor
Loss of good speech/slurred speech (loss of coordination of muscles involved in speech production)

Causes: stroke, tumour, trauma, degenerative diseases

26
Q

What are the signs of a cerebellar stroke?

A
  1. Headache, vertigo, nausea + vomiting
    - onset is sudden + severe
  2. Eye changes
    - usually affects on eye + contributes to vertigo
    - nystagmus
    - ptosis (drooping eyelid)
    - miosis (constricted pupil)
  3. Dysarthria + dysphagia
    - dysarthria = motor disorder of speech, weakening the muscles of the mouth, face and resp system
    - speech may be slurred, monotonous, hoarse, may be some drooling
    - dysphagia = difficulty chewing/swallowing - incoordination of muscles of throat + oesophagus
  4. Ataxia
    - loss of balance + coordination while walking
  5. Arm weakness + incoordination
    - usually only in one arm