Control Lecture 15: The Cerebellum

Question 1

What are the functions of the Cerebellum?

Answer 1

• Coordination and Balance
• Regulation of movement
• Posture and equilibrium
• Coordiantes appropriate time, force and duration of muscle contraction (synergy)
• (May store interactions for pattern and movement; also may have linguistic and creative functions)

Question 2

How is the Cerebellum attached to the brainstem?

Answer 2

Cerebellar peduncles:

Superior peduncle connects to the midbrain, middle peduncle connects to the pons and inferior pedcunle to the medulla.

Question 3

What is the gross anatomy of the Cerebellum?

Answer 3

• Consists of two hemispheres divided by the vermis
• The primary fissure divides the anterior and posterior lobes
• Flocculus and tonsils are important lobes of the cerebellum

Question 4

How is the Cerebellum functionally divided?

Answer 4

Spinocerebellum: Comprises of the vermis and adjacent region of the hemispheres. Coordinates muscles involved in posture and locomotion.

Cerebrocerebellum: (Neocerebellum) Comprises of lateral hemispheres. Has a real in coordination of distal limbs, fine and skilled targeted movement of hands.

Vestibulocerebellum: (Archicerebellum) - the most primitive. This composes of the flocculonodular node and part of the vermis. This has a role in coordination of muscles in maintaining balance and constancy of the visual field.

Question 5

What are the connections of the Vestibulocerebellum?

Answer 5

Connected to the vestibular apparatus. It uses the vestibular division of CN VIII and nuclei. This information reaches the flocculus and the nodules via the ICP. It also adjusts the muscles and eye movements in response to the vestibular stimuli via connections to the neck (LMN) and vestibulospinal pathway (LMN) again through the ICP.

Question 6

Describe the Vestibulospinal pathway.

Answer 6

1. When there is a change in balance nerves in the vestibule start firing. They send vestibulocerebellar afferents to the cerebellum via the ICP.
2. Efferent fibres are sent to adjust this information known as cerebellar vestibular efferents.
3. Vestibulospinal pathways reach LMN here in the vestibular nucleus to go to the body to maintain balance.
4. Neurones are also sent to the head to keep the gaze or move the head to help us look where we are going. Axons therefore connect with CN III, CN IV and CN VI via the medial longitudinal fasiculus.

Question 7

What is the role of the spinocerebellum?

Answer 7

• Regulates body and limb movement (more specifically those in locomotion)
• Receives unconscious proprioception
• Adjusts muscle tone and execution of movements using Golgi Tendon Organ/msucle spindles

Question 8

What is the role of the cerebrocerebellum?

Answer 8

Control of fine motor skills and target movements of limbs, particularly hands

Question 9

Describe the spinocerellum and cerebrocerebellum connections.

Answer 9

1. Proprioceptive information via the right side for example - replaying tension and tone - goes through the cerebellum using the inferior cerebellar peduncles. This is part of the spinocerelleum pathway.
   
   2. The cerebellum needs to know what the cerebrum wants to do with the muslces, bringing in the cerebrocerebellum pathway. The left side of the cerebrum will eventually control the LMN. The information from the left side of the cerebrum reaches the pons on the left and the olivary nuclei in the left. This information needs to cross the midline. This contains information on what the cerebrum wants to do. The information from the cortex crosses at the MCP and from the olivary nucleus via the ICP.
   3. The cerebellum the adjusts this information.
      The cerebrum then has the option to send information to the motor cortex (via the thalamus), reticular nuclei or red nucleus. This travels via the superior cerebellar peduncle. This information recrosses the midline.

Question 10

What is the reticulospinal pathway?

Answer 10

Extrapyrimidal pathway involved in locomotion and posture

Question 11

What pathway controls muscle tone?

Answer 11

Rubrospinal pathway

Question 12

What is Ataxia?

Answer 12

Uncoordinated movement

Question 13

What type of ataxia is commonly due to a medulloblastoma?

Answer 13

Truncal Ataxia

* Inability to stand or sit without falling over 
* Typically due to a Midline lesion affecting vestibulocerebellum - the vermis and floccus which control muscles of the trunk 
* Most commonly due to medulloblastoma - midline tumour that affects mainly children 
* Incoordination of eye movement (nystagmus) can also be seen

Question 14

What type of ataxia is commonly seen in chronic alcoholics?

Answer 14

Gait Ataxia

- Patients typically have a wide-based gait and look at their legs 
- They lose the sense of being able to know what is going on with the muscles 
- Lesion of spinocerebellum  Most common in chronic alcoholics due to degeneration of cerebellar neurons in paravermal areas

Question 15

What is the presentation of patients with a cerebrocerebellum lesion?

Answer 15

• Past-pointing or Dysmetria
• Dysdiadochokinesia
• Tremor of intent
• Adiadochokinesia
• Dysarthria

Question 16

True or False: The Cerebellum works at an unconscious contralateral level.

Answer 16

False: Unconscious ipsilateral