Anatomy of basal ganglia and cerebellum

Question 1

Identify labels 1-4

Answer 1

1 = anterior lobe

2 = primary fissure

3 = posterior lobe

4 = horizontal fissure

5 = flocculus

Question 2

Idenitfy the following structures A-D

Answer 2

A = falx cerebri

B = tentorium cerbelli

C = posterior cranial fossa

D = falx cerebri

Question 3

The cerebellum is attached to the brainstem via 3 stalks termed peduncles. Name these peduncles.

Answer 3

1 = superior cerebellar peduncle

2 = middle cerebellar peduncle

3 = inferior cerebellar peduncle

Question 4

What is located in the deep grey matter of the cerebellum?

Answer 4

Deep cerebellar nuclei

Question 5

Name the 3 layers of the cerebellar cortex and identify them on this histology section

Answer 5

A = granule cell layer

B = molecular layer

C = purkinje cell layer

Question 6

Where do important afferents (to the cerebellum) arrive from and where do they enter the cerebellum?

Answer 6

Spinal cord, cerebral cortex and vestibular apparatus via the vestibular nuclei

They enter via the cerebellar peduncles and project mainly to the granule cell layer

Question 7

Where do efferent projections arise from the cerebellum?

Answer 7

From all 3 lobes of the cerebellum the only output is via the axons of Purkinje fibres which mainly synapse on neurons of the deep cerebellar nuclei and subsequently contribute to coordinating the functions of all of the motor tracts of the brainstem and spinal cord (CST, VST, RST)

Question 8

Where do most efferent axons of the deep cerebellar nuclei cross?

Answer 8

They cross the midline and synapse in the thalamus. The thalamus in turn sends fibres to the motor cortex

Question 9

What are the 3 functional divisions of the cerebellum?

Answer 9

Pontocerebellum, vesibulocerebellum, spinocerebellum

Question 10

What do the cerebellar hemispheres influence and what would a lesion here result in?

Answer 10

The ipsilateral side of the body, therefore lesions also lead to ipsilateral signs and symptoms

Question 11

What would be the clinical consequences of a unilateral hemispheric lesion of the cerebellum?

Answer 11

Distubrance of coordination in limbs which can result in intention tremor and unsteady gait in the absene of weakness or sensory loss

Question 12

What would be the clinical consequences of bilateral cerebellar dysfunction?

Answer 12

Slowed, slurred speech (dysarthria), bilateral incoordination of the arms and a staggering, wide based gait (cerebellar ataxia)

Question 13

What would be the clinical consequences of a midline lesion of the cerebellum?

Answer 13

Disturbance of postural control, patientwill tend to fall over when standing or sitting despitte preserved limb coordination

Question 14

What would be the clinical consequences of acute alcohol exposure to the cerebellum?

Answer 14

Typically results in bilateral cerebellar hemisphere dysfunction and presents with cerebellar ataxia

Question 15

What are the functions of the basal ganglia?

Answer 15

To facilitate purposeful movement, inhibit unwanted movements and also has a role in posture and muscle tone

Question 16

What are basal ganglia?

Answer 16

Masses of grey matter located at the base of each cerebellar hemisphere

Question 17

Name the 5 locations of basal ganglia

Answer 17

Putamen, substantia nigra, caudate nucleus, globus pallidus and subthalamic nucleus

Question 18

In which condition is there degeneration of dopaminergic neurons of the substantia nigra and what clinical signs would be expected as a result of this?

Answer 18

Parkinson’s disease - resting tremor, akinesia and rigidity

Question 19

How do the basal ganglia work with the motor cortex to enhance normal movement?

Answer 19

Direct pathway - enhances outflow of thalamus, enhancing the desired movement

Pyramidal neurones under voluntary control issue command to move

Question 20

How do the basal ganglia work with the motor cortex to supress unwanted movement?

Answer 20

Indirect pathway - inhibits outflow of thalamus

Question 21

What side of the body is affected in a unilateral lesion of the basal ganglia?

Answer 21

Contralateral side of the body (in contrast to cerebellar lesions)

Question 22

What motor signs do lesions of the basal ganglia cause?

Answer 22

Changes in muscle tone

Dyskinesias (abnormal, involuntary movements) including; tremor (sinusoidal movements), chorea (rapid, asymmetrical movements usually affecting distal limb musculature) & myoclonus (muscle jerks)

Lesions of the basal ganglia generally do not cause paralysis, sensory loss, loss of power, or ataxia

Question 23

What is the basic pathology behind Huntigton’s disease?

Answer 23

Progressive degeneration of the basal ganglia and cerebral cortex causing chorea and progressive dementia