Movement Disorders

Question 1

What is the basal ganglia?

Answer 1

A group of structures found deep within the cerebral hemispheres, including;

• putamen
• caudate nucleus
• globus pallidus
• substantia nigra

Question 2

Identify structures 1 and 2 of the tegmentum (ventral aspect of midbrain)

Answer 2

1= Red Nucleus

2= Substantia Nigra

Question 3

What is the function of the substantia nigra?

Answer 3

Major source of dopamine

Question 4

Identify structures 1 and 2 of the cerebellum

Answer 4

Question 5

What is the normal function of the basal ganglia?

Answer 5

Takes an idea/ motor plan supplied by the primary motor cortex and determines the most appropriate set of movements

Direct and indirect pathways- direct is excitatory, indirect is inhibitory

Question 6

What is the normal function of the cerebellum?

Answer 6

Cerebellum looks at the position of the limbs (needs input from sensory proprioceptors) and determines the most appropriate sequence of movements to conduct the motor plan

Question 8

Using the pathway, explain why the direct pathway has and excitatory effect on the cortex facilitating appropriate movement

Answer 8

Starting at the putamen (ignoring Dopamine)

• The direct pathway inhibits the internal globus pallidus segment which inhibits the inhibitory effect of GABA on the Thalamus
• Inhibiting the inhibitor = excites the thalamus to release gluatmate and stimulate the cortex

Question 9

Using the pathway, explain why the indirect pathway inhibits inappropriate movement

Answer 9

Stating at the putamen (ignoring dopamine)

• The indirect pathway inhibits, the inhibition of the substantia nigra nucleus i.e. it ACTIVATES it to release Glutamate
• Glutamate release activates the substantia nigra reticulata which has an inhibitory effect on movement
• Activation of an inhibitory pathway = net inhibition

Question 10

What is major defect in Parkinson’s Disease?

Answer 10

Loss of Dopamine from the substantia nigra

Question 11

What type of dopamine receptors exist in the direct pathway?

Answer 11

D₁ receptors

Question 12

What type of dopamine receptors exist in the indirect pathway?

Answer 12

D₂ receptors

Question 13

Using the pathway, explain what the overall effect on movement is in Huntington’s Chorea

Answer 13

Huntington’s is an autosomal dominant disorder

There is degeneration of the inhibitory pathway on the GPe

Loss of inhibition of inhibitory neurones = GPe is inhibitory on the STN, you therefore get less Glutamate release and less inhibition of movement

Overall effect= loss of inhibition → hyperkinetic disorder

Question 14

Using the pathway, explain what the overall effect on movement is with Hemiballismus

Answer 14

Hemiballismus involves a defect at the STN

You therefore have less excitation of the inhibitory pathway i.e. less inhibition of the thalamus

Hemiballismus is a hyperkinetic disorder

Question 15

Using the pathway, explain why Parkinson’s is a disease of decreased movement

Answer 15

Parkinsons is a disease of less dopamine

Normally: dopamine excites the direct pathway (excitatory) and inhibitis the indirect pathway causing net excitation of the cortex

Parkinsons: less dopamine = less excitment of the direct pathway and less inhibition of the indirect pathway causing a net effect of less cortex excitation

Question 16

What are the classic signs of Parkinson’s Disease

Answer 16

• Pill Rolling Tremor
• Lead Pipe Rigity
• Bradykinesia
• Psychiatric features

Question 17

What is lead pipe rigidity?

Answer 17

Ridigity throughout the course of limb movement

Question 18

What are the classic features of cerebellar lesions

Answer 18

• Dysdiadochokinesis
• Ataxia
• Nystagmus (flickering eye movement)
• Intention tremor
• Slurred Speech
• Hypotonia

Mneumonic ‘DANISH’

Question 19

Which regions of the body do the different regions of the cerebellum control?

Answer 19

Vermis controls the trunk

Cerebral hemispheres deal with distal limbs

Question 20

Do cerebellar lesions affect the ipsialateral or contralateral sides of the body?

Answer 20

Ipsilateral