8 Movement Disorders

Question 1

Muscle wasting can be caused by a lower motor neuron lesion. What else can cause it?

Answer 1

Disuse- can cause muscle wasting

Question 2

Basal ganglia anatomy: fill in the missing labels

Answer 2

• Globus pallidus: external and internal segment
• Caudate + putamen = striatum (functionally related)
• Putamen + globus pallidus = lentiform nucleus

Question 3

What is the role of the substantia nigra? (SNc)

Answer 3

Source of dopamine in midbrain

Question 4

How does the cerebellum connect with the rest of the CNS? (route)

Answer 4

• Superior cerebellar peduncle- connects to midbrain
• Middle cerebellar peduncle- connects to pons
• Inferior cerebellar peduncle- connects to medulla

Question 5

Explain why cerebellar lesions (eg tumours) can cause hydrocephalus.

Answer 5

Cerebellum sits above 4th ventricle

Question 6

What is the normal function of the basal ganglia thought to be?

Answer 6

Reinforcing appropriate movements and removing inappropriate ones

Question 7

Explain the role of dopamine in movement with relation to the motor cortex.

Answer 7

Dopamine- kickstarts movement

• Excites direct pathway: Stimulates D1 receptors on striatal neurones
• Inhibits indirect pathway: activates inhibitory D2 receptors on striatal neurones

Question 8

Explain why if the substantia nigra is affected unilaterally (rare) then there will be contralateral signs.

Answer 8

Basal ganglia regulate ipsilateral motor cortex BUT decussation of corticospinal tract.

Question 9

Explain how parkinson’s disease is caused with reference to the substatia nigra and dopamine.

Answer 9

Degeneration of dopaminergic neurones in SNc

Loss of dopamine driven facilitation of movement via both pathways

Question 10

What are the signs and symptoms of Parkinson’s disease?

Answer 10

1. Tremor
2. Rigidity
3. Bradykinesia
   
   1. Hypophonia (quiet speech- slow movement of larynx and tongue)
   2. Decreased facial movement/mask like faces
   3. Micographia (small handwriting)
   4. Festinating gait
4. Dementia
5. Depression

Question 11

Using the following diagram- explain why a loss of dopamine causes reduced movement in Parkinson’s disease.

Answer 11

Dopamine inhibits indirect pathway which is inhibitory so there excitatory overall

Dompanine stimulates direct pathway

So loss of dopamine means reduced excitation of the cortex causing symptoms such as bradykinesia.

Question 12

Outline the function of the cerebellum.

Answer 12

1. Sequencing and coordination of movements
   
   1. Work with basal ganglia to coordinate movement from sensory inputs

Question 13

What are the signs of cerebellar disease? (6)

Answer 13

DANISH

Dysdiodokinesia

Ataxia

Nystagmus

Intention tremor

Slurred/Staccato speech

Hypotonia

Question 14

How is Huntington’s chorea caused?

Answer 14

• Autsomal dominant
• Progressive
• Early onset (30-50 years)
• Associated- loss of inhibitory projections from striatum to globus pallidus externus
• HYPERKINETIC FEATURES
  
  • Increased movement- breaks taken off thalamus

Question 15

What are the features of Huntington’s chorea?

Answer 15

• Chorea- dance like movements- increase motor cortex activation
• Dystonia- uncomfortable contracts- agonist and antagonist contract at same time due to loss of coordination
• Loss of co-ordination
• Cognitive decline and behavioural disturbances

Question 16

What is Hemiballismus?

Answer 16

Rare disorder

Damage to subthalamic nucleus which normally inhibits thalamus via Globus Pallidus internus

(May be due to sub-cortical stroke (lacunar infarct))

Causes:

UNILATERAL EXPLOSIVE BALLISTIC MOVEMENTS

Question 17

Damage to cerebellum- are they ipsilateral or contralateral signs?

Answer 17

Ipsilateral input from spinal cord

(Contralateral input from sensory cortices)

Contralateral output to sensory cortices

Ipsilateral signs as decussation of corticospinal pathway