Movement Disorders

Question 1

How do the basal ganglia and cerebellum work together to provide voluntary movement?

Answer 1

Prefrontal cortex -> idea/ motor plan

• > basal ganglia -> most appropriate set of of movements (direct pathway facilitates appropriate movements, indirect pathway inhibits inappropriate - dopamine from SNc)
• > cerebellum ( appropriate sequence

Question 2

Describe the structures signals move through between the cortex, basal ganglia and cerebellum to provide voluntary movement

Answer 2

Cortico- basal ganglia circuit:
cerebral cortex -> input nuclei (striatum, substantia nigra) + relay/ output nuclei (internal & external Globus pallidus, substantia nigra) -> pedunculopontine tegmental nuclei -> thalamus -> cerebral cortex

Cortico-cerebellum circuit:
Cerebral cortex -> pontine nuclei -> cortex + cerebellar nuclei -> thalamus -> cortex

Basal ganglia PPTg -> cerebellum

Slide 10

Question 3

Describe the direct pathway for voluntary movement

Answer 3

Cortex (glutamate) -> putamen (GABA/ substance P) -> Globus pallidus internal (GABA) -> Thalmus (glutamate) -> cortex

All glutamate signals are excitatory and all GABA are inhibitory so
Excitation - inhibition - inhibition - excitation. 2 negatives = + so net excitation (thalmus is always excitatory on the cortex) = facilitation of movement

Question 4

What is the pedunculopontine tegmental nuclei (PPTg)?

Answer 4

Connection between basal ganglia and cerebellum

Question 5

Describe the indirect pathway for voluntary movement

Answer 5

Cortex (glutamate) -> putamen (GABA/ enkephalin) -> Globus pallidus external (GABA) -> substantia nigra (glutamate) -> Globus pallidus internal (GABA) -> thalmus (glutamate) -> cortex

All GABA signals are inhibitory and all glutamate signals are excitatory so: excitation - inhibition - inhibition - excitation - inhibition - excitation
2 negatives = +
Overall one inhibition
-> inhibits inappropriate movements

Question 6

How is dopamine involved in the direct and indirect pathways?

Answer 6

Dopamine from the substantia nigra acts on the putamen and stimulates the direct pathway via D1 receptors, it inhibits the indirect pathway via D2 receptors

Overall excitation of cortex = movement

Question 7

Explain the pathophysiology behind Huntington’s chorea and the signs

Answer 7

Autosomal dominant progressive, - increased movement from too much dopamine so indirect pathway inhibited and so inappropriate movements aren’t inhibited

Signs:
Early stages associated loss inhibitory projections from striatum to GPe -> hyperkinetic features

choreiform movements (dance like), dystonia (uncomfortable contractions of agonists and antagonists simultaneously -> odd postures),
incoordination, 
psychiatric features (cognitive decline and behavioural disturbances) 

Early onset 30-50yrs

Question 8

Describe the pathophysiology behind Parkinson’s disease and the sings

Answer 8

Degeneration of dopaminergic neurones in SNc - Loss of dopamine release from substantia nigra so overall excitation of indirect pathway (inhibits movements) and inhibition of direct pathway (lack of appropriate movements)

Tremor, 
rigidity (lead pipe resistance), bradykinesia (walk slowly trouble start/ stop - festinating gait, in tongue/ larynx = hypophonia),
psychiatric features,
Decreased facial movement/ mask like,
Micrographia (small handwriting),
Dementia,
Depression

Question 9

What is hemiballismus?

Answer 9

Increased movement - damage to subthalamic nucleus -> less inhibition of thalmus

Rare disorder

Can be caused by sub-cortical stroke (lacunar infarct)

Causes unilateral explosive (ballistic) movements

Question 10

Signs of a cerebllar disease, where will be affected depending on where the lesion is in the cerebellum?

Answer 10

Can present with vomiting/ vertigo/ difficulty walking

Ipsilateral signs to lesion:
DANISH
Dysdiadochokinesis (can’t do rapid coordination)
Ataxia
Nystagmus (flickering eye movements)
Intention tremor (finger nose test, worsened as target approaches)
Slurred speech (dysarthria)
Hypotonia (pendular reflexes) 

(Occlusion of three cerebral arteries produce similar syndromes)

Hemisphere lesions = affect more distal movements
Trunks centre lesions = affect more proximal movements

Question 11

What makes up the striatum?

Answer 11

Caudate nucleus + putamen

Receives input from substantia nigra and cortex
- functionally related

Question 12

If there is a lesion in the basal ganglia which side of the body will be affected?

Answer 12

Contralateral side

(but often bilateral due to neurodegeneration)

Look at slide 6

Question 13

If there is a lesion in the cerebellum which side of the body will be affected? What could a cerebellar lesion cause?

Answer 13

Ipsilateral side

See slide 5

Can cause hydrocephalus

Question 14

What’s the vermis?

Answer 14

The middle point of the cerebellum connecting the two hemispheres

Deals with trunk, hemispheres with the ipsilateral side of the body

Question 15

What’s the full name of the substantia nigra?

Answer 15

Substantia nigra pars compacta

Source of dopamine in midbrain

Question 16

What makes up the lentiform nucleus?

Answer 16

Putamen + Globus pallidus

Anatomically related only

Question 17

Describe the cortico- basal ganglia circuit

Answer 17

(Cortico-striatal pathway) Cortex -> lentiform nucleus -> (pallidu- thalamo- cortical pathway) thalmus -> cortex

Question 18

What’s the normal function of the basal ganglia?

Answer 18

Unclear but probable role in reinforcing appropriate movements (direct pathway) and removing inappropriate movements (indirect pathway)

Question 19

How does the cerebellum communicate with the rest of the CNS?

Answer 19

Via the cerebellar peduncles

Superior CP - connects to midbrain
Middle CP - connects to pons
Inferior CP - connects to medulla

Sits above the 4th ventricle

Question 20

What are the normal functions of the cerebellar?

Answer 20

Obscure but has a clear role in sequencing and co-ordination of movements

Uses sensory information (from proprioceptive neurones/ sensory contralateral sensory cortices/ ipsilateral spinal cord) to decide the most appropriate sequence of movements to perform an action

Outputs to contralateral motor cortex