6a.) Movement Disorders & Basal Ganglia

Question 1

What are the basal ganglia?

Answer 1

Regions of grey matter situated deep to cortex in cerebral hemispheres and in midbrain

Question 2

State the basal ganglia

Answer 2

• Caudate nucleus
• Putamen
• Globus pallidus
• Subthalamic nucleus
• Substantia nigra pars compacta

Question 3

Where is the caudate nucleus found?

Answer 3

C shaped nucleus lining the/lying lateral to the lateral ventricle

Question 4

Wher is the globus pallidus found?

Answer 4

Immediately medially (squished close together with) to the putamen

Question 5

Where is the putamen found?

Answer 5

Lateral to the globus pallidus (but also squished against it) and connected to caudate nucleus by grey matter bridges

Question 6

Where is the substantia nigra found?

Answer 6

Midbrain (mickey mouse’s eyebrows)

Question 7

Where is the subthalamic nucleus found?

Answer 7

Inferior to thalamus

Question 8

State the two regions of the substantia nigra

Answer 8

• Substantia nigra pars compacta (more dorsal)
• Substanita nigra pars reticulata (more ventral)

Question 9

Which basal ganglia is a source of dopamine in the midbrain?

Answer 9

Substantia nigra pars compacta (SNc)

Question 10

Which two basal ganglia make up the striatum?

Answer 10

Caudate and the putamen

Question 11

Which two basal ganglia make up the lentiform nucleus?

Answer 11

Putamen and globus pallidus

Question 12

Is the striatum (made up of caudate nucleus and putamen) functionally related?

Answer 12

Yes

*Caudate & putamen were originally a single structure however axons of the corticospinal system descended down and punctured through causing them to become partially separted (still connected by grey matter bridges)- this is why they are called the striatu due to their striated appearance

Question 13

Are the structures in the lentiform nucleus (putamen & globus pallidus) functionally related?

Answer 13

No, they are structurally related but NOT ANATOMICALLY related

Question 14

State the two segments of the globus pallidus

Answer 14

• Internal segment
• External segment

Question 15

Where does the striatum receive input from?

Answer 15

• Substantia nigra compacta
• Cortex

Question 16

The basal ganglia communicate with the motor cortex via the…..?

Answer 16

Thalamus

*Can think of thalamus as the bouncer/door man- to talk to the cortex you have to go through the thalamus

Question 17

The thalamus is always excitatory/inhibitory on the cortex

Which one?

Answer 17

Excitatory

Question 18

Discuss the role of the basal ganglia

Answer 18

Their role is unclear however we think that they have a role in reinforcing appropriate movements and removing inappropriate movements e.g. to pick up a cup of tea, you need to do certain movemtns such as finger flexion (finger extension wouldn’t allow you to pick up the cup). There are two pathways:

• Direct pathway: faciliates appropriate movements (excitatory to the motor cortex)
• Indirect pathway: inhibits inappropriate movements (inhibitory to the motor cortex)

Question 19

Describe the role of dopamine in the basal ganglia and their relations/functions with the motor cortex

Answer 19

Dopamine facilitates movements by exciting the motor cortex:

• Dopamine excites the direct pathway by activating excitatory D1 receptors on striatal neurones in the direct pathway
• Dopamine inhibits indirect pathway by activating inhibitory D2 receptors on striatal neurones in the indirect pathway

Question 20

What is the main role of the basal ganglia?

Answer 20

Stimulate motor cortex

Question 21

Which side of cortex do basal ganglia regulate?

Answer 21

Basal ganglia regulate the ipsilateral cortex

Question 22

Explain the pathophysiology of P

Answer 22

Chronic and progressive movement disorder caused by degeneration of dopaminergic neurones in the substantia nigra compacta; hence, the dopamine-driven facilitation of movement via both pathways (direct and indirect) is lost.

Question 23

State, and explain, 8 symptoms of Parkinsons disease

Answer 23

• Tremor: unclear mechanism but may be due to dysfunction of indirect pathway which would usually supress unwanted movements
• Rigidity: uknown mechanism, may be related to lack of coordination between agonists and antagonists
• Bradykinesia: slow movements due to loss of cortical excitation
• Hypophonia: quiet speech due to bradykinesia of layrnx and tongue
• Decreased facial movement/mask like facies: bradykinesia of face
• Micrographia: small handwriting due to bradykinesia in hands
• Dementia: possible progression of currently unknown causative agent e.g. protein aggregates
• Depression: basal ganglia also have role in cognition and mood

Question 24

What type of tremor is seen in Parkinsons?

Answer 24

Pill rolling tremor

Question 25

Describe the gate of someone with Parkinson's disease

Answer 25

Parkinsonian (also known as festinating) gait: * Slow to start * Then will shuffle * Slow/find it difficult to stop * Slow to turn * Flexion of trunk/limbs/neck

Question 26

What type of rigidity is seen in Parkinsons disease?

Answer 26

Lead pipe rigidity

Question 27

State the inheritance pattern of Huntington's chorea

Answer 27

Autosomal dominant

Question 28

At what age is Huntingtons chorea onset?

Answer 28

Early onset at about 30-50 years old

Question 29

Describe the pathophysiology of Huntington's chorea

Answer 29

Progressive degeneration of neurones in brain. The early stages are asscoiated with loss of inhibitory projections from striatumto GPe (globus pallidus external segment). This leads to hyperkinetic features because we have lost inhibition to the thalamus

Question 30

State, and explain, four symptoms of Huntington's chorea

Answer 30

* **Chorea:** dance like movements due to increased motor cortex activation * **Dystonia:** uncomfortable contractions of agonists and antagonists simultaneously leading to odd postures caused by overactivity in agonist/antagonist muslces and loss of coordination between these * **Loss of coordination:** similar to above (idea that lost coordination of agonists and antagonists) * **Cognitive decline and behavioural disturbances:** basal ganglia have role in higher metnal functions

Question 31

What is hemiballismus? (include its pathophysiology)

Answer 31

Rare movement disorder caused by damage to the subthalamic nucleus which normally inhibits the thalamus via GPi; it causes unilateral explosive (ballistic) movements

Question 32

What are ballistic movements?

Answer 32

Ballistic movement can be defined as muscle contractions that exhibit maximum velocities and accelerations over a very short period of time. They exhibit high firing rates, high force production, and very brief contraction times.

Question 33

State one possible cause of hemiballismus

Answer 33

Sub-cortical stroke (lacunar infarct)

Question 34

Does hemiballismus affect both sides?

Answer 34

No, affects one side; the side contralateral to the damaged subthalamic nucleus

Question 35

Do basal ganglia lesions affect the contralateral or ipsilateral side? Discuss.

Answer 35

* Basal ganglia regulate the ipsilateral cortex; however, the motor cortex regulates the contralteral muscles (as our motor corticospinal tracts decussate). Hence, unilateral basal ganglia lesions will affect the contralateral side * \*NOTE: unilateral basal ganglia lesions are rare; often basal ganglia lesions are bilateral due to neurodegeneration*

Question 36

Describe the anatomy of the cerebellum

Answer 36

* Two cerebellar hemispheres * Midline vermis separates the two hemispheres

Question 37

Describe which part of body each of the following parts of the cerebellum deals with: * Vermis * Hemispheres

Answer 37

* Vermis: trunk * Hemispheres: ipsilateral side of body

Question 38

Broadly, what is the role of the cerebellum in motor function?

Answer 38

*Remember, basal ganglia determine what is appropriate.* * Cerebellum looks at current position of limbs and determines an appropriate sequence to conduct motor plan in * "sequencing and coordination of movements"

Question 39

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

Answer 39

Cerebellar peduncles

Question 40

How many cerebellar peduncles are there? Name each one and state what each one connects with?

Answer 40

* Superior cerebellar peduncle: midbrain * Middle cerebellar peduncle: pons * Inferior cerebellar peduncle: medulla

Question 41

Where is the cerebellum in relation to the 4th ventricle?

Answer 41

Question 42

Explain how cerebellar lesions can cause hydrocephalus?

Answer 42

Occlude 4th ventricle- impaired drainage of CSF

Question 43

Basal ganglia and cerebellum work together; true or false?

Answer 43

True

Question 44

Why does the cerebellum need vast sensory inputs from proprioceptive neurones and sensory cortices?

Answer 44

In order to determine the best motor sequence, it needs to know the current position of the limb

Question 45

Describe the sensory inputs the cererbellum

Answer 45

* Sensory input from ipsilateral spinal cord * Sensory input from contralteral sensory cortices

Question 46

State, and explain, 6 signs of cerebellar disease *\*THINK DANISH*

Answer 46

* **Dysdiadochokinesis:***difficulty with rapidly alternating movements (presumabley due to proble with sequencing pronation-supination-pronation etc..)* * **Ataxia:** *unsteady gait as a result of difficulty sequencing lower limb muscle contractions as well as loss of unconscious proprioception from lower limbs* * **Nystagmus**: *flickering eye movements due to malcoordination of extraocular muslces* * **Intention tremor:** *tremor that worsens as target is approached* * **Slurred speech (dysarthria)**: *caused by malcoordination of laryngeal and tongue musculature* * **Hypotonia:** *unclear mechanism*

Question 47

Alongside the 6 signs of cerebellar disease, what symptoms may a patient with cerebellar disease present with?

Answer 47

Vomitting, vertigo, difficulty walking

Question 48

How may an occlusion of the three cerebellar arteries present?

Answer 48

Present similar to a cerebellar lesion: * Dysdiadochokinesis * Ataxia * Nystagmus * Intention tremor * Slurred speech (dysarthria) * Hypotonia

Question 49

What kind of reflexes may someone with a cerebellar lesion have?

Answer 49

Pendular reflexes due to hypotonia

Question 50

Describe why cerebellar lesions cause ipsilateral signs of cerebellar disease

Answer 50

* Cerebellum receives sensory input from ipsilateral spinal via dorsal spinocerebellar tract (regarding current position of limbs) * Cerebellum also receives sensory input from contralateral cortex via the cortico-pontine pathway and the pontocerebellum pathway- regarding what the motor cortex proposes to do *(allowing the cerebellum to determine an appropriate sequence)* * Cerebellum hemisphere projects back to contralateral cortex (with a proposed sequence of actions) * Motor fibres from primary motor cortex project to appropriate muscle fibres via the lateral corticospinal tract- which decussates in medulla * Since information from cerebella hemisphere has crossed midline to twice, cerebellar disease has signs on ipsilatera side

Question 51

Describe lateralisation of the cerebellum

Answer 51

Question 52

Explain, using a diagram, why basal ganglia lesions present on contralateral side

Answer 52

Idea that inputs to basal ganglia come from ipsilateral cortex and outputs from basal ganglia go to ipsilateral cortex. Then lateral cortical spinal tract decussates so symptoms are on contralateral side