8 - Movement Disorders

Question 1

What is the striatum?

Answer 1

• A nucleus made up of the caudate nucleus and putamen
• Striatum was punctured through by corticospinal tract
• Role in facilitating voluntary movement

Question 2

Where is the substantia nigra and what is the importance of this?

Answer 2

- Source of dopamine for the basal ganglia

• Degenerates in Parkinson’s disease
• Mickey Mouse’s ears (see PET scan)

Question 3

Label the following parts of the basal ganglia in this coronal section of the brain.

Answer 3

- Caudate nucleus is C-shaped like the lateral ventricles. Has a head, body, tail

- Lentiform nucleus: global pallidus medially and putamen laterally

Question 4

In general terms what is the direct and indirect pathway from the putamen (striatum) to the motor cortex and the effect of both?

Answer 4

Question 5

What is the role of the basal ganglia?

Answer 5

• Take a motor plan from the prefrontal cortex and determine the most appropriate set of movements
• Direct pathway facilitates appropriate movements and indirect pathway facilitates inappropriate movements
• Dopamine helps the pathways

Question 6

What is the role of the cerebellum in voluntary motor movement?

Answer 6

• Assess the position of the limbs via proprioceptors to determine an appropraite sequence for the motor plan

Question 7

What structures is the cerebellum closesly related to?

Answer 7

• Outgrowth of the hind brain so connected to pons and medulla via peduncles (superior, middle, inferior all corresponding to brain stem)
• Tonsillar herniation can compress medulla
• Forms roof of 4th ventricle

Question 8

Explain how the direct and indirect pathway have excitatory and inhibitory effects on the motor cortex in normal function.

Answer 8

Direct: Putamen has inhibitory effect on internal global pallidus which in turn inhibits the inhibition of GP on the thalamus so excitatory

Indirect: Putamen inhibits the global pallidus which inhibits the inhibition on the subthalamic nucleus so the substantia nigra can inhibit the thalamus so inhibitory

THALAMUS ON ITS OWN IS ALWAYS EXCITATORY

Question 9

How can dopamine affect the excitatory and inhibitory effects of the basal ganglia and the motor cortex?

Answer 9

• Dopamine excites the direct pathway and inhibits the inhibitory pathway so overall excitation

- Direct pathway: D1 Dopamine receptors

- Indirect pathway: D2 Dopamine receptors

• Different receptors in the putamen causing different responses
• Inhibition of inhibition

Question 10

What is the basal ganglia made up of?

Answer 10

• Striatum
• Pallidum (with two nuclei)
• Substantia nigra (with its two distinct parts)
• Subthalamic nucleus

Question 11

In the exam how did Steve say we could be examined on the basal ganglia?

Answer 11

• Given the pathway and then need to know where to stimulate/destroy to treat a disease or if there is a lesion at one part of the pathway what would be the pathology.
• If there is a lesion ignore everything upstream!!!
  e. g deep brain stimulation destroys subthalamic nucleus to treat Parkinson’s??

Question 12

What are the features of Huntington’s disease?

Answer 12

• Autosomal dominant with age 30-50 onset

- Hyperkinetic

• Choreiform movements: increase motor activity
• Dystonia: loss of coordination between ant/agonists
• Incoordination
• Psychiatric features
• Cognitive decline and behaviour disturbances

Question 13

What is the pathology behind Huntington’s disease and what does it cause hyperkinetic movements?

Answer 13

• Degeneration of the inhibitory neurones between striatum and globus pallidus externa so loss of inhibition on GPe!!! Less inhibition of inhibition!!!
• Less inhibition of GPi and SNr on thalamus so more excitation

Question 14

What is hemiballismus?

Answer 14

• Type of chorea involving Irregular, involuntary, large amplitude flinging rotary movements by the limbs confined to one side of the body
• Can also be due to a subcortical stroke but in HD it is due to degeneration of contralateral subthalamic nucleus so lack of inhibition on thalamus

Question 15

What is the relevance of the cerebellum being the roof of the fourth ventricle?

Answer 15

Cerebellar lesions like tumours can lead to hydrocephalus

Question 16

What is the classic triad of Parkinson’s disease and what are some other features of this disease?

Answer 16

- Pill rolling tremor

- Lead pipe rigidity

- Bradykinesia (loss of cortical excitation)

• Psychiatric features e.g depression as basal ganglia involved in mood
• Cog wheeling (rigidity on tremor)
• Festinating gait
• Hypophonia (bradykinesia of tongue and larynx)
• Mask like face (bradykinesia of facial muscles)
• Micrographia (bradykinesia of hands)
• Dementia

Question 17

What is the patholophysiology of Parkinson’s disease?

Answer 17

• Degeneration of the dopaminergic neurones in the pars compacta of the substantia nigra so there is a loss of dopamine so less excitation

Question 18

When do you get clasp knife rigidity?

Answer 18

Upper motor neurone lesion

Question 19

If you have a lesion in the basal ganglia what side of the body is affected and why?

Answer 19

- Contralateral when unilateral but usually bilateral degeneration so symmetrical

• Make sure you know the labels on the diagram (red is response from green and decussates, purple is the start)

Question 20

If you have a lesion in the cerebellum what side of the body is affected and why?

Answer 20

IPSILATERAL: two decussations

• Input from spindles to ipsilateral cerebellum
• Output from cerebellum decussates to motor cortex
• Output back from motor cortex decussates back, both corticopontine and corticospinal tracts
• Make sure you know labels and the pathways

Question 21

What makes the pons striated?

Answer 21

Axons stemming from pontine nucleus, due to synapse from corticopontine tract, and decussating over

Question 22

What are the signs of a cerebellar lesion?

Answer 22

IPSILATERAL DANISH

- Dysdiadochokinesis: R or L handed?

- Ataxia

- Nystagmus (fast phase towards lesion side due to malcoordination of extraocular muscles)

- Intention tremor: past pointing

- Slurred speech/Dysarthria: drunk speech caused by malcoordination of laryngeal and tongue

musculature

- Hypotonia: pendular reflexes

Can also have vomiting, vertigo, difficulty walking. Occlusion of the three cerebellar arteries produce similar syndromes

Question 23

What would be the difference in signs between a cerebellar lesion in the vermis and the hemispheres?

Answer 23

Vermis: affects trunk so may slump to one side on sitting

Hemispheres: affects distal limbs

Question 24

How do the basal ganglia communicate with the motor cortex?

Answer 24

• Through the thalamus
• Increased thalamic activity causes increased cortical activity

Question 25

A patient has suffered from a spinal cord injury which has led to complete bilateral destruction of the C3 and C4 cord segments, will they have upper motor neurone or lower motor neurone lesions?

Answer 25

- Both - C3 and C4 will have lower motor signs - Below C4 will have upper motor neurone signs

Question 26

A patient has suffered from a spinal cord injury which has led to transection between C3 and C4, will they have upper or motor neurone signs?

Answer 26

Only upper motor neurone signs from C4 down

Question 27

What is the differential diagnosis for this case and what population of motor neurones are affected?

Answer 27

- Motor neurone disease - Mainly lower - Slurred speech due to wasting of tongue muscles - Thought to be immune mediated, environmental toxins or due to infection with viral agents

Question 28

What makes up the striatum and the lentiform nucleus?

Answer 28

Question 29

Which side of the brain has she had neurone degeneration in?

Answer 29

- Right side substantia nigra pars compacta - Lack of dopamine so lack of excitation due to less direct pathway and more indirect pathway

Question 30

Which structures may be damaged if you were to surgically resect this tumour?

Answer 30

- Cerebellar meningioma from tentorium cerebelli - May damage internal acoustic meatus, jugular foramen, brain stem etc (google)

Question 31

Is this a upper motor neurone or lower motor neurone lesion?

Answer 31

**- Upper motor neurone** - Even if didn't say acute flaccid paralysis, to have upper and lower limbs affected need to be upper motor neurone as the bodies all arise close together in posterior limb of internal capsule. - If was lower motor neurone, would need to destroy large amounts of spinal cord to have both limbs affected

Question 32

What is in the genu of the internal capsule?

Answer 32

Upper motor neurone cell bodies to the face

Question 33

What pattern of facial weakness is likely to be present in this patient and has there been any grey matter damage?

Answer 33

- Right side of face but forehead sparing as upper motor neurone lesion (think about facial nerve last session) - Thalamus, caudate and lentiform all may have been damage as in close proximity, loss of fine motor control

Question 34

What is found in the anterior limb of the internal capsule?

Answer 34

- Corticocerebellar tracts so involved in balance and posture

Question 35

Answer 35

- Loss of dopamine decreases putamen activity - Less putamen activity means less inhibition of GPi - Increase GPi activity means inhibition of thalamus - Less thalamus activity means decreased activity of the cortex

Question 36

Answer 36

AXONS! no decussation yet, more caudal

Question 37

Where is the insular cortex and what is its function?

Answer 37

- Involved in sensory experience and emotional valence, especially taste cortex - If you remove the insular you get to the putamen of the lentiform nucleus

Question 38

If you went from lateral to medial in the basal ganglia, what are the structures?

Answer 38

- Insular cortex - Putamen (with caudate nucleus on top which might appear twice as C shaped) - Globus Pallidus - Internal capsule - Thalamus - Third ventricle

Question 39

Where is the corpus callosum on this transverse section?

Answer 39

Seen above lateral ventricles in the coronal section

Question 40

How does the internal capsule look in coronal and transver section?

Answer 40

- Diagonal in coronal - V shaped in transverse

Question 41

Label the different visible ventricles on this cross section of the brain.

Answer 41

Lateral ventricles appear twice like the caudate nucleus as C shaped

Question 42

Label the different part of the midbrain.

Answer 42

- Cerebral peduncles are the ears - Nose is where CNIII and EDW nucleus are - PAG involved in the perception of pain and contains progesterone receptors. Also involved in urinary continence - Tears are sensory pathways - Douvle chin is colliculi

Question 43

What is the function of the anterior limb?

Answer 43

Connects the cortex to the cerebellar so if you have a stroke here can get ataxia

Question 44

What is the topology of the posterior limb of the internal capsule?

Answer 44

- Motor bit at the front FAL - Sensory bit at the back FAL - Think about pure motor and pure sensory strokes

Question 45

Label the coronal section of the brain.

Answer 45

Question 46

If a patient has a complete destruction of C3 and C4, what are some functions that they will lose apart from sensory and motor losses?

Answer 46

- Loss of automatic breathing so need ventilation - Loss of sexual function - Bladder and bowel incontinence