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Neuroscience/Clinical II S1 > L4 - Motor disorders 18/11 > Flashcards

L4 - Motor disorders 18/11 Flashcards

Understand the symptoms of major movement disorders including Parkinson’s disease, motor neuron disease, and ataxia Understand how the relevant pathology gives rise to the symptoms of these disorders Understand some of the limitations of the current biological explanations of these disorders

1
Q

What do you want the motor cortex to do?

A

Issues descending motor commands for muscle activation

Regulates activity levels in spinal cord circuits

Is where the upper motor neuron begins

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2
Q

What would you predict to be the symptoms of motor cortex damage?

A

Impaired movement, poor high level coordination, and weakness of movement of VOLUNTARY movement

Upper motor neuron syndrome

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3
Q

What is Cerebal Palsy a result of?

A

Damage to the motor cortex

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4
Q

When does the injury causing CP occur?

A

Often occurs pre or peri-natally (about 50% of cases associated with premature birth)

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5
Q

What can you expect with CP?

A

Stiffness and weakness of muscles
Poor coordination
Affects the upper motor neurons
Most common movement disorder in children, affecting 2 in every 1000 births

Can vary in range

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6
Q

What is stroke caused by?

A

Interruption of the blood supply to the cortex (often motor cortex) - if neurons aren’t getting blood this is not healthy

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7
Q

What do the symptoms of stroke depend on?

A

Extent and location of damage but usually typical of motor cortex damage

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8
Q

What is affected during stroke?

A

Upper motor neurons

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9
Q

What is FAST?

A

Face, Arms, Speech, Time.
Time is important to minimise the damage.

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10
Q

What are the two main causes of stroke?

A

Cerebral haemorrhage and Cerebral Ischaemia

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11
Q

What is cerebral Haemorrhage?

A

Often results from an aneurysm. Blood is toxic to neural tissue. Prevention of bursting - maintain low blood pressure, avoid strenuous activity.
Could be treated by clipping the blood vessel of the aneurysm

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12
Q

What is cerebral ischaemia?

A

Caused by an interruption of the blood supply to part of the brain due to blockage of a blood vessel. Can be caused by specific PLUGS (thrombus or emboli) or cardiovascular disease (atherosclerosis)
BAD because lack of oxygen and glucose leads to excitotoxicity and neuronal cell death.

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13
Q

What is Fine Motor Control ( as damage to the motor cortex)

A

Most prominent symptoms and most widespread across causes of motor cortex damage are often those relating to fine motor control

The homunculus - large representations for these activites, unlikely to be missed by damage.

Stroke - positioning of middle cerebral artery.

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14
Q

What is Upper Motor Neuron Syndrome?

A

Collection of symptoms that result from damage to UMNs (in cortex, where they originate, or their pathways - spinal cord)
Leads to lack of voluntary control of muscles via lower motor neurons, but a lack of regulation of LMNs and spinal reflex circuits.
Reflexes can thus become abnormal e.g the babinski reflex is indicative of a UMN problem.

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15
Q

Why is separating the impact of damage on cognitive and motor function difficult?

A
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16
Q

What is the basal ganglia?

A

A group of nuclei lying deep within cerebral hemispheres

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17
Q

What is the role of the basal ganglia in motor control?

A

Not fully understood but dysfunction is implicated in many disorders

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18
Q

Basal Ganglia: Disinhibitory gating of motor cortex output (Refer to diagram slide 24 on L4)

A

At rest – Inhibition is sent out of the basal ganglia, then out of the thalamus and to the cerebral cortex.

At excitation, sent out of the basal ganglia, to the thalamus where it is disinhibited and then increased at the motor cortex

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19
Q

What happens in Parkinson’s when disruption of normal basal ganglia function is implicated?

A

Involuntary tremor, slowness of movement, rigidity
Difficulty initiating voluntary movements

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20
Q

Huntingdon’s disease - what happens in disruption of normal basal ganglia function?

A

Sudden, jerky, involuntary movements with no purpose
No weakness, ataxia or sensory deficit

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21
Q

Tourette’s syndrome - what happens in disruption of normal basal ganglia function?

A

Sudden, repetitive, [involuntary] movements or utterances

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22
Q

Tardive Dyskinesia - What happens in disruption of normal basal ganglia function?

A

Repetitive, involuntary, purposeless movements
Difficulty in stopping movements

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23
Q

Hemiballismus - what happens in disruption of normal basal ganglia function?

A

Violent, involuntary movements
(ballistic movements)

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24
Q

What is the frequency of PD?

A

2nd most common neurodegenerative disease after Alzheimer’s?
Affects 3/1000 people, 1/100 in 60s, 1/25 in 80s
Around 10% of cases occur due to mutation of one of several genes.

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25
Q

Why is it useful to study genetic causes of primarily ‘non-genetic’ diseases, as these often occur in a small minority of affected people…?

A

Most (~90% or more) cases of these diseases are sporadic.

But, some (1-10%, depending on disease) are caused by mutations in a single gene

E.g. for PD, mutations at 19 gene locations have been implicated
(so not a single faulty gene, but some are more common)
^^^^^^^^^^^^^^^^^^^^^^^^
Alzheimer’s Disease
Other Dementias
Parkinson’s Disease
Motor Neuron Disease
Epilepsy
Stroke
Others!

26
Q

Genetic causes of primarily ‘non-genetic’ diseases.

A

If a gene mutation is reliably associated with the common clinical phenotype…

….it may be telling us about the downstream molecular/cellular events responsible for the condition overall

GENE –> PROTEIN –> CELL BEHAVIOUR –> CNS PATHWAY –> PD!

This can make the ‘puzzle’ more tractable, giving a clue for developing drugs which target the affected proteins, their building blocks or further downstream processes

Develop gene therapy techniques to alter the faulty genetic messages

27
Q

What is Paucity of spontaneous movement?

A

Insufficiency of movement

28
Q

What is Bradykinesia?

A

Very slow movements

29
Q

What is Akinesia?

A

No movements

30
Q

What is increased muscle tone?

A

Rigidity

31
Q

What is resting tremor?

A

@4-5HZ - PILL ROLLING

32
Q

What is a treatment of PD?

A

The drug L-dopa - huge milestone in neurology.

32
Q

What are two more symptoms of PD?

A

Shuffling gait and flexed posture, impaired balance, Mask-like expression

32
Q

REFER TO VIDEO OF BASAL GANGLIA DYSFUNCTION IN PARKINSONS.

A
33
Q

What is the limit of L-DOPA and how does PD arise*?

A

Following degeneration of nigrostriatal neurons, therefore drugs that increase dopamine availability stop being effective as there are too few functioning cells left to release dopamine properly into the striatum.

ALSO does not address the non-motor systems.

34
Q

DIAGRAM SLIDE 37

A
35
Q
A
36
Q
A
37
Q
A
38
Q
A
39
Q
A
40
Q

Deep brain stimulation for PD

A

Electrical stimulation of specific BG structures to counteract excessive inhibitory output.

41
Q

Deep brain stimulation - limitations

A

Not similarly effective for all (see optional reading, Kuusimäki et al.)

And, crucially, DBS also fails to deal with non-motor symptoms

Confounded by DBS typically being used in later stage disease

It may actually make some non-motor symptoms worse

42
Q

What is alpha-synuclein?

A

A problematic protein - like amyloid for alzheimer’s.
Misfolding and aggregation into what are called Lewy bodies, is a hallmark of PD.

This happens throughout the brain.
Dopamine neurons in substantia nigra may be particulary vulnerable.

43
Q

What is a strength of the ALPHA-S and Lewy bodies explanation?

A

May account for non-motor symptoms unlike dopamine

44
Q

Overview of motor control

A

Cortex issues commands based on integration of sensory inputs
(via upper motor neurons, UMNs)
A ‘copy’ is sent to basal ganglia and cerebellum
BG and Cb feedback to cortex (via thalamus)
The command that actually reaches lower motor neurons (LMNs) is thus continually modulated by BG and Cb

45
Q

How many CNS neurons does the Cerebellum contain?

A

Approx. half total number of CNS neurons

46
Q

What are the two types of impairment as a result of damage to the cerebellum?

A

Disturbances of posture or gait
Decomposition of movement

DESCRIBED AS ATAXIA

47
Q

Describe voluntary movements after damage to the cerebellum

A

Voluntary movements lose fluidity and appear mechanical, slow and robot-like.

48
Q

What is the tremor associated with the cerebellum damage

A

Intention tremor - unliked the PD resting tremor

49
Q

What is Dysarthria?

A

Disruption of fine control of speech. slurring
As a result of cerebellum dysfunction.

50
Q

What is ataxia?

A

A collection of disorders, unified by their symptoms, rather than their causes

51
Q

Define Ataxia?

A

Can be defined most simply as a loss of voluntary co-ordination of muscles – it is thus a neurological finding in a patient, and not a disease (though it may be caused by various diseases)

52
Q

What are the three subtypes of ataxia?

A

Focusing on types of symptom: cerebellar, sensory, vestibular

Focusing on type of cause: acquired, hereditary, late onset cerebellar dysfunction

Focussing on more detailed diagnosis: Freidrich’s ataxia, ataxia-telangiectasia, spinocerebellar ataxia, episodic ataxia, vitamin-E deficiency related.

53
Q

What is motor neuron disease?

A

Motor neuron degeneration and muscle wasting (as muscles aren’t being activated)

Degenerative, progressive, incurable. 2-5 years is more normal to live with it whilst Hawking lived with it for 55 years.

54
Q

What is the cause of motor neuron disease?

A

10% of cases have genetic component - environmental, toxic, viral and other factors implicated in the other 90% - basically unknown.

55
Q

What is motor neuron incidence?

A

Anyone, but more common in men
2.6 per 100,000 persons per year in women
3.9 per 100,000 persons per year in men

But risk strongly modulated by age

Lifetime risk is 2.1 per 1000 in women, 2.9 per 1000 in men.

About 5,000 people in the UK have it right now

Symptoms, rate of progression and life expectancy highly variable.

Typically LE is 2-5 years from diagnosis
~10% of suffers live for >10 years

56
Q

What is the misconception with ALS and MND?

A

Often, the term MND is used interchangeably with ALS (amyotrophic lateral sclerosis), but in fact ALS is one subtype of MND (the most common).

57
Q

What is the general distinction of subtypes of MND related to?

A

Effects on either upper or lower motor neurons (or both)

ALS affects both - all motor neurons, all muscles.

58
Q

What is the complication of MND that leads to death?

A

Impaired respiratory function

59
Q
A

Neuroscience/Clinical II S1 (6 decks)

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