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Neurology > Motor Neurone disease > Flashcards

Motor Neurone disease Flashcards

1
Q

What is a neuron?

A

A nerve cell

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2
Q

What is a motor neuron?

A

A nerve CELL that forms part of a nerve that transmits information from the motor cortices in the brain to the muscles

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3
Q

Are motor neurons afferent or efferent?

A

Efferent

They take information FROM the spinal cord to the muscles

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4
Q

What 2 types of motor neuron are there? Describe the difference?

A

Upper motor neuron: from the motor cortex to the level of exit from the spinal cord

Lower motor neuron: from the spinal cord to the muscle

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5
Q

Describe the journey of a motor impulse from the motor cortex to the muscle?

Which parts of the journey involve upper and lower motor neurons?

A

UPPER MOTOR NEURON:

Motor cortex

Corona radiata

Internal capsule

Through the brainstem

Into spinal cord where it travels down in it’s tract, e.g. corticospinal tract

Synapses with a lower motor neuron

LOWER MOTOR NEURON

Leaves the spinal cord and travels to the muscle

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6
Q

Define paresis?

A

Weakness

Impaired ability to move a body part in response to will

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7
Q

Define paralysis?

A

Complete inability to move a body part in response to will

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8
Q

Define ataxia?

A

Incoordination

Willed movements are clumsy, ill-directional

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9
Q

Define involuntary movement?

A

A spontaneous movement of a body part, independently of will

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10
Q

Define apraxia?

A

Difficulty with the motor planning needed to perform tasks or movements

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11
Q

It’s a bit confusing, motor neurons are actually the cell rather than the nerve, but there is misuse of the word.

Where are the lower motor neuron CELL bodies found?

A

Either in the anterior horn of spinal cord

Or in the cranial nuclei in the brainstem

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12
Q

How is muscle tone regulated?

Draw out a diagram.

A

By muscle spindles - stretch receptors in cells

They detect stretch and send information to spinal cord via sensory neurons
There it synapses with interneuron
Which synapses with the (gamma) motor neuron which goes back to the muscle and makes it contract

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13
Q

Which motor neuron’s innervate muscle spindles?

A

Gamma motor neurons

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14
Q

What problems occur in lower motor neuron disorders?

A

Everything goes down

Muscle tone goes down
Muscle wasting
Reflexes depressed

Also, fasciculation

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15
Q

What problems occur in upper motor neuron disorders?

A

Everything goes up

Muscle tone increase
Tendon reflexes increase
Emotional lability increased

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16
Q

Which motor tract controls the muscles of the head and neck?

A

Corticobulbar tract

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17
Q

Define spasticity?

A

When certain muscles are continuously contracted.

This causes stiffness or tightness of the muscles

It can interfere with normal movement, speech, and gait.

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18
Q

Define flaccidity?

A

No muscle contraction is occurring so there is no muscle tone

This causes weakness, floppiness and paralysis

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19
Q

Why does an upper motor neuron lesion causes spasticity?

A

UMN lesion prevents impulses getting from the brain to the muscle via the cort-spin tract

BUT it will not prevent impulses getting to muscle from the reflex arc

ALSO since the cort-spin tract is not working, it is not able to inhibit excess reflexes caused by the reflex arc

SO you get continual muscle contraction caused by the now uninhibited reflex arc = spasticity

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20
Q

Why does a lower motor neuron lesion cause flaccidity?

A

LMN lesion prevents impulses getting from the brain to the muscle via the cort-spin tract

AND it prevents impulses getting to the muscle from the reflex arc, since the LMN is part of the reflex arc

SO the muscles receive no impulses at all, no muscle contraction = flaccidity

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21
Q

What causes spasticity:

  • an UMN lesion
  • or an LMN lesion?
A

An upper motor neuron lesion

22
Q

What causes flaccidity:

  • an UMN lesion
  • or an LMN lesion?
A

A lower motor neuron lesion

23
Q

What 2 roles does the corticospinal tract have?

A

Transmission of impulses from the motor cortex to the muscles

Inhibition of excessive reflexes generated by the reflex arc

24
Q

Describe a standard, basic reflex arc?

A

Receptor generates impulse, after finger touches hot pan

Impulse travels to sensory nerve, to relay nerve, to motor nerve

Impulse reaches effector muscle causes a contraction so finger moves away

BYPASSES THE BRAIN

25
Q

What does ALS stand for?

What’s another name for it?

A

Amyotrophic lateral sclerosis

The American name for motor neurone disease

26
Q

What is motor neuron disease?

A

Degeneration of motor neurons in the motor cortex and spinal cord

Affects both upper and lower motor neurons

Technically, it is a general term that refers to a group of conditions affecting the motor neurons

27
Q

Which neurons, upper or lower, are affected in motor neuron disease?

28
Q

Name some diseases that come under the umbrella of motor neuron disease?

A

ALS: amyotrophic lateral sclerosis

Progressive bulbar palsy

Spinal muscular atrophy
Kennedy’s disease

29
Q

Which is the most common motor neuron disease?

A

ALS
Amyotrophic lateral sclerosis

(which we just call motor neuron disease in Britain)

30
Q

Which gender are more commonly affected by motor neuron disease?

A

Males slightly more that females

31
Q

What is the average age of onset of motor neuron disease?

A

Middle age to around the 60s

32
Q

What causes motor neurone disease?

A

Unknown! But there are several factors that are thought to contribute:

Premature ageing of motor cells
Viral infection
Chemicals
Biochemistry
Genetic
33
Q

Explain the theory of how premature ageing can contribute to motor neuron disease developing?

A

Premature ageing destroys some motor cells

This puts more pressure on the remaining motor cells to perform all the original functions

This extra pressure damages the remaining cells

34
Q

What problems associated with biochemistry are thought to contribute to development of motor neuron disease?

A

It is though that chronic calcium deficiency plays a role

35
Q

There is a gene mutation that has been found to have links with motor neuron disease.

What chromosome is this mutation on?

A

Chromosome 21

36
Q

How many pairs of chromosomes are there in the body?

37
Q

Describe how cells die because of motor neuron disease?

A

Similarly to cell death caused by other neurodegenerative diseases

Oxidative neuron (nerve cell) damage
Aggregation of abnormally large amounts of protein
Apoptosis

38
Q

Clinical features of motor neuron disease?

A

Often patients begin to notice clumsiness, tripping more often, weakness

Symmetrical weakness and wasting, beginning at the extremities

Reflex problems: hypo or hyperreflexic

Fasciculation

Cramps

Progressive degeneration of muscles resulting in spastic paraparesis

At late stages, breathing muscles are affected, this is what causes death

39
Q

Which nerves are NOT affected in motor neuron disease?

A

Sensory nerves
Motor nerves to the eyes and sphincters

So no loss of eye movement and no incontinence

40
Q

What is the usual life expectancy of motor neuron disease?

A

2-5 years from diagnosis

41
Q

What helps us distinguish between motor neuron disease and MS?

A

In motor neuron disease, sphincters are never affected so there is never incontinence

There often is with MS

42
Q

What helps us distinguish between motor neuron disease and myasthenia gravis?

A

In motor neuron disease, eye movement is never affected

It often is in myasthenia gravis

43
Q

How can patients with motor neuron disease become either hyper or hyporeflexic?

A

Motor neuron disease effects upper and lower motor neurons

So it can cause either, or both these problems in muscles

44
Q

What are fasciculations and why do they occur?

Is it a LMN or UMN problem?

A

Fluttering, twitching of muscles

It occurs as the surviving axons branch out to new motor units and attempt to innervate them

It is an LMN problem

45
Q

What is spastic paraparesis?

Why does it occur in motor neuron disease?

A

Weakness and stiffness of the muscles

Lesions are in the UMN and LMNs, so both spasticity and flaccidity occur

46
Q

Diagnosis of motor neuron disease?

A

Examination:

  • UMN and LMN signs
  • no sensory loss
  • progressive pattern
  • fasciculations

Neurophysiology nerve conduction studies usually appear normal?

47
Q

Management of motor neuron disease?

A

Drugs:

  • sodium channel blocker: riluzole
  • GABA agonist: baclofen

Ventilation support in later stages

Paraenteral feeding, if swallowing is affected

Physiotherapy may help with weakness

48
Q

How does riluzole help in motor neuron disease?

What type of drug is it?

A

It may slow progression

It is a sodium channel blocker

49
Q

What is progressive bulbar palsy?

A

A type of motor neuron disease affecting muscles of the head and neck

So they get problems with speech and swallowing

50
Q

Clinical feature of progressive bulbar palsy?

A

Dysphagia
Slurring of speech
Choking
Dysphonia: difficulty making sounds

Atrophy and fasciculation of tongue

51
Q

What is hereditary spastic paraplegia?

A

A genetic condition that results in spastic paraplegia

Stiffness and weakness of muscles

52
Q

Clinical features of hereditary spastic paraplegia?

A

Stiffness
Difficulty walking
Spastic gait
Mild urgency incontinence

High arched feet, clawing of toes

Clonus: shaking, due to high tone

Neurology (23 decks)

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