Neuromuscular Disease Flashcards

1
Q

What are the two potential causes for neuromuscular junction disease?

A

A failure of the NMJ to release sufficient ACh, or a failure of the muscle to respond to this ACh

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2
Q

What is the consequence of failure to release or respond to ACh in neuromuscular junction disease?

A

Reduced/absent muscle contraction

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3
Q

What are some ways to recognise muscle weakness caused by neuromuscular junction disease?

A

It is usually bilateral, and gets worse with repeated use

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4
Q

What is the motor end plate?

A

The synapses formed between motor neurones and muscles

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5
Q

What is curare? This is toxic if given how?

A

A plant like compound which occupies the same position as the ACh receptor but it does not open ion channels so there is no muscle contraction / IV or IM

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6
Q

What is Botulism? Who is it often seen in?

A

An organism present in soil causing food and wounds to become infected / IVDU

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7
Q

What are the two main pre-synaptic NMJ diseases?

A

Botulism and Lambert-Eaton syndrome

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8
Q

What is the clinical presentation of Botulism?

A

Rapid onset weakness without sensory loss

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9
Q

What is the pathophysiology behind Lambert-Eaton syndrome?

A

There are antibodies to pre-synaptic Ca++ channels which leads to less vesicle (containing ACh) release

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10
Q

Lambert-Eaton syndrome is often a paraneoplastic syndrome. It has a strong association with what?

A

Small cell lung cancer

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11
Q

How will patients with Lambert-Eaton syndrome present?

A

Proximal weakness, affecting the lower and then upper limbs

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12
Q

How is Lambert-Eaton syndrome treated?

A

3,4-diaminopyridine

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13
Q

What autoantibodies are seen in myasthenia gravis?

A

Postsynaptic ACh receptors

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14
Q

What is the only postsynaptic NMJ disorder?

A

Myasthenia gravis

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15
Q

Describe the two peak incidences of myasthenia gravis?

A

Young females in the 3rd decade of life, or males in the 6th/7th decades of life

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16
Q

What happens to the incidence of antibody positive myasthenia gravis?

A

It increases with age and is more common in males

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17
Q

ACh autoantibodies are found in what % of people with myasthenia gravis? If these are not found, what other autoantibody can you look for?

A

80-90% / Anti-musc

18
Q

What is a clinical feature which is closely associated with myasthenia gravis and may be the cause behind the pathology?

A

Thymus problems e.g. hyperplasia or thymoma

19
Q

What is the typical clinical feature of myasthenia gravis?

A

Typically fluctuating weakness which gets worse throughout the day

20
Q

What are some of the most common muscles/muscle groups that myasthenia gravis would present in?

A

Extraocular, facial and bulbar weakness

21
Q

Give some examples of how the muscle weakness in myasthenia gravis might present?

A

Eye shutting by the end of the day, speech that becomes slurred with talking, inability to finish a meal because of difficulty swallowing/chewing

22
Q

If limb weakness occurs in myasthenia gravis, is it typically distal or proximal?

A

Proximal

23
Q

Describe the acute treatment of myasthenia gravis?

A

ABCDE if required, ACh inhibitor (pyridostigmine), IV immunoglobulins and thymectomy

24
Q

What are some long term treatment options for myasthenia gravis?

A

Steroids (prednisolone) or steroid sparing agents (azathioprine)

25
Q

What are some emergency treatment options for myasthenia gravis?

A

Plasma exchange or immunoglobulin

26
Q

What is a myasthenic crisis? What are some things that can trigger one?

A

A severe, acute exacerbation of symptoms / infection, drugs (gentamicin/anti-arrhythmics), pregnancy and stress

27
Q

If myasthenia gravis was to cause death in a patient, what would be some potential causes for this?

A

Respiratory failure or aspiration pneumonia, side effects of immunosuppression in the elderly

28
Q

The smallest contractile unit is the muscle fibre, these are each surrounded by a thin layer of what?

A

Endomysium

29
Q

20-80 muscle fibres are grouped together to form a what? This is then surrounded by what?

A

Fascicle / perimysium

30
Q

A large number of fascicles are ensheathed by what?

A

Epimysium

31
Q

What are fasciculations? These are usually a sign of disease where?

A

Visible spontaneous switches of muscle / the motor neurone

32
Q

What is myotonia?

A

The failure of a muscle to relax after use

33
Q

What are some signs that might be seen in dermatomyositis?

A

Shawl sign, heliotrope rash, Gottron’s papules on knuckles and extensor surfaces

34
Q

What marker is raised in poly and dermatomyositis? What medication do they respond to?

A

CK / steroids

35
Q

In inclusion body myositis, there is characteristic sparing of what part of the body?

A

Thumb

36
Q

How is myotonic dystrophy inherited? How are most muscular dystrophies inherited?

A

Autosomal dominant / X linked recessive

37
Q

Duchenne and Becker muscular dystrophy are both associated with defects in what?

A

Dystrophin

38
Q

Which drugs are the most likely to cause problems with the muscles?

A

Steroids and statins

39
Q

What happens in rhabdomyolysis?

A

Damage to the skeletal muscle causes leakage of toxic intracellular contents into the plasma which can cause renal failure and DIC

40
Q

What is the triad of rhabdomyolysis?

A

Myalgia, muscle weakness and myoglobinuria