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Y3 NEUROLOGY > Neuromuscular Disease > Flashcards

Neuromuscular Disease Flashcards

1
Q

How does curare affect cholinergic transmission and muscle contraction?

A

Competes for and blocks ACh receptor so no muscle stimulation occurs

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2
Q

Curare is only toxic when administered how?

A

Intravenous

Intramuscular

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3
Q

How does Botox affect cholinergic transmission and muscle contraction?

A

Cleaves proteins involved in ACh vesicle formation and blocks vesicle docking to prevent exocytosis

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4
Q

What happens molecularly in Lambert Eaton myasthenic syndrome?

A

Antibodies attack presynaptic Ca channels resulting in less NT release

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5
Q

Which cancer is associated with Lambert Eaton syndrome?

A

Small cell carcinoma (typically of the lung)

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6
Q

Which disease is the most common neuromuscular junction disorder?

A

Myasthenia gravis

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7
Q

Autoantibodies attack what in myasthenia gravis? What does this cause?

A 
ACh receptors (MUSK receptors)
Triggers inflammatory cascades that damage the folds of the postsynaptic membrane
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8
Q

When do symptoms start in myasthenia gravis?

A

When ACh receptors reduced to 30% of normal

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9
Q

A patient must have Autoantibodies to suggest myasthenia gravis. True/False?

A

False

Patient with fatigue and weakness without antibodies may still have it

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10
Q

Which organ must be screened/assessed in people with myasthenia gravis? What other investigations can be performed?

A 
Thymus (arrange CT chest to check for thymoma or hyperplasia)
Ice test to reduce ptosis
Autoantibody screen
Electromyography
Muscle biopsy
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11
Q

Females are more affected than males by myasthenia gravis. True/False? What age group is most commonly affected?

A

True

20-30s

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12
Q

List clinical features of myasthenia gravis

A

Fluctuating weakness (typically proximal limbs)
Tiredness at end of the day
Extraocular weakness (ptosis, diplopia, ophthalmaplegia) - DIFFICULTY READING
Facial and bulbar weakness - DIFFICULTY CHEWING

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13
Q

What is the acute treatment for myasthenia gravis?

A 
Acetylcholinesterase inhibitor (pyridosigmine)
IV immunoglobulin/ plasma exchange
Thymectomy
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14
Q

What are muscle fasciculations?

A

Visible fine fast spontaneous twitches that occur in denervated muscle that become excited
Indicates problem in motor neurone

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15
Q

What is myotonia? It occurs due to a problem in what ion channel?

A

Failure of muscle relaxation after use

Chlorine channel

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16
Q

What is the commonest muscular dystrophy?

A

Myotonic dystrophy

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17
Q

List clinical features of myotonic dystrophy

A 
Myotonia
Weakness
Cataracts ('christmas tree')
Ptosis
Frontal balding
Cardiac defects
18
Q

What is the synapse between a motor neurone and muscle called?

A

Motor end plate

19
Q

What ion channel is responsible for the release of acetylcholine into the synaptic cleft?

A

Ca voltage-gated channel

20
Q

What is the outcome of acetylcholine binding to the post-synaptic receptor?

A

Renders the membrane potential permeable to sodium and potassium ions and depolarisation starts an action potential at motor end plate

21
Q

What drug is used to manage Lambert Eaton myasthenic syndrome?

A

3-4 diaminopyridine

22
Q

Name two pre-synaptic disorders affecting the NMJ

A

Botulinism

Lambert Eaton myasthenic syndrome

23
Q

Which part of the NMJ does myasthenia gravis affect?

A

Post-synaptic membrane

24
Q

What is the long term management for myasthenia gravis?

A

Immunomodulators
Steroids
Steroid sparing agents (azathioprine, mycophenolate)

25
Q

Which drug should be avoided in myasthenia gravis?

A

Gentamicin

26
Q

What are the three main types of muscle found within the body?

A

Skeletal
Smooth
Cardiac

27
Q

What are the three main types of muscle FIBRES found within the body?

A
  1. Slow oxidative
    2a. Fast oxidative
    2b. Fast glycotic
28
Q

Outline the process of muscle contraction

A
  1. ATP is hydrolysed into ADP and Pi which binds to the mysosin head forming a crossbridge
  2. Crossbridge attaches to actin
  3. Myosin head pivots and bends as it pulls on actin, sliding towards the M line (ADP + Pi are released)
  4. New ATP attaches to myosin head and crossbridge detaches
  5. ATP splits into ADP + Pi and myosin head cocks
29
Q

What are the four main clinical signs of muscle disease?

A

Myalgia
Muscle weakness
Wasting
Hyporeflexia

30
Q

Name the two main causes of immune-mediated muscle disorder

A

Polymyositis

Dermatomyositis

31
Q

List the main causes of muscle disorders

A 
Immune
Inherited
Congenital
Infective
Toxic (drugs, venoms)
32
Q

What is the characteristic clinical picture suggesting inclusion body myositis?

A

Slowly progressive weakness occuring in 60s with thumb sparing
Little response to steroid

33
Q

What is the mechanism behind muscular dystrophy?

A

Abnormality in protein causing movement of muscle

34
Q

Which micro-organisms most commonly cause muscle disorders?

A

Viral (coxsachie, trypanosomiasis)
Cistercosis (uncooked pork)
Borellia

35
Q

What class of drug, in particular, can cause myopathy as a common side effect?

A

Statins

36
Q

What is rhabdomyolysis?

A

Damage to skeletal muscle causes leakage of large quantities of toxic intracellular contents into plasma

37
Q

What is the potential aetiology of rhabdomyolysis?

A

Crush injury
Toxin
Post convulsion
Extreme exercise

38
Q

List the clinical features of rhabdomyolysis

A

Triad of myalgia, weakness, myoglobinuria

39
Q

List potential complications of rhabdomyolysis

A

Acute renal failure

Disseminated intravascular coagulation

40
Q

What is the genetic mechanism behind myotonic dystrophy?

A

Chromosome 19 trinucleotide expansion

41
Q

What is the broad presenting picture in NMJ disease?

A

Fatiguable motor symptoms with no sensory symptoms

42
Q

What is the first and second line investigation in myasthenia gravis?

A
  1. AChR antibodies

2. MUSK antibodies

Y3 NEUROLOGY (22 decks)

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