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Z Year3 Neuro Conditions > Myasthenia Gravis > Flashcards

Myasthenia Gravis Flashcards

1
Q

What is Myasthenia Gravis (MG)?

A

chronic autoimmune disorder of post-synaptic membrane at NMJ in skeletal muscle

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2
Q

How common is MG?

A

uncommon

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3
Q

What type of immune cells are involved in MG?

A

both T and B cells

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4
Q

What type of reaction is happening in MG?

A

Type II hypersensitivity

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5
Q

What is found in 80-90% of MG?

A

detectable antibodies against the nicotinic acetylcholine receptor (AChR)

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6
Q

What are RF for MG?

A
  1. FHx of autoimmune disorders
  2. Genetic markers
  3. Cancer-targeted therapy
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7
Q

When is MG more common in women?

A

young 20-30

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8
Q

When is MG more common in men?

A

60-70

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9
Q

What is MG associated with?

A
  • thymic hyperplasia
  • thymic atrophy
  • thymic tumour
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10
Q

What are common symptoms in MG?

A
  1. Muscle fatigability
  2. Ptosis
  3. Diplopia
  4. Dysphagia
  5. Dysarthria
  6. Facial paresis
  7. Proximal limb weakness
  8. Reflexes normal
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11
Q

What are the muscle groups affected in order in MG?

A
  1. Extraocular
  2. Bulbar
  3. Face
  4. Neck
  5. Limb girdle
  6. Trunk
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12
Q

When are symptoms of MG exacerbated by?

A
  1. Pregnancy
  2. Low K+
  3. Infection
  4. Over treatment
  5. Change of climate
  6. Etc
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13
Q

What are possible DDx of MG?

A
  1. Lambert-Eaton myasthenic syndrome (LEMS)
  2. Botulism
  3. Penicillamine-induced myasthenia gravis
  4. Primary myopathies
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14
Q

What are possible investigations for MG?

A
  1. Serum acetylcholine receptor (AChR) antibody analysis: positive
  2. Muscle-specific tyrosine kinase (MuSK) antibodies: maybe positive
  3. Serial Pulmonary function tests
  4. EMG
  5. CT
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15
Q

What would serial pulmonary function tests show in MG?

A

myasthenic crisis: low FVC and low NIF

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16
Q

What would EMG show in MG?

A

decremental muscle response to repetitive nerve stimulation

17
Q

Why would you do a CT in MG?

A

to exclude thymoma

18
Q

What is the treatment for acute severe for MG?

A
  1. 1st line: Intubation + mechanical ventilation + plasma exchange of IV Ig and corticosteroid
  2. 2nd line: Eculizumab or rituximab
19
Q

What is the 1st line treatment for MG mild disease?

A

anticholinesterase inhibitors: pyridostigmine (max 1.2g/d)

20
Q

How do anti cholinesterase inhibitors work?

A
  1. which stops breakdown of acetylcholine
  2. so increases concentration of acetylcholine
  3. so helps to counteract effect of acetylcholine receptor antibodies
21
Q

What other management is used in mild MG?

A
  • corticosteroid e.g. prednisone to recue production of autoantibodies
  • thymectomy: reduce muscle weakness
22
Q

What are possible cholinergic SE?

A
  1. Increase salivation
  2. Lacrimation
  3. Sweat
  4. Vomiting
  5. Miosis
  6. Diarrhoea
23
Q

What is the management for moderate MG?

A

1st line: pyridostigmine
-thymectomy
-Plasma exchange or IV Ig
2nd line eculizumab or rituximab

24
Q

What is the management of MG severe post crisis?

A

1st line: pyridostigmine plus immunosuppressant

  • intermittent IV Ig
  • thymectomy
  • plasma exchange
25
Q

What are possible complications of MG?

A
  1. Pyridostigmine-induced adverse reaction
  2. Respiratory failure
  3. Impaired swallowing
  4. Acute aspiration
  5. Secondary pneumonia
  6. Plasma exchange-induced adverse reaction
  7. IVIG-induced adverse reactions
26
Q

What is the prognosis of MG?

A

normal life span

27
Q

How common is a myasthenic crisis? What is this crisis?

A

15%-20% of patients with MG experience a myasthenic crisis: hard to differentiate from cholinergic crisis – decreased function of breathing muscles

28
Q

What is the patho of MG?

A

autoantibodies against AChR at NMJ (some patients may have anti-MuSK antibodies)

29
Q

What are thymus associations of MG?

A
  • Thymic hyperplasia (70%)

- Thymoma (10%)

30
Q

Why is the thymus involved in MG?

A
  • adults with myasthenia gravis, the thymus has clusters of immune cells similar to lymphoid hyperplasia
  • usually only happens in the spleen and lymph nodes during an active immune response
31
Q

What can individuals with MG develop?

A

thymomas (tumours of the thymus gland) – usually harmless but can turn malignant

32
Q

How does the muscles fatigue change in MG?

A

with use

33
Q

What is the patho of Lamber eaton Myasthenic syndrome?

A
  1. autoantibodies against presynaptic VGCC at NMJ

2. Repeated Use leads to build up of synaptic Ca2+ so increased contraction

34
Q

How does the muscle weakness change in LEMS?

A

muscles weakness improves with use

35
Q

What are the symptoms of LEMS?

A
  1. Difficulty walking
  2. Weakness in upper arms and shoulder
  3. Similar symptoms to MG
  4. Autonomic: dry mouth, constipation, incontenece
36
Q

What are signs of LEMS?

A
  1. Symptom improvement following use

2. Hyporeflexia

37
Q

What are the associations of LEMS?

A
  1. Small cell lung cancer: paraneoplastic

2. Autoimmune disease

38
Q

What test can be used for MG

A

Simpson test (shut eyes then ptosis as all Ach used up)

Z Year3 Neuro Conditions (34 decks)

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