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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
What are possible complications of MG?
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
What is the prognosis of MG?
normal life span
27
How common is a myasthenic crisis? What is this crisis?
15%-20% of patients with MG experience a myasthenic crisis: hard to differentiate from cholinergic crisis – decreased function of breathing muscles
28
What is the patho of MG?
autoantibodies against AChR at NMJ (some patients may have anti-MuSK antibodies)
29
What are thymus associations of MG?
- Thymic hyperplasia (70%) | - Thymoma (10%)
30
Why is the thymus involved in MG?
- 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
What can individuals with MG develop?
thymomas (tumours of the thymus gland) – usually harmless but can turn malignant
32
How does the muscles fatigue change in MG?
with use
33
What is the patho of Lamber eaton Myasthenic syndrome?
1. autoantibodies against presynaptic VGCC at NMJ | 2. Repeated Use leads to build up of synaptic Ca2+ so increased contraction
34
How does the muscle weakness change in LEMS?
muscles weakness improves with use
35
What are the symptoms of LEMS?
1. Difficulty walking 2. Weakness in upper arms and shoulder 3. Similar symptoms to MG 4. Autonomic: dry mouth, constipation, incontenece
36
What are signs of LEMS?
1. Symptom improvement following use | 2. Hyporeflexia
37
What are the associations of LEMS?
1. Small cell lung cancer: paraneoplastic | 2. Autoimmune disease
38
What test can be used for MG
Simpson test (shut eyes then ptosis as all Ach used up)

Z Year3 Neuro Conditions (34 decks)

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