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Neurology > Neuromuscular Disorders > Flashcards

Neuromuscular Disorders Flashcards

1
Q

Describe the pathway that occurs over the neuromuscular junction

A
  1. AP
  2. Opening of voltage gated calcium channels
  3. Calcium influx
  4. Vesicles of ACh are released
  5. ACh diffuses across
  6. Binds to ACh receptors
  7. Permeable to sodium and potassium
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2
Q

What is the name of the enzyme that breaks down ACh

A

Acetylcholinesterase

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3
Q

How does curare work?

A

Occupies the same position as ACh receptor but does not open ion channel - no muscle contraction leads to no respiration

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4
Q

How does novichok work?

A

Inhibits cholinesterase

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5
Q

Name two presynapic disorders

A
  • Clostridium botulinum

- Lambert Eaton Myasthenic Syndrome

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6
Q

Describe clostridium botulinum

A

Organism present in soil and food that can infect wounds. Exotoxin inhibits ACh release by cleavage of pre-synaptic proteins involved in vesicle formation and blocks vesicle docking on presynaptic membrane - rapid onset weakness without sensory loss

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7
Q

What can botox be used for medically?

A

To relax muscles

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8
Q

Describe Lambert Eaton Myasthenic syndrome

A

Antibodies to presynaptic Ca2+ channels leads to less vesicle release

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9
Q

What is Lambert Eaton associated with?

A

Small cell carcinoma

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10
Q

State the treatment for Lambert Eaton syndrome?

A

Pyridostigmine

3.4- diaminopyridine

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11
Q

What is Myasthenia Gravis?

A

Autoimmune disorder where antibodies to acetyl choline receptors are produced, reducing the number of functioning receptors leading to muscle weakness and fatigue

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12
Q

Describe the pathophysiology of Myasthenia Gravis

A
  1. T cells are activated by unfolded AChR subunits
  2. B cells are stimulated to produce anti-AChR IgG antibodies
  3. Thymic cells are attacked by these antibodies and release anti-AChR immune complexes
  4. These activate antigen presenting cells
  5. Antibodies block the binding of ACh
  6. Ultimately causing destruction of muscle end plate folds
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13
Q

When do females tend to present with MG?

A

20s

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14
Q

When do males tend to present with MG?

A

70/80s

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15
Q

State the clinical features of MG

A

Weakness typically fluctuating and worse through the day

Most common - extraocular, facial, bulbar and proximal limb weakness

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16
Q

What is the acute treatment of MG?

A

Acetylcholinesterase inhibitor (pyridostigmine)
IV immunoglobulin
Thymectomy

17
Q

What is the chronic treatment of MG?

A

Steroids
Steroid sparing agents - azathioprine and mycophenolate
Immunomodulation
Plasma exchange/immunoglobulin

18
Q

What do people with MG die of?

A

Respiratory failure
Aspiration pneumonia
Side effects of immunosuppression

19
Q

Define fasciculations

A

Visible, fast, fine spontaneous twitch. May occur in healthy muscle - stress/caffeine/fatigue or in denervated muscle that becomes hyper-excitable

20
Q

Define myotonia

A

Failure of muscle relaxation after use due to defect in chloride channel - delay in release of grip

21
Q

What are the signs/symptoms of muscle disease?

A

Myalgia
Muscle weakness
Wasting
Hyporeflexia

22
Q

Give an example of immune mediated muscle disease

A

Dermatomyositis and polymyositis

23
Q

How is degenerative muscle disease characterised?

A

Thumb sparing

24
Q

What are muscular dystrophies?

A

Inherited, non-inflammatory progressive disease that have no central or peripheral nerve abnormality

25
Q

What is myotonic dystrophy?

A

Autosomal dominant, multisystem involvement, trinucleotide repeat disorder

26
Q

How does myotonic dystrophy present?

A

Myotonia, weakness, cataracts, ptosis, frontal balding, cardiac defects

27
Q

Name the infective causes of muscular dystrophies

A

Coxsacchie, uncooked pork (cistercercosis), borrelia

28
Q

What is rhabdomyolysis?

A

Dissolution of muscles, damage to skeletal muscle causes leakage of large quantities of toxic intraceullar contents into plasma

29
Q

In what circumstances can rhabdomyolysis occur?

A

Crush injuries, toxins, post convulsions, extreme exercise, alcoholic collapse, acute renal failure, DIC

30
Q

What is the triad of symptoms in rhabdomyolysis?

A
  1. Myalgia
  2. Muscle weakness
  3. Myoglobinuria
31
Q

What is sarcopenia?

A

Loss of skeletal muscle mass and function, primarily a disease of the elderly

32
Q

Describe the muscle power grading

A

0 - no movement
1 - flicker when attempting to contract
2 - some movement if gravity removed
3 - movement against gravity but not resistance
4 - movement against resistance but not full strength
5 - normal strength

Neurology (29 decks)

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