Clinical Approach to Disorders of the Neuromuscular Junction (Hon)

Question 1

What are some disorders that act at the presynaptic region of the NMJ?

Answer 1

1) Lambert-Eaton myasthenic syndrome (LEMS)

2) Botulism

Question 2

What are some disorders that act at the postsynaptic region of the NMJ?

Answer 2

Myasthenia gravis

Question 3

Myasthenia gravis is caused by a defect of neuromuscular transmission due to?

Answer 3

An antibody mediated attack upon nicotinic acetylcholine receptors (AChR)

Question 4

Myasthenia gravis has a high frequency of what HLA haplotypes?

Answer 4

1) HLA-B8

2) HLA-DR3

Question 5

What are general characteristic symptoms of Myasthenia gravis?

Answer 5

1) Fluctuating weakness
2) Ocular muscle weakness leading to ptosis and diplopia
3) Clinical response to cholinergic drugs

Question 6

What antibodies are found with Myasthenia gravis?

What are the two major classifications of Myasthenia Gravis?

Answer 6

Acetylcholine receptor antibodies

Ocular and Generalized

Question 7

What EMG finding is seen with Myasthenia gravis?

Answer 7

Decremental response on repetitive stimulation

Question 8

What test can be used to diagnose Myasthenia gravis?

Answer 8

Ice Bag Test

Question 9

What is unique when it comes to prednisone (steroid) treatment with myasthenia gravis?

Answer 9

Start with low dose and gradually increase if needed

Question 10

What antibiotic is the most significant in avoiding with Myasthenia gravis patients?

Answer 10

Aminoglycosides

Question 11

What is Myasthenic crisis?

How does it present?

What is done to treat it?

Answer 11

1) Rapid deterioration of the disease
2) Aspirations, respiratory failure
3) Stop anticholinesterase meds and give plasma exchange and IVIg

Question 12

What is the big clue regarding cholinergic crisis?

Answer 12

Presence of miosis and or fasciculations

Question 13

In Myasthenia Gravis patients that have no detectable anti-AChR Abs, what Antibody can be found instead?

Which sex is more common with this?

What is found in double seronegativity (no ACHr or MuSK Ab)

Answer 13

1) MuSK
2) Women
3) Anti-LRP-4 Antibodies

Question 14

Lambert – Eaton Myasthenic Syndrome (LEMS) is due to an autoimmune attack agonist?

What is it often associated with?

Answer 14

1) Voltage-gated calcium channels on presynaptic nerve terminal
2) Small cell lung cancer

Question 15

What is the clinical presentation of LEMS?

Answer 15

1) DTR loss
2) Dry mouth
3) Myalgia
4) Impotence
5) Proximal weakness
6) Strength improve after exercise

DDIMPS

Question 16

What EMG finding is seen with LEMS?

Answer 16

Incremental response on fast repetitive stimulation

Question 17

With Botulism, the toxin blocks?

Answer 17

Presynaptic mechanisms for release of ACh

Question 18

What is the clinical presentation of Botulism?

Answer 18

1) Dry, sore mouth and throat
2) Blurred vision
3) N/V

Question 19

Nerve “Gases” such as Sarin acts by?

What does this cause?

Death is due to?

Answer 19

1) Inhibiting Ach esterase at NM junction
2) End organ overstimulation
3) Respiratory failure