4 - Neuromuscular Disease

Question 1

What are the three types of neuromuscular junction disorders?

Answer 1

• Presynaptic
• Synaptic
• Postsynaptic

Question 2

Give an example of a presynaptic neuromuscular junction disorder

Answer 2

• Botulism

- Lambert-Eaton Syndrome

Question 3

Give an example of a synaptic neuromuscular junction disorder

Answer 3

• Acetylcholinesterase inhibitors

Question 4

Give an example of a postsynaptic neuromuscular junction disorder

Answer 4

• Myasthenia Gravis

- Snake Venom

Question 5

Describe the disease state of myasthenia gravis

Answer 5

Anti-Acetylcholine Receptor Antibodies attack the postsynaptic muscle membrane decreasing the number of receptors and blocking the remaining receptors

Question 6

Describe the disease state of Lambert Eaton syndrome

Answer 6

Anti-Calcium Channel antibodies attack the presynaptic neuron membrane and prevent Acetylcholine release

Question 7

Describe the disease state of botulism

Answer 7

Botulinum toxin acts at the presynaptic neuron membrane and prevent release of acetylcholine

Question 8

Lecture question: Why is AST higher than ALT in alcohol-related liver disease? Remember ALT is more specific for liver disease.

Answer 8

• AST actually comes from the muscle
• Alcohol is a muscle toxin is well
• Or it could be rhabdomyalysis

Question 9

What is the threshold for initiating mechanical ventilation in patients with a neuromuscular disease?

Answer 9

• Negative Inspiratory Force (NIF) less negative than -30 cmH2O
• That is from 0 to -30 cmH2O, you should probably intubate or at least initiate NiPPV (BiPAP or CPAP)
• Forced Vital Capacity

Question 10

Compare the difference between myasthenia gravis and Lamber-Eaton in terms of location of defect

Answer 10

Myasthenia gravis
- Post-synaptic

Lamber-Eaton
- Pre-synaptic

Question 11

Compare the difference between myasthenia gravis and Lamber-Eaton in terms of classic tumor association

Answer 11

Myasthenia gravis
- Thymus cancer

Lamber-Eaton
- Lung cancer

Question 12

Compare the difference between myasthenia gravis and Lamber-Eaton in terms of symptom prominence

Answer 12

Myasthenia gravis
- Ocular, upper extremities

Lamber-Eaton
- Hip girdle

Question 13

Compare the difference between myasthenia gravis and Lamber-Eaton in terms of reflexes

Answer 13

Myasthenia gravis
- Normal on stretch

Lamber-Eaton
- Hypoactive or absent

Question 14

Compare the difference between myasthenia gravis and Lamber-Eaton in terms of response to muscle stimulation

Answer 14

Myasthenia gravis
- Symptoms worsen

Lamber-Eaton
- Symptoms improve