Neuromuscular Junction Disorders

Question 1

What is post activation exhaustion

Answer 1

Decrease in CMAP amplitude seen 5 minutes after isometric contraction

Question 2

Myasthenia gravis vs lambert eaton syndrome: quantal content vs quantal response

Answer 2

MG: normal quantal content, but decrease quantal response
LES: decreased quantal content, normal quantal response

Question 3

Which NMJ has normal CMAP and which has abnormal CMAP

Answer 3

MG has normal CMAP. Botulism and LES have abnormal CMAP.

Question 4

Treatment of MG

Answer 4

Thymectomy, anticholinesterase (pyridostigmine), steroids, plasmapharesis, IVIg

Question 5

Treatment of botulism

Answer 5

Antitoxin

Question 6

High rate repetitive simulation Findings seen in NMJ disorders

Answer 6

MG -decrement and partially repaired
LES - 200-300% increment
Botulism - mild increment

Question 7

Which NMJ is better with exercise and which is worse with exercise

Answer 7

MG is worse with exercise and LES is better with exercise

Question 8

Which limbs are affected first in LES

Answer 8

Lower limbs (quadriceps)

Question 9

What is post activation facilitation

Answer 9

Isometric contraction increases CMAP amplitude because of improvement in neuromuscular transmission because of bombardment of ACh

Question 10

Etiology of MG

Answer 10

Autoimmune response against postsynaptic muscle specific tyrosine kinase ACh receptors

Question 11

Which NMJ disorder has proximal fatigue and weakness

Answer 11

MG and LES

Question 12

What is the most common muscle weakness seen in MG

Answer 12

Ocular weakness (ptosis)

Question 13

Diagnostic test for MG

Answer 13

Edrophonium (tensilon) test - improvement begins in 1 minute. Edrophonium is a short acting cholinesterase inhibitor

Question 14

Which NMJ disorder is associated with thymus disorder/thymoma

Answer 14

MG

Question 15

Prior to doing a repetitive nerve stimulation study, what changes must be done to meds

Answer 15

Stop cholinesterase inhibitors 12 hours before study

Question 16

Which NMJ includes facial or bulbar symptoms, and what are they?

Answer 16

MG and botulism - ptosis, diplopia, dysphagia, dysarthria

Question 17

Most sensitive test for NMJ disorder

Answer 17

Single fiber EMG

Question 18

What kind of cancer is LES associated with

Answer 18

Small cell carcinoma

Question 19

MG vs LES Miniature endplate potential and frequency of potential

Answer 19

MG = reduced MEPP, normal frequency
LES = normal MEPP, reduced frequency

Question 20

What causes jitter

Answer 20

]

Question 21

Finding on repetitive nerve stimulation study for NMJ disorder

Answer 21

> 10% decrement in amplitude between first and fifth waveform

Question 22

SNAP findings of NMJ disorders

Answer 22

Normal

Question 23

Treatment of LES

Answer 23

Steroids, plasmapheresis, guanidine (increases ACh), IVIg

Question 24

CMAP finding of NMJ disorder

Answer 24

Normal or reduced amplitude

Question 25

Etiology of botulism

Answer 25

Clostridium botulinum toxin blocks presynaptic release of Ach

Question 26

Etiology of LES

Answer 26

Autoimmune response against voltage gated calcium channels of presynaptic membrane decreasing calcium entry into cell which decreases release of Ach

Question 27

Which NMJ disorder has normal and abnormal MSR

Answer 27

``` Normal = MG Abnormal = LES and botulism ```

Question 28

MG vs LES vs Botulism: postsynaptic vs presynaptic

Answer 28

``` MG = postsynaptic problem LES = presynaptic problem Botulism = presynaptic problem ```