Disorders of the Neuromuscular Junction

Question 1

autoimmune disorder that is characterized as muscle weakness due to dysfunction of the neuromuscular junction

Answer 1

myasthenia gravis

Question 2

the most common disorder of neuromuscular transmission

Answer 2

myasthenia gravis

Question 3

myasthenia gravis in which autoantibodies attack the acetylcholine receptor, resulting in reduction of the number of receptors over time

Answer 3

seropositive

Question 4

myasthenia gravis in which the patient has no detectable levels of autoantibodies against acetylcholine receptors

Answer 4

seronegative

Question 5

what antibodies may be present in patients with seronegative myasthenia gravis?

Answer 5

antibodies directed against MuSK

Question 6

presents at birth as weakness due to the mother with myasthenia gravis who passes antibodies through the placenta

Answer 6

congenital myasthenia

Question 7

what is the cardinal feature of myasthenia gravis?

Answer 7

fluctuating skeletal muscle weakness

Question 8

when does the skeletal muscle weakness get worse or improve?

Answer 8

worse later in day or with exercise

improves with rest

Question 9

what are the 2 clinical forms of weakness in myasthenia gravis?

Answer 9

ocular
generalized

Question 10

what is the presentation called when a patient cannot pull facial muscles into a complete smile?

Answer 10

myasthenic sneer

Question 11

what is the presentation called when myasthenia gravis affects the neck muscles?

Answer 11

dropped head syndrome

Question 12

what does myasthenia gravis of the respiratory muscles cause? and what could cause this (4)?

Answer 12

myasthenic crisis

surgery
infection
medications
tapering immunosuppression

Question 13

what will NOT change in myasthenia gravis? (2)

Answer 13

sensation
reflexes

Question 14

what is the diagnostic criteria for myasthenia gravis? (2)

Answer 14

fatigability/weakness of muscle + improvement with anticholinesterase drugs

Question 15

what diagnostic can test ptosis in myasthenia gravis?

Answer 15

ice pack test will improve ptosis

Question 16

what are the 3 serologic tests for myasthenia gravis?

Answer 16

acetylcholine receptor antibodies
MuSK antibodies
autoimmune thyroid labs

Question 17

why would we do a chest CT in myasthenia gravis?

Answer 17

to look for thymoma

Question 18

what are 2 electrophysiologic studies for myasthenia gravis?

Answer 18

repetitive nerve stimulation studies
single-fiber electromyography (EMG)

Question 19

what is the 1st line treatment for myasthenia gravis in a stable patient?

Answer 19

oral anticholinesterase (pyridostigmine)

Question 20

what should we watch for when using pyridostigmine?

Answer 20

cholinergic crisis

Question 21

what is the 2nd line treatment for myasthenia gravis in a stable patient? (2)

Answer 21

chronic immunosuppressive agents:

azathioprine
oral glucocorticoid

Question 22

what are 2 options for treatment of myasthenia gravis in patient who is in potential crisis?

Answer 22

plasmapheresis
IVIG

Question 23

what are the 3 uses for plasmapheresis and IVIG?

Answer 23

myasthenic crisis
preop before thymectomy
bridge to slower acting immunotherapies

Question 24

what can be done for a patient with myasthenia gravis in a case of thymoma or nonthymomatous autoimmunity?

Answer 24

thymectomy

Question 25

what must be done before performing a thymectomy on a patient?

Answer 25

control weakness first

Question 26

what is the clinical course of myasthenia gravis? (2)

Answer 26

symptom-free periods are lost progression peaks withing few years of onset

Question 27

myasthenic syndrome associated with small cell carcinoma characterized by weakness of proximal limb muscles that improves with activity

Answer 27

lambert-eaton syndrome

Question 28

what is the diagnostic for lambert-eaton syndrome?

Answer 28

EMG

Question 29

what is the treatment for lambert-eaton syndrome? (3)

Answer 29

plasmapheresis + *immunosuppressants* prednisone azathioprine

Question 30

toxin of Clostridium b. that prevents the release of acetylcholine at the neuromuscular junctions and autonomic synapses

Answer 30

botulism

Question 31

a patient with botulism will most likely have what in their history?

Answer 31

hx of ingestion of possibly contaminated canned food 72 hrs prior

Question 32

a patient presents with diplopia, dilated pupils, ptosis, facial weakness, dysphagia, respiratory difficulty, limb weakness, and postural hypotension. what are they likely experiencing?

Answer 32

botulism

Question 33

what will likely be seen in botulism if we do an electrophysiological study?

Answer 33

increased muscle response to fast rate stimulation

Question 34

what is the treatment for botulism?

Answer 34

3,4 diaminopyridine *(K channel blocker)*