Exam 4 Myasthenia Gravis

Question 1

Myasthenia Gravis is?

Answer 1

Autoimmune dis of myoneural jxn

Question 2

Myasthenia Gravis pathophys?

Answer 2

Ab’s attack acetylcholine receptors (AChR) on post gang membrane of NMJ
Thymus abn in most

Question 3

Myasthenia Gravis basic defect?

Add’l defect?

Answer 3

↓ # of AChR on postsynap mm membrane

Postsynap folds flatten ->
↓ efficiency of transmission
ACh released normally but fails to trigger mm APs

Question 4

Myasthenia Gravis presentation? (6)

Answer 4

Proximal Skeletal mm weak/fatigue
Eyelid and EOM weak
Weak chewing, speaking, swallow
Weak respiratory mm
DTR normal
Worse w/ activity, better w/ rest

Question 5

Myasthenia Gravis tests? (4)

Answer 5

Repetitive mm activities = reproduce sxs

Tensilon Test = Anticholinesterase -> ↓ACh breakdown -> ↑stim of limited AChRs = improved mm strength

ACh receptor Ab test:
+ = diagnostic,
- result does not r/o

EMG = decremental response to stim

CT/MRI of thorax for thymoma

Question 6

Lambert-Eaton Myasthenic Synd is?

Presentation?

Answer 6

Impaired presynap release of ACh
U from CA-caused immune response

↓ or no DTRs
Dry mouth, Impotence
Nerve stim = incremental response

Question 7

Drug-induced Myasthenia U from?

Answer 7

Aminoglycoside ABX

Procainamide (antiarrhy)

Question 8

Neurasthenia presentation?

Answer 8

Weakness/fatigue
MM testing = jerky release
EMG = normal
Tensilon Test = negative

Question 9

Thyroid dysfxn and MG?

Answer 9

Hyper or hypo can produce mm weakness

Question 10

Progressive External Ophthalmoplegia is?

Answer 10

Rare disorder of EOM w/ proximal mm weakness

Question 11

MG tx? (5)

Answer 11

Anticholinesterase (Pyridostigmine): ↑ mm strength
Thymectomy: remission
Immunosupp: if AChE doesn’t work
Plasmapheresis: for acute exacerb, crisis, refractory
IVIG