Ob Med: Myasthenia Gravis In Pregnancy

Front 1

What is myasthenia gravis (MG)

Back 1

Autoimmune neuromuscular disorder
Antibodies to (nicotinic) acetylcholine receptor
Fatiguable weakness eye, bulbar, limb, respiratory muscles

Front 2

What are the two clinical forms of MG?

Back 2

Occular (OMG)
Generalized

Front 3

What tumour is commonly associated with MG?

In what percentage of individuals with MG is it found?

Back 3

Thymoma

10-15%

Front 4

When is the incidence of myasthenia gravis greatest for females? (i.e. what decades of life?)

Back 4

2nd and 3rd decades

Front 5

What autoantibodies are most commonly associated with MG?

For pts with MG, what percentage have positive antibodies with:

a) occular dz
b) generalized dz

Back 5

ACh-R and MuSK
(acetylcholine receptor and muscle-specific receptor tyrosine kinase

a) 50%
b) 90%

Front 6

How is MG diagnosed?

Back 6

Besides tests
Tension test
Serology
Nerve conduction studies

Front 7

In pregnancy, what percentage of pts with MG:

a) worsen
b) improve
c) stay the same

Back 7

a) 40%
b) 30%
c) 30%

Front 8

What percentage of patients with MG have post-partum exacerbations?

Back 8

30%

Front 9

What time period confers the greatest risk of mortality for MG?

What should be avoided in this year?

Back 9

First year of diagnosis

Pregnancy

Front 10

What factors can precipitate a MG crisis?

Back 10

Physical stress
Emotional stress
Infection

Front 11

When during pregnancy and the pueriperum is risk of a MG exacerbation greatest?

Back 11

1T
PP

Front 12

List and explain the 3 types of MG exacerbations/crises

Back 12

Myasenthic Crisis
severe weakness, can't swallow, breath
Refractory Crisis
myasenthic crisis refractory to meds
Cholinergic Crisis
N/V/D, weakness, abdo pain from too much cholinergic meds

Front 13

What antepartum management strategies can reduce myasenthic crises?

Back 13

Reduce emotion and physical stress
bedrest
treat infections

Front 14

What is the most common autoimmune condition associated with MG?

What other autoimmune disorders are less-commonly associated?

Back 14

Autoimmune thyroiditis (8%)

Also more rarely:
RA
SLE

Front 15

During the initial assessment of a pregnancy women with MG, what should be observed and tested?

Back 15

Baseline motor strength
Respiratory status & PFTs
TSH
EKG (rare focal myocardial necrosis)
Thymus imaging (if not done)

Front 16

Broadly what medications/treatment modalities are used to treat MG?

Back 16

Cholinesterase inhibitors
(e.g. pyridostigmine (Mestinon))
Chronic Immunotherapies
(e.g. prednisone, azathioprine, cyclosporine, mycophenolate, cyclophosphamide)
Rapid Immunotherapies
plasmapheresis, IVIg

Front 17

At high doses of pyridostigmine what is a patient with MG at risk for?

List symptoms of this condition.

Back 17

Cholinergic crisis

Nausea
Vomiting
Diarrhea
Abdominal pain
Weakness

Front 18

Of the possible chronic immunomodulators, what is probably the safest to use in pregnancy?

Which should be avoided?

Back 18

Glucocorticoids
(Azathioprine, cyclosporine)

Avoid
mycophenolate
cyclophosphamide

Front 19

What is a patient in myasthenic crisis at risk for?

Back 19

Death

Respiratory failure
Aspiration

Front 20

As part of antepartum/intrapartum management, what specialities should be consulted/involved?

Back 20

Anesthesia
Endocrinology
Neonatology

Front 21

What are neonates born to women with MG at risk for?

What percentage of neonates are at risk?

What is the risk of recurrence of this to neonates in successive pregnancies?

Back 21

Neonatal MG (transient)

(passive maternal IgG autoantibodies)

10-20%
(more likely when mom is clinically symptomatic)

75%

Front 22

What are possible fetal adverse effects in a pregnant women with MG?

Back 22

Decreased movement
Decreased breathing
Polyhydramnios (decreased swallowing)
Arthrogryposis multiplex congenita
most severe, possible joint contractures and lung hypoplasia

Front 23

Does MG affect:

1) 1st stage labour
2) 2nd stage labour

How should respiratory status be monitored intrapartum?

Back 23

1) No - uterine smooth muscle not affected
2) Yes (can) - fatigue with pushing)

Resp rate
O2 saturation
(Watch for fatigue, intubate if necessary)

Front 24

What type of second stage delivery might be recommended?

Back 24

Passive Second Stage
Oxytocin
Operative delivery

Front 25

A pre-eclamptic patient with MG presents with hypertension, what medications should be avoided?

Back 25

MgSO4
Labetolol (beta-blockers)
~CCBs

Front 26

What medications are appropriate for hypertension control and seizure treatment?

Back 26

HTN
Methyldopa
Hydralizine
Seizure
Lorazepam
Phenytoin

Front 27

How should pyridostigmine be given intrapartum?

Back 27

IV
(unreliable PO absorption)

Front 28

What classes of antibiotics should be avoided in patients with MG?

Back 28

Amnioglycosides
Fluoroquinolones
(less so ampicillin, macrolides)