Myasthenia Gravis Flashcards by Jeremiah Sokol

Define MG

An autoimmune disorder of the neuromuscular

Fluctuating motor weakness

Ocular, bulbar, limb, respiratory muscles

How well did you know this?

Not at all

Perfectly

What does myasthenia gravis affect

Bulbar nerves of the medulla

How well did you know this?

Not at all

Perfectly

What are the consequences of bulbar damage

Difficulty:
Speaking
Swallowing
Dysphasia

How well did you know this?

Not at all

Perfectly

What causes MG

Antibody mediators

Immunological attack at proteins in the post-synaptic membrane

How well did you know this?

Not at all

Perfectly

What is ocular MG

Muscle weakness
Limited to the eyelids and extraocular muscles

How well did you know this?

Not at all

Perfectly

What is generalized MG

Involve variable combinations of weakness:

Bulbar
Limbs
Respiratory
Facial
Weakness of neck

How well did you know this?

Not at all

Perfectly

What are the pulmonary consequences of MG

Respiratory failure
Atelectasis
Alveolar consolidation poor control of secretions

How well did you know this?

Not at all

Perfectly

What are the pulmonary consequences of MG

Respiratory failure
Atelectasis
Alveolar consolidation poor control of secretions

How well did you know this?

Not at all

Perfectly

What is the typical course of MG

Onset can be:
Subtle
Intermittent
Sudden

Head to toe

How well did you know this?

Not at all

Perfectly

When do women show signs of MG

2-3rd decade

How well did you know this?

Not at all

Perfectly

When do women show signs of MG

2-3rd decade

How well did you know this?

Not at all

Perfectly

What antibody disrupts transmission of ACh

IgG

How well did you know this?

Not at all

Perfectly

What does Ptosis mean for

Drooping eye

How well did you know this?

Not at all

Perfectly

What does diploid mean for

Double vision

How well did you know this?

Not at all

Perfectly

What does disarthria mean for

People cannot articulate words

How well did you know this?

Not at all

Perfectly

What does dysphasia mean

Difficulty swallowing

How well did you know this?

Not at all

Perfectly

Explain the ice pack test for MG

Only done with ocular MG

Transmission is better at lower temperatures

Let it sit for 2 minutes

Sensitivity is 80%

How well did you know this?

Not at all

Perfectly

What MG test is outdated

Edrophonium test (Tensilon)

What did the Edrophonium test do

Confirm MG

Distinguished between myasthenic crisis vs cholinergic crisis

Was unreliable

What did you use if you had adverse effects to Edrophonium test

Atropine

What is the seropositive test

Test the blood to see if they have:

AChR antibodies

MuSK antibodies

Only 50% with ocular

Why does MuSK stand for

Muscle-specific receptor tyrosine kinase

What is the seronegative MG test

90% of generalized MG patients lack AChR and MuSK antibodies

What are the three electrodiagnostic studies for MG

Nerve Conduction Studies

Electromyography

Single-fiber electromyography

Explain the single-fiber electromyography (SFEMG)

Most sensitive test available Special needle records action potential of two muscle fibers innervated by the same motor axon When stimulated, second fiber will signal after causing a “jitter” Not widely available

Describe the repetitive nerve stimulation (RNS) test for MG

Stimulate the motor nerve 6-10x Normal response: no change in compound muscle action potential amp MG response: progressive decline in CAMP amp after 4-5x (>10% decline = +)

Describe electomyography

Evaluates electric activity of muscle at rest and with voluntary action

Why is the thymus assessed with MG

Antibodies are produced by thymus A thymoma or thymus mass may cause it CT or MRI

What does a CXR look like with MG

Normal, unless atelectasis

What is MG crisis

There form of an exacerbation

How often should NIF or VC be done with MG

Q4 In severe situations, Q2

What do you do when monitoring MG for respiratory failure

VC NIF SpO2 ABG

What NIF indicates Respiratory failure with MG

More positive than -30cmH2O

What O2 saturation indicates respiratory failure with MG

<92%

What MEP indicates respiratory failure with MG

<40cmH2O

What FVC indicates respiratory failure with MG

<20cmH2O or a decrease >30% prior

What Respiratory Rate indicates respiratory failure with MG

>30 breaths/min

What are treatment strategies for MG

Increase ACh to receptors Immunosuppressive and immunomodulatory agent (plasma exchange) Surgery

What medication increases the ACh to junction

Pyridostigmine (mestinon) Also inhibits acetylcholinesterase Effective in mild cases

What immunosuppressant is first used for MG

Used when symptomatic on acetylcholinesterase Initially glucocorticoid until safer med is available

What are ideal immunosuppressants meds for MG

Azathioprine Mycophenolate mofetl Cyclosporine

What immunomodulating treatment is used for MG

Plasma exchange (removal of AChR antibodies) Intravenous immune globulin (IVIG)

What are the additional chronic managements for MG

Avoids meds that exacerbate MG Seek vaccination