MG Flashcards
A patient presents with ptosis, diplopia, difficulties with chewing and swallowing, and an expressionless face, what diagnosis?
Myasthenia Gravis
What is MG?
(Rare) Autoimmune disease that involved antibodies against the Ach receptors at the neuromuscular junction and muscle specific receptor tyrosine kinase
What lab abnormality is present in most patients with MG?
Thymic abnormalities (Thymus is where T cell mature)
What must you always remember with MG?
“Ming to Ground” = It presents in a descending pattern
What signs and symptoms are common with MG?
Fatigue, eye, speech, and swallowing difficulties. Can then progress down to the respiratory muscles.
Often better in the morning
There are lots of triggers for MG, what are some general categories?
Anesthetics, neuromusclular blocking agents, Abx, anticonvulsants, Penacillamine, cardio meds, steroids, muscle relaxants, ophthalmic drugs.
What is penicillamine?
A medication used as a form of immunosuppression to treat RA
What might you find on PE in MG?
Fatigability of muscles! (lay down and then look up, the lids eventually drop). Normal sensation, normal reflexes. Slack jaw and ptosis on exam
Put the MG patient’s head down and force them to look up, you notice lid fall. What’s the name of this test?
Simpson test
If a MG patient’s follows your finger up and down, and as you go up one lid lags. What’s this test?
Cogan lid twitch sign
What are two tests you can do to confirm the diagnosis of MG?
Tensilon Test (Short-acting Ach-esterase inhibitor) = if marked clinical improvement
Ice pack test = neuromuscular transmission is improved at cooler temperatures
What blood tests can be done to confirm the diagnosis of MG?
Seropositive for Ab against Ach receptors (NACHR – nicotinic acetocholinesterase receptor) or Muscarinic Tyrosine Kinase (MUSK)
Mostly go with binding
What if a patient is seronegative but still have the sxs and confirmatory tests are positive?
May still be MG but need to consider other autoimmune diseases
Can also do Electrophysiologic testing
What if on a CT an incidental finding of thymus abnormalities is seen, what should you do?
Consider Ab testing for MG
What electrophysiologic test finding would confirm MG?
Repetitive nerve stimulation = A “U” shape
There is no cure for MG, but what are some treatment options?
Acetylcholinesterase inhibitors; immunomodulation; immunosuppression (corticosteroids); surgery; IV-Ig & PLEX (for respiratory distress)
How does an Acetylcholinesterase inhibitor work?
Inhibits enzymes that breakdown Ach – works for about an hour
What treatment is best for younger patients to create symptomatic relief and possibly lead to remission?
Thymectomy – but can take up to 10 years for remission
If a patient has a slow progression of their FVC, as monitored in the ICU, what is going on?
Respiratory Crisis
What are the treatment options for respiratory crisis?
IVIg - ~$10,000 per infusion
Plasma Exchange (PLEX) – primary choice
How do you classify MG?
1-5 (5 = the worst with intubation)
