MYASTHENIA GRAVIS (quick pearls)

8 Dec

Submitted by Amit Kumar, M.D.m_jpg0420f1

Quick Pearls:

Pathology: Auto-antibodies against ACh post-synaptic receptors

Common symptoms:

  • Ocular (ptsosis, diplopia),
  • bulbar (fatigable chewing, dysarthria, dysphagia),
  • loss of facial expessions,
  • neck/proximal limb weakness,
  • respiratory failure leading to myasthenia crisis (often tested via negative inspiratory force and vital capacity- NIF/VC)
  • Concerning if NIF and VC approach 25cmH2O and 15mg/kg body weight respectively.



-Bedside tests (higher risk for False+): Edrophonium “tensilon” test (acetylcholinesterase), ice-pack test

-Serum tests: ACh-R antibodies (more common), muscle-specific receptor tyrosine kinase (MuSK) antibodies

-Other: Repetitive nerve stimulation –> Fatigable


-Thymic hyperplasia (85%), thymoma (15%). Prophylactic thymectomy recommended for <60y.

autoimmune thyroid dx (3-8%)


-Pyridostigmine (anticholinesterase)

-Chronic immunotherapies (glucocorticoids, azathioprine, cyclosporin, etc.)

-Rapid immunotherapies: plasmaphresis (usually every other day for total of 5 sessions), IVIG (total dose of IVIG is 2 g/kg, usually over 2-5 days)

Fun fact:

MANY medications are contraindicated in MG:
-Certain Antibiotics: Macrolides (Azithromycin, Erythromycin), Gentamicin, Kanamycin, Neomycin, Streptomycin, Tobramycin; Fluoroquinolones: Ciprofloxacin
-Cardiovascular drugs: Quinidine, Procainamide, Quinine Calcium channel blockers, Beta-blockers
-Neuromuscular Blocking Agents: Succinylcholine, d-tubocurarine or Any other neuromuscular blocking agent
-Narcotics: Meperidine, Morphine
-Any medication with the potential to suppress respiratory drive
Other medications: Iodinated contrast agents, Magnesium Preparations, Especially intravenous Magnesium but also PO such as Maalox, Steroids, Botulinum Toxin

***A good rule-of-thumb in generalized MG is to assume that any medication may exacerbate MG and to watch for worsening following the introduction of a new medication.


  1.  Pal S, Sanyal D. Jaw muscle weakness: a differential indicator of neuromuscular weakness–preliminary observations. Muscle Nerve 2011; 43:807.<>
  2.  Lennon VA. Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology 1997; 48:S23.<>?
  4.  September 2015 EMRAP- Drugs not to use in Myasthenia Gravis

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