What is the role of pharmacological testing in the evaluation of myasthenia gravis (MG)?

Updated: Aug 27, 2018
  • Author: Abbas Jowkar, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

In patients with MG, the number of AChRs at the NMJ is low, which results in a decreased number of interactions between ACh and its receptor. ACh released from motor nerve terminals is metabolized by AChE. As a result, pharmacologic inhibition of AChE increases ACh concentration at the NMJ, improving the chance for interactions between ACh and its receptor. Edrophonium (tensilon) is a short-acting AChE inhibitor that improves muscle weakness in patients with MG.

This test evaluates weakness (eg, ptosis, partial or complete ophthalmoplegia, and forced hand grip) in an involved group of muscles before and after intravenous (IV) administration of edrophonium. Blinding of both the examiner and the patient increases the validity of the test.


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