Fast Five Quiz: Myasthenia Gravis Workup

Richard Nowak, MD, MS


July 08, 2021

SFEMG offers a reasonable substitute for RNS in patients with ocular MG, showing near 100% sensitivity among this patient subgroup. RNS is more specific for a postsynaptic disorder of neuromuscular transmission.

RNS test results are more likely to be abnormal in patients with generalized MG than in patients with purely ocular MG.

It is typical to start with RNS and then complete SFEMG if other diagnostic test results remain unrevealing.

The anti-AChR antibody test result is positive in approximately 70%-80% of patients with generalized MG but about 50% of patients with ocular MG.

Anti-AChR antibodies (blocking type) are present in about half of patients with generalized MG but only 30% of patients with ocular disease. Of note, however, less than 1% of patients with MG have anti-AChR-antibodies (blocking type) without detectable binding or modulating antibodies, rendering this test alone not especially clinically valuable.

Learn more about electrodiagnostic studies in patients with suspected MG.


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