RNS testing

We analyzed the results of RNS tests performed during the diagnostic workup for MG. The RNS test was conducted using the following standard protocol in every patient: The baseline compound muscle action potential (CMAP) was measured during supramaximal stimulation, and the postexercise CMAP was obtained after 20 seconds of maximal exercise.¹⁵ Five low-frequency (3-Hz) RNSs were applied immediately after and at 1, 3, and 5 minutes after maximal exercise. During each stimulus train, the amplitude of the first CMAP and the lowest amplitude of the remaining CMAPs were calculated. A decrease in CMAP amplitude in any stimuli train of ≥10% was defined as abnormal.¹⁶ The RNS test was conducted in a consistent manner on the following five muscles in every patient: the OO, NA, ADM, FCU, and TR muscles. To minimize any immobilization problems, the stimulator was secured with tape during the test. The test was performed on the more-affected side if the ocular symptom distribution was asymmetric. Patients who responded abnormally on the RNS test for any muscle were classified as the RNS-test-positive group, while other patients were classified as the RNS-test-negative group.