Repetitive Nerve Stimulation: Sensitivity and Specificity
For generalized myasthenia, sensitivity ranges 53-100%. Sensitivity is only 10% for ocular myasthenia. Specificity not assessed, though anecdotes put it at 70-80%.
The test is done by repetitively stimulating a nerve and looking at the muscular response; at 2 Hz stimulation, the amplitude of response should decrease over time. At higher frequency stimulation, there is a variable response (i.e. decrease or constant amplitude) because of increased calcium in the synaptic cleft.