Repetitive Nerve Stimulation
What is repetitive nerve stimulation and what does it show in Myasthenia Grevis?
Repetitive Nerve Stimulation involves the repeated transcutaneous electrical stimulation of all the motor fibers within a peripheral nerve, which generates successive impulses.
These impulses travel down the nerve, across the Neuromuscular Junction dysfunction, and into the muscle, from which consecutive electrical responses (CMAPs) are recorded.
In Myasthenia Grevis, progressive failure of transmission across an increasing number of Neuromuscular Junction dysfunctions with repeated stimulation results in activation of fewer muscle fibers, and progressively smaller CMAPs.
This decrement in CMAP size with low-frequency (2 to 3 Hz) Repetitive Nerve Stimulation confirms Neuromuscular Junction dysfunction.
Decrement may be transiently repaired and CMAP amplitude transiently restored by brief voluntary exercise of the tested muscle between rounds of Repetitive Nerve Stimulation (repair of decrement and postexercise facilitation).
Decrement may also improve with anticholinesterase inhibitor administration.
