Routine motor and sensory nerve conduction studies in myasthenia gravis must be performed before moving on to electrodiagnostic studies, which demonstrate a defect of neuromuscular transmission in the disease. Routine nerve conduction studies are performed to ensure the integrity of any nerve that subsequently will be used in repetitive nerve stimulation.
The following two studies are commonly performed:
Repetitive nerve stimulation of a muscle at 2-3 Hz
Single-fiber electromyography (SFEMG), aimed at evaluating neuromuscular block, jitter, and fiber density
SFEMG is more sensitive than repetitive nerve stimulation in assessing myasthenia gravis. However, SFEMG is technically more difficult and much more dependent on the experience and skill of the testing physician. Therefore, repetitive nerve stimulation is the most frequently performed neurophysiologic test of neuromuscular transmission.
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