Single-fiber EMG (SFEMG)
If your doctor suspects you have myasthenia gravis, a chronic disease that causes weakness of your voluntary muscles, she might order a test called a single-fiber EMG (SFEMG).
An EMG is a machine that detects activity in your muscles. A single-fiber EMG is a special type of EMG that tests single strands of your muscle fibers. Your doctor will insert a needle electrode into the area where you are experiencing pain. You might feel some discomfort, but the test does not take very long. The SFEMB is used to diagnose myasthenia gravis and is considered to be the most sensitive test for this condition. Your doctor will review the results with you and work with you on a treatment plan.