What is single-fiber electromyography (SFEMG)?

Updated: Mar 13, 2019
  • Author: Pradeep C Bollu, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Single-fiber electromyography (SFEMG) is a selective EMG recording technique that allows identification of action potentials (APs) from individual muscle fibers. It was initially described in the early 1960s but gained popularity after the publication of Stålberg and Trontelj's monograph, Single Fibre Electromyography, in 1979.

The selectivity of the technique results from the small recording surface (25 µm in diameter), which is exposed at a port on the side of the electrode, which is 3 mm from the tip (see image below). The selectivity of the recording is further heightened by using a high-pass filter of 500 Hz. Identification of APs from individual muscle fibers by SFEMG uniquely allows measurement of 2 features of the motor unit: fiber density and neuromuscular jitter. [1, 2, 3, 4]

Diagram of a single-fiber electromyography electro Diagram of a single-fiber electromyography electrode within a motor unit. Light-colored symbols indicate muscle fibers belonging to one motor unit. The electrode is positioned to record the action potential from one muscle fiber with maximum amplitude. In this example, no other muscle fibers from the same motor unit are within the recording territory of the electrode (yellow semicircle).

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