Needle electromyography: Basic concepts.

Needle electromyography (EMG) is the technique of recording and analyzing the electrical signals derived from individual muscle fibers of motor units, at rest and during voluntary contraction, using a needle recording electrode inserted into the muscle. Needle EMG entails inserting a needle electrode into a muscle, recording and amplifying the electrical signals generated from resting or contracting muscle fibers, and interpreting the signals to determine the function of the muscle fibers and motor units. Many factors affect the recorded signals during needle EMG, including the types of needle electrodes and filters and amplifier settings. Different semiquantitative and quantitative methods of analysis of the recorded signals are available, each with advantages and disadvantages. While needle EMG is a safe technique, potential risks include pain, bleeding, and pneumothorax.