Electromyogram

Synonyms

Electrodiagnostic test; EMG

Definition

Electromyogram (EMG) is electrodiagnostic recording of electric potentials or voltage detected by a needle electrode inserted into skeletal muscle. EMG records the variation in electrical potential of insertion, spontaneous, and voluntary activity of muscles with a recording needle electrode. The American Association of Electrodiagnostic Medicine Glossary of Terms provides a uniform agreed-upon framework for expressing electric phenomena encountered in studying patients with EMG.

EMG of the facial muscles is used as an adjunct to neurologic examination of the face to determine the state and function of the facial muscles following facial nerve injury.

Fibrillation Potential

This is the action potential of a single muscle fiber occurring spontaneously or after movement of a needle electrode. Fibrillation potentials usually fire at a constant rate and are indicative of muscle denervation. In the early stage following facial nerve injury,...