An electromyogram is a diagnostic test involving the placement of small needles into the muscles to assess the electrical activity of muscle and nerve function.

An EMG showing abnormal electrical muscle activity may indicate nerve degeneration (neuropathy) from nerve root compression, disc herniation, or indicate conditions, such as muscular dystrophy and amyotrophic lateral sclerosis (Lou Gehrig disease).

An EMG is typically performed on patients with muscle weakness in order to determine if the pathology originates from the muscles or the nerves.