Electromyography (EMG) is an electro diagnostic medicine technique for evaluating and recording the electrical activity produced by muscles. An electromyography detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated.
Except in the case of some purely primary myopathic conditions EMG is usually performed with another electro diagnostic medicine test that measures the conducting function of nerves. This is called a nerve conduction studies (NCS). Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder.
Needle EMG may aid with the diagnosis