EMG and NCS
As part of the workup to determine the cause of your pain, your provider may decide to order an electromyogram (EMG) and nerve conduction study (NCS). An optional test called a galvanic skin response (GSR) may also be performed at the same time. These studies help your provider to determine whether there is an issue with your nervous system that could be causing your pain. Typically, the NCS, EMG, and GSR are all performed at the same appointment.
Nerve Conduction Study
NCS is performed by placing non-invasive electrodes on the skin and stimulating your nerves with electrical impulses. Both motor and sensory nerve conductions are studied. The electrical responses are recorded and assessed to determine whether your condition is coming from a problem with the nerve or muscle.
With the EMG, your provider studies the electrical activity of your muscles by placing a needle in the muscle and recording the electrical activity at rest and with activation of the muscle. The EMG differs from the NCS because the nerves are not actually tested. Information about the nerves is obtained indirectly through testing the muscle responses.
Galvanic Skin Response
GSR is a specialized type of NCS that specifically studies the response of your sympathetic nervous system to an electrical impulse. Abnormalities with the GSR can indicate the presence of a small fiber neuropathy, such as diabetic peripheral neuropathy.