Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons). Motor neurons transmit electrical signals that cause muscles to contract. An EMG translates these signals into graphs, sounds or numerical values that a specialist interprets. EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission.
Your physician may order you an EMG if you have signs or symptoms of a nerve or muscle disorder. Based on your results, they may be able to help diagnose or rule out a number of conditions including; muscular dystrophy, diseases affecting the connection between the nerve and the muscle, disorders of nerves outside the spinal cord, or disorders that affect the nerve foot, such as a herniated disk in the spine.
During your procedure, your physician or a technician will place surface electrodes at certain locations on your skin where you're experiencing symptoms. The electrodes will transmit a tiny electrical current that you may feel as a twinge or spasm. During the needle EMG, your neurologist will assess whether there is any spontaneous electrical activity when the muscle is at rest – activity that isn't present in health muscle tissue – and the degree of activity when you slightly contract the muscle. Once your procedure is complete, you may experience some temporary, minor bruising where the needle was inserted into your muscle.