EMG

EMG stands for electromyography. During an EMG examination, the electrical activity of muscles and/or nerves is recorded.

Electrodes are placed on the skin or a needle is inserted into the muscle. The electrodes pick up the electrical signals that a muscle emits when it contracts. The way these electrical signals are transmitted determines whether there is an abnormality in the muscle or nerve.

Conditions in which signal transmission is reduced include nerve damage or muscle diseases. EMG testing shows what causes symptoms such as muscle weakness, tingling, numbness, or pins and needles.

What does the examination involve?

An EMG examination takes 30 to 75 minutes and involves the following steps:

• The examiner attaches several electrodes to the skin over the muscle being tested. The skin must be clean and oil-free; otherwise, the electrodes will not adhere well. The electrodes then do not make good contact, which disrupts the transmission of the electrical signal.
• These adhesive electrodes are connected to a device that generates small, painless electrical pulses. In response to this pulse, the muscle contracts, which may cause, for example, the hand to move slightly. The level of muscle activity is displayed on a computer screen.
• If the EMG examination is done with a needle, the needle is inserted into the muscle. Measurement with needle electrodes is more accurate than with adhesive electrodes. The needles can be a bit painful.
• At a later time, the patient’s own doctor will discuss the results with the patient.