Doctors use an electromyogram or EMG, a diagnostic procedure, to assess numbness or paralysis, muscle weakness or spasms, and the cause of pain in the arms, hands, legs, feet, and face. When the doctor uses this test, it will identify problems with nerve-to-muscle signal transmission.

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Electromyogram Testing

Sometimes, our Southwest Scoliosis Doctors, Richard Hostin, MD, Devesh Ramnath, MD, Ishaq Y. Syed, MD, Shyam Kishan, MD, and Kathryn Wiesman, MD, will need to order extra testing to diagnose or help devise a treatment plan. Because of this, the doctor may order an electromyogram or EMG to look at the nerve roots to determine their working condition.

In short, an electromyogram (EMG) looks at the function of the nerve roots leaving the spine.  In addition, it does this by looking at how well the electrical currents in the nerves transmit to the muscles. Also, pressure on the nerves or damage to the nerves changes the way they transmit electrical current. This shows up in the muscles as they react to the information being sent to them from the brain by the nerves. When ordering electrical tests to diagnose spine problems, an EMG works with another test that identifies electrical signals going from the body to the brain.  These are called somatosensory evoked potentials (SSEPs).

EMG Machine for testing nerve damage ( electromyography )

Reason to conduct an EMG Test?

By looking for abnormal electrical signals in the muscles, an EMG can show nerves being irritated or pinched as they leave the spine to the arm or leg.  As an example, an EMG can compare to a test of the wiring of a lamp. If a working bulb lights up, you can assume that the wiring works. If the bulb does not light up you can assume that the wiring needs attention.  As an example, the lamp could be unplugged or short-circuited.  Using the muscles like the light bulb, the EMG determines the condition of the nerves that supply those muscles.  Just like the wiring on the lamp.  If the EMG finds muscles working improperly, the doctor will infer that a pinched or damaged nerve exists.  

How does the EMG work?

The doctor will insert tiny electrodes into the muscles of the legs.  Then the doctor will stimulate the nerve going to the muscle.  After that, the doctor will measure the time for the electrical signal to reach the muscle and make the muscle tighten.

Limitations of the EMG

An EMG does not show why the problem occurred or what causes it. The test looks primarily at how the muscles react to the nerve problem. However, a problem in the nerve could exist anywhere between the spine and the muscle.  Also, the location may not necessarily occur in the spine.  Still, an EMG helps to determine the damage to a nerve and if a herniated disc or another problem puts pressure on the nerve roots. Also, the test may appear normal when a damaged nerve exists.  This refers to what doctors call a “false negative,” meaning the test results look negative, even though actually positive.

Risks associated with an EMG

There are few risks associated with EMG. For instance, anytime a doctor inserts a needle into the body, a small chance of infection will exist. However, the risk is almost absent in this type of test.


If you or a loved one suffers from spinal pain, you owe it to yourself to call Southwest Scoliosis and Spine Institute at 214-556-0555 to make an appointment.