This shows up in the muscles as they react to the information being sent to them from the brain – by the nerves. Pressure on the nerves or damage to the nerves changes the way they transmit electrical current. It does this by looking at how well the electrical currents in the nerves are being transmitted to the muscles. What it is: An electromyogram (EMG) test looks at the function of the nerve roots leaving the spine.
This risk is almost absent in an EMG test. Anytime a needle is inserted into your body there is a small chance of infection. There are few risks associated with an EMG. This is called a “false negative,” meaning the test results look negative even though they are actually positive. Another limitation of the EMG is that result of the test may normal when the nerve is actually damaged. There could even be a problem in the nerve somewhere between the spine and the muscle, and it may not necessarily be in the spine itself. The test looks primarily at how your muscles are reacting to the nerve problem. What are the limitations?Īn EMG does not show why there is a problem with the nerves in your spine or what is causing it. The nerve going to each muscle is then stimulated to see how long it takes the electrical signal to reach the muscle and make the muscle tighten. Tiny electrodes are inserted into the muscles of the legs. If the EMG finds that the muscles are not working properly, your doctor can assume that the nerves must be getting pinched somewhere. Using the muscles like the light bulb in the lamp, the EMG is able to determine the condition of the nerves that supply those muscles, just like the wiring on the lamp. If the bulb does not light up you can assume that something is probably wrong with the wiring-the lamp is unplugged or a short circuit has occurred.
If a working bulb is placed into the lamp and it lights up, you can assume that the wiring is okay. The EMG is similar to testing the wiring on a lamp. Why is it done?īy looking for abnormal electrical signals in the muscles, the EMG can tell your doctor whether a nerve is being irritated or pinched as it leaves the spine on its way down your arm or leg. When ordering electrical tests to diagnose spine problems, EMG is combined with a test showing electrical signals going from the body to the brain, called an SSEP or somatosensory evoked potentials test. This shows up in the muscles as they react to the information being sent to them from the brain by the nerves. Home / Patient Info / Diagnostic Tests / Electromyogram (EMG) What is it?Īn electromyogram (EMG) looks at the function of the nerve roots leaving the spine.
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