A Myelogram , also called EMG or electromyography, is a procedure that involves inserting needle electrodes through the skin into a muscle. A myelogram can be used to detect weakness of the muscles or the pathology of the spinal cord. The electrical activity detected by the electrodes is displayed on a piece of equipment called an oscilloscope that resembles a TV screen with wavy lines crossing it. The presence, size and shape of the waves produced on the screen tell your doctor how able your muscle is to respond to nerve stimulation, and can assist in the diagnosis of problems involving the nervous system.

People undergoing electromyography may experience mild to moderate pain from the procedure. Some mild soreness may be felt at the site of the insertion after the test, and for the next few days. If you plan to undergo the test, plan to rest awhile afterwards and take ibuprofen or acetaminophen (aspirin) for pain if you become too uncomfortable. (Be sure to disclose to your doctor and the person performing the procedure and pain meds you currently take or will be taking the day of the procedure). If OTC pain medications don't relieve your pain, you may want to ask your doctor about a stronger pain medication to take for a brief time after the procedure.

Electromyography is most useful for determining whether problems with the spinal nerve roots are the cause of pain in the legs, and if so, which nerve roots are involved. A myelogram test is less often performed, in favor of more highly detailed medical imaging studies such as the MRI and CT. The myelography procedure is performed to test for spinal problems such as radiculopathy, problems with the blood vessels to the spine, herniated discs, and spinal stenosis. A myelogram uses a special dye (contrast material) and X-rays (flouroscopy) to take medical images of the vertebral bones and the fluid-filled space (subarachnoid space) between the bones in your spine (spinal canal). With these medical images, doctors can see if nerve roots are impacted and if look for a possible narrowing of the spinal canal as a cause of back pain. The doctors and radiologists who look at these images can also look for bulging or herniated discs, infection, tumors, and arthritis.

The spinal canal contains the spinal cord, spinal nerve roots, and the subarachnoid space. A doctor uses a thin needle to inject a dye into the subarachnoid space. The injected dye disperses into the subarachnoid space so that the spinal canal and nerves traveling through and exiting the spinal cord can be seen more clearly. Medical images may be taken continuously before and after the injection of the dye. If the diagnosticians want more information, a CT scan is done following the X-Rays, while the dye is still present.

Today, myelograms are not typically performed unless X-Rays and/or more detailed tests such as CT/MRI fail to produce definitive results. A myelogram may be performed in clinic after a X-Ray and/or CT/MRI images fail to show any structural abnormalities to the spine and nerve roots.