A Myelogram is able to show the passage of contrast material in the space around the spinal cord (the subarachnoid space) using a real-time form of X-ray called fluoroscopy, in which organs can be seen over time (like a movie) rather than in the static image called an x-ray or radiograph.

During the exam, a needle is placed usually in the lower back (lumbar puncture) and contrast material is injected into the subarachnoid space  in order for the radiologist to view and evaluate the status of the spinal cord, nerve roots, and intervertebral disks. Detailed picture images of the spinal cord and spinal column are produced for diagnosis.

The contrast material is monitored using fluoroscopy and X-rays of the contrast material around the spinal cord and nerve roots are taken in order to document abnormalities.  In many cases, the myelogram is followed by a CT to better define abnormalities.  This combination of studies is known as CT myelography.

Myelography is generally used to show whether herniations of the material between the vertebral bodies (intervertebral disks) are pushing on nerve roots or the spinal cord.

It is also a strong evaluation tool to depict conditions association with degeneration of the bones and soft tissues surrounding the spinal canal, called spinal stenosis. In this condition, the spinal canal narrows and surrounding tissues enlarge due to the development of bony spurs (osteophytes).

Myelography can also be used to assess conditions when MRI technology cannot be performed, or in addition to MRI to evaluate tumors, infection, inflammation of the arachnoid membrane that covers the spinal cord, and spinal lesions caused by disease or trauma. The test is also valuable in evaluating surgical treatment.