A myelogram uses X-rays (fluoroscopy) and a special dye called contrast material to make pictures of bones and nerves of the spine (spinal canal).

The spinal canal contains the spinal cord and nerve roots surrounded by a fluid-filled space called the subarachnoid space. For a myelogram, the dye (which contains iodine) is put into the subarachnoid space. X-ray pictures are taken as the dye moves into different areas of the subarachnoid space.

A myelogram can be used to find:

• A blockage in the spinal canal that may be caused by a tumor or by a spinal disc that has ruptured (herniated).
• Inflammation of the membrane (arachnoid membrane) that covers the brain and spinal cord.
• Problems of the blood supply to the spinal cord.
• Problems of the spinal cord and the nerves that branch off from the spinal cord.