A myelogram uses X-rays and a special dye called contrast material to make pictures of the bones and the fluid-filled space (subarachnoid space) between the bones in your spine (spinal canal). A myelogram may be done to find a tumor, an infection, problems with the spine such as a herniated disc, or narrowing of the spinal canal caused by arthritis.
The spinal canal holds the spinal cord, spinal nerve roots, and the subarachnoid space.

The cause of arm or leg numbness, weakness, or pain.
Narrowing of the spinal canal (spinal stenosis).
A tumor or infection causing problems with the spinal cord or nerve roots.
A spinal disc that has ruptured (herniated disc).
Inflammation of the membrane that covers the brain and spinal cord.
Problems with the blood vessels to the spine.
A myelogram may help find the cause of pain that cannot be found by other tests, such as an MRI or a CT scan.
Your doctor will tell you if you need to change how much you eat and drink before the myelogram. You may be asked to increase the amount of water you drink before the test. Follow the instructions exactly about eating and drinking, or your test may be canceled.

Are taking any medicines. You may need to stop taking some medicines for 2 days before the test.
Are or might be pregnant.
Have bleeding problems or take blood-thinning medicines.
Have ever had a severe allergic reaction.
Have diabetes, especially if you take metformin (Glucophage).
Have epilepsy or a seizure problem.
Are allergic to any medicines, contrast material, or iodine dye.
Have asthma.
Have had kidney problems.
Arrange to have someone take you home and stay with you after the test.