Check this out about myelograms brain-spine.com/helpbook/myelogram.html (if we can put that here)
A myelogram is a relatively safe, special x-ray examination of the spinal cord and canal. Liquid contrast medium is injected into the spinal canal and makes these structures visible on a fluoroscope screen, x-ray film, and CT scan. It is important to tell your doctor if you are allergic to IODINE. Myelograms are used to diagnose
disc problems, spinal tumors, or other structural abnormalities. When ordering a myelogram, the doctor will carefully explain the procedure to you. Special risks of myelography include nausea, vomiting, headache, a 1 in 10,000 chance of seizure, and possible need for a blood patch (explained in the next section) if delayed headaches persist.