I've had a few myelogram, as Gerry said they set up an IV and do it with contrast (dye) it's one of the many ways specialists can get further detail on our vertebrae injuries and highlights problematic areas in great detail. It didn't hurt but I remember the strong emphasis on lying flat for about 4 hours after the procedure, not sitting up at all and no moving of the head. Apparently the contrast can give you a bad headache if you move around and sit up, so be sure to lie flat after it. My last one was in 2010 and first one in 1977, little had changed procedure wise but the time spent lying after had decreased, it may well be they have improved even further and the need to lie flat no longer required.