The myelography will make the narrow opening between the spinal cord and the surrounding meninges visible. For this purpose, a contrast medium is injected into this liquid-filled cavity (called subarachnoid space), mostly in the lumbar spine region.
Then computer tomography x-ray is performed. Due to the contrast medium, the subarachnoid space as well as distribution of the liquid will show up on the x-ray and thus can be examined and assessed. This method is mostly used to diagnose herniated discs.