Some patients with implanted metal devices cannot undergo MRI scanning. In order to assess the spinal cord in these patients, a special type of CT called a CT Myelogram can be done. In this test, contrast dye is not injected into the blood but rather into the cerebrospinal fluid (CSF) that coats our brain and spinal cord. This injection is done by means of a 'spinal tap' or 'lumbar tap' (similar to that described above except that dye is inserted rather than having fluid removed). Local anesthetic is given prior to the needle being placed in the lower back.