Myelography is an imaging examination that involves the introduction of a spinal needle into the spinal canal and the injection of contrast material in the space around the spinal cord (the subarachnoid space) and nerve roots using a real-time form of x-ray called fluoroscopy.
Your doctor may recommend a myelogram to detect abnormalities affecting the spinal cord, the spinal canal, the spinal nerve roots and the blood vessels that supply the spinal cord to show whether herniations of the material between the vertebral bodies, termed the intervertebral disks, are pushing on nerve roots or the spinal cord.
A myelogram can also be used to depict a condition that often accompanies degeneration of the bones and soft tissues surrounding the spinal canal, termed spinal stenosis. In this condition, the spinal canal narrows as the surrounding tissues enlarge due to the development of bony spurs (osteophytes) and the adjacent ligaments. Myelography can also be used to assess: tumors; infection; inflammation of the arachnoid membrane that covers the spinal cord; or spinal lesions caused by disease or trauma when MR imaging cannot be performed, or in addition to MRI.
A myelogram is performed by having the patient lie face-down on the examination table. The radiologist will use the fluoroscope, which projects radiographic image onto the monitor, to visualize the spine and determine the best place to inject the contrast material. At the site of the injection, the skin will be cleaned and then numbed with a local anesthetic. The needle is advanced, usually under fluoroscopic guidance, until its tip is positioned within the subarachnoid space within the spinal canal, at which time a free slow flow of fluid is obtained.
The contrast material is then injected through the needle, the needle is removed and the skin at the puncture site is again cleaned. The patient is then positioned on the table, usually lying on their abdomen. Again using the fluoroscope for guidance, the radiologist then slowly tilts the x-ray table allowing the contrast material to flow up or down within the subarachnoid space and to surround the nerve roots or the spinal cord. As the table is tilted, the radiologist monitors the flow of contrast material with fluoroscopy, focusing on the area that correlates with the patient's symptoms.
Additional x-ray images may be obtained by the radiologist and technologist. A computed tomography (CT) scan is frequently performed immediately following the conclusion of the myelography while contrast material is still present within the spinal canal. This combination of imaging studies is known as CT myelography. A myelography examination is usually completed within 30 to 60 minutes. A CT scan will add another 15 to 30 minutes to the total examination time.
Low dose radiation produces internal images.
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