What Is a Myelogram?

A myelogram is an imaging examination of the spine performed after contrast material has been injected directly into your spinal canal to outline the spinal cord, nerve roots, and other spinal structures on X-ray and CT.

Conventional myelography utilizes a special form of X-ray called fluoroscopy (“real-time” X-ray) and an iodine-containing contrast material that is injected directly into the spinal canal. When contrast material is injected into the spinal canal, it is clearly visible on fluoroscopic and CT images and allows the radiologist to better detect abnormalities. While the injection is monitored with fluoroscopy, regular X-ray images are also obtained for documentation.

CT myelography is now almost always performed in conjunction with conventional myelography. CT uses X-ray pictures taken from multiple different angles to create cross-sectional images that appear as “slices” of the bones and surrounding structures.

A myelogram is usually performed to evaluate for suspected compression of the spinal cord and/or nerve roots. Pressure on these structures typically causes a combination of pain, weakness, and numbness in the neck, back, or extremities. The most common causes of these symptoms are:

• Disk herniations, in which there is abnormal protrusion or extrusion of disk material between adjacent vertebrae into the spinal canal.
• Spinal stenosis, which often accompanies degeneration of the bones and soft tissues surrounding the spinal canal. In this condition, the spinal canal narrows as the surrounding tissues enlarge due to the development of bony spurs (osteophytes) and thickening of the adjacent ligaments.

In many cases myelography is performed after other studies, such as magnetic resonance imaging (MRI) or computed tomography (CT) scans, have not yielded enough information. Myelography can also be used to evaluate tumors, infections, suspected leakage of spinal fluid, and other conditions affecting the spine when MRI imaging cannot be performed or when it does not provide sufficient information. For patients who cannot have an MRI scan because they have a pacemaker or other implanted metallic device, CT myelography is often the best alternative.

A myelogram can often help determine if surgical treatment may be indicated and can help in surgical planning. In patients who already have spinal instrumentation (screws, plates, rods, etc.), your doctor may order CT myelography because the surgical hardware can produce extensive artifacts on MRI imaging that makes evaluation difficult.