Why is Myelography Performed?

This X-ray helps evaluate back injuries and persistent numbness, low back pain, or weakness.

-- To detect herniated discs, tumors, injuries, enlarged blood vessels, and other abnormalities, especially compression of the spinal cord.

-- To evaluate problems in the spinal cord before surgery.

-- To detect injuries to the nerve roots branching off the spinal cord.

-- To detect tumors in the lower part of the brain

How The Test is Performed

The test is performed in a hospital radiology department or in the health care provider's office by an X-ray technician. You will be asked to lie on the X-ray table and assume various positions. If the X-ray is to determine injury, care will be taken to prevent further injury. The X-ray machine will be positioned over the lumbosacral area of the spine. You will be asked to hold your breath as the picture is taken so that the picture will not be blurry. Usually 3 to 5 pictures are taken.

Contrast dye injected into the cerebrospinal fluid (which surrounds the brain and spinal cord) makes it possible to view internal structures with the help of fluoroscopy, a type of moving X-ray.

A myelogram is an X-ray or CT scan of the spine that is performed after dye has been injected into the spinal fluid. See the document on lumbar puncture for more information about the dye insertion portion of this procedure.

-- Local anesthesia is administered at the site where the spinal needle will be inserted.

-- A long needle is inserted into the spinal canal, with the help of a fluoroscope, and guided to the subarachnoid space, between the layers of membrane that surround the spinal cord.

-- Once the needle is in place, a contrast dye is injected and X-ray pictures are taken.

-- To move the dye to structures of interest, you may be slowly titled head down during parts of the test. Care will be taken to prevent the contrast dye from entering the brain.
 

Normal Values

The X-ray shows normal structures for the age of the patient. The doctor examines the X-ray images, called a myelogram, for signs of abnormalities. Abnormalities can also be detected by observing the flow of the contrast dye under a fluoroscope. If the spinal canal is blocked or narrowed, the dye will not spread evenly or will be blocked, and the contour of the spinal cord will also be distorted.
 

Special Considerations

There are a number of back problems that the X-ray will not detect because they involve the muscles, nerves, and other soft tissues. A or lumbosacral spine MRI are better options for soft tissue disorders.

What Abnormal Results Mean

The test will detect abnormalities such as fractures, dislocations, thinning of the bone (osteoporosis), and deformities in the curvature of the spine. The test may also detect bone spurs, disc problems (see herniated disk), and degeneration of the vertebrae.