A myelogram is an imaging procedure designed to determine whether there is anything actively pressing against the spinal cord, nerves or nerve roots, causing pain in the back or numbness and weakness in the arms and/or legs. This is performed by using a real-time form of x-ray called fluoroscopy.

A myelogram may be performed along with other spinal exams, such as a Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scan. It is particularly useful for assessing the spine following surgery and for assessing disc abnormalities in patients who cannot undergo MRI.

A myelogram is most commonly used to detect abnormalities affecting the spinal cord, the spinal canal, the spinal nerve roots and the blood vessels that supply the spinal cord, including:

• to show whether a herniation of the intervertebral disk between the successive vertebral bodies is compressing the nerve roots or the spinal cord
• 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 called osteophytes and thickening of the adjacent ligaments.

A myelogram can also be used to assess the following conditions when an MRI cannot be performed:

• tumors involving the bony spine, meninges, nerve roots or spinal cord
• infection involving the bony spine, intervertebral discs, meninges and surrounding soft tissues
• inflammation of the arachnoid membrane that covers the spinal cord
• spinal lesions caused by disease or trauma.

As the patient lies face down on the examination table, the radiologist will use the fluoroscope, which projects radiographic images in a movie-like sequence onto the monitor, to visualize the spine and determine the best place to inject the contrast material.

The contrast material usually is injected into the lower lumbar spinal canal, because it is considered easier and safer. Occasionally, if it is deemed safer or more useful, the contrast material will be injected into the upper cervical spine.

At the site of the injection, the skin will be cleaned and then numbed with a local anesthetic. Depending on the location of the puncture, the patient will be positioned on his/her side or on the abdomen (prone position). 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 cleansing of the skin at the puncture site is repeated. Then, the patient is positioned on the table, usually lying face down.

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.

At this point, the patient may be repositioned on his/her side and additional x-ray images may be obtained by the radiologist and technologist. While these images are being obtained, it is important for the patient to remain as still as possible.

When these images have been completed, the table is returned to the horizontal position, and the patient is allowed to roll onto his/her back and assume a position of greater comfort while the images are checked by the radiologist.

You will feel a brief sting when local anesthetic is injected under the skin and you will feel slight pressure on your back as the spinal needle is inserted. Positioning the needle can occasionally cause sharp pain.