What is Myelography?
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 and nerve roots (the subarachnoid space) using a real-time form of x-ray called fluoroscopy.
When the contrast material is injected into the subarachnoid space, the radiologist is able to view and evaluate the status of the spinal cord, the nerve roots and the meninges. The meninges are the membranes which surround and cover the spinal cord and nerve roots. Myelography provides a very detailed picture (Myelogram) of the spinal cord, nerve roots, subarachnoid space and spinal column. The radiologist views the passage of contrast material in real-time within the subarachnoid space as it is flowing using fluoroscopy but also takes permanent images, called x-rays or radiographs, of the contrast material around the spinal cord and nerve roots in order to document abnormalities involving or affecting these structures. In most cases, the Myelogram is followed by a computed tomography (CT) scan to better define the anatomy and any abnormalities.
What are some common uses of the procedure?
Magnetic resonance imaging (MRI) is often the first imaging exam done to evaluate the spinal cord and nerve roots. However, on occasion, a patient has a medical device, such as a cardiac pacemaker, that may prevent him or her from undergoing MRI. In such cases, Myelography and/or a CT scan, in lieu of MRI, is performed to better define abnormalities.
Myelography 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 (osteophytes) and thickening of the adjacent ligaments.
Myelography can also be used to assess the following conditions when MR imaging cannot be performed, or in addition to MRI (when MR does not provide sufficient information):
- 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
A Myelogram can show whether surgical treatment is promising in a given case and, if it is, can help in planning surgery. In patients with spinal instrumentation (screws, plates, rods, etc.), MR imaging may not be optimal because of artifacts generated by these instruments. In these cases your doctor may decide to order CT Myelography.
What are the benefits vs. risks?
Myelography is relatively safe and painless. When a contrast material is injected into the subarachnoid space surrounding the nerve roots and spinal cord, it allows the radiologist to view outlines of the different areas of the spine that usually are not visible or distinguishable on x-rays. X-rays usually have no side effects when used in the diagnostic range necessary for this procedure.
Although it is uncommon, headache associated with the needle puncture is a risk. The headache, when it occurs following Myelography, usually begins when the patient begins to sit upright or stand. One of the common features of this type of headache is that it is improved when the patient lays flat. When present, the headache usually begins within 2-3 days after the procedure. Rest while lying flat and increased fluid intake readily relieve mild headaches, but more severe headaches may call for medication. In rare circumstances some patients may continue to experience spinal headaches, which may necessitate a special, but simple, procedure to help with the headache called a blood patch.
Adverse reactions to the injection of contrast material during a Myelogram are infrequent and usually mild in nature, including itching, rash, sneezing, nausea or anxiety. The development of hives or wheezing is rare, but may require treatment with medication. More severe reactions involving the heart or lungs are rare.
Other rare complications of Myelography include nerve injury from the spinal needle and bleeding around the nerve roots in the spinal canal. In addition, the meninges covering the spinal cord may become inflamed or infected. Seizures are a very uncommon complication of Myelography. There is a very small risk that pressure changes within the spinal canal caused by the introduction of a needle below the site of an obstruction will block the flow of fluid within the subarachnoid space of the spinal canal, which can make urgent surgery necessary.
A Myelogram uses X-rays and a special dye called contrast material to make pictures of the bones and the fluid-filled space (subarachnoid space) between the bones in your spine (spinal canal). A Myelogram may be done to find a tumor, an infection, problems with the spine such as a herniated disc, or narrowing of the spinal canal caused by arthritis.
The spinal canal holds the spinal cord, spinal nerve roots, and the subarachnoid space.
During the test, a dye is put into the subarachnoid space with a thin needle. The dye moves through the space so the nerve roots and spinal cord can be seen more clearly. Pictures may be taken before and after the dye is used. To get more information from the test, a CT scan is often done after the X-rays, while the dye is still in your body.
Why is it done?
A Myelogram is done to check for:
- The cause of arm or leg numbness, weakness, or pain.
- Narrowing of the spinal canal (spinal stenosis).
- A tumor or infection causing problems with the spinal cord or nerve roots.
- A spinal disc that has ruptured (herniated disc).
- Inflammation of the membrane that covers the brain and spinal cord.
- Problems with the blood vessels to the spine.
- A Myelogram may help find the cause of pain that cannot be found by other tests, such as an MRI or a CT scan.