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 It Is 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.
This test may help find the cause of pain that can't be found by other tests, such as an MRI or a CT scan.
How To Prepare
Your doctor will tell you if you need to change how much you eat and drink before the myelogram. You may be asked to increase the amount of water you drink before the test. Follow the instructions your doctor gives you about eating and drinking.
If you take a medicine that prevents blood clots, your doctor may tell you to stop taking it before your test. Or your doctor may tell you to keep taking it. (These medicines include aspirin and other blood thinners.) Make sure that you understand exactly what your doctor wants you to do.
Be sure you have someone to take you home. Anesthesia and pain medicine will make it unsafe for you to drive or get home on your own.
How It Is Done
The test is done by a doctor in a radiology center or in the radiology department of a hospital.
You will need to take off jewelry that might be in the way of the X-ray picture. You may need to take off all or most of your clothes above the waist. (You may be allowed to keep on your underwear if it doesn't get in the way of the test.) You will be given a gown to wear during the test.
During the test
You will have a spinal tap to put the dye into your spinal canal. You will lie on your stomach or side on an X-ray table. The doctor cleans an area on your lower back. A numbing medicine is put into your skin.
After the area is numb, a thin needle is put into the spinal canal. A stream of X-rays (fluoroscopy) is used to help the doctor place the needle in the right area. A sample of spinal canal fluid may be taken before the dye is put in the canal.
After the dye is put in, you will lie still while the X-ray pictures are taken.
After the pictures are taken, a small bandage is put on your back where the needle was put in. You will be told what to do after the test.
How long the test takes
- A myelogram usually takes 30 minutes to 1 hour.
How It Feels
You will feel a quick sting from a small needle that has medicine to numb the skin on your back. You will also feel some pressure as the long, thin spinal needle is put into your spinal canal. You may feel a quick, sharp pain down your buttock or leg when the needle is moved in your spine. You may find it hard to lie on your stomach or side during this test.
The dye may make you feel warm and flushed and have a metallic taste in your mouth. Some people feel sick to their stomach or have a headache. Tell your doctor how you are feeling.
There is some risk of problems with this test.
- Some people who have a myelogram develop a headache, nausea, or vomiting after the test. The headache may last for 24 hours. In rare cases, a seizure may occur after the dye is put into the spinal canal.
- There is a small risk of a seizure if the dye moves to the brain. So if you lie down, you need to keep your head raised higher than your body.
- There is a small risk of infection at the needle site or bleeding into the spinal canal.
- In rare cases, the hole made by the needle in the sac around the spine doesn't close normally. This can allow spinal fluid to leak out. This leak may need to be repaired through a procedure called an epidural blood patch. To do the patch, your doctor injects some of your own blood to cover the hole.
- There is a small risk of having an allergic reaction to the dye. You will be given medicine for a reaction.
- In rare cases, inflammation of the spinal cord, weakness, numbness, paralysis, or loss of control of your bowel or bladder may develop.
- Also in rare cases, the dye may cause blockage of the spinal canal. If this occurs, surgery is usually needed.
- There is a risk of damage to cells or tissue from being exposed to radiation, including the small amounts used in CTs, X-rays, and other medical tests. Over time, exposure to radiation may cause cancer and other health problems. But in most cases, the risk of getting cancer from being exposed to small amounts of radiation is low. It is not a reason to avoid these tests for most people.
Your doctor will talk to you about the results of your test.
The dye flows evenly through the spinal canal.
The spinal cord is normal in size, position, and shape. The nerves leaving the spinal cord are normal.
No narrowing or blockage of the spinal canal is seen.
Inflammation of the membrane (arachnoid membrane) that covers the spinal cord is seen.
One or more nerves leaving the spinal cord are pinched.