A myelogram is a diagnostic imaging test generally done by a radiologist. It uses a contrast dye and X-rays (fluoroscopy) or computed tomography (CT) to look for problems in the spinal canal. Problems can develop in the spinal cord, nerve roots, and other tissues. This test is also called myelography.

The contrast dye is injected into the spinal column before the procedure. The contrast dye appears on an X-ray screen. This allows the radiologist to see the spinal cord, subarachnoid space, and other nearby structures more clearly than with standard X-rays of the spine.

The radiologist may also use a CT scan when doing a myelogram. A CT scan is an imaging test that uses X-rays and a computer to make detailed images of the body. A CT scan shows detailed images of the spinal canal. CT scans show more details than standard X-rays.

A myelogram may be done to assess the spinal cord, subarachnoid space, or other structures for changes or abnormalities. It may be used when another type of exam, such as a standard X-ray, doesn't give clear answers about the cause of back or spine problems. Myelograms may be used to evaluate many diseases, including:

• Herniated discs. These are discs that bulge and press on nerves or the spinal cord.
• Spinal cord tumors.
• Infection or inflammation of tissues around the spinal cord.
• Spinal stenosis. This is a breakdown and swelling of the bones and tissues around the spinal cord. This breakdown makes the canal narrow.
• Bone spurs.
• Arthritic discs.
• Tumors.
• Cysts. These are noncancerous (benign) capsules that may be filled with fluid or solid matter.
• The tearing away or injury of spinal nerve roots.
• Arachnoiditis. This is inflammation of a delicate membrane that covers the nerve roots in the lower spine.

There may be other reasons for your doctor to recommend a myelogram. Talk with your doctor about the reason for your test.

You may want to ask your doctor about the amount of radiation used during the procedure. And about the risks related to your situation. It's a good idea to keep a record of your radiation exposure so that you can inform your doctor. These include previous CT scans and other types of X-rays. Risks associated with radiation exposure may be related to the cumulative number of X-ray exams or treatments over a long period.

Tell your doctor if you're pregnant or think you may be. Radiation exposure to the fetus may cause birth defects.

There is a risk of an allergic reaction to the contrast dye. Be sure to let your doctor know if you have any allergies, especially to shellfish or iodine, ever had a reaction to any contrast dye, or have any kidney problems.

There is a small risk of seizure after the injection. This is because the contrast is injected into the cerebrospinal fluid (CSF), which also surrounds the brain. Some medicines may place you at greater risk for seizure, and you may be asked to stop taking these for 48 hours before and after the study. Make sure your doctor has a list of all medicines (prescribed and over-the-counter) and all herbs, vitamins, and supplements that you're taking.

Because this procedure involves a lumbar puncture, these potential complications may happen:

• A small amount of CSF can leak from the needle insertion site. This can cause headaches after the procedure. If there's a persistent leak, the headache can be bad.
• There is a slight risk of infection because the needle breaks the skin's surface, providing a possible entry point for bacteria.
• You could have short-term numbness of the legs or lower back pain.
• There is a risk of bleeding in the spinal canal or in the soft tissues around it.

There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor before the procedure.

• Your doctor will explain the procedure to you and ask if you have any questions.
• You'll be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if anything isn't clear.
• Follow any directions you're given for not eating or drinking before the test.
• Tell your doctor or the radiologist if you have ever had a reaction to any contrast dye or if you're allergic to iodine.
• Tell your doctor if you have a history of seizures or are taking any medicines for seizures.
• Tell your doctor if you have a history of bleeding disorders. Or if you are taking any blood-thinner (anticoagulant) medicine, aspirin, or other medicines that affect blood clotting. You may need to stop these medicines before the procedure.
• Tell your doctor if you have heart disease, asthma, thyroid problems, kidney disease or diabetes.
• Give your doctor a list of all prescribed and over-the-counter medicines, herbs, vitamins, and supplements that you're taking.

You may be asked to stay in the hospital for several hours afterward if you have the procedure as an outpatient. Plan to have another person drive you home.

Your doctor may give you other instructions on what to do before the procedure.

A myelogram may be done on an outpatient basis or as part of your stay in a hospital. The procedure takes about an hour but may vary depending on your condition and the clinic's practices.

Generally, a myelogram follows this process:

1. You'll be asked to remove any clothing, jewelry, or other objects that may get in the way of the procedure.
2. If you're asked to remove your clothing, you'll be given a gown to wear.
3. You will be reminded to empty your bladder before the start of the procedure.
4. You'll lie on your stomach or side on a padded table.
5. Your back will be cleaned with an antiseptic solution and draped with sterile towels.
6. The radiologist will numb the skin of your lower spine by injecting a numbing medicine using a thin needle. This injection may sting for a few seconds, but it makes the procedure less painful.
7. A needle will be inserted through the numbed skin, between 2 spinal bones (vertebrae), and into the subarachnoid space where the spinal fluid is located. You'll feel some pressure while the needle goes in, but it shouldn't be painful. You must stay very still.
8. The radiologist may remove some of the spinal fluid from the spinal canal. Next, a small amount of contrast dye will be injected into the spinal canal through the needle. You may feel a warming sensation and a metallic taste in your mouth when the contrast dye is injected. This should last only a few minutes. Then you'll lie on your stomach, if you're not already in this position.
9. The X-ray table will be tilted in various directions to allow gravity to help move the contrast dye to different areas of your spinal cord. You'll be held in place by a special brace or harness. More contrast dye may be given during this process through the secured lumbar puncture needle.
10. The needle is then removed and the X-rays or CT scan pictures are taken.
11. You should tell the radiologist right away if you feel any numbness, tingling, headache, or lightheadedness during the procedure.

You may have discomfort during the myelogram. The radiologist will use all possible comfort measures and complete the procedure as quickly as possible to reduce any discomfort or pain.

You need to sit or lie down for several hours after the procedure to reduce your risk of developing a cerebral spinal fluid leak.

You'll be asked to drink extra fluids to rehydrate after the procedure. This helps your body wash out the contrast dye and replace the spinal fluid that was removed. It also reduces the chance of developing a headache.

A nurse will keep track of your vital signs (blood pressure, temperature, pulse, and respirations) frequently after the test. You'll be given pain medicine if you develop a headache.

When you have completed the recovery period, you'll be taken to your hospital room or discharged to your home.

Once you are at home, tell your doctor about any changes, including:

• Numbness and tingling of the legs.
• Blood or other drainage from the injection site.
• Pain at or near the injection site.
• Nausea or vomiting.
• Inability to urinate.
• Fever.
• A stiff neck.
• Leg numbness.
• Headaches.
• Allergic reaction (such as rash, itching, sneezing, anxiety, etc.) to contrast dye.

If the headaches persist for more than 24 hours after the procedure or generally get worse, especially when you change positions, you should contact your doctor.

You may be instructed to limit your activity for 24 hours after the procedure. Generally, if you don't have any problems, you may return to your normal diet and activities.

Your doctor may give you other instructions after the procedure, depending on your situation.

Before you agree to the test or procedure, make sure you know:

• The name of the test or procedure.
• The reason you're having the test or procedure.
• What results to expect and what they mean.
• The risks and benefits of the test or procedure.
• What the possible side effects or complications are.
• When and where you're to have the test or procedure.
• Who will do the test or procedure and what that person's qualifications are.
• What would happen if you didn't have the test or procedure.
• Any alternative tests or procedures to think about.
• When and how you'll get the results.
• Who to call after the test or procedure if you have questions or problems.
• How much you'll have to pay for the test or procedure.