Get to know myelogram, an examination of the spinal canal

Definition

What is a myelogram?

A myelogram is a test using X-rays and a special dye called a contrast material to create images of the bones and fluid-filled spaces (subarachnoid spaces) between the bones in your spine (spinal canal). A myelogram can be done to find tumors, infections, problems with the spine such as a herniated disc, or narrowing of the spinal canal caused by arthritis.

The spinal canal consists of the spinal cord, spinal nerve roots, and the subarachnoid space. During the test, the dye is introduced into the subarachnoid space with a thin needle. The dye moves through the space so that the nerve roots and spinal cord can be seen more clearly. Pictures can be taken before and after the dye has been used. To get more information from the test, a CT scan is often done after an X-ray, while the dye is still in your body.

When do I need to have a myelogram?

A myelogram may be done to assess the spinal cord, subarachnoid space, or other structures for abnormalities, especially when other types of examinations, such as standard X-rays, are inconclusive. Myelogram can be used to evaluate many diseases, including, but not limited to, the following:

• herniated disc (disc that protrudes and presses on the nerves and / or spinal cord)
• spinal cord tumor or brain tumor
• infection and / or inflammation of the tissue around the spinal cord and brain
• spinal stenosis (degeneration and swelling of the bones and tissues around the spinal cord that create a narrow canal)
• ankylosing spondylitis (a disease that affects the spine, causing bones to grow together)
• bone spurs
• arthritic discs
• degenerative disc disease
• cysts (benign lumps that may contain fluid)
• spinal cord root injury
• arachnoiditis (inflammation of the smooth membrane covering the brain)

There may be other reasons for your doctor to recommend a myelogram.

Precautions & warnings

What should I know before undergoing a myelogram?

CT or MRI scans have replaced the need for a myelogram in most cases. Myelogram is often done with a CT scan to create more detailed images of the spine. If a tumor is seen on the myelogram or if the lumbar injection causes complete blockage of the spinal canal, you may need immediate surgery.

Process

What should I do before undergoing a myelogram?

Your doctor will provide detailed instructions on how to prepare for your myelogram. You should tell your doctor about any medications being taken and any allergies, especially to iodinated contrast materials. Also tell your doctor about any new illnesses or other medical conditions.

In particular, doctors need to know if:

• You are taking medication that needs to be stopped a few days before the procedure
• do you have a history of reactions to the contrast material used for the myelogram

Some drugs must be stopped a day or two before myelography. This includes certain medications such as antipsychotics, antidepressants, blood thinners, and some other medications. The most important type of medicine to stop is blood thinners (anticoagulants). If you are taking blood thinners you should talk to your doctor about alternative methods of maintaining anticoagulants while you have your myelogram.

Usually patients are advised to increase their fluid intake the day before their scheduled myelogram, as it is important to be well hydrated. Solid foods should be avoided for several hours prior to the examination, but foods in liquid form can be continued.

You may be asked to remove some or all of your clothing and to wear certain clothing during the examination. You may also be asked to remove jewelry, remove dental utensils, glasses, and metal objects or clothing that might interfere with the x-ray image.

What is the usual process for a myelogram?

You will have an injection in the spine to inject the dye into your spinal canal. You will lie on your stomach or side on the X-ray table. The doctor will clean the area on your lower back. An anesthetic will be injected into your skin.

After the area is numbed, a thin needle is inserted into the spinal canal and a stream of X rays (fluoroscopy) is used to help the doctor place the needle in the canal area. A spinal canal fluid sample can be taken before the dye is inserted into the canal. After the dye is put in, you will lie still while the X-ray image is taken. After the picture is taken, a small bandage will be placed on your back where the needle is inserted. You will be told what to do after the test.

What should I do after undergoing a myelogram?

This test usually takes 30 minutes to 1 hour. You may need to lie in bed with your head raised for 4 to 24 hours after the test. To prevent seizures, do not bend over or lie down with your head lower than your body. Avoid strenuous activities, such as running or heavy lifting, for at least 1 day after the exam. Drink lots of water afterward. The doctor will provide instructions on the consumption of common medicines.

Explanation of the Test Results

What do my test results mean?

Your doctor will talk to you about your test results.

Normal:

• the dye flows evenly through the spinal canal
• The spinal cord is normal in terms of size, position and shape. The nerves leaving the spinal cord are normal
• no visible narrowing or blockage of the spinal canal

Abnormal :

• the dye stream is blocked or diverted. This may be due to a ruptured hernia disc, spinal stenosis, nerve injury, abscess, or tumor. There is inflammation of the membrane (arachnoid membrane) covering the spinal cord
• one or more nerves leaving the spinal cord pinched

What can affect the test results?

The reason you may not be able to take this test or the results of the test will be useless are if you:

• is pregnant. Myelogram examination is not usually done during pregnancy, because radiation can damage the development of the baby (fetus)
• unable to lie still during the test
• have had surgery on the spine or have a curved spine, severe arthritis, or some type of spinal injury or disability. This condition makes it difficult to place a needle with dye into the spinal canal