What is a myelogram?
A myelogram, also known as myelography, is a diagnostic imaging procedure performed by a radiologist. It combines the use of a contrast substance with X-rays or computed tomography (CT) to evaluate abnormalities of the spinal canal, including the spinal cord, nerve roots, and other tissues.
The contrast "dye" is injected into the spinal column before the procedure. This substance, or dye, causes the tissue under study to be visible.
After the contrast dye is injected it appears on an X-ray screen allowing the radiologist to view the spinal cord, subarachnoid space, and other surrounding structures more clearly than with standard X-rays of the spine.
The radiologist will also use a CT scan when performing a myelogram. A CT or CAT scan is a diagnostic imaging procedure using a combination of X-rays and computer technology to produce cross-sectional images both horizontally and vertically across the body. These images, called slices, show detailed images of the spinal canal. CT scans provide more detail than standard X-rays.
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Anatomy of the spine
The spinal column is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas.
- The cervical area consists of seven vertebrae in the neck.
- The thoracic area consists of 12 vertebrae in the chest area.
- The lumbar area consists of five vertebrae in the lower back area.
- The sacrum has five, small fused vertebrae.
- The four coccygeal vertebrae fuse to form one bone, called the coccyx or tailbone.
The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back. The bones of the spine and a sac containing cerebrospinal fluid surround it. The spinal cord carries sense and movement signals to and from the brain and controls many reflexes.
A myelogram may be performed to assess the spinal cord, subarachnoid space, or other structures for abnormalities, particularly when another type of examination, such as a standard X-ray, is inconclusive. Myelograms may be used to evaluate many diseases, including, but not limited to, the following:
- Herniated discs
- Spinal cord or brain tumors
- Ankylosing spondylitis. A disease that affects the spine, causing the bones to grow together
- Bone spurs
- Arthritic discs
- Cysts. Benign capsules that may be filled with fluid or solid matter
- Tearing away or injury of spinal nerve roots
- Arachnoiditis. Inflammation of a delicate membrane covering the brain
There may be other reasons for your doctor to recommend a myelogram.
You may want to ask your doctor about the amount of radiation used during the procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time.
If you are pregnant or suspect that you may be pregnant, you should notify your doctor. Radiation exposure to the fetus may cause birth defects.
Because a contrast dye is used during the procedure, there is risk of allergic reaction to the substance. Studies show that 85 percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your doctor know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.
Because the contrast is injected into the cerebrospinal fluid which also surrounds the brain, there is a small risk of seizure after the injection. Some medications may place you at greater risk for seizure and you may be asked to stop taking a medication for 48 hours before and after the study.
Because this procedure involves a lumbar puncture, the following potential complications may occur:
- A small amount of CSF can leak from the needle insertion site. This can cause headaches after the procedure. If there is a persistent leak the headache can be severe.
- There is a slight risk of infection because the needle breaks the skin's surface, providing a possible portal of entry for bacteria.
- A temporary numbness to the legs or lower back pain may be experienced.
- There is a risk of bleeding in the spinal canal.
- There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
- Your doctor will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
- You will be asked to sign a consent form that gives your permission to do the procedure. Read the form carefully and ask questions if something is not clear.
- Generally, fasting is required prior to administering contrast dye. Your doctor will instruct you prior to the procedure of any necessary fasting requirements.
- Notify the radiologist if you have ever had a reaction to any contrast dye or if you are allergic to iodine.
- Notify the radiologist if you are pregnant or suspect that you may be pregnant.
- Notify your doctor of all medications (prescribed and over-the-counter) and herbal supplements that you are taking. You may be asked to stop some of your medications prior to the procedure.
- Sedation may be given prior to the procedure to help you relax.
- Notify the doctor if you have a history of seizures or if you are taking any prescribed medications for seizures.
- Notify your doctor if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop these medications prior to the procedure.
- If the procedure is performed on an outpatient basis, you may be asked to remain in the hospital for several hours following the procedure. You should plan to have another person drive you home.
- Based on your medical condition, your doctor may request other specific preparation.
A myelogram may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.
Generally, a myelogram follows this process:
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- You will be asked to remove any clothing, jewelry or other objects that may interfere with the procedure.
- If you are asked to remove your clothing, you will be given a gown to wear.
- You will be reminded to empty your bladder prior to the start of the procedure.
- During the procedure, you will lie on your stomach on the fluoroscopy table.
- Your back will be cleansed with an antiseptic solution and draped with sterile towels.
- The radiologist will anesthetize the skin by injecting a local anesthetic that numbs the site. This injection may sting for a few seconds, but makes the procedure less painful.
- A needle will be inserted through the numbed skin and into the subarachnoid space where the spinal fluid is located. You will feel some pressure while the needle is inserted, but you must remain still during the insertion of the needle.
- The radiologist will remove some of the spinal fluid from the spinal canal. Next, a portion of contrast dye will be injected into the spinal canal through the needle. You may feel a warming sensation when the contrast dye is injected.
- The X-ray table will be tilted in various directions to allow gravity to move the contrast dye to different areas of your spinal cord. You will be held in place by a special brace or harness. More contrast dye may be administered during this process through the secured lumbar puncture needle.
- The needle is then removed and required X-rays or CT scan pictures will be taken.
- You should notify the radiologist if you feel any numbness, tingling, headache, or lightheadedness during the procedure.
You may experience discomfort during the myelogram. The radiologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
You should remain in the sitting or laying position for several hours after the procedure to reduce your risk of developing a CSF leak.
You will be asked to drink additional fluids to rehydrate after the procedure. This helps to replace the spinal fluid that was withdrawn and reduces the chance of developing a headache.
A nurse will monitor your vital signs (blood pressure, temperature, pulse, and respirations) frequently after the test. Analgesic agents may be administered if you develop a headache.
When you have completed the recovery period, you will be taken to your hospital room or discharged to your home.
Once you are at home, notify your doctor of any abnormalities, such as numbness and tingling of the legs, blood or other drainage from the injection site, pain at or near the injection site, inability to urinate, fever, stiff neck, or headaches. If the headaches persist for more than 24 hours after the procedure, or when you change positions, you should contact your doctor.
You may be instructed to limit your activity for 24 hours following the procedure. Generally, if no complications occur, you may return to your normal diet and activities.
Your doctor may give you additional or alternative instructions after the procedure, depending on your particular situation.