What is Myelogram?
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 (the subarachnoid space) and nerve roots using a real-time form of x-ray called fluoroscopy or CT Scan.
An x-ray (radiograph) is a noninvasive medical test that helps physicians diagnose and treat medical conditions. Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body. X-rays are the oldest and most frequently used form of medical imaging.
When the contrast material is injected into the subarachnoid space, the radiologist is able to view and evaluate the status of the spinal cord, nerve roots, and meninges, which are the membranes which surround and cover the spinal cord and nerve roots. Myelography provides a very detailed picture (myelogram) of the spinal cord 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 may take 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 medical devices, such as a cardiac pacemaker, that may prevent him or her from undergoing MRI. Sometimes, myelography and/or a CT scan is performed in conjunction with MRI 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 herniations of the material between the vertebral bodies, termed the intervertebral disks, are pushing on 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 the adjacent ligaments.
Myelography can also be used to assess the following conditions when MR imaging cannot be performed, or in addition to MRI:
- 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.
How should I prepare?
Your physician will give you detailed instructions on how to prepare for your myelogram.
You should inform your physician of any medications you are taking and if you have any allergies, especially to barium or iodinated contrast materials. Also inform your doctor about recent illnesses or other medical conditions.
Specifically, the physician needs to know if (1) you are taking medications that need to be stopped a few days before the procedure and (2) whether you have a history of reaction to the contrast material used for the myelogram.
Some drugs should be stopped one or two days before myelography. These include certain antipsychotic medications, antidepressants, blood thinners, and drugs—especially metformin—that are used to treat diabetes. The most important type of medication that must be stopped is blood thinners (anticoagulants). If you are taking blood thinners, you should speak with your physician about alternative methods of maintaining anticoagulation while you are undergoing a myelogram. For example, intravenous blood thinners such as heparin can be used after stopping the conventional, more long-acting blood thinners.
Many drugs used to treat seizures are not indicated before a myelogram. Therefore, it is also important that medical staff know in advance if you have a seizure disorder and they can help you plan to stop taking the seizure medications a few days before the myelogram. Although reactions to the iodinated contrast material used in the myelogram are extremely uncommon, you should inform your physician if you have previously had a severe allergic reaction to contrast material or other medication. In addition, please mention if you have any allergies to other non-medical substances or have a history of asthma. If this is the case, you will be watched especially carefully to check for a reaction when injecting the contrast material. Allergy to iodine-containing substances can be especially risky. Usually patients are advised to increase their fluid intake the day before a scheduled myelogram, as it is important to be well hydrated. Solid foods should be avoided for several hours before the exam, but fluids may be continued.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, dentures, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby. See the Safety page (www.RadiologyInfo.org/en/safety/) for more information about pregnancy and x-rays.
At the conclusion of the myelogram, the patient usually remains in an observation area for 1-2 hours and is discharged. Unless you are to spend the night in hospital, you should arrange to have a relative or friend take you home.
Safety page (www.RadiologyInfo.org/en/safety/) for more information about pregnancy and x-rays.
For more information go to Radiologyinfo.org