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Myelography is an x-ray examination of the spinal cord and the space surrounding it, called the subarachnoid space. The x-ray film, or myelogram, is taken after injecting a radiopaque contrast material through a needle placed in this space. Myelography can demonstrate distortions of the spinal cord, the spinal canal within which it lies, and the spinal nerve roots connected to it. It is an effective means of identifying spinal lesions caused by disease or trauma.
This exam, done about 350,000 times a year in the United States, is relatively safe and painless. Almost all myelograms done by CRA are followed by a CT scan which greatly increases the diagnostic efficacy. A myelogram is done to provide a very detailed picture of the spinal cord and spinal column, and of any abnormalities that may be present. Often myelography is performed when magnetic resonance imaging (MRI) cannot be performed or has not provided adequate information.
Myelography can identify a herniated or ruptured intervertebral disk. Slipped disk is a common term for this problem. The disks are pads of rubbery tissue that lie between the the bones that make up the spine. Disks act to cushion the vertebrae when the backbone comes under pressure, whether from heavy lifting, sudden strain, change in position, or injury. There may be sudden severe back pain if the disk ruptures, or pain may develop gradually with advancing age as the disks degenerate. The lower part of the back is most often affected. A myelogram can accurately locate the disk or disks involved, and show whether disk tissue is pressing on nerves connected to the spinal cord. This information is especially important when surgical treatment is a possibility.
People with spinal arthritis sometimes develop sharp outgrowths of vertebral bone called bone spurs; these may press on spinal nerves and cause pain. Here again, a myelogram can indicate whether surgery might help. The exam also can identify a condition called spinal stenosis where the entire spinal canal is narrowed. Tumors may develop within the spinal cord or surrounding tissues. In addition, cancer from elsewhere in the body may spread to the spine. A myelogram will accurately locate a tumor mass in this region and may suggest the most effective treatment. Other conditions that may be shown by a myelogram include infection, inflammation of the arachnoid membrane that covers the spinal cord, abnormalities of blood vessels that supply the spinal cord, and traumatic injuries.
What to expect with your procedure
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 are avoided for several hours before the exam, but fluids may be continued.
You should provide the radiologist or technologist with a list of drugs you are taking. Some drugs should be stopped one or two days before myelography. They include certain antipsychotic medications, antidepressants, blood thinners, and drugs especially metformin that are used to treat diabetes; it is necessary to consult with the radiology nursing staff to review your medicines the day before your scheudled exam.
It is important that medical staff know if you have had seizures, or that you are or might be pregnant. If you smoke, stopping the day before the test will lessen the chance of your becoming nauseous or having headache after myelography.
You will be asked to empty your bladder just before the exam begins so as not to have to interrupt it. If you have had a severe allergic reaction to medication or anything else, or have a history of asthma, you will be watched especially carefully to check for a reaction when injecting the contrast material. Allergy to iodine-containing substances should be reported to the radiology staff and my necessitate pre-medication.
You will need to remove any jewelry near the area of your body being examined. After disrobing, you will be given a hospital gown to wear. You will be monitored for a short period after the procedure. Unless you are to spend the night in hospital, you should arrange to have a relative or friend take you home.
Preparing for your procedure
While lying face-down on the x-ray table, fluoroscopy is performed and images of the spine are projected onto the screen of a monitor. After locating the best placement for the needle, your skin will be cleaned and numbed with a local anesthetic. You will be positioned lying face down while the spinal needle is inserted.
If needed, a small amount of cerebrospinal fluid will be withdrawn for lab studies. Iodine-containing contrast material is then injected and the x-ray table is slowly tilted. During this time, the flow of contrast is monitored by fluoroscopy. You will be asked to lay as still as possible while the table is tilted at different angles and x-rays are taken. The exam focuses on the area where you are feeling symptoms: the lower back area, the middle part of the back, or the neck. A foot rest and straps or supports will keep you from sliding out of position. A computed tomography (CT) scan sometimes is done immediately after myelography while contrast material is still present in the spinal canal. This combination of imaging studies is known as CT myelography.
You will feel a brief sting when local anesthetic is injected, and slight pressure as the spinal needle is inserted. Positioning the needle may cause occasional sharp pain. Although you may find the face-down position uncomfortable or have trouble breathing deeply or swallowing, the position is not usually maintained for very long. When contrast material is injected you may feel some cramping, pressure or warmth. Headache, flushing, or nausea may follow contrast injection. Seizures are possible, but are rare.
Myelography itself usually takes 15-30 minutes, and a CT scan adds another 30 minutes to the total examination time. Patients usually stay in a recovery area for two to three hours, resting with the head elevated at a 30° to 45° angle. You will be encouraged to take fluids at this time to help eliminate contrast material from your body and prevent headache. You will be asked not to engage in strenuous physical activity or bend over for one or two days. This will ensure that what contrast material remains will not get to the level of the brain. You should notify your health professional if you experience fever higher than 100.4°F, excessive nausea or vomiting, severe headache for more than 24 hours, neck stiffness, or numbness in your legs. You should also report if you have trouble urinating or passing stool.