Myelography is a specialized medical imaging technique used to obtain detailed pictures of the spinal canal, the surrounding nerve roots, and the spinal cord itself. This procedure involves injecting a contrast agent, or dye, into the cerebrospinal fluid (CSF) space that surrounds the spinal cord, making these soft tissues visible on X-ray imaging. The contrast material shows up brightly white, allowing a physician to see the outline of the spinal cord and how surrounding structures may be impacting it. Imaging is typically performed using real-time X-rays (fluoroscopy) and is almost always followed immediately by a Computed Tomography (CT) scan to capture highly detailed cross-sectional images of the spine.
Why Doctors Use Myelography
Doctors often recommend a myelogram to diagnose conditions affecting the spine, especially when Magnetic Resonance Imaging (MRI) or standard CT scans have been inconclusive. This test is particularly valuable for patients who cannot undergo an MRI due to having a pacemaker, cochlear implants, or certain types of metal hardware. The procedure helps to precisely locate the source of back, neck, or leg pain, weakness, or numbness.
The primary diagnostic goal is to identify points of compression on the spinal cord or spinal nerve roots. Conditions like spinal stenosis, where the spaces in the spine narrow, or a herniated disc that bulges and presses on nerves, are clearly visualized. It is also employed to evaluate spinal tumors, cysts, bone spurs, and the extent of injuries to the spinal nerve roots. By showing how the contrast dye flows and is blocked, the procedure provides functional information about the spinal fluid space that other imaging may not capture.
The Myelography Procedure
The myelography procedure is typically performed by a radiologist in an outpatient setting and usually takes about 45 minutes to an hour. The patient lies on an examination table, and the skin on the lower back is cleansed with an antiseptic solution. A local anesthetic is then injected to numb the area where the spinal needle will be inserted, which may cause a brief stinging sensation.
The radiologist uses fluoroscopy (live X-ray) to guide a thin needle into the subarachnoid space, the area containing the CSF. Once positioned, a small amount of CSF may be withdrawn for testing, and the iodine-based contrast dye is slowly injected. The patient may feel a sensation of pressure or warmth during this injection.
After the dye is injected, the examination table is gently tilted in various directions, sometimes with the patient secured by a harness. This positioning allows gravity to move the contrast agent to the specific area of the spine being examined, such as the cervical or thoracic region. The radiologist monitors the dye’s movement in real-time using fluoroscopy to capture initial images. The process is then completed with a detailed CT scan, which provides high-resolution, cross-sectional views of the contrast-filled spinal canal.
Preparation and Post-Procedure Care
Proper preparation before a myelogram helps ensure the procedure is safe and effective. Patients are usually instructed to fast from solid food for several hours before the exam, though clear liquids may be allowed. Patients must discuss all medications with the doctor beforehand, as some, particularly blood thinners like aspirin, may need to be temporarily stopped to reduce the risk of bleeding.
Arranging for transportation is mandatory, as patients cannot drive themselves home after the procedure due to potential sedation and monitoring. After the procedure is complete, the patient is monitored for about an hour before being discharged. The primary aspect of post-procedure care is preventing a post-dural puncture headache.
To minimize this risk, patients are instructed to keep their head slightly elevated with one or two pillows for up to 24 hours and avoid lying flat. Staying well-hydrated is encouraged, as drinking extra fluids helps the body replace the spinal fluid and flush the contrast dye out of the system. Strenuous activity, heavy lifting, and bending over should be avoided for at least 24 hours.
Potential Risks and Safety Considerations
While myelography is a safe procedure, patients should be aware of potential risks, the most common being the post-dural puncture headache, often called a spinal headache. This headache occurs in a small percentage of patients (up to 10%) and is caused by a persistent leak of cerebrospinal fluid from the needle insertion site. Spinal headaches are characteristically worse when sitting or standing and are relieved by lying down, sometimes lasting for a few days.
If a severe spinal headache does not improve with rest and hydration, a follow-up procedure called a blood patch may be performed to seal the leak. Other less frequent complications include temporary nerve irritation causing pain, tingling, or numbness in the legs, or bleeding at the puncture site. There is a small risk of an allergic reaction to the contrast dye or a rare risk of infection, such as meningitis, that requires immediate medical attention. Patients should contact their doctor immediately if they experience a fever, a stiff neck, or a headache that lasts longer than 24 hours.