Myelography is a medical imaging procedure that uses a specialized contrast dye and X-rays or computed tomography (CT) scans to visualize the spinal canal. This diagnostic tool helps medical professionals examine the spinal cord, nerve roots, and the subarachnoid space, which is the fluid-filled area surrounding the spinal cord. By introducing the contrast material, structures difficult to see on standard X-rays become more clearly visible.
Why Myelography is Performed
Medical professionals often recommend myelography when there is a need to investigate conditions affecting the spinal canal, particularly when other imaging methods have not provided sufficient information. This procedure can help diagnose various issues, including herniated discs, where the cushioning discs between vertebrae bulge and press on nerves or the spinal cord. It is also used to identify spinal stenosis, a narrowing of the spinal canal that can exert pressure on the spinal cord and nerve roots. Myelography assists in detecting spinal tumors and infections of the membranes surrounding the spinal cord, such as meningitis.
While magnetic resonance imaging (MRI) is frequently the initial imaging choice for spinal concerns due to its non-invasive nature and detailed soft tissue visualization, myelography remains a useful alternative for specific patient needs. For instance, individuals with implanted metal devices, such as pacemakers or certain surgical hardware, may not be able to undergo an MRI due to safety concerns or image distortion. In such cases, myelography provides a diagnostic pathway. It can also offer additional insights in situations where MRI results are inconclusive or when a more dynamic view of the spinal structures is beneficial.
How Myelography is Performed
The myelography procedure involves introducing a contrast dye into the subarachnoid space of the spinal canal. This is typically achieved through a lumbar puncture, often referred to as a spinal tap, where a thin needle is inserted into the lower back between two vertebrae. Before the needle insertion, the skin in the area is cleaned with an antiseptic solution and numbed with a local anesthetic to minimize discomfort. A small amount of cerebrospinal fluid (CSF) may be withdrawn for laboratory analysis during this step.
Once the needle is correctly positioned, the contrast dye is slowly injected into the spinal canal. This dye, which contains iodine, highlights the spinal cord and nerve roots against the surrounding fluid. During the injection and subsequent imaging, the patient lies on an examination table that may be tilted in various directions. This tilting allows gravity to help the contrast material flow throughout different sections of the spinal canal.
Real-time X-ray imaging, known as fluoroscopy, is often used to guide the procedure and observe the contrast movement. Following the dye injection, additional images are taken using either standard X-rays or a CT scan, which provides cross-sectional views of the spinal structures. The entire imaging process typically takes about 20 to 30 minutes, though the overall procedure may last around an hour.
Important Considerations
Before a myelography, patients receive specific instructions to ensure the procedure’s safety and effectiveness. These often include avoiding food or drink for several hours prior to the exam, though clear fluids may be permitted. Patients should also inform their medical team about all medications they are taking, as some, such as blood thinners or certain psychiatric medications, may need to be temporarily stopped. It is also important to discuss any allergies, especially to iodine or contrast materials.
After the myelography, patients are typically monitored for one to two hours in a recovery area. To help prevent a post-procedure headache, which is a common side effect, patients are usually advised to lie flat or keep their head slightly elevated for several hours. Drinking plenty of fluids is also encouraged to help the body eliminate the contrast dye and replenish spinal fluid.
While mild headaches are common and often resolve with rest and fluids, more severe or persistent headaches may occasionally require additional treatment. Other potential effects, though rare, include temporary leg numbness, lower back pain, allergic reactions to the dye, infection at the injection site, or, very rarely, seizures. Patients are advised to avoid strenuous activities for a day or two and to contact their healthcare provider if they experience symptoms like fever, stiff neck, or worsening pain.