A myelogram shows detailed images of your spinal canal, spinal cord, and the nerves branching off from it. It works by injecting a contrast dye into the fluid-filled space surrounding your spinal cord, then taking X-rays or CT scans. The dye outlines structures that don’t show up well on standard imaging, creating a silhouette of your spinal cord and nerve roots that reveals compression, blockages, or abnormal growths.
How the Contrast Dye Creates the Image
During a myelogram, a radiologist inserts a needle into your lower back (similar to a lumbar puncture) and injects contrast material into the subarachnoid space, the fluid-filled area that surrounds your spinal cord. The contrast shows up white on X-rays and CT scans, so as it flows through that space, it highlights the shape and boundaries of your spinal cord and nerve roots. Anywhere the dye can’t flow normally, or where the silhouette looks distorted, points to a problem.
After the dye is injected, you’ll typically have a series of X-rays taken in different positions, followed by a CT scan. This combination is important: the X-rays capture your spine while you’re upright and weight-bearing, while the CT scan adds cross-sectional detail. That two-step approach gives your doctor a more complete picture than either test alone.
Conditions a Myelogram Can Detect
A myelogram is used to identify problems affecting the structures inside your spinal canal. The most common findings include:
- Spinal stenosis: narrowing of the spinal canal that squeezes the spinal cord or nerves
- Herniated or bulging discs: disc material pushing into the spinal canal and pressing on nerves
- Nerve root compression: pinching of the nerves where they exit the spine
- Spinal tumors: growths inside or near the spinal canal that displace or compress the cord
- Arachnoiditis: inflammation of the thin membrane covering the spinal cord, which can cause nerves to clump together
- Bone spurs: bony overgrowths that narrow the space available for the spinal cord and nerves
Myelography is particularly useful for spinal tumors and disc problems, where the contrast dye can reveal exactly how much space the abnormality is taking up and whether it’s blocking the normal flow of spinal fluid.
Why a Myelogram Instead of an MRI
MRI is the go-to imaging test for most spinal problems, so if your doctor ordered a myelogram, there’s usually a specific reason. The most common one is that you can’t have an MRI. People with certain metal implants, pacemakers, or spinal hardware often can’t go into an MRI machine safely, making a CT myelogram the best alternative for detailed spinal imaging.
But myelograms also have a genuine diagnostic advantage in some situations. Because the test includes upright, weight-bearing images, it can reveal narrowing that only appears when gravity is compressing your spine. An MRI, by contrast, is taken while you’re lying flat, which can make stenosis look less severe than it actually is. Studies have found that CT myelography detects spinal stenosis with about 94% sensitivity, compared to roughly 76% for MRI. In patients with narrowing at multiple spinal levels, CT myelography identified additional affected levels that MRI missed in 58% of cases.
Your doctor may also order a myelogram when MRI results are inconclusive, or when they need clearer images around existing spinal hardware that creates artifacts on MRI.
What the Procedure Feels Like
The procedure typically takes 30 to 60 minutes. You’ll lie on your stomach or side on a tilting table. After numbing a spot on your lower back with local anesthetic, the radiologist guides a thin needle into the spinal canal using real-time X-ray (fluoroscopy) to ensure accurate placement. The needle passes through the ligaments between your vertebrae before reaching the fluid-filled space around the cord.
You’ll feel pressure during the needle insertion and possibly a brief sting. Once the contrast is injected, some people notice a warm sensation or temporary increase in their usual back or leg symptoms as the dye flows around the nerves. The table may be tilted at different angles to help the contrast move to the areas your doctor wants to examine. After the X-rays are taken, you’ll typically be moved to a CT scanner for additional images.
Preparation Before the Test
You’ll need to stop eating and drinking for six hours before the exam, though you can take essential medications with a small sip of water. If you take aspirin or aspirin-containing products, stop them at least five days before the procedure. Other blood thinners require a conversation with your prescribing doctor about when to pause them, since the timeline varies by medication.
Recovery and Side Effects
After the myelogram, you’ll spend one to two hours in a recovery area while staff monitor your vital signs. Some facilities keep patients resting with the head elevated at a 30 to 45 degree angle for up to four hours. This head-up position helps prevent the most common side effect: a headache caused by the puncture in the membrane surrounding the spinal fluid.
Post-procedure headaches happen because spinal fluid can leak slowly through the needle puncture site. They’re typically worse when sitting or standing and improve when lying down. Most resolve within a day or two. For the first one to two days after your myelogram, you should avoid strenuous activity and bending over.
Other possible side effects include nausea, dizziness, and temporary soreness at the injection site. Serious complications like infection or allergic reaction to the contrast dye are rare.
Reading Your Results
Normal results show contrast dye flowing evenly through the spinal canal with no areas of blockage, compression, or irregularity. The spinal cord and nerve roots appear as smooth, well-defined silhouettes against the bright contrast.
Abnormal results show disruptions in that flow. A herniated disc appears as an indentation pushing into the contrast column. Stenosis shows up as narrowing of the contrast-filled space at one or more levels. Tumors create filling defects, areas where the contrast is displaced or blocked entirely. Arachnoiditis may appear as nerve roots clumped together rather than fanning out normally. Your radiologist will document the specific location and severity of any findings, and your referring doctor will use that information alongside your symptoms to determine next steps.