A myelogram is a specialized diagnostic imaging procedure used to examine the spinal canal, including the spinal cord, nerve roots, and surrounding tissues. This test involves injecting a contrast dye into the cerebrospinal fluid (CSF) that bathes these structures. Once the dye is introduced, X-rays or computed tomography (CT) scans are performed to capture detailed images. The contrast material highlights abnormalities within the spinal canal, allowing healthcare providers to identify problems that might not be visible on standard X-rays alone.
Key Diagnostic Applications
A myelogram is useful for diagnosing conditions affecting the spine. It provides detailed information about spinal cord compression, which occurs when something presses on the spinal cord. This compression can be caused by herniated discs, bone spurs (osteophytes), tumors, or cysts, which can narrow the spinal canal and press on the spinal cord.
The procedure is also effective in identifying nerve root compression, often referred to as radiculopathy, which leads to pain, numbness, or weakness in areas supplied by the affected nerves. Myelograms can reveal how structures like bulging discs or thickened ligaments are pressing on these nerve roots as they exit the spinal column.
Spinal stenosis, a narrowing of the spinal canal, is another condition where myelography offers insights. This narrowing can be due to degeneration and swelling of bones and tissues around the spinal cord, which the contrast dye outlines. Myelograms are also used to identify and precisely localize cerebrospinal fluid (CSF) leaks, a condition that can cause severe headaches and other neurological symptoms due to a reduction in CSF volume.
When evaluating spinal trauma or injury, a myelogram can help assess the extent of nerve damage or spinal cord involvement. While other imaging methods may show bone fractures, a myelogram provides clearer visualization of the soft tissues and neural structures, revealing how they are affected by the injury. This detailed view is important for planning treatment and understanding the impact on neurological function.
When Other Imaging Is Not an Option
Myelography is considered when other imaging techniques, such as Magnetic Resonance Imaging (MRI) or standard CT scans, are not suitable or have provided inconclusive results. One reason for choosing a myelogram is contraindications to MRI. Patients with certain metallic implants, like pacemakers, aneurysm clips, or cochlear implants, cannot undergo an MRI due to the strong magnetic fields involved.
In cases where previous MRI or CT scans have yielded unclear information about a patient’s spinal condition, a myelogram offers a clearer picture. For example, extensive spinal hardware from prior surgeries can create artifacts on MRI, obscuring the view of the spinal canal and nerve roots. CT myelography can provide better visualization.
Myelography also offers advantages in situations requiring dynamic imaging, meaning imaging the spine in different positions, such as flexion or extension. This dynamic assessment can reveal issues that only become apparent with movement that a static MRI might miss. For instance, some forms of spinal stenosis may only cause compression when the spine is in a particular position, and a myelogram illustrates these changes.
Important Factors to Consider
Before undergoing a myelogram, patients will receive preparation instructions. It is recommended to avoid eating or drinking for about 6 hours before the procedure, though medications may be taken with a small amount of water. Patients should inform their healthcare provider about all medications, especially blood thinners like aspirin or warfarin, as these may need to be adjusted or temporarily stopped prior to the exam to minimize bleeding risks.
During the procedure, a radiologist will clean and numb an area on the spine. A thin needle is then inserted into the spinal canal to inject the contrast dye into the CSF space. After the dye is injected, X-rays or a CT scan will be performed, often with the patient repositioned on a tilting table to allow the contrast dye to flow to different areas of the spinal cord. The procedure takes about 45 to 60 minutes.
Following the myelogram, patients are advised to remain flat or with their head slightly elevated for a few hours to reduce the risk of headache, a common side effect. Drinking extra fluids for the remainder of the day is also encouraged to help flush the contrast dye. Other common side effects include nausea, vomiting, or dizziness.
While generally safe, complications can occur. These include infection at the injection site, bleeding, or an allergic reaction to the contrast dye. A persistent headache due to CSF leakage may occur, sometimes treated with a blood patch procedure where the patient’s own blood is injected to seal the leak.