Myelography

What is a myelogram?

• A myelogram is a procedure where special non-ionic contrast material (dye) is placed in the spinal canal in order to view the spinal canal, spinal cord and the spinal nerve roots. A myelogram also views the spine's vertebrae and disks as well as other parts of the spine's anatomy.

  In years past, a myelogram was the primary study used to assess the way the spine, spinal cord and nerve roots were developed as well as how spine structures (vertebrae, disks, facet joints, other spine structures, and abnormal tissue) interacted with the spinal cord and spinal nerves.

  In most instances, a spine-focused physician first orders an imaging study such as magnetic resonance imaging (MRI) or computed tomography (CT scan) when they are questioning whether a patient's problem is related to the spine, spinal cord or spine nerves. When an imaging study such as MRI or CT does not answer the question but the physician still feels the spine is the source of the problem, a myelogram might be ordered.

When is a myelogram Ordered?

• A myelogram is usually ordered by a neurosurgeon, orthopedic surgeon, neurologist or other spine specialist when they are looking for further information about how the spinal canal acts on or affects the spinal cord or nerve roots.

  Usually a myelogram is ordered when the physician is concerned that your spinal cord or spine nerves are compressed and this compression is not confidently visualized on the MRI or CT imaging study. A myelogram provides a different view of the spinal cord and in particular the spinal nerves and might be the only way compression on these structures can be clearly confirmed. Sometimes your physician orders a myelogram after surgery to help in the identification of the cause of residual or new pain. Occasionally a myelogram is obtained to evaluate for possible leakage of cerebral spinal fluid (CSF).

  A CT scan of the spine may be obtained after the myelogram is performed since additional valuable information is sometimes gained from the CT study with the contrast present in the spinal canal.

How is the myelogram Procedure Performed?

• The procedure is performed by placing a thin needle into the spinal canal into the space which contains the spinal nerves and spinal cord. The spinal cord and nerves are bathed in a water-like fluid called cerebral spinal fluid or CSF. The spinal cord, spinal nerve roots and CSF are contained by a thick tissue layer called the dura matter.

  A physician or their immediate assistant will typically discuss the procedure including how the exam is done, the potential risks of the procedure and an informed-consent is obtained. Most spine problems are related to the lower back and therefore most myelograms are performed in the lumbar region. For problems in the neck or cervical spine, the contrast can be placed in the lower lumbar region and moved to the neck. Some neuroradiologists prefer to place the contrast directly in the cervical spine region using a more special cervical spine approach (often called C1/2 puncture) to the spinal canal when performing a cervical myelogram to reduce contrast mixing. Occasionally the lower lumbar spine cannot be accessed or a unique problem is present where the upper neck or cervical route is either the best or the only approach to the spinal canal.

  When undergoing a myelogram, you are usually placed prone (on your stomach) on the myelogram table with your lower back exposed. Your lower lumbar region is thoroughly cleansed with antiseptic solution (either an iodine solution occasionally with additional alcohol or chloroprep sterilizing solution). Using the fluoroscope, the approach to the spinal canal is visualized by the neuroradiologist and local anesthetic is injected into the skin and to the tract the spinal needle will take. After the anesthetic is injected, the spinal needle is placed into the skin and using the fluoroscope for guidance, the needle is directed into the spinal canal through the dura matter into the area where the spinal nerves and CSF are. When the needle is in the sac where the nerves are (called the thecal sac), needle tip position is confirmed by observing spinal fluid coming through the needle. At this point, a syringe and long extension tube containing the contrast material are connected to the spinal needle and the contrast is slowly injected into the thecal sac where the spinal fluid and contrast bathe the nerve roots and spinal cord.

  After injection of an adequate amount of contrast material, several fluoroscopic x-ray images of the spinal canal is obtained (now with contrast in the thecal sac) in order to visualize the spinal nerves and spinal cord. In general the neuroradiologist is obtaining images to demonstrate how structures indent or compress the spinal nerves or spinal cord.

  If the cervical and thoracic regions are being evaluated with the myelogram in addition to the lumbar area, you are secured in a table shoulder harness, your neck is properly positioned and extended backward with your chin supported and you are tipped head down to move the contrast material to the neck.

  If the cervical region is being studied alone, contrast material can be placed in the lumbar region and moved to the neck as described above by tipping head down and moving the dye. Some neuroradiologists prefer to place the contrast directly into the neck or cervical spine region when performing a cervical myelogram to avoid mixing or dilution of the contrast. In these instances the cervical region is cleansed with antiseptic solution, a drape is placed and after injecting local anesthetic the needle is placed with the guidance of the fluoroscope into the cervical spinal canal.

  By either approach, after contrast is placed or moved to the cervical spinal canal, fluoroscopic images of the cervical spine, cervical spinal cord and cervical spinal nerves are obtained.

Post-myelogram CT:

Following the myelogram, a CT scan may be obtained to better evaluate the spine structures that are acting upon or compressing the spinal cord or spinal nerve roots. The CT images provide information that is complementary to the myelogram fluoroscopic images. The myelogram fluoroscopic images and CT images are typically interpreted by the neuroradiologist together to obtain a more comprehensive and complete understanding of what is affecting the spinal cord or spinal nerve roots.  

What information is sent to my Doctor?

• Myelogram Report:

  After the myelogram has been obtained, the study is interpreted by the neuroradiologist and a report is dictated. This report is sent to your referring physician. Your referring physician then has the myelogram images and report of the procedure available to help better understand your spine problem.

What should I do before a myelogram?

• Prior to a myelogram, you should consult the institution you are having your study performed at to receive their pre-myelogram instructions.

  Typically there will be some restriction in diet (such as fluids in the morning).

  If you have a known allergy to iodine dye or x-ray contrast material, you will probably be instructed to take an oral steroid preparation before the procedure.

  If you are on any blood thinners, you will likely have to discontinue this medication prior to the procedure and might need to obtain blood work to confirm normal coagulation. With non-steroidal anti-inflammatory drugs such as aspirin, the medication is often discontinued for several days before the procedure.

  It is best to bring your spine films or prior imaging studies such as on a disc, so the neuroradiologist has more information about your spine and spine problem.

What should I do after a myelogram?

• After a myelogram it is best to rest and drink fluids to flush out the contrast material injected in the spinal canal.