Myelography is a radiological diagnostic procedure used to visualize the spatial relationships in the spinal canal. Due to non-invasive diagnostic procedures such as computed tomography or magnetic resonance imaging, myelography has lost importance. However, it is often used as an additional diagnostic procedure for specific problems, especially spinal root compression syndromes.
What is myelography?
This invasive diagnostic procedure may be used when compression of the spinal cord and/or spinal or spinal cord nerves is suspected. Myelography is the term used for an x-ray constrast examination to visualize the spinal canal or subarachnoid space (spinal CSF space), the spinal cord, and the outgoing spinal nerves. This invasive diagnostic procedure is generally used in cases of suspected compression of the myelon (spinal cord) and/or the spinal or spinal cord nerves when other imaging procedures such as computed tomography (CT) or magnetic resonance imaging (MRI) are not sufficient to make a detailed diagnosis. By injecting a contrast agent into the subarachnoid space followed by radiographs in different projections or from different perspectives, the spatial relationships for the myelon and spinal cord nerves can be visualized.
Function, effect, and goals
Various spinal impairments associated with nerve damage in the spinal canal may justify the indication for myelography when CT or MRI cannot provide sufficient information. In general, these are due to degenerative spinal diseases, which can cause, for example, spinal stenosis (narrowing of the spinal canal) with pressure-related damage to the nerve structures. These manifest themselves in the form of pain, sensory disturbances in the legs and arms, and loss of strength. Myelography may also be indicated in cases of suspected neuroforaminal stenosis (local narrowing of one or more nerve root exit orifices). In addition, the diagnostic procedure is often used as a planning aid prior to spinal surgery such as decompression or spondylodesis. The aim of myelography is to provide an image of the spatial conditions in the spinal canal in order to determine and assess the extent and location of potential nerve, vertebral body or intervertebral disc damage. For this purpose, blood coagulation values are checked by means of a blood analysis prior to the examination and blood-thinning medication is discontinued to avoid the risk of bleeding. In addition, an x-ray of the spine is often performed prior to myelography to determine optimal access to the spinal canal for the puncture. Following local anesthesia of the puncture site, the water-soluble contrast medium (10 to 20 ml) is injected in the area of the lumbar spine with a cannula (lumbar puncture) so that it can be distributed in the dural tube (meningeal tube). Existing constrictions modify the flow of contrast medium and are made visible by the subsequent X-ray images. Anterior (a.p.) radiographs can be used to visualize the space conditions in the spinal cord space and the spinal cord nerves through contrast medium recesses based on the distribution of the contrast medium. Oblique radiographs allow assessment of the spinal cord nerve outlets, while lateral radiographs during anteflexion and retroflexion (forward and backward bending) of the upper body allow conclusions to be drawn about the space conditions in the spinal canal. In addition, a computed tomography scan can be performed subsequently (myelo-CT). The combination of contrast injection and cross-sectional imaging provides the most detailed information for assessing and detecting spinal canal stenosis and nerve compression. To avoid or minimize the headache that may result from the transient pressure changes in the cerebrospinal fluid (CSF) space as a result of the puncture, 24 hours of bed rest should be maintained following myelography. Furthermore, a sufficiently high fluid intake should be ensured to quickly compensate for the loss of nerve fluid.Rare MR (rapid acquisition with relaxation enhancement myelography) myelography can also be used to obtain extremely rapid water-specific images that provide information on obstruction of the subarachnoid space, for example, by tumors.
Risks, side effects, and hazards
Complications can generally rarely be observed with myelography. The most common side effect is a temporary headache caused by the loss of nerve fluid. In addition, injury to a blood vessel can cause hemorrhage into the spinal canal (epidural hematoma), which can result in nerve damage. If the myelography needle (cannula) is misplaced, the outgoing nerves of the spinal cord may be damaged, causing pain, sensory disturbances as well as paralysis. Since myelography is an invasive procedure due to the skin injury caused by the puncture, infection can occur as a result of germ spread. This can be merely superficial or affect deeper structures of the spine such as the vertebral body, intervertebral disc or spinal cord. In the worst case, an ascending inflammation of the spinal cord and meninges can manifest itself. If the dura (spinal cord skin) is not independently occluded, CSF may continuously leak out of the puncture site, often resulting in surgical closure. Myelography may be contraindicated in the presence of hyperthyroidism (hyperthyroidism) due to the iodine-containing contrast agents used. Similarly, hypersensitivity to iodine, which can lead to anaphylactic shock (severe circulatory shock), may preclude myelography when appropriate.