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CT myelography involves a lumbar or cervical spine puncture with contrast injected into the spinal canal, followed by CT. The image to the right is a fluoroscopic (X-Ray) image illustrating contrast being injected into the lumbar spinal canal/thecal sac by lumbar puncture. Afterwards, the patient is moved to the CT scanner for CT mylography, resulting in images such as those depicted below.
In CT myelography, the contrast acts the same way as it does when administered by IV in that it is high in attenuation and therefore bright on CT. This allows for detailed imaging of the spinal canal. If you consider a T2 image of the spine, the CSF surrounding the spinal cord in the spinal canal is very bright and helps outline the anatomy and canal contour. The contrast on a CT myelogram gives similar information as the bright T2 CSF on MR. During myelography, if there is a significant narrowing or a block of the CSF flow within the spinal canal, the injected contrast will not flow across that level.
Axial CT image of the lumbar spine shows contrast in the thecal sac surrounding the nerve roots. Notice the metal hardware in the vertebral body, may have rendered and MRI of the spine, challenging to interpret
Another Axial CT image shows contrast in the thecal sac within the thoracic spine. Notice here how the conus medullaris is outlined by contrast with smaller adjacent nerve roots
This sagittal CT image of the lower thoracic spine in this patient shows a disc buldge at T9-T10 causing ventral canal narrowing indicative of degenerative disc disease.
A coronal CT image from the myelogram shows contrast surrounding the cord as well as extending into the neural foramen.
Indications
- Spinal stenosis, nerve root compression
- CSF leak
- MRI inadequate or contraindicated
Advantages
- Defines extent of subarachnoid space, identifies spinal block
Disadvantages
- Invasive, complications (CSF leak, headache, contrast reaction, etc.)
- Ionizing radiation and iodinated contrast
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