Why Combine CT Scanning with Myelography?
To understand a CT scan with myelography, it is important to first understand the two components.
A Computerized Tomography (CT or CAT) scan helps to diagnose different spinal conditions including congenital spinal deformities, spondylolysis (or vertebral stress fracture), and other vertebral fractures. The scan provides a radiographic image of a single body plane. It is particularly good at imaging hard tissue such as bony structures. The equipment is shaped like a donut or ring with a movable table that slides in and out of the ring. The scanning system includes a computer that creates pictures represented as cross-sections or slices of the target anatomy, such as a specific part of the spine. Capturing similar images is not possible with traditional x-rays.
A Myelogram (also known as myelography) is a diagnostic tool that uses radiographic contrast media (dye) that is injected into the spinal canal’s fluid (cerebrospinal fluid, CSF). After the dye is injected, the contrast dye serves to illuminate the spinal canal, cord, and nerve roots during imaging. Thus, when a CT scan and myleography are combined, images are produced that clearly show both the bony structures of the spine and the nerve structures. Myelograms are much less commonly performed today than in the past but may still be indicated in special situations and with complex problems. These images are invaluable to physicians as they diagnose a patient’s spine problem.
The procedure is often performed in a hospital x-ray department or a special radiology center. Pre-test instructions include:
- Make arrangements for transportation home after the procedure. Patients are not permitted to drive immediately following this procedure.
- Do not eat or drink anything after midnight the night before the test.
- Leave valuables at home.
- If a prior x-ray, CT scan, or MRI study is available, bring it to the test facility.
- Patients who take medication to control diabetes or seizures, or who take blood thinners, must discuss the need for this medication with their referring physician prior to the test. Certain drugs may need to be stopped 24 to 48 hours before testing.
- Patients should inform the radiology technician if they are pregnant or suffer from allergy to IVP (intravenous pyelography) or other contrast dye, angina, kidney disorder, epilepsy or seizure. Patients should also inform the radiology technician of all medications taken.
How the Procedure is Performed
The test has two parts: injecting contrast dye into the spine and then taking pictures. First, the patient is positioned lying on his or her back or side on a movable table that slides into a CT scanner. Next, the skin area is prepared with an antiseptic to help prevent infection. A local anesthetic is injected to numb the area prior to injection of the contrast dye.
Sometimes the injection of the contrast dye is called a cervical or lumbar ‘puncture’ or ‘spinal tap’. In other words, some of the cerebrospinal fluid (CSF) is removed and replaced with the same amount of contrast dye. Before the ‘puncture’ begins, the patient’s body is properly positioned.
The patient is positioned on his or her back.
The patient is positioned on his or her side with the knees tucked up under the chin (or as close to the chin as possible). Bringing the knees up under the chin creates more space between the vertebrae. Under fluoroscopic guidance (an advanced type of imaging technology) the needle is positioned into the spinal canal through one or two puncture or tap sites. Fluoroscopy is also used to monitor the injection of the contrast dye and to view it as it percolates within the CSF around the nerve roots and spinal cord. The radiology technician may tilt the movable table to help move the contrast dye where it is needed. Patients are asked to be still and hold their breath briefly as each picture of the spine is captured during the CT scan.
After the Procedure
After the procedure the patient is transferred to an observation area for several hours. When released, the patient’s ‘at home’ instructions include:
- Keep the head elevated. Do not bend over or lie flat. This will help to keep the contrast material out of the head.
- Rest for several hours after the test and drink plenty of fluids.
- Do not exercise the same day as the procedure.
- Notify the referring physician if any of the following symptoms develop: increased headache, increased drowsiness, fever, seizures, or weakness in the extremities.
Risks Associated with Myelography
The risks of this procedure are associated with myelography. Most patients do not experience any side effects. The most common side effect is headache, which usually clears up in one to two days with rest and fluids. Other side effects include nausea, dizziness, generalized achiness, seizure, or infection (rare). Headache may develop when spinal fluid leaks into the tissue around the spine. If headache persists, some of the patient’s blood, drawn from a vein in the arm, is injected into the epidural space (called a blood patch). This procedure stops cerebrospinal fluid from leaking and helps to resolve the patient’s headache.
The CT scan with myelography can be a helpful and necessary diagnostic procedure. However, feelings of anxiety before and during myelography with CT scan are normal. Feel free to contact to express any concerns or to ask additional questions about the procedure.