A CT myelogram is a diagnostic imaging test that combines a computed tomography (CT) scan with the injection of a contrast dye into the spinal fluid. This procedure provides detailed visualization of the spinal canal, nerve roots, and surrounding structures. By highlighting the cerebrospinal fluid (CSF), a CT myelogram helps healthcare providers identify abnormalities within the spine.
Why a CT Myelogram is Performed
A CT myelogram is often performed when other imaging methods, such as X-rays, conventional CT scans, or MRI, do not provide sufficient information to diagnose a spinal condition. This test is useful for pinpointing the exact location and extent of issues affecting the spinal cord and nerves. It helps diagnose conditions that cause pressure on the spinal cord or nerve roots.
This diagnostic tool can reveal issues including herniated discs, spinal stenosis, and spinal tumors. It can also identify spinal infections, inflammation, or problems with spinal fluid circulation. For patients who cannot undergo an MRI due to implanted medical devices or severe claustrophobia, a CT myelogram serves as an effective alternative.
Preparing for the Procedure
Before a CT myelogram, patients receive specific instructions to ensure the test can be performed safely and effectively. Fasting is usually required for several hours before the procedure. Inform the medical team about all current medications, especially blood thinners, as these may need to be temporarily stopped.
Disclose any allergies, particularly to contrast dyes, iodine, or local anesthetics. The healthcare provider will review any pre-existing conditions, such as kidney problems, bleeding disorders, or diabetes, to assess potential risks. Arrange for transportation home after the procedure, as driving is not advised immediately afterward.
The Procedure Itself
The CT myelogram procedure begins with the patient lying on an exam table, often on their stomach, with a pillow placed under the abdomen for comfort. The lower back area is thoroughly cleaned and draped. A local anesthetic is then injected to numb the skin and underlying tissues, which may cause a brief stinging sensation.
Next, a thin needle is carefully inserted into the subarachnoid space, the area surrounding the spinal cord that contains cerebrospinal fluid, usually in the lower back. This step, known as a lumbar puncture or spinal tap, is guided by X-ray imaging (fluoroscopy) to ensure precise needle placement. Once the needle is correctly positioned, a small amount of contrast dye is injected into the spinal canal.
The contrast dye highlights the spinal cord, nerve roots, and the inner lining of the spinal canal, making them visible on imaging. The exam table may be tilted to allow the contrast dye to flow to different areas of the spine. After the dye has dispersed, the needle is removed, and CT images are taken to capture detailed views of the spinal structures.
What Happens After the Procedure
Following a CT myelogram, patients are monitored in a recovery area for several hours. It is recommended to lie flat for two to four hours, with the head slightly elevated, to minimize the risk of a post-myelogram headache. Staying well-hydrated by drinking plenty of fluids is encouraged to help flush the contrast dye and aid in spinal fluid replacement.
Patients might experience mild side effects such as headache, nausea, or dizziness. A headache is the most common side effect and typically improves when lying down. If a headache persists for more than 24 hours or worsens, or if other concerning symptoms like fever, increased drowsiness, or weakness in the extremities occur, patients should contact their healthcare provider. The results are usually available within a few days and will be communicated by the ordering physician.
Potential Considerations
The most common complication is a post-myelogram headache, which can occur due to a small leak of cerebrospinal fluid from the needle insertion site. This type of headache is often positional, worsening when sitting or standing and improving when lying flat.
Other less common risks include infection at the injection site, bleeding around the nerve roots, or an allergic reaction to the contrast dye. Although rare, nerve injury from the spinal needle or seizures can occur. The procedure might not be suitable for individuals with certain bleeding disorders, severe kidney disease, or an active infection at the puncture site. Pregnant individuals are advised against a CT myelogram unless absolutely necessary.