MRI Myelography - Uses and Contraindications

Introduction:

MRI (magnetic resonance imaging) myelography or MR myelogram is a medical imaging technique used to detect abnormalities in the spinal cord and nerve roots and to visualize the subarachnoid spaces. Subarachnoid spaces consist of cerebrospinal fluid (CSF), blood vessels, and cisterns (spaces between two meninges). MR myelography produces fast spin-echo images with a fat suppression technique and maximum intensity projection (MIP). In addition, MRI myelography enhances the intensity of CSF with background tissue signal subtraction.

What Are the Uses of MRI Myelography?

MRI myelography is used in the diagnosis of the following conditions:

• Leakage of CSF [cerebrospinal fluid] (a clear liquid surrounds the brain and spinal cord).

• Spinal trauma.

• Spinal infection.

• Planning of radiation therapy (use of ionizing radiation for killing cancer cells in cancer treatment).

• A tumor (cancer) of the spine.

• Planning of surgery in relation to the nerve roots.

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• Magnetic resonance imaging studies on spine and skull base.

• Find out the degree of pressure exerted on thecal sac (outer covering of the spinal cord).

• Disk herniation (bulging out of the disc into the spinal canal compresses the spinal nerves causing back pain).

• Disc migration (displacement of the disc).

• Facet arthrosis syndrome (a disease in which damage to the facet joints causes low back pain).

• Spinal stenosis (narrowing of the spinal spaces).

• Spondylolisthesis (a condition in which vertebrae slip out of place and exert pressure on the bone).

• Arachnoid cyst (a fluid-filled sac in the brain and spinal cord).

• Intra medullary cyst and tumors (a growth develops within the spinal cord).

How Do You Prepare for an MRI Myelography Scan?

• Inform your doctor about your medical conditions and your regular medicines.

• Tell your doctor if you had allergic reactions to contrast material from your previous scan.

• Tell your doctor if you are afraid of closed spaces (claustrophobic). They may give you medicine that makes you feel comfortable and reduces your anxiety.

• You may be asked to remove any metal jewelry or accessories, as magnets are used in this procedure. If you have any metal inside your body, such as pacemakers or cochlear implants, you cannot undergo this procedure.

• Inform your doctor if you are pregnant. Injection of the contrast material during the scan is not recommended in pregnant women in their first trimester. It is considered safe during the second and third trimesters at 3.0 tesla (T) or less.

How Is MRI Myelography Performed?

• Magnetic resonance imaging myelography is done using the same equipment as magnetic resonance imaging (MRI). During this procedure, patients may be asked to lie down on the table and moved into the scanner.

• The radiologist injects local anesthesia into the skin of the target site. After that, they inject 0.5 mL diluted gadolinium-based contrast material (a special dye) into the spinal cord in the space between the third and fourth lumbar vertebrae (L3-L4) [intrathecal region]. Gadolinium rarely causes allergic reactions. Patients might be asked to roll on the table to properly distribute contrast material into the target area, such as the spinal cord and nerve roots. They may keep a pillow or blankets to make you comfortable.

• MRI myelography is performed as a single shot TSE, with TR (repetition time) 8000 ms, TE (time to echo) 1000 ms (milliseconds), and TSE (turbo spin-echo) 256 and acquisition time 3:36.

• Images are automatically reconstructed as maximum intensity projections (MIP) and produce nine consecutive images at 22.5 degrees intervals, extending from right lateral to left lateral projection.

• MRI myelography is highly sensitive in the diagnosis of CSF (cerebrospinal fluid) leaks at the exact spinal levels.

• The contrast resolution of MRI is superior to CT (computed tomography), myelography, and radioisotope cisternography (a nuclear medicine imaging technique used to detect cerebrospinal fluid leak).

• Once patients are ready, the magnetic resonance imaging machine produces a strong magnetic field around them, and radio waves are directed to the target area to produce the images of the required area.

• During the scan, patients may be provided with earphones to block the loud noise heard from the scanner during the imaging process. The technician will communicate with patients from a separate room through an intercom.

• Patients may be asked not to move during the procedure, affecting the image quality. Sometimes, patients may be asked to hold their breath for a few seconds at varying times to get better images. The final images will appear on the computer screen.

• After the test, patients can continue their regular activities. They are instructed to drink plenty of water to flush out the contrast material from the body used in this procedure. Nausea (urge to vomit), vomiting, headache, and skin rashes may occur as a side effects of the procedure due to the contrast material used.

What Are the Contraindications of MRI Myelography?

• Magnetic surgical clips or staplers.

• Intracranial aneurysm clips (surgical treatment for brain aneurysm [enlargement of an artery caused by weakness in the arterial wall] by placing the metal clip).

• Any electrically or magnetically activated implant such as a cardiac pacemaker, insulin pump bio stimulator, neurostimulator, hearing aids, or cochlear implant.

• Metallic foreign bodies such as bullets in the body.

Conclusion:

Magnetic resonance imaging myelography is a noninvasive imaging technique. MR myelography is the first-line imaging technique recommended for lower back pain. The advantage of magnetic resonance imaging myelography is that it does not use ionizing radiation and the imaging time is short. Both the superior and inferior extent of the spinal cord are shown in this scan. This procedure does not require hospitalization. MRI myelography has more accuracy in diagnosing intrinsic spinal cord diseases than myelography. Magnetic resonance imaging myelography shows the degree of compression of spinal nerves with more accuracy.

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