MRI Myelography - Uses and Contraindications

Introduction:

MRI (magnetic resonance imaging) myelography or MRI 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). MRI 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 is a clear liquid that 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 concerning the nerve roots.

• 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 Does an Individual Prepare for an MRI Myelography Scan?

Patient Preparation:

• The patient should inform the doctor about the medical conditions and regular medicines.

• Tell the doctor if they have allergic reactions to contrast material from any previous scan.

• Tell the doctor if the patient fears closed spaces (claustrophobic). The doctor may give medicine that makes them feel comfortable and reduces their anxiety.

• The patient may be asked to remove any metal jewelry or accessories, as magnets are used in this procedure. Patients cannot undergo this procedure if they have any metal inside their body, such as pacemakers or cochlear implants.

• Inform the doctor if the woman is 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?

The detailed procedure of MRI myelography is as follows:

• Patient Positioning: 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 move into the scanner.

• Sedation for Myelogram: 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 the patient comfortable.

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

• Images are automatically reconstructed as maximum intensity projections (MIP) and produce nine consecutive images at 22.5-degree 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.

• Blockage of Loud Noise: 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.

• Not to Move: 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.

• Drink Plenty of Water: 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 effect of the procedure due to the contrast material used.

How Long Does It Take to Recover From MRI Myelography?

After the procedure, the patient is monitored for one to two hours to check for allergic reactions. The patient will be instructed to lie down and rest to reduce the risk of headache. The patient should avoid strenuous exercise and limit bending, twisting, and lifting for the first 24 to 48 hours. The patient may resume their normal activities three to five days after the procedure.

What Are the Contraindications of MRI Myelography?

The contraindications of MRI myelography are as follows:

• Magnetic surgical clips or staplers.

• Intracranial aneurysm clips (surgical treatment for a brain aneurysm in which there is an 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.

What Are the Side Effects of MRI Myelography?

The side effects of MRI myelography are as follows:

• Mild pain and discomfort at the injection site.

• Mild headache.

• Nausea.

• Dizziness.

• Allergic reactions to contrast dye.

• Spinal headache.

• Back pain.

• Fever.

• Infection at the site of injection.

• Neurological symptoms.

• Allergic nephropathy (contrast dye may affect the kidneys).

Conclusion:

Magnetic resonance imaging myelography is a noninvasive imaging technique. MRI 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.