What is it?

Magnetic resonance imaging (MRI) is a fairly new test that does not use radiation. Rather, magnetic and radio waves are used to create computer-generated images. MRI pictures can scan multiple layers of the spine and show abnormalities of bones and soft tissues, such as nerves and ligaments. The MRI is probably the most commonly used to evaluate the spine.

Why is it done?

The MRI shows the spine in very clear detail, including information about the bones, ligaments, muscles, nerves and discs. It can show if there is a loss of water in the nucleus pulposus, which occurs in the earliest stage of disc degeneration. An MRI can be used to show facet joint arthritis, spinal stenosis (narrowing of the spinal canal), or a herniated disc (protrusion or rupture of the intervertebral disc). The test is useful for diagnosing any condition in which the anatomy of the spine and its soft tissues need to be seen clearly.

How is it done?

You will be asked to lie on a table that slides into a machine with a large, round tunnel. The machine's scanner takes many pictures that are watched and monitored by a technician. The MRI scanner is noisy. You might be offered headphones to listen to music while the scan is taking place. The tunnel that you lie in is narrow and may cause some patients to feel claustrophobic. You might be given a mild sedative to make the experience more tolerable. Newer MRI machines, called open MRI scanners, are sometimes more comfortable for patients who experience claustrophobia. The procedure takes 30-60 minutes.

What are the limitations?

There is little the MRI does not show. However, X-rays and CT scans have a role in adding helpful information in spine conditions that require them.

What are the risks?

There appear to be no known risks associated with exposure to the magnetic waves used during an MRI. These waves can cause problems however, if you have any metal objects in your body that could be attracted to the strong magnetic field. For example if you had any type of metal clips or implants used in a previous surgery, including a pacemaker, make sure to inform the technician. X-rays may be taken of your head before the test to verify there are no metal fragments in your eyes or brain that could move when the magnet is turned on.