Do You Need a Discogram or an MRI?
Author: Dr. Hamid Abbasi
DATE: 15 Feb 2019
Depending on the suspected source of your back pain, your doctor may recommend a discogram or an MRI. Why choose one or the other? Which one makes the most sense for you?
What is a Discogram?
A discogram is a diagnostic procedure used to isolate the disc or discs that are causing back pain. A discogram is usually not ordered at an initial evaluation. Rather, it is used after more conservative measures, such as medication and physical therapy, fail to relieve back pain after at least 4 to 6 months. It is most commonly used before surgery to identify precisely which intervertebral disc or discs are the root of the problem.
The major advantage of a discogram over an MRI is that a discogram can confirm that the patient’s symptoms are being caused by a disc problem. An MRI cannot do this.
Typically, a local anesthetic is used to numb any pain between the surface of your skin and the disc. Then a guide needle is inserted until it reaches the disc’s outer surface. A smaller disc needle is threaded through the guide needle into the center of the disc. After all of the needles are placed for each disc to be studied, the discs are pressurized one by one. This means that a small amount of a contrast dye is injected into the center of each disc. The dye fills in tiny cracks on the exterior of the disc, creating clearly defined images that can be viewed on a monitor, so your doctor will be able to see which disc is causing your back pain. An X-ray or CT scan may also be performed to obtain additional views.
During the study, you may feel nothing or you may feel pressure or pain. If the procedure causes pain that is similar to the back pain that you’ve been experiencing, spinal fusion of any troublesome disc or discs may provide a solution.
Are Discograms Safe?
Discograms are considered safe, but any medical procedure does carry some risk. Although rare, possible risks include infection, bleeding, headache, nausea, or an allergic reaction to the contrast dye. In some cases, the discogram can actually make the back pain worse, but this outcome is uncommon. A discogram can also cause temporary numbness or injury to surrounding nerves or blood vessels in the spine.
Before the discogram is performed, you may need a blood test to be sure your kidney function and blood clotting time is normal. Be sure that your doctor knows about any medications that you take and whether or not you have any allergies, especially to any anesthesia medications or contrast dye. If you may be pregnant or if you take any type of blood thinners or aspirin products, you doctor needs to know this, too.
You will probably be asked to avoid eating or drinking after midnight before the discogram is performed. Wear comfortable clothing, and leave any jewelry at home. A discogram usually takes 30 to 60 minutes to perform, but you may be at the imaging center for up to 3 hours. You may be given a sedative before the procedure, so ask someone to drive you home.
It’s normal to have some pain at the injection site or in the low back for several hours after the discogram. Ice packs will help. Call your doctor if you experience any severe pain or fever.
What is an MRI?
An MRI (also known as magnetic resonance imaging) uses a powerful magnetic field, radio frequency pulses, and a computer to create images of organs, soft tissue, bone, and other internal body structures. In some cases, a contrast dye is injected through an intravenous line. The dye highlights certain parts of the soft tissue, which makes the images more clear. An MRI usually takes 30 minutes to an hour.
The MRI unit looks like a large cylinder and is surrounded by a magnet. The patient lies on a table that slides into the cylinder. Some MRI machines are open on the sides. These open units are helpful for larger patients or those with claustrophobia.
If your doctor orders an MRI of your spine, the results will show your spinal cord and the discs, ligaments, and vertebrae that make up your spine. An MRI is useful in diagnosing:
- compression fracture
- degenerated, bulging, or herniated discs
- congenital spinal anomalies
- damage caused by trauma
- inflammation of the spinal cord or nerves
- infection or inflammation affecting the spine, discs, and spinal cord
- abnormal spinal anatomy or alignment
Discograms are invasive procedures, which means that some sort of medical instrument is inserted into your body. MRIs, on the other hand, are noninvasive, which means that no instruments or needles are inserted into your body unless an IV contrast dye is used. If you do need a contrast study, the dye used for an MRI is less likely to cause an allergic reaction than the dye used for a discogram. Should a reaction to the MRI contrast dye occur, it is usually mild and easily controlled.
MRIs have a number of other advantages as well. Unlike an X-ray or CT scan, there’s no radiation. The images produced by MRIs are clearer and more detailed than with some other imaging options, so MRIs offer the best view of the spinal cord, ligaments, and nerves. MRIs are also more sensitive about picking up tumors, abscesses, and other soft tissue masses near the spinal cord.
Are MRIs Safe?
MRIs are very safe, but there are a few precautions. The magnetic field that is used during the study is not harmful unless the patient has implanted medical devices that contain metal. Most patients with orthopedic implants need not worry, but patients who have cochlear (ear) implants, some types of clips used for brain aneurysms, metal coils placed within blood vessels, and cardiac defibrillators and pacemakers should not have an MRI.
If the patient can’t remain perfectly still during the study, the quality of the images will suffer. A very irregular heartbeat can also affect image quality. In patients who have poor kidney function, the contrast dye can cause nephrogenic systemic fibrosis if administered in high doses.
If you are afraid of feeling claustrophobic in the MRI cylinder, talk to your doctor about taking a mild sedative before the study. Or perhaps a facility with an open MRI unit might be a better way for you to go. Jewelry can interfere with the magnetic field so leave it at home along with hearing aids and any metal or electronic items. Removable dental work, eyeglasses, and body piercings can also interfere with clear MRI images, so it’s best to leave these behind as well.
Only an experienced spine specialist can determine whether a discogram or an MRI is best for you. For expert guidance, contact a specialist at Inspired Spine or call (727) MY-SPINE.