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Disc Stimulation (Discography)

For convenience purposes, the spine can be divided into an anterior (front) section and a posterior (back) section, that work together to maintain proper function. The anterior section contains the vertebral bodies and the intervertebral discs and is the primary load-bearing part of the spine. The posterior portion, which contains the zygapophyseal (Z or facet) joints, lamina, and the transverse and spinous processes, controls the motions of the spine and provides for all musculotendonous insertions on the spine. In the low back, the usual location of injury is the intervertebral disc which is usually injured by bending forward while twisting to pick something up, often with an outstretched arm.

The lumbar spine has an average of 5 vertebrae (normal range 4-6) with an intervertebral disc interposed between adjacent vertebral bodies. A cartilaginous endplate exists between the disc and the adjacent vertebral bodies and is considered part of the disc. The disc itself is comprised of a central nucleus pulposus surrounded peripherally by the annulus fibrosis. The annulus fibrosis consists of some 17 concentric collagen fiber layers that surround the nucleus. The layers are arranged in alternating orientation of parallel fibers lying approximately 65° from the vertical, similar to a radial tire.

In normal young adults, the nucleus is a semifluid mass of mucoid material. The nucleus is comprised of approximately 70-90% water in a young healthy disc but generally decreases with age. The primary nuclear constituents include glycosaminoglycans, proteoglycans, and collagen. Type II collagen predominates in the nucleus. Proteoglycans are the largest molecules in the body and possess an enormous capacity to attract water through oncotic forces. These forces increase their weight by 250% and result in a gel-like composition with a consistency similar to toothpaste. Biomechanically, the nucleus can display properties of either a solid or liquid substance depending on the transmitted loads and its posture.

Injuries to the disc can vary from mild to severe. In mild injuries portions of the annulus can tear, resulting is a sort of "back sprain". These tears often heal, but on occasion can lead to chronic pain. With more severe injuries, the nucleus pulposis can be extruded through the annulus (otherwise know as a herniated disc), and this material can press on a nerve resulting in weakness in the muscles that that nerve innervates and/or numbness in the area of the skin that transmits sensory input through that nerve. On rare occasion a substantial amount of disc material can herniate so as to press on the spinal cord or the nerves at the bottom of the spine and result in more severe weakness or even the loss of bowel or bladder function, this is a medical emergency.

What is a discogram for?

As technology advances we are able to see more and more detailed anatomy with imaging studies such as MRI scans. As we age however, our discs exhibit normal "wear and tear" which can make MRI scans abnormal even in patients without pain. Studies show that by the time we reach the age of 50, about half of us have abnormalities on MRI scans, even if we don't have pain.

A good physician tries to correlate the findings on a patient's physical examination with the imaging studies that are available. It is frequently difficult however, to determine if a disc is causing pain, especially if the findings are subtle on MRI scans. In these cases, a discogram is used to determine if a disc is causing pain. A discogram is the only way to absolutely confirm that a disc is what is producing back pain in a patient.

In addition, many physicians will order a CT scan after the discogram to better see the anatomy of the disc and the exact location of any tears in the annulus which might be present.

How is a discogram administered?

Certain medications may increase the risk of complications. If you are taking aspirin you should stop it 5 days prior to the procedure. If you are on Coumadin (warfarin), heparin, Lovenox (enoxoparin), Ticlid (ticlopidine), Plavix (clopidogrel), or other blood thinning agents such as anti-inflammatory agents, please let your physician know at least one week prior to the procedure. You can continue to use Celebrex (celecoxib), Vioxx (roficoxib), or Bextra (Valdecoxib) before the procedure. Do not take your regular pain medications for six hours before or after the procedure. You should continue to take your routine medications (such as high blood pressure and diabetes medications) before the procedure. If you are on antibiotics please notify your physician, he may wait to do the procedure. If you have an active infection or fever we will not do the procedure.

You should not eat or drink anything (except your routine medications) for the eight hours prior to the procedure; this again, lowers the chance of having complications. You are expected to have a ride to and from the procedure. The procedure usually takes about one hour though you may be at the facility for as long as three hours. Once you arrive to the facility, a nurse will place an IV in your arm and administer intravenous antibiotics. After this has been done and the doctor is ready, you will be taken to the room and positioned on the table. Local anesthetic will be injected into the skin and underlying tissues to decrease the discomfort of introducing the spinal needle.

Once the local anesthetic is working the spinal needle is advanced into the disc using bones as landmarks. Your physician will use flouroscopy (a live x-ray) and other technical aids to ensure that the needle is in the right place. Your physician will usually perform a discogram on two to four discs at the time of the procedure.

When the needles are in the disc, you physician will then inject contrast into the discs one at a time. While the contrast is being injected into the disc, your physician will ask you to describe how you are feeling. This is the most important part of the test, it is important that you let your physician know if and when you feel pain, and if you feel pain is it exactly the same as your normal pain, similar to your normal pain, or different than your normal pain. If the pain becomes severe, let your physician know and he will stop the test.

After performing the discogram at each of the levels, your physician may inject a local anesthetic and/or steroid into each of the discs to make any pain that you are still having go away.

Following the injection, you will be asked to stay at the surgery center for about 20-30 minutes until you adequately recover from the anesthesia. While recovering, you will be monitored for any adverse reactions to the procedure. Once you are feeling well enough to walk, you will be allowed to leave with your ride. If you are having a CT scan following the procedure, you will need to go directly to the imaging center for this test.

You should follow-up with your physician within two weeks after the procedure to review the results of your discogram and discuss possible treatment options.

What are the risks of a discogram?

With any operation or injection procedure there are risks. In the case of discography these risks are small.

The most common side-effect is a temporary increase in pain. This is fairly common and may last for 24 to 72 hours after the procedure.

As with any injection through the skin, it is possible for bacteria to gain entry causing an infection. Infection is the most ominous problem that might develop from this procedure. If an infection develops in this disc (discitis) it might require surgery and/or long-term intravenous antibiotics to treat. The risk of discitis is about one percent when antibiotics are not given. Your physician will give intravenous antibiotics and place antibiotics into the disc to prevent this complication. In this scenario, the risk of infection is much under one percent.

Rarely there can be an allergy to the contrast material. This risk is increased if you have a previous risk of allergy to contrast, iodine, or shellfish. If you have a history of any of these allergies you need to let your physician know. Allergic reactions can vary from a mild rash to a severe problem with constriction of the airway. Your physician can do things to minimize this risk if there is a history of allergy.

It is theoretically possible that a nerve could be damaged. In the procedure, the needle is inserted very slowly, and if the lining around the nerve were touched there would be pain in the leg. The doctor would then change the position of the needle slightly to avoid any risk of damage to the nerve.

Sometimes a patient's blood pressure falls at the time of the injection. If so, the doctor will use the venous canula inserted before the epidural procedure commenced so that intravenous fluids or medication, if necessary, can rapidly control the blood pressure.

If your doctor injects corticosteroid, side-effects may occur as a result. If you have diabetes, you may notice that your blood sugars are elevated for 2-3 days following the procedure. If they are, usually only monitoring is required. However, if you are concerned, call your physician. Corticosteroids may also cause fluid retention, weight gain, alterations in skin pigmentation at the site of injection, fluid and electrolyte alterations and/or gastrointestinal upset. These side-effects are usually not serious.

If you have any questions about the procedure or any of the information you have just read, please ask the staff or your doctor. They will be more than happy to answer any questions you may have.