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What is a discogram? A discogram is a radiological procedure where x-ray dye (contrast agent) is injected into the disc between two vertebrae of the spine. At the same time as the injection, the physician performing the study records any verbal comments the patient provides at the time of the injection. If concordant pain is elicited by the injected dye, a positive test is recorded. The positive test indicates presence of potential pain generator inside the disc. Discogram may be followed with CT scan of the spine to understand further characteristics of the disordered disc.
What will the x-rays reveal? A normal disc consists of a central jelly - like material called the nucleus pulposis. This is surrounded by a thicker fibro cartilaginous ring called the anulus fibrosis. The normal disc acts like a cushion between two vertebrae of the spine. When a disc gets injured or undergoes abnormal aging, tiny cracks occur in the outer annulus. These are called anular fissures or tears and may be a cause of pain. When these fissures enlarge, some of the central jelly material may squeeze through these cracks and protrude outside the normal disc causing some pressure on the adjacent nerve roots, thereby resulting in pain. These disc protrusions are referred to as herniations. In more advance cases of "disc aging", the entire disc degenerates, and there is no longer any distinction between the nucleus and annulus. The radiologist will be able to identify what is wrong with the injected disc space and will comment on that in the report.
Will the procedure hurt? One of the main purposes of the discogram is to try to find out where your pain may be originating from in the spine. Therefore, if a disc that is known to be abnormal by either an MRI, myelogram, or prior CT scan is injected, you may experience some degree of discomfort or pain, ranging from mild to severe in intensity. Of course, this can be soothed almost immediately afterwards by directly injecting some numbing medicine (lidocaine or xylocaine) directly into the disc space. As the numbing medicine wears off within several hours, you may re-experience some discomfort. You can always take some form of pain medication afterwards for relief. Again, keep in mind the main directive in performing the study - trying to evaluate the source of pain such that your physician knows its location. Only by knowing where your pain originates from can the physician then come up with an appropriate plan for treatment.
Are all injected discs painful? No. Normal discs may only cause a minimal degree of pressure or produce no symptoms at all. Abnormal discs that have annular tears, herniations, or degenerated discs may reproduce your discomfort or induce a different pain response that you are not familiar with.
Are the side effects the same as the myelogram? No. Since the spinal canal is not punctured, the two exams are very different. The needle used in discography is inserted only into the disc cushion between any two vertebrae. No fluid is collected as is during the myelogram. There is no cause for the development of headaches or any other potential side effects that may be associated with the myelogram.
Are there any complications with the discogram procedure? As with any invasive procedure when a needle is introduced into the body, there is always the chance for introducing infection. One may develop a soft tissue infection or even a disc space infection. Of course, the likelihood of this is quite small. However, if this were to occur, you may develop symptoms typical of any infection - increasing pain and fever. You might then be treated as with any other infection and may be given antibiotics. Very rarely, if a disc space infection were to occur, you may even require surgery to drain any possible abscess that might form. In the rare event of a disc space infection, this would typically occur within the first several weeks following the procedure. Of course, steps are taken to minimize the chance of this ever happening. The radiologist who is performing the study is dressed in sterile surgical attire, and the area to be examined is initially thoroughly cleansed with antiseptic solution, whereupon, a sterile surgical drape is applied over the region. Another potential complication is bleeding, although this is usually minimal and is of no concern unless you are taking blood thinners or anticoagulants at the time of the exam. You should always inform the radiologist if there is a question as to any medication you are currently on.
Will I be able to leave immediately afterwards, or is there an observation period like the myelogram. Immediately following the discogram, most patients undergo a CT scan of the injected disc levels. This requires that you simply lie on the CT table and additional pictures are taken without any further injections. This provides further information regarding the anatomy of the disc space. The CT scan usually takes between 5 - 10 minutes and then you are free to go home. Are there any further restrictions or precautions to take after going home? No. Once you are through, there are no precautions that you must follow. Of course, you may still have some lingering discomfort, which you may treat with pain medications.
What if I have an allergy? You should always alert your physician if you are an allergic individual. If you do have a true allergy to the numbing medicine used, usually lidocaine or xylocaine, or even to iodine (used in most radiographic contrast fluids), your physician should decide if it is still necessary to undergo the procedure. If they feel that it is still warranted, you can be pre-medicated with a short dose of steroids for 1-2 days and then undergo the procedure in a more controlled environment. If there are specific questions, please ask the radiologist on duty.
Should I take my normal medications on the day of the exam? Yes, you should continue with your normal medications. However, you should stop taking aspirin or any other blood thinners (anticoagulants) well ahead of your scheduled appointment if it is safe to do so. Usually, this means stopping aspirin approximately 5 days prior to your exam. Please notify the radiologist if you are on any such anticoagulants at the time of making your appointment in order to avoid any unnecessary delays.
Should I eat a normal breakfast the morning of the exam? There are no specific dietary restrictions on the day of the exam. A light breakfast or recent meal should not interfere with the exam.
May I drive myself home after the study? Although, there are no physical restrictions following the discogram, in contrast to the myelogram, it is still not advisable to drive yourself home, since you may still have some discomfort and may not be fully able to safely drive a car.
When will the exam results be ready? Usually, the results will be ready by the end of the same day of your exam. Your doctor will then get the films and typed up report, so they may go over the results with you at your next appointment.
Is this procedure covered by insurance?
Which studies support the use of discography?
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Fig:
X-ray picture after discogram