Because determining the origin of pain is complicated, an interventional pain physician is likely to order some tests for a patient. These tests help pinpoint the cause of pain and, in turn, help the doctor create a custom treatment plan. One of these tests is a discography, which involves an injection into one or more of the patient's intervertebral discs.
The spine is composed of 24 vertebrae. There are seven cervical (neck) vertebrae, twelve thoracic (upper and mid back) vertebrae and five lumbar (lower back) vertebrae. In between these vertebrae are discs called intervertebral discs, which acts as shock absorbers.
These discs are made up of two substances - nucleus pulposus (the disc's center, which contains water and proteoglycans), and annulus fibrosus (this surrounds the nucleus pulposus and is made up of layer upon layer of collagen fibers). These layers are packed together tightly and make for a very tough structure that keeps the fluid in the nucleus pulposus from leaking.
Even though these discs are strong, resilient structures, they can wear out over time or become damaged, resulting in cracks, tears (called fissures) and bulging. When this happens, pain may occur.
Discography allows interventional pain physicians to see a disc’s internal structure and establish whether or not it is the source of pain. Even though discography has been proven to be reliable in helping physicians make a pain diagnosis, it is done only after other tests have proven to be inconclusive in pinpointing the source of pain.
A patient who is a good candidate for discography is one who has been experiencing persistent spinal pain, is suspected of having a disc abnormality and has had non-invasive tests that proved inconclusive. The patient must be willing to undergo treatment directed at the disc.
Patients are given an IV and a local anesthetic applied to the skin to help them relax. Then, the doctor injects the patient with a dye, which makes the disc’s structure more visible on an x-ray monitor. Through this, the doctor is able to see whether or not the disc is torn, bulging, leaking or otherwise damaged.
Another type of discography used in the pain clinic is provocation discography. In this, the doctor attempts to duplicate the patient's pain so that its origin may be located. If a normal disc is injected, the patient will feel some pressure, but not any pain. If a damaged or worn out disc is injected, pain will be felt.