Figure 1: Discogram x-ray showing
needle injecting dye (white)
into the L4-5 disc
Discography is used to evaluate if the intervertebral discs are the source of a patient's pain. [Figure 1 ] The test is usually done in patients with chronic back or neck pain where the source of the pain has not been able to be diagnosed by more conventional methods such as X-ray, myelography, CT, or MRI. There are two phases to the procedure. First, after numbing the skin with local anesthesia, a special spinal needle is placed under x-ray guidance (using fluoroscopy) within the center of the spinal disc (nucleus pulposus) and a dye fluid is injected to pressurize the disc. One or several discs may be injected and studied during the examination. Following injection of the discs, x-rays and a CT scan are taken that image both the inner and outer layers (annulus fibrosus) of the disc.
The main diagnostic importance to the discogram is the patient's response to the injection of the contrast material. If a patient's typical pain is felt with injection of a particular disc, that disc is believed to be at least in part a source of the patients pain. Since a pain anesthetic is also injected along with the contrast material, if the patient experiences first pain, then relief, it is support that the cause of the patient's pain has been identified.
Since the main goal of a discogram is to provoke pain with disc injection, the discogram is a temporarily painful test. It is known as a provocative test as its goal is to provoke the patient's symptoms. Unfortunately, since the patients pain response is of primary importance, a discogram cannot be properly performed under heavy sedation or general anesthesia.